bims-mitmed 2023-10-08 papers

bims-mitmed

Biomed News

on Mitochondrial medicine

Issue of 2023‒10‒08
twenty-six papers selected by
Dario Brunetti, Fondazione IRCCS Istituto Neurologico

Wide diagnostic and genotypic spectrum in patients with suspected mitochondrial disease.
Nuclear genome influences mitochondrial DNA.
Mitochondrial Targeted Interventions for Aging.
Long term survival and abnormal liver fat accumulation in mice with specific thymidine kinase 2 deficiency in liver tissue.
Zika virus modulates mitochondrial dynamics, mitophagy, and mitochondria-derived vesicles to facilitate viral replication in trophoblast cells.
Mechanisms and regulation of human mitochondrial transcription.
Significant decrease of maternal mitochondria carryover using optimized spindle-chromosomal complex transfer.
Base editing of organellar DNA with programmable deaminases.
Mitochondrial transfer in hematological malignancies.
Use of 31 P magnetisation transfer magnetic resonance spectroscopy to measure ATP changes after 670 nm transcranial photobiomodulation in older adults.
Metabolomics and mitochondrial dysfunction in cardiometabolic disease.
p53 contributes to cardiovascular diseases via mitochondria dysfunction: A new paradigm.
Fast, multiplexable and efficient somatic gene deletions in adult mouse skeletal muscle fibers using AAV-CRISPR/Cas9.
Why researchers should use human embryo models with caution.
Complete mitochondrial DNA profile in stroke: a geographical matched case-control study in Spanish population.
Clinical and genetic analyses of a Swedish patient series diagnosed with ataxia.
A PrP EGFR signalling axis controls neural stem cell senescence through modulating cellular energy pathways.
KDM5-mediated activation of genes required for mitochondrial biology is necessary for viability in Drosophila.
ClpP/ClpX deficiency impairs mitochondrial functions and mTORC1 signaling during spermatogenesis.
Tissue morphology influences the temporal program of human brain organoid development.
Gene therapies for rare diseases are under threat. Scientists hope to save them.
Human embryo models made from pluripotent stem cells are not synthetic; they aren't embryos, either.
Alternate splice variants of the mitochondrial fission protein DNM1L/Drp1 regulate mitochondrial dynamics and cell fate in ovarian cancer.
Metabolic Regulation of Aged Hematopoietic Stem Cells: Key Players and Mechanisms.
A milder form of molybdenum cofactor deficiency type A presenting as Leigh's syndrome-like phenotype highlighting the secondary mitochondrial dysfunction: a case report.
Mitochondrial proteins encoded by the 22q11.2 neurodevelopmental locus regulate neural stem and progenitor cell proliferation.

Orphanet J Rare Dis. 2023 Oct 02. 18(1): 307

Wide diagnostic and genotypic spectrum in patients with suspected mitochondrial disease.

Kristina Grigalionienė, Birutė Burnytė, Laima Ambrozaitytė, Algirdas Utkus.

  BACKGROUND: Mitochondrial Diseases (MDs) are a diverse group of neurometabolic disorders characterized by impaired mitochondrial oxidative phosphorylation and caused by pathogenic variants in more than 400 genes. The implementation of next-generation sequencing (NGS) technologies helps to increase the understanding of molecular basis and diagnostic yield of these conditions. The purpose of the study was to investigate diagnostic and genotypic spectrum in patients with suspected MD. The comprehensive analysis of mtDNA variants using Sanger sequencing was performed in the group of 83 unrelated individuals with clinically suspected mitochondrial disease. Additionally, targeted next generation sequencing or whole exome sequencing (WES) was performed for 30 patients of the study group.RESULTS: The overall diagnostic rate was 21.7% for the patients with suspected MD, increasing to 36.7% in the group of patients where NGS methods were applied. Mitochondrial disease was confirmed in 11 patients (13.3%), including few classical mitochondrial syndromes (MELAS, MERRF, Leigh and Kearns-Sayre syndrome) caused by pathogenic mtDNA variants (8.4%) and MDs caused by pathogenic variants in five nDNA genes. Other neuromuscular diseases caused by pathogenic variants in seven nDNA genes, were confirmed in seven patients (23.3%).
CONCLUSION: The wide spectrum of identified rare mitochondrial or neurodevelopmental diseases proves that MD suspected patients would mostly benefit from an extensive genetic profiling allowing rapid diagnostics and improving the care of these patients.

Keywords:  Genetic diagnosis; Mitochondrial disease; Next generation sequencing; Variants; Whole exome sequencing; mtDNA; nDNA

DOI:  https://doi.org/10.1186/s13023-023-02921-0
Nat Rev Genet. 2023 Oct 06.

Nuclear genome influences mitochondrial DNA.

Henry Ertl.

DOI: https://doi.org/10.1038/s41576-023-00667-w
Cold Spring Harb Perspect Med. 2023 Oct 03. pii: a041199. [Epub ahead of print]

Mitochondrial Targeted Interventions for Aging.

