bims-bicyki Biomed News
on Bicaudal-C1 and interactors in cystic kidney disease
Issue of 2023‒07‒09
ten papers selected by
Céline Gagnieux
École Polytechnique Fédérale de Lausanne (EPFL)


  1. Kidney360. 2023 Jul 07.
      Polycystic kidney diseases (PKDs) are genetic disorders characterized by the formation and expansion of numerous fluid-filled renal cysts, damaging normal parenchyma, and often leading to kidney failure (KF). Although, PKDs comprise a broad range of different diseases, with substantial genetic and phenotypic heterogeneity, an association with primary cilia represents a common theme. Great strides have been made in the identification of causative genes, furthering our understanding of the genetic complexity and disease mechanisms, but only one therapy so far has shown success in clinical trials and advanced to FDA approval. A key step in understanding disease pathogenesis and testing potential therapeutics is developing orthologous experimental models that accurately recapitulate the human phenotype. This has been particularly important for PKD because cellular models have been of limited value, however, the advent of organoid usage has expanded capabilities in this area but does not negate the need for whole organism models where renal function can be assessed. Animal model generation is further complicated in the most common disease type, autosomal dominant PKD (ADPKD), by homozygous lethality and a very limited cystic phenotype in heterozygotes, while for autosomal recessive PKD (ARPKD), mouse models have a delayed and modest kidney disease, in contrast to humans. However, for ADPKD, the use of conditional/inducible and dosage models have resulted in some of the best disease models in Nephrology. These have been employed to help understand pathogenesis, facilitate genetic interaction studies, and to perform preclinical testing. Whereas, for ARPKD, employing alternative species and digenic models has partially overcome these deficiencies. Here, we review the experimental models that are currently available and most valuable for therapeutic testing in PKD, their applications, success in preclinical trials, advantages and limitations, and where further improvements are needed.
    DOI:  https://doi.org/10.34067/KID.0000000000000209
  2. bioRxiv. 2023 Jun 14. pii: 2023.06.13.544839. [Epub ahead of print]
      In Chlamydomonas cilia, the ciliopathy-relevant TRP channel PKD2 is spatially compartmentalized into a distal region, in which PKD2 binds the axoneme and extracellular mastigonemes, and a smaller proximal region, in which PKD2 is more mobile and lacks mastigonemes. Here, we show that the two PKD2 regions are established early during cilia regeneration and increase in length as cilia elongate. In abnormally long cilia, only the distal region elongated whereas both regions adjusted in length during cilia shortening. In dikaryon rescue experiments, tagged PKD2 rapidly entered the proximal region of PKD2-deficient cilia whereas assembly of the distal region was hindered, suggesting that axonemal docking of PKD2 requires de novo ciliary assembly. We identified Small Interactor of PKD2 (SIP), a small PKD2-related protein, as a novel component of the PKD2-mastigoneme complex. In sip mutants, stability and proteolytic processing of PKD2 in the cell body were reduced and PKD2-mastigoneme complexes were absent from mutant cilia. Like the pkd2 and mst1 mutants, sip swims with reduced velocity. Cilia of the pkd2 mutant beat with normal frequency and bending pattern but were less efficient in moving cells supporting a passive role of the PKD2-SIP-mastigoneme complexes in increasing the effective surface of Chlamydomonas cilia.
    DOI:  https://doi.org/10.1101/2023.06.13.544839
  3. bioRxiv. 2023 Jun 14. pii: 2023.06.14.544972. [Epub ahead of print]
      Cilia regeneration is a physiological event, and while studied extensively in unicellular organisms, it remains poorly understood in vertebrates. In this study, using Xenopus multiciliated cells (MCCs) as a model, we demonstrate that, unlike unicellular organisms, deciliation removes the transition zone (TZ) along with the ciliary axoneme. While MCCs immediately begin the regeneration of the ciliary axoneme, surprisingly, the assembly of TZ was delayed. Instead, ciliary tip proteins, Sentan and Clamp, were the first to localize to regenerating cilia. Using cycloheximide (CHX) to block new protein synthesis, we show that the TZ protein B9d1 is not a component of the cilia precursor pool and requires new transcription/translation providing insights into the delayed repair of TZ. Moreover, CHX treatment led MCCs to assemble fewer (∼ ten compared to ∼150 in controls) but about wild-type length (78% of WT) cilia by gradually concentrating ciliogenesis proteins like IFT43 at a select few basal bodies, highlighting the exciting possibility of protein transport between basal bodies to facilitate faster regeneration in cells with multiple cilia. In summary, we demonstrate that MCCs begin regeneration with the assembly of ciliary tip and axoneme followed by TZ, questioning the importance of TZ in motile ciliogenesis.
