Biology subjects

Orniacki, C.

Publications and source records attributed to Orniacki, C..

3 recordsLinked to original sources

bioRxiv2024

Nuclear pores safeguard the integrity of the nuclear envelope

Nuclear pore complexes (NPCs) constitute giant channels within the nuclear envelope that mediate nucleocytoplasmic exchange. NPC diameter is thought to be regulated by nuclear envelope tension, but how such diameter changes are physiologically linked to cell differentiation, where mechanical properties of nuclei are remodeled and nuclear mechanosensing occurs, remains unstudied. Here we used cryo-electron tomography to show that NPCs dilate during differentiation of mouse embryonic stem cells into neural progenitors. In Nup133-deficient cells, which are known to display impaired neural differentiation, NPCs however fail to dilate. By analyzing the architectures of individual NPCs with template matching, we revealed that the Nup133-deficient NPCs are structurally heterogeneous and frequently disintegrate, resulting in the formation of large nuclear envelope openings. We propose that the elasticity of the NPC scaffold mechanically safeguards the nuclear envelope. Our studies provide a molecular explanation for how genetic perturbation of scaffolding components of macromolecular complexes causes tissue-specific phenotypes.

cell biology↗

bioRxiv2023

Y-complex nucleoporins independently contribute to nuclear pore assembly and gene regulation in neuronal progenitors

From their essential function in building up the nuclear pore complexes, nucleoporins have expanded roles beyond nuclear transport. Hence, their contribution to chromatin organization and gene expression has set them as critical players in development and pathologies. We previously reported that Nup133 and Seh1, two components of the Y-complex subunit of the nuclear pore scaffold, are dispensable for mouse embryonic stem cell viability but required for their survival during neuroectodermal differentiation. Here, a transcriptomic analysis revealed that Nup133 regulates a subset of genes at early stages of neuroectodermal differentiation, including Lhx1 and Nup210L, encoding a newly validated nucleoporin. These genes were also misregulated in Nup133{triangleup}Mid neuronal progenitors, in which NPC basket assembly is impaired, as previously observed in pluripotent cells. However, a four-fold reduction of Nup133, despite affecting basket assembly, is not sufficient to alter Nup210L and Lhx1 regulation. Finally, these two genes are also misregulated in Seh1-deficient neural progenitors that only show a mild decrease in NPC density. Together these data reveal a shared function of Y-complex nucleoporins in gene regulation during neuroectodermal differentiation, which seem independent of nuclear pore basket assembly.

cell biology↗

bioRxiv2020

Specific ZNF274 binding interference at SNORD116 activates the maternal transcripts in Prader-Willi syndrome neurons

Prader-Willi syndrome (PWS) is characterized by neonatal hypotonia, developmental delay, and hyperphagia/obesity. This disorder is caused by the absence of paternally-expressed gene products from chromosome 15q11-q13. We previously demonstrated that knocking out ZNF274, a KRAB-domain zinc finger protein capable of recruiting epigenetic machinery to deposit the H3K9me3 repressive histone modification, can activate expression from the normally silent maternal allele of SNORD116 in neurons derived from PWS iPSCs. However, ZNF274 has many other targets in the genome in addition to SNORD116. Depleting ZNF274 will surely affect the expression of other important genes and disrupt other pathways. Here we used CRISPR/Cas9 to delete ZNF274 binding sites at the SNORD116 locus to determine whether activation of the maternal copy of SNORD116 could be achieved without altering ZNF274 protein levels. We obtained similar activation of gene expression from the normally silenced maternal allele in neurons derived from PWS iPSCs, compared to ZNF274 knockout, demonstrating that ZNF274 is directly involved in the repression of SNORD116. These results suggest that interfering with ZNF274 binding at the maternal SNORD116 locus is a potential therapeutic strategy for PWS.

genetics↗