Sophia Z Liu, Ying Ann Chiao, Peter S Rabinovitch, David J Marcinek.

Changes in mitochondrial function play a critical role in the basic biology of aging and age-related disease. Mitochondria are typically thought of in the context of ATP production and oxidant production. However, it is clear that the mitochondria sit at a nexus of cell signaling where they affect metabolite, redox, and energy status, which influence many factors that contribute to the biology of aging, including stress responses, proteostasis, epigenetics, and inflammation. This has led to growing interest in identifying mitochondrial targeted interventions to delay or reverse age-related decline in function and promote healthy aging. In this review, we discuss the diverse roles of mitochondria in the cell. We then highlight some of the most promising strategies and compounds to target aging mitochondria in preclinical testing. Finally, we review the strategies and compounds that have advanced to clinical trials to test their ability to improve health in older adults.

DOI: https://doi.org/10.1101/cshperspect.a041199
PLoS One. 2023 ;18(10): e0285242

Long term survival and abnormal liver fat accumulation in mice with specific thymidine kinase 2 deficiency in liver tissue.

Qian Zhao, Xiaoshan Zhou, Jingyi Yan, Raoul Kuiper, Sophie Curbo, Anna Karlsson.

Deficiency in thymidine kinase 2 (TK2) causes mitochondrial DNA depletion. Liver mitochondria are severely affected in Tk2 complete knockout models and have been suggested to play a role in the pathogenesis of the Tk2 knockout phenotype, characterized by loss of hypodermal fat tissue, growth retardation and reduced life span. Here we report a liver specific Tk2 knockout (KO) model to further study mechanisms contributing to the phenotypic changes associated with Tk2 deficiency. Interestingly, the liver specific Tk2 KO mice had a normal life span despite a much lower mtDNA level in liver tissue. Mitochondrial DNA encoded peptide COXI did not differ between the Tk2 KO and control mice. However, the relative liver weight was significantly increased in the male Tk2 KO mouse model. Histology analysis indicated an increased lipid accumulation. We conclude that other enzyme activities can partly compensate Tk2 deficiency to maintain mtDNA at a low but stable level throughout the life span of the liver specific Tk2 KO mice. The lower level of mtDNA was sufficient for survival but led to an abnormal lipid accumulation in liver tissue.

DOI: https://doi.org/10.1371/journal.pone.0285242
Front Immunol. 2023 ;14 1203645

Zika virus modulates mitochondrial dynamics, mitophagy, and mitochondria-derived vesicles to facilitate viral replication in trophoblast cells.

Jae Kyung Lee, Ok Sarah Shin.

  Zika virus (ZIKV) remains a global public health threat with the potential risk of a future outbreak. Since viral infections are known to exploit mitochondria-mediated cellular processes, we investigated the effects of ZIKV infection in trophoblast cells in terms of the different mitochondrial quality control pathways that govern mitochondrial integrity and function. Here we demonstrate that ZIKV (PRVABC59) infection of JEG-3 trophoblast cells manipulates mitochondrial dynamics, mitophagy, and formation of mitochondria-derived vesicles (MDVs). Specifically, ZIKV nonstructural protein 4A (NS4A) translocates to the mitochondria, triggers mitochondrial fission and mitophagy, and suppresses mitochondrial associated antiviral protein (MAVS)-mediated type I interferon (IFN) response. Furthermore, proteomics profiling of small extracellular vesicles (sEVs) revealed an enrichment of mitochondrial proteins in sEVs secreted by ZIKV-infected JEG-3 cells, suggesting that MDV formation may also be another mitochondrial quality control mechanism manipulated during placental ZIKV infection. Altogether, our findings highlight the different mitochondrial quality control mechanisms manipulated by ZIKV during infection of placental cells as host immune evasion mechanisms utilized by ZIKV at the placenta to suppress the host antiviral response and facilitate viral infection.

Keywords:  mitochondria-derived vesicles (MDVs); mitochondrial quality control; mitophagy; nonstructural protein 4A (NS4A); zika virus (ZIKV)

DOI:  https://doi.org/10.3389/fimmu.2023.1203645
Nat Rev Mol Cell Biol. 2023 Oct 02.

Mechanisms and regulation of human mitochondrial transcription.

Benedict G Tan, Claes M Gustafsson, Maria Falkenberg.

The expression of mitochondrial genes is regulated in response to the metabolic needs of different cell types, but the basic mechanisms underlying this process are still poorly understood. In this Review, we describe how different layers of regulation cooperate to fine tune initiation of both mitochondrial DNA (mtDNA) transcription and replication in human cells. We discuss our current understanding of the molecular mechanisms that drive and regulate transcription initiation from mtDNA promoters, and how the packaging of mtDNA into nucleoids can control the number of mtDNA molecules available for both transcription and replication. Indeed, a unique aspect of the mitochondrial transcription machinery is that it is coupled to mtDNA replication, such that mitochondrial RNA polymerase is additionally required for primer synthesis at mtDNA origins of replication. We discuss how the choice between replication-primer formation and genome-length RNA synthesis is controlled at the main origin of replication (OriH) and how the recent discovery of an additional mitochondrial promoter (LSP2) in humans may change this long-standing model.