    DOI:  https://doi.org/10.1101/2023.06.14.544972
  4. NPJ Genom Med. 2023 Jul 07. 8(1): 16
      Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic cause of kidney failure and is primarily associated with PKD1 or PKD2. Approximately 10% of patients remain undiagnosed after standard genetic testing. We aimed to utilise short and long-read genome sequencing and RNA studies to investigate undiagnosed families. Patients with typical ADPKD phenotype and undiagnosed after genetic diagnostics were recruited. Probands underwent short-read genome sequencing, PKD1 and PKD2 coding and non-coding analyses and then genome-wide analysis. Targeted RNA studies investigated variants suspected to impact splicing. Those undiagnosed then underwent Oxford Nanopore Technologies long-read genome sequencing. From over 172 probands, 9 met inclusion criteria and consented. A genetic diagnosis was made in 8 of 9 (89%) families undiagnosed on prior genetic testing. Six had variants impacting splicing, five in non-coding regions of PKD1. Short-read genome sequencing identified novel branchpoint, AG-exclusion zone and missense variants generating cryptic splice sites and a deletion causing critical intron shortening. Long-read sequencing confirmed the diagnosis in one family. Most undiagnosed families with typical ADPKD have splice-impacting variants in PKD1. We describe a pragmatic method for diagnostic laboratories to assess PKD1 and PKD2 non-coding regions and validate suspected splicing variants through targeted RNA studies.
    DOI:  https://doi.org/10.1038/s41525-023-00362-z
  5. Int J Surg Case Rep. 2023 Jul 05. pii: S2210-2612(23)00582-5. [Epub ahead of print]108 108453
      INTRODUCTION AND IMPORTANCE: Polycystic kidney disease is a cillopathy characterized by the formation of numerous cysts in the kidneys, sometimes associated with extra-renal forms. Diagnosis is often by chance, or by other complications such as hematuria, urinary tract infections or, rarely, compression of neighboring organs.CASE PRESENTATION: We report the case of a patient consulted for a symptomatology similar to that of acute pancreatitis, whose investigation objectified compression of the main bile duct by a voluminous right kidney polycystic in a CT scan.
    CLINICAL DISCUSSION: For this compressive complication of the polycystic kidney, a nephrectomy was performed after embolization of the renal artery, given the haemorrhage risk.
    CONCLUSION: A polycystic kidney should be removed in the event of a compressive complication and, given the risk of haemorrhage, should preferably be preceded by embolization.
    Keywords:  Bile duct compression; Embolization; Nephrectomy; Polycystic kidney
    DOI:  https://doi.org/10.1016/j.ijscr.2023.108453
  6. bioRxiv. 2023 Jun 01. pii: 2023.05.31.543107. [Epub ahead of print]
      Cilia are hairlike protrusions that project from the surface of eukaryotic cells and play key roles in cell signaling and motility. Ciliary motility is regulated by the conserved nexin-dynein regulatory complex (N-DRC), which links adjacent doublet microtubules and regulates and coordinates the activity of outer doublet complexes. Despite its critical role in cilia motility, the assembly and molecular basis of the regulatory mechanism are poorly understood. Here, utilizing cryo-electron microscopy in conjunction with biochemical cross-linking and integrative modeling, we localized 12 DRC subunits in the N-DRC structure of Tetrahymena thermophila . We also found that the CCDC96/113 complex is in close contact with the N-DRC. In addition, we revealed that the N-DRC is associated with a network of coiled-coil proteins that most likely mediates N-DRC regulatory activity.
