Biology subjects

Familiari, N. E.

Publications and source records attributed to Familiari, N. E..

5 recordsLinked to original sources

bioRxiv2026

Spindle pole proteins confine chromosomes to ensure their expulsion during female meiosis

Animal oocytes undergo highly asymmetric divisions to expel excess copies of their genome into compact cells called polar bodies. This requires tight clustering and cortical positioning of meiotic chromosomes, yet the mechanism remains incompletely understood. Using C. elegans oocytes, we found that the meiotic spindle pole protein ZYG-9/ch-TOG delocalizes from microtubules to spread along the surface of chromosomes and prevent their dispersal in meiotic anaphase. This effect was more pronounced in the absence of the spindle, where ZYG-9 formed into a micron-scale droplet that enveloped all chromosomes. Purified ZYG-9 was sufficient to bind DNA and coat reconstituted chromatin. Mutations that perturb ZYG-9-DNA binding impaired chromosome packaging into polar bodies, resulting in oocytes carrying extra chromosomes and reduced fertility. We propose that liquid-like assemblies of spindle pole proteins are repurposed as surface-acting glue to tightly package meiotic chromosomes into polar bodies, thus ensuring oocytes have the correct genome copy number.

cell biology↗

bioRxiv2025

TRIM37 recognizes a bipartite degron to ubiquitinate centrosome substrates

Dysregulation of the E3 ubiquitin ligase TRIM37 is associated with tumor formation and Mulibrey nanism, a recessive developmental syndrome. TRIM37 regulates steady-state levels of centrosome proteins and limits their ectopic assembly, but how it recognizes and ubiquitinates its substrates is poorly understood. We found that TRIM37 directly ubiquitinates the centrosome-forming protein Cep192 at 7 lysines clustered near its C-terminus. TRIM37 binds Cep192 at a C-terminal intrinsically disordered region followed by an ASH domain (IDR+ASH8). Mutation of the 7 lysines or the IDR+ASH8 domain increased Cep192 levels and stability in cells, indicating loss of TRIM37-based regulation. Fusing IDR+ASH8 to an unrelated protein (GFP-EB1) was sufficient to enable its degradation via TRIM37. Biochemical assays revealed that IDR+ASH8 is primarily monomeric and binds TRIM37 via two separate coiled-coil motifs with mid-nanomolar affinity. We propose that the IDR+ASH8 motif is a bipartite degron for TRIM37, enabling it to target centrosome proteins and adjust their levels.

cell biology↗

bioRxiv2025

In vitro reconstitution of minimal human centrosomes

CDK5RAP2/CEP215 is a key pericentriolar material (PCM) protein that recruits microtubule-nucleating factors at human centrosomes. Using an in vitro reconstitution system, we show that CDK5RAP2 is sufficient to form micron-scale scaffolds around a nanometer-scale nucleator in a PLK-1-regulated manner. CDK5RAP2 assemblies recruited and activated gamma tubulin ring complexes ({gamma}-TuRCs) which, in the presence of /{beta} tubulin, generated microtubule asters. We found that F75 in CDK5RAP2 is partially needed to recruit {gamma}-TuRC yet is indispensable for {gamma}-TuRC activation. Furthermore, our system recapitulated key features of centrosome-amplified cancer cells. CDK5RAP2 scaffolds selectively recruited the molecular motor KifC1/HSET, which enhanced concentration of /{beta} tubulin, microtubule polymerization, and clustering of the assemblies. Our results highlight the specificity and selectivity of in vitro generated CDK5RAP2 scaffolds and identify a minimal set of components required for human centrosome assembly and function. This minimal centrosome model offers a powerful tool for studying centrosome biology and dysfunction in human health and disease.

cell biology↗

bioRxiv2024

eIF4ET regulates meiotic proteome levels to enable oocyte formation and storage

Animals store oocytes in a dormant state for weeks to decades before ovulation. The homeostatic programs oocytes use to endure long-term storage are poorly understood. Using female nematodes as a short-lived model, we found that oocyte formation and storage required IFET-1, the conserved eIF4E-Transporter protein (eIF4ET). IFET-1 co-assembled with CAR-1 (Lsm14) to form micron-scale condensates in stored oocytes, which dissipated after oocyte activation. Depletion of IFET-1 destabilized the stored oocyte proteome, leading to lower translation, a decline in microtubule maintenance proteins, and errors in microtubule organization and meiotic spindle assembly. Deleting individual domains within IFET-1 impaired oocyte storage without affecting oocyte formation. Thus, in addition to establishing a healthy oocyte reserve in young mothers, IFET-1 ensures that correct levels of cytoskeletal proteins are maintained as oocytes age. Human eIF4ET also localized to micron-scale puncta in dormant oocytes in a reproductively healthy patient. Our results clarify the role for eIF4ET in maintaining the oocyte reserve and further support eIF4ET dysfunction as an upstream cause of embryonic aneuploidy and age-related infertility.

developmental biology↗

bioRxiv2024

Phospho-regulated tuning of viscoelastic properties balances centrosome growth and strength

Centrosomes are membranelles organelles containing centrioles encapsulated by pericentriolar material (PCM). PCM nucleates microtubules that help position and segregate chromosomes during mitosis, yet how PCM resists microtubule-mediated forces is poorly understood at the material level. Here, we show that PLK-1 phosphorylation of SPD-5 tunes the dynamics and material properties of the PCM scaffold in C. elegans embryos. Microrheology of reconstituted PCM condensates reveals that PLK-1 phosphorylation decreases SPD-5 dynamics and increases condensate viscoelasticity. Similarly, in embryos, phospho-mimetic SPD-5 is less dynamic than wild-type SPD-5, which itself is less dynamic than phospho-null SPD-5. PCM built with phospho-null SPD-5 is smaller than normal, but its assembly can be partially rescued by reducing microtubule-dependent forces. The same is true for PCM built with phospho-mimetic SPD-5, yet the underlying causes are distinct: under force, phospho-null SPD-5 fails to assemble, while phospho-mimetic SPD-5 forms hyper-stable foci that fail to cohere into a uniform, spherical mass. Both mutants have defects with chromosome segregation and viability. Thus, tuning of SPD-5 phosphorylation optimizes PCM material properties to achieve correct PCM size, integrity, and function. Our results demonstrate how regulated chemical modification of a scaffolding protein modulates the material properties and function of a membraneless organelle.

cell biology↗