DOI: https://doi.org/10.1038/s41580-023-00661-4
PLoS Biol. 2023 Oct;21(10): e3002313

Significant decrease of maternal mitochondria carryover using optimized spindle-chromosomal complex transfer.

Xiaoyu Liao, Wenzhi Li, Kaibo Lin, Wei Jin, Shaozhen Zhang, Yao Wang, Meng Ma, Yating Xie, Weina Yu, Zhiguang Yan, Hongyuan Gao, Leiwen Zhao, Jiqiang Si, Yun Wang, Jiaying Lin, Chen Chen, Li Chen, Yanping Kuang, Qifeng Lyu.

Mutations in mitochondrial DNA (mtDNA) contribute to a variety of serious multi-organ human diseases, which are strictly inherited from the maternal germline. However, there is currently no curative treatment. Attention has been focused on preventing the transmission of mitochondrial diseases through mitochondrial replacement (MR) therapy, but levels of mutant mtDNA can often unexpectedly undergo significant changes known as mitochondrial genetic drift. Here, we proposed a novel strategy to perform spindle-chromosomal complex transfer (SCCT) with maximal residue removal (MRR) in metaphase II (MII) oocytes, thus hopefully eliminated the transmission of mtDNA diseases. With the MRR procedure, we initially investigated the proportions of mtDNA copy numbers in isolated karyoplasts to those of individual oocytes. Spindle-chromosomal morphology and copy number variation (CNV) analysis also confirmed the safety of this method. Then, we reconstructed oocytes by MRR-SCCT, which well developed to blastocysts with minimal mtDNA residue and normal chromosomal copy numbers. Meanwhile, we optimized the manipulation order between intracytoplasmic sperm injection (ICSI) and SCC transfer and concluded that ICSI-then-transfer was conducive to avoid premature activation of reconstructed oocytes in favor of normal fertilization. Offspring of mice generated by embryos transplantation in vivo and embryonic stem cells derivation further presented evidences for competitive development competence and stable mtDNA carryover without genetic drift. Importantly, we also successfully accomplished SCCT in human MII oocytes resulting in tiny mtDNA residue and excellent embryo development through MRR manipulation. Taken together, our preclinical mouse and human models of the MRR-SCCT strategy not only demonstrated efficient residue removal but also high compatibility with normal embryo development, thus could potentially be served as a feasible clinical treatment to prevent the transmission of inherited mtDNA diseases.

DOI: https://doi.org/10.1371/journal.pbio.3002313
Nat Rev Mol Cell Biol. 2023 Oct 04.

Base editing of organellar DNA with programmable deaminases.

Jin-Soo Kim, Jia Chen.

Mitochondria and chloroplasts are organelles that include their own genomes, which encode key genes for ATP production and carbon dioxide fixation, respectively. Mutations in mitochondrial DNA can cause diverse genetic disorders and are also linked to ageing and age-related diseases, including cancer. Targeted editing of organellar DNA should be useful for studying organellar genes and developing novel therapeutics, but it has been hindered by lack of efficient tools in living cells. Recently, CRISPR-free, protein-only base editors, such as double-stranded DNA deaminase toxin A-derived cytosine base editors (DdCBEs) and adenine base editors (ABEs), have been developed, which enable targeted organellar DNA editing in human cell lines, animals and plants. In this Review, we present programmable deaminases developed for base editing of organellar DNA in vitro and discuss mitochondrial DNA editing in animals, and plastid genome (plastome) editing in plants. We also discuss precision and efficiency limitations of these tools and propose improvements for therapeutic, agricultural and environmental applications.

DOI: https://doi.org/10.1038/s41580-023-00663-2
Biomark Res. 2023 Oct 05. 11(1): 89

Mitochondrial transfer in hematological malignancies.

Xiaodong Guo, Can Can, Wancheng Liu, Yihong Wei, Xinyu Yang, Jinting Liu, Hexiao Jia, Wenbo Jia, Hanyang Wu, Daoxin Ma.

  Mitochondria are energy-generated organelles and take an important part in biological metabolism. Mitochondria could be transferred between cells, which serves as a new intercellular communication. Mitochondrial transfer improves mitochondrial defects, restores the biological functions of recipient cells, and maintains the high metabolic requirements of tumor cells as well as drug resistance. In recent years, it has been reported mitochondrial transfer between cells of bone marrow microenvironment and hematological malignant cells play a critical role in the disease progression and resistance during chemotherapy. In this review, we discuss the patterns and mechanisms on mitochondrial transfer and their engagement in different pathophysiological contexts and outline the latest knowledge on intercellular transport of mitochondria in hematological malignancies. Besides, we briefly outline the drug resistance mechanisms caused by mitochondrial transfer in cells during chemotherapy. Our review demonstrates a theoretical basis for mitochondrial transfer as a prospective therapeutic target to increase the treatment efficiency in hematological malignancies and improve the prognosis of patients.