    DOI:  https://doi.org/10.1101/2023.05.31.543107
  7. Urologiia. 2023 May; 53-57
      INTRODUCTION: Kidney transplantation, which provides a high quality of life for patients with terminal chronic renal failure worldwide, is recognized as one of the main achievements of modern medicine. Graft dysfunction is an urgent problem, the one-year survival rate of renal transplants is from 93% (from cadaveric donors) to 97% (from living donors), the five-year survival rate is on average 95%. The aim of the study consisted in determining the features of renal graft blood flow in the early post-transplantation period.MATERIALS AND METHODS: The results of operative treatment of 110 patients who underwent orthotopic kidney transplantation for various reasons were analyzed. The indication for transplantation was chronic kidney disease of 5 st in the outcome of the main disease: in 70 (64%) in chronic glomerulonephritis, in 22 (20%) patients in autosomal dominant polycystic kidney disease, 10 (9%) patients in diabetic nephropathy, in 8 (7%) patients in chronic pyelonephritis. The five-year survival rate of the renal graft during catamnestic follow-up was 88%. All patients underwent ultrasound dopplerography of a renal graft in dynamics from the first day to discharge.
    RESULTS: After transplantation of a renal graft, blood flow disorders are caused by swelling in the early postoperative period, but further to discharge there was a normalization of the blood flow rates of the renal graft. Which suggests a satisfactory functional state of the renal graft and is a favorable prognostic feature. Reduced blood flow in the graft and increased resistance index (RI) in ultrasound with dopplerography are signs of developing graft dysfunction.
    CONCLUSION: In almost all cases, postoperative postoperative renal transplant transplants continued to cause blood flow disturbances due to early postoperative edema. The use of ultrasound and Doppler imaging to assess graft status is a diagnostically valuable non-invasive method.
    Keywords:  blood flow; chronic kidney disease; dopplerography; kidney transplant; nephrotransplant
  8. Cells. 2023 May 11. pii: 1367. [Epub ahead of print]12(10):
      Neuroinflammation is a unifying factor among all acute central nervous system (CNS) injuries and chronic neurodegenerative disorders. Here, we used immortalized microglial (IMG) cells and primary microglia (PMg) to understand the roles of the GTPase Ras homolog gene family member A (RhoA) and its downstream targets Rho-associated coiled-coil-containing protein kinases 1 and 2 (ROCK1 and ROCK2) in neuroinflammation. We used a pan-kinase inhibitor (Y27632) and a ROCK1- and ROCK2-specific inhibitor (RKI1447) to mitigate a lipopolysaccharide (LPS) challenge. In both the IMG cells and PMg, each drug significantly inhibited pro-inflammatory protein production detected in media (TNF-α, IL-6, KC/GRO, and IL-12p70). In the IMG cells, this resulted from the inhibition of NF-κB nuclear translocation and the blocking of neuroinflammatory gene transcription (iNOS, TNF-α, and IL-6). Additionally, we demonstrated the ability of both compounds to block the dephosphorylation and activation of cofilin. In the IMG cells, RhoA activation with Nogo-P4 or narciclasine (Narc) exacerbated the inflammatory response to the LPS challenge. We utilized a siRNA approach to differentiate ROCK1 and ROCK2 activity during the LPS challenges and showed that the blockade of both proteins may mediate the anti-inflammatory effects of Y27632 and RKI1447. Using previously published data, we show that genes in the RhoA/ROCK signaling cascade are highly upregulated in the neurodegenerative microglia (MGnD) from APP/PS-1 transgenic Alzheimer's disease (AD) mice. In addition to illuminating the specific roles of RhoA/ROCK signaling in neuroinflammation, we demonstrate the utility of using IMG cells as a model for primary microglia in cellular studies.
    Keywords:  NF-κB; ROCK inhibitors; ROCK1; ROCK2; RhoA; microglia; neuroinflammation
    DOI:  https://doi.org/10.3390/cells12101367