bims-nucpor 2023-07-09 papers

Issue of 2023‒07‒09
two papers selected by
Sara Mingu, Johannes Gutenberg University

Cells. 2023 May 13. pii: 1380. [Epub ahead of print]12(10):

Temporal Changes in Nuclear Envelope Permeability during Semi-Closed Mitosis in Dictyostelium Amoebae.

Kristina Mitic, Irene Meyer, Ralph Gräf, Marianne Grafe.

The Amoebozoan Dictyostelium discoideum exhibits a semi-closed mitosis in which the nuclear membranes remain intact but become permeabilized to allow tubulin and spindle assembly factors to access the nuclear interior. Previous work indicated that this is accomplished at least by partial disassembly of nuclear pore complexes (NPCs). Further contributions by the insertion process of the duplicating, formerly cytosolic, centrosome into the nuclear envelope and nuclear envelope fenestrations forming around the central spindle during karyokinesis were discussed. We studied the behavior of several Dictyostelium nuclear envelope, centrosomal, and nuclear pore complex (NPC) components tagged with fluorescence markers together with a nuclear permeabilization marker (NLS-TdTomato) by live-cell imaging. We could show that permeabilization of the nuclear envelope during mitosis occurs in synchrony with centrosome insertion into the nuclear envelope and partial disassembly of nuclear pore complexes. Furthermore, centrosome duplication takes place after its insertion into the nuclear envelope and after initiation of permeabilization. Restoration of nuclear envelope integrity usually occurs long after re-assembly of NPCs and cytokinesis has taken place and is accompanied by a concentration of endosomal sorting complex required for transport (ESCRT) components at both sites of nuclear envelope fenestration (centrosome and central spindle).

Keywords: Dictyostelium; centrosome; mitosis; nuclear envelope; nuclear pore complex

DOI: https://doi.org/10.3390/cells12101380

Biol Reprod. 2023 Jul 03. pii: ioad069. [Epub ahead of print]

ADAD1 is required for normal translation of nuclear pore and transport protein transcripts in spermatids of Mus musculus.

Sarah Potgieter, Christopher Eddy, Aditi Badrinath, Lauren Chukrallah, Toby Lo, Gayatri Mohanty, Pablo E Visconti, Elizabeth M Snyder.

ADAD1 is a testis-specific RNA binding protein expressed in post-meiotic spermatids whose loss leads to defective sperm morphology and male infertility. However, the drivers of the Adad1 phenotype remain unclear. Morphological and functional analysis of Adad1 mutant sperm demonstrated defective DNA compaction, abnormal head shaping, and reduced motility. RNA sequencing of Adad1 mutant testes revealed minimal transcriptome changes however ribosome association of many transcripts was reduced, suggesting ADAD1 may be required for their translational activation. Additionally, immunofluorescence of proteins encoded by select transcripts showed delayed protein accumulation. Further analyses demonstrated impaired subcellular localization of multiple proteins suggesting protein transport is also abnormal in Adad1 mutants. To clarify the mechanism giving rise to this, the manchette, a protein transport microtubule network, and the LINC complex, which connects the manchette to the nuclear lamin, were assessed across spermatid development. Proteins of both displayed delayed translation and/or localization in mutant spermatids implicating ADAD1 in their regulation, even in the absence of altered ribosome association. Finally, ADAD1's impact on the nuclear pore complex (NPC), a regulator of both the manchette and the LINC complex, was examined. Reduced ribosome association of NPC encoding transcripts and reduced NPC protein abundance along with abnormal localization in Adad1 mutants confirmed ADAD1 is required for normal translation of the NPC in post-meiotic germ cells. Together, these studies lead to a model whereby ADAD1's influence on nuclear transport leads to deregulation of the LINC complex and the manchette, ultimately generating the range of physiological defects observed in the Adad1 phenotype. Summary sentence: ADAD1 is a post-meiotic spermatid RNA binding protein that is required for normal translation of mRNAs important for post-meiotic differentiation and mRNAs associated with nuclear and intracellular transport.

Keywords: LINC complex; RNA-binding proteins; manchette; microtubules; nuclear pore complex; protein transport; spermatids; spermiogenesis; translation regulation

DOI: https://doi.org/10.1093/biolre/ioad069