Keywords:  Extracellular mitochondria; Extracellular vesicles; Hematological malignancies; Mitochondrial transfer; Tunneling nanotubes

DOI:  https://doi.org/10.1186/s40364-023-00529-x
Aging Cell. 2023 Oct 06. e14005

Use of 31 P magnetisation transfer magnetic resonance spectroscopy to measure ATP changes after 670 nm transcranial photobiomodulation in older adults.

Elizabeth J Fear, Frida H Torkelsen, Elisa Zamboni, Kuan-Ju Chen, Martin Scott, Glenn Jeffery, Heidi Baseler, Aneurin J Kennerley.

  Mitochondrial function declines with age, and many pathological processes in neurodegenerative diseases stem from this dysfunction when mitochondria fail to produce the necessary energy required. Photobiomodulation (PBM), long-wavelength light therapy, has been shown to rescue mitochondrial function in animal models and improve human health, but clinical uptake is limited due to uncertainty around efficacy and the mechanisms responsible. Using 31 P magnetisation transfer magnetic resonance spectroscopy (MT-MRS) we quantify, for the first time, the effects of 670 nm PBM treatment on healthy ageing human brains. We find a significant increase in the rate of ATP synthase flux in the brain after PBM in a cohort of older adults. Our study provides initial evidence of PBM therapeutic efficacy for improving mitochondrial function and restoring ATP flux with age, but recognises that wider studies are now required to confirm any resultant cognitive benefits.

Keywords:  31P magnetic resonance spectroscopy; ageing brain; cell metabolism; magnetisation transfer; photobiomodulation

DOI:  https://doi.org/10.1111/acel.14005
Life Sci. 2023 Oct 01. pii: S0024-3205(23)00772-5. [Epub ahead of print] 122137

Metabolomics and mitochondrial dysfunction in cardiometabolic disease.

Abhishek Shastry, Kimberly Dunham-Snary.

  Circulating metabolites are indicators of systemic metabolic dysfunction and can be detected through contemporary techniques in metabolomics. These metabolites are involved in numerous mitochondrial metabolic processes including glycolysis, fatty acid β-oxidation, and amino acid catabolism, and changes in abundance of these metabolites is implicated in the pathogenesis of cardiometabolic diseases (CMDs). Epigenetic regulation and direct metabolite-protein interactions modulate the metabolism, both within cells and in the circulation. Dysfunction of multiple mitochondrial components stemming from mitochondrial DNA mutations are implicated in disease pathogenesis. This review will summarize the current state of knowledge regarding: i) the interactions between metabolites found within the mitochondrial environment during CMDs, ii) various metabolites' effects on cellular and systemic function, iii) how harnessing the power of metabolomic analyses represents the next frontier of precision medicine, and iv) how these concepts integrate to expand the clinical potential for translational cardiometabolic medicine.

Keywords:  Cardiometabolic disease; Circulating metabolites; Metabolic profiling; Metabolomics; Mitochondria; Redox balance

DOI:  https://doi.org/10.1016/j.lfs.2023.122137
Free Radic Biol Med. 2023 Sep 28. pii: S0891-5849(23)00661-5. [Epub ahead of print]

p53 contributes to cardiovascular diseases via mitochondria dysfunction: A new paradigm.

Hao Wang, Wei Yu, Yibo Wang, Ruihao Wu, Yifei Dai, Ye Deng, Shijun Wang, Jinxiang Yuan, Rubin Tan.

  Cardiovascular diseases (CVDs) are leading causes of global mortality; however, their underlying mechanisms remain unclear. The tumor suppressor factor p53 has been extensively studied for its role in cancer and is also known to play an important role in regulating CVDs. Abnormal p53 expression levels and modifications contribute to the occurrence and development of CVDs. Additionally, mounting evidence underscores the critical involvement of mitochondrial dysfunction in CVDs. Notably, studies indicate that p53 abnormalities directly correlate with mitochondrial dysfunction and may even interact with each other. Encouragingly, small molecule inhibitors targeting p53 have exhibited remarkable effects in animal models of CVDs. Moreover, therapeutic strategies aimed at mitochondrial-related molecules and mitochondrial replacement therapy have demonstrated their advantageous potential. Therefore, targeting p53 or mitochondria holds immense promise as a pioneering therapeutic approach for combating CVDs. In this comprehensive review, we delve into the mechanisms how p53 influences mitochondrial dysfunction, including energy metabolism, mitochondrial oxidative stress, mitochondria-induced apoptosis, mitochondrial autophagy, and mitochondrial dynamics, in various CVDs. Furthermore, we summarize and discuss the potential significance of targeting p53 or mitochondria in the treatment of CVDs.

Keywords:  Cardiovascular diseases; Mitochondria; Mitochondrial dynamics; Mitochondrial transplantation; Mitophagy; ROS; p53

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.09.036
Nat Commun. 2023 09 30. 14(1): 6116

Fast, multiplexable and efficient somatic gene deletions in adult mouse skeletal muscle fibers using AAV-CRISPR/Cas9.

Marco Thürkauf, Shuo Lin, Filippo Oliveri, Dirk Grimm, Randall J Platt, Markus A Rüegg.

Molecular screens comparing different disease states to identify candidate genes rely on the availability of fast, reliable and multiplexable systems to interrogate genes of interest. CRISPR/Cas9-based reverse genetics is a promising method to eventually achieve this. However, such methods are sorely lacking for multi-nucleated muscle fibers, since highly efficient nuclei editing is a requisite to robustly inactive candidate genes. Here, we couple Cre-mediated skeletal muscle fiber-specific Cas9 expression with myotropic adeno-associated virus-mediated sgRNA delivery to establish a system for highly effective somatic gene deletions in mice. Using well-characterized genes, we show that local or systemic inactivation of these genes copy the phenotype of traditional gene-knockout mouse models. Thus, this proof-of-principle study establishes a method to unravel the function of individual genes or entire signaling pathways in adult skeletal muscle fibers without the cumbersome requirement of generating knockout mice.

DOI: https://doi.org/10.1038/s41467-023-41769-7
Nature. 2023 Oct 02.

Why researchers should use human embryo models with caution.

Janet Rossant, Jianping Fu.



Keywords:  Developmental biology; Medical research; Stem cells

DOI:  https://doi.org/10.1038/d41586-023-03062-x
Mitochondrion. 2023 Oct 02. pii: S1567-7249(23)00084-3. [Epub ahead of print]

Complete mitochondrial DNA profile in stroke: a geographical matched case-control study in Spanish population.

Ana Onieva, Joan Martin, Daniel R Cuesta-Aguirre, Violeta Planells, Marta Coronado-Zamora, Katrin Beyer, Tomas Vega, Jose Eugenio Lozano, Cristina Santos, M Pilar Aluja.

  INTRODUCTION: Stroke, the second leading cause of death worldwide, is a complex disease influenced by many risk factors among which we can find reactive oxygen species (ROS). Since mitochondria are the main producers of cellular ROS, nowadays studies are trying to elucidate the role of these organelles and its DNA (mtDNA) variation in stroke risk. The aim of the present study was to perform a comprehensive evaluation of the association between mtDNA mutations and mtDNA content and stroke risk.MATERIAL AND METHODS: Homoplasmic and heteroplasmic mutations of the mtDNA were analysed in a case-controls study using 110 stroke cases and their corresponding control individuals. Mitochondrial DNA copy number (mtDNA-CN) was analysed in 73 of those case-control pairs.
RESULTS: Our results suggest that haplogroup V, specifically variants m.72C>T, m.4580G>A, m.15904C>T and m.16298T>C have a protective role in relation to stroke risk. On the contrary, variants m.73A>G, m.11719G>A and m.14766C>T appear to be genetic risk factors for stroke. In this study, we found no statistically significant association between stroke risk and mitochondrial DNA copy number.
CONCLUSIONS: These results demonstrate the possible role of mtDNA genetics on the pathogenesis of stroke, probably through alterations in mitochondrial ROS production.

Keywords:  Mitochondrial DNA; Mitochondrial DNA copy number; Mitochondrial haplogroups; Stroke

DOI:  https://doi.org/10.1016/j.mito.2023.10.001
J Neurol. 2023 Oct 03.

Clinical and genetic analyses of a Swedish patient series diagnosed with ataxia.

Sorina Gorcenco, Efthymia Kafantari, Joel Wallenius, Christin Karremo, Erik Alinder, Sigurd Dobloug, Maria Landqvist Waldö, Elisabet Englund, Hans Ehrencrona, Klas Wictorin, Kristina Karrman, Andreas Puschmann.

  Hereditary ataxia is a heterogeneous group of complex neurological disorders. Next-generation sequencing methods have become a great help in clinical diagnostics, but it may remain challenging to determine if a genetic variant is the cause of the patient's disease. We compiled a consecutive single-center series of 87 patients from 76 families with progressive ataxia of known or unknown etiology. We investigated them clinically and genetically using whole exome or whole genome sequencing. Test methods were selected depending on family history, clinical phenotype, and availability. Genetic results were interpreted based on the American College of Medical Genetics criteria. For high-suspicion variants of uncertain significance, renewed bioinformatical and clinical evaluation was performed to assess the level of pathogenicity. Thirty (39.5%) of the 76 families had received a genetic diagnosis at the end of our study. We present the predominant etiologies of hereditary ataxia in a Swedish patient series. In two families, we established a clinical diagnosis, although the genetic variant was classified as "of uncertain significance" only, and in an additional three families, results are pending. We found a pathogenic variant in one family, but we suspect that it does not explain the complete clinical picture. We conclude that correctly interpreting genetic variants in complex neurogenetic diseases requires genetics and clinical expertise. The neurologist's careful phenotyping remains essential to confirm or reject a diagnosis, also by reassessing clinical findings after a candidate genetic variant is suggested. Collaboration between neurology and clinical genetics and combining clinical and research approaches optimizes diagnostic yield.

Keywords:  Hereditary ataxia; Next-generation sequencing; Post-NGS phenotyping

DOI:  https://doi.org/10.1007/s00415-023-11990-x
J Biol Chem. 2023 Oct 04. pii: S0021-9258(23)02347-5. [Epub ahead of print] 105319

A PrP EGFR signalling axis controls neural stem cell senescence through modulating cellular energy pathways.

Bradley R Groveman, Benjamin Schwarz, Eric Bohrnsen, Simote T Foliaki, James A Carroll, Aleksandar R Wood, Catharine M Bosio, Cathryn L Haigh.

  Mis-folding of the prion protein (PrP) is known to cause neurodegenerative disease, however the native function of this protein remains poorly defined. PrP has been linked with many cellular functions, including cellular proliferation and senescence. It is also known to influence epidermal growth factor receptor (EGFR) signalling, a pathway that is itself linked with both cell growth and senescence. Adult neural stem cells (NSCs) persist at low levels in the brain throughout life and retain the ability to proliferate and differentiate into new neural lineage cells. Knock-out (KO) of PrP has previously been shown to reduce NSC proliferative capacity. We used PrP KO and wild type (WT) NSCs from adult mouse brain to examine the influence of PrP on cellular senescence, EGFR signalling, and the downstream cellular processes. PrP KO NSCs showed decreased cell proliferation and increased senescence in in vitro cultures. Expression of EGFR was decreased in PrP KO NSCs compared with WT NSCs and additional supplementation of EGF was sufficient to reduce senescence. RNAseq analysis confirmed that significant changes were occurring at the mRNA level within the EGFR signalling pathway and these were associated with reduced expression of mitochondrial components and correspondingly reduced mitochondrial function. Metabolomic analysis of cellular energy pathways showed that blockages were occurring at critical sites for production of energy and biomass, including catabolism of pyruvate. We conclude that, in the absence of PrP, NSC growth pathways are downregulated as a consequence of insufficient energy and growth intermediates.

Keywords:  EGFR; PrP; epidermal growth factor; glycolysis; mitochondria; prion; senescence

DOI:  https://doi.org/10.1016/j.jbc.2023.105319
Development. 2023 Oct 06. pii: dev.202024. [Epub ahead of print]

KDM5-mediated activation of genes required for mitochondrial biology is necessary for viability in Drosophila.

Michael F Rogers, Owen J Marshall, Julie Secombe.

  Histone modifying proteins play critical roles in the precise regulation of the transcriptional programs that coordinate development. KDM5 family proteins interact with chromatin through demethylating H3K4me3 as well as demethylase-independent mechanisms that remain less understood. To gain fundamental insights into the transcriptional activities of KDM5 proteins, we examined the essential roles of the single kdm5 ortholog of Drosophila during development. KDM5 performs critical functions in the larval neuroendocrine prothoracic gland, providing a model to define its role in regulating key gene expression programs. Integrating genome binding and transcriptomic data, we identify that KDM5 regulates the expression of genes critical for the function and maintenance of mitochondria, and we find that loss of KDM5 causes morphological changes to mitochondria. This is key to the developmental functions of KDM5, as expression of the mitochondrial biogenesis transcription factor Ets97D, homolog of GABPα, is able to suppress the altered mitochondrial morphology as well as the lethality of kdm5 null animals. Together, these data establish KDM5-mediated cellular functions that are important for normal development and could contribute to KDM5-linked disorders when dysregulated.

Keywords:  Demethylase; KDM5; Mitochondria; Prothoracic gland; Transcription

DOI:  https://doi.org/10.1242/dev.202024
Commun Biol. 2023 Oct 05. 6(1): 1012

ClpP/ClpX deficiency impairs mitochondrial functions and mTORC1 signaling during spermatogenesis.

Chenxi Guo, Yuan Xiao, Jingkai Gu, Peikun Zhao, Zhe Hu, Jiahuan Zheng, Renwu Hua, Zhuo Hai, Jiaping Su, Jian V Zhang, William S B Yeung, Tianren Wang.

Caseinolytic protease proteolytic subunit (ClpP) and caseinolytic protease X (ClpX) are mitochondrial matrix peptidases that activate mitochondrial unfolded protein response to maintain protein homeostasis in the mitochondria. However, the role of ClpP and ClpX in spermatogenesis remains largely unknown. In this study, we demonstrated the importance of ClpP/ClpX for meiosis and spermatogenesis with two conditional knockout (cKO) mouse models. We found that ClpP/ClpX deficiency reduced mitochondrial functions and quantity in spermatocytes, affected energy supply during meiosis and attenuated zygotene-pachytene transformation of the male germ cells. The dysregulated spermatocytes finally underwent apoptosis resulting in decreased testicular size and vacuolar structures within the seminiferous tubules. We found mTORC1 pathway was over-activated after deletion of ClpP/ClpX in spermatocytes. Long-term inhibition of the mTORC1 signaling via rapamycin treatment in vivo partially rescue spermatogenesis. The data reveal the critical roles of ClpP and ClpX in regulating meiosis and spermatogenesis.

DOI: https://doi.org/10.1038/s42003-023-05372-2
Cell Stem Cell. 2023 Oct 05. pii: S1934-5909(23)00324-7. [Epub ahead of print]30(10): 1351-1367.e10

Tissue morphology influences the temporal program of human brain organoid development.

Ilaria Chiaradia, Ivan Imaz-Rosshandler, Benedikt S Nilges, Jerome Boulanger, Laura Pellegrini, Richa Das, Nachiket D Kashikar, Madeline A Lancaster.

  Progression through fate decisions determines cellular composition and tissue architecture, but how that same architecture may impact cell fate is less clear. We took advantage of organoids as a tractable model to interrogate this interaction of form and fate. Screening methodological variations revealed that common protocol adjustments impacted various aspects of morphology, from macrostructure to tissue architecture. We examined the impact of morphological perturbations on cell fate through integrated single nuclear RNA sequencing (snRNA-seq) and spatial transcriptomics. Regardless of the specific protocol, organoids with more complex morphology better mimicked in vivo human fetal brain development. Organoids with perturbed tissue architecture displayed aberrant temporal progression, with cells being intermingled in both space and time. Finally, encapsulation to impart a simplified morphology led to disrupted tissue cytoarchitecture and a similar abnormal maturational timing. These data demonstrate that cells of the developing brain require proper spatial coordinates to undergo correct temporal progression.

Keywords:  brain; cell fate; cytoarchitecture; development; differentiation; morphology; neurogenesis; organoids; spatial transcriptomics; stem cells

DOI:  https://doi.org/10.1016/j.stem.2023.09.003
Nature. 2023 Oct 06.

Gene therapies for rare diseases are under threat. Scientists hope to save them.

Heidi Ledford.



Keywords:  Business; Drug discovery; Gene therapy; Medical research; Society

DOI:  https://doi.org/10.1038/d41586-023-03109-z
Cell Stem Cell. 2023 Oct 05. pii: S1934-5909(23)00327-2. [Epub ahead of print]30(10): 1290-1293

Human embryo models made from pluripotent stem cells are not synthetic; they aren't embryos, either.

Hannah L Landecker, Amander T Clark.

Embryo models are potentially highly impactful for human health research because their development recapitulates otherwise inaccessible events in a poorly understood area of biology, the first few weeks of human life. Casual reference to these models as "synthetic embryos" is misleading and should be approached with care and deliberation.

DOI: https://doi.org/10.1016/j.stem.2023.09.006
bioRxiv. 2023 Sep 20. pii: 2023.09.20.558501. [Epub ahead of print]

Alternate splice variants of the mitochondrial fission protein DNM1L/Drp1 regulate mitochondrial dynamics and cell fate in ovarian cancer.

Zaineb Javed, Dong Hui Shin, Weihua Pan, Sierra R White, Yeon Soo Kim, Amal Taher Elhaw, Shriya Kamlapurkar, Ya-Yun Cheng, J Cory Benson, Ahmed Emam Abdelnaby, Rebecca Phaeton, Hong-Gang Wang, Shengyu Yang, Mara Lisa Grove Sullivan, Simon C Watkins, Steven J Mullett, Stacy Lynn Gelhaus, Nam Y Lee, Lan Coffman, Katherine Marie Aird, Mohamed Trebak, Mythreye Karthikeyan, Vonn Walter, Nadine Hempel.

Aberrant mitochondrial fission/fusion dynamics have previously been reported in cancer cells. While post translational modifications are known regulators of GTPases of the mitochondrial fission/fusion machinery, we show for the first time that alternate splice variants of the fission protein Drp1 (DNM1L) have specific and unique roles in ovarian cancer, adding to the complexity of mitochondrial fission/fusion regulation in tumor cells. We find that ovarian cancer specimens express a Drp1 alternate splice transcript variant lacking exon 16 of the variable domain. High expression of Drp1 lacking exon 16 relative to other transcripts is associated with poor patient outcome. Unlike the unspliced variant, expression of Drp1 lacking exon 16 leads to decreased association of Drp1 to mitochondrial fission sites, more fused mitochondrial networks, enhanced respiration and TCA cycle metabolites, and is associated with a more tumorigenic phenotype. These effects can also be reversed by specific siRNA-mediated inhibition of the endogenously expressed transcript lacking exon 16. Moreover, lack of exon 16 abrogates mitochondrial fission in response to pro-apoptotic stimuli and leads to decreased sensitivity to chemotherapeutics. These data emphasize the significance of the pathophysiological consequences of Drp1 alternate splicing and divergent functions of Drp1 splice variants, and strongly warrant consideration of Drp1 splicing in future studies.

DOI: https://doi.org/10.1101/2023.09.20.558501
Exp Hematol. 2023 Sep 29. pii: S0301-472X(23)01733-2. [Epub ahead of print]

Metabolic Regulation of Aged Hematopoietic Stem Cells: Key Players and Mechanisms.

Nazanin Karimnia, James Harris, Shen Y Heazlewood, Benjamin Cao, Susan K Nilsson.

  Aging is accompanied by a gradual decline in the function and regenerative capacity of hematopoietic stem cells (HSCs), which leads to increased susceptibility to blood disorders. Recent studies have highlighted the critical role of metabolic regulation in governing the fate and function of HSCs, and alterations in metabolism play a critical role in the age-related changes observed in HSCs. Metabolic processes including glycolysis, mitochondrial function, nutrient sensing and inflammation, profoundly influence the maintenance, self-renewal and differentiation potential of the HSC pool. This review focuses on the metabolic alterations that occur in HSCs during aging and the systemic factors which contribute to HSC metabolic dysregulation, leading to impaired cellular function and reduced regenerative capacity. We highlight the impact of age-associated changes in oxidative stress, mitochondrial dysfunction, nutrient availability and inflammation on HSC metabolism and function. Targeting metabolic pathways and modulating key regulators of metabolism hold promise for reducing age-related HSC dysregulation, thus maintaining functional potential as a path towards healthy aging. Exploiting these metabolic interventions has the potential to improve hemopoietic recovery, enhance immune function and pave the way for novel therapeutic interventions to combat age-related blood disorders.

Keywords:  Aging; autophagy; hematopoietic stem cell; metabolism; mitochondria; niche; nutrients

DOI:  https://doi.org/10.1016/j.exphem.2023.09.006
Front Neurol. 2023 ;14 1214137

A milder form of molybdenum cofactor deficiency type A presenting as Leigh's syndrome-like phenotype highlighting the secondary mitochondrial dysfunction: a case report.

Montaha Almudhry, Asuri N Prasad, C Anthony Rupar, Keng Yeow Tay, Suzanne Ratko, Mary E Jenkins, Chitra Prasad.

  Background: Molybdenum cofactor deficiency (MoCD) (OMIM# 252150) is an autosomal-recessive disorder caused by mutations in four genes involved in the molybdenum cofactor (MOCO) biosynthesis pathway.Objectives: We report a milder phenotype in a patient with MOCS1 gene mutation who presented with a Leigh-like presentation.
Case report: We present the case of a 10-year-old boy who was symptomatic at the age of 5 months with sudden onset of dyskinesia, nystagmus, and extrapyramidal signs following a febrile illness. Initial biochemical, radiological, and histopathological findings a Leigh syndrome-like phenotype; however, whole-exome sequencing detected compound heterozygous mutations in MOCS1 gene, c.1133 G>C and c.217C>T, confirming an underlying MoCD. This was biochemically supported by low uric acid level of 80 (110-282 mmol/L) and low cystine level of 0 (3-49), and a urine S-sulfocysteine at 116 (0-15) mmol/mol creatinine. The patient was administered methionine- and cystine-free formulas. The patient has remained stable, with residual intellectual, speech, and motor sequelae.
Conclusion: This presentation expands the phenotypic variability of late-onset MoCD A and highlights the role of secondary mitochondrial dysfunction in its pathogenesis.

Keywords:  Leigh-like phenotype; MOCS1; dystonia; molybdenum cofactor deficiency; stroke

DOI:  https://doi.org/10.3389/fneur.2023.1214137
Mol Psychiatry. 2023 Oct 04.

Mitochondrial proteins encoded by the 22q11.2 neurodevelopmental locus regulate neural stem and progenitor cell proliferation.

Philip D Campbell, Isaiah Lee, Summer Thyme, Michael Granato.

Microdeletion of a 3Mb region encompassing 45 protein-coding genes at chromosome 22q11.2 (22q11.2DS) predisposes individuals to multiple neurodevelopmental disorders and is one of the greatest genetic risk factors for schizophrenia. Defective mitochondrial function has been hypothesized to contribute to 22q11.2DS pathogenesis; however, which of the six mitochondrial genes contribute to neurodevelopmental phenotypes and their underlying mechanisms remain unresolved. To systematically test 22q11.2DS genes for functional roles in neurodevelopment and behavior, we generated genetic mutants for each of the 37 conserved zebrafish orthologs and performed high throughput behavioral phenotyping using seven behavioral assays. Through this unbiased approach, we identified five single-gene mutants with partially overlapping behavioral phenotypes. Two of these genes, mrpl40 and prodha, encode for mitochondrial proteins and, similar to what we observed in mrpl40 and prodha mutants, pharmacologic inhibition of mitochondrial function during development results in microcephaly. Single mutant analysis shows that both mrpl40 and prodha mutants display aberrant neural stem and progenitor cell proliferation, with each gene regulating distinct cell populations. Finally, double mutants for both mrpl40 and prodha display aggravated behavioral phenotypes and neural stem and progenitor cell analysis reveals a previously unrecognized partially redundant role for mrpl40 and prodha in regulating radial glia-like cell proliferation. Combined, our results demonstrate a critical role for mitochondrial function in neural stem and progenitor cell populations in the developing vertebrate brain and provide compelling evidence that mitochondrial dysfunction during neurodevelopment is linked to brain volume and behavioral phenotypes observed in models of 22q11.2DS.

DOI: https://doi.org/10.1038/s41380-023-02272-z