Biology subjects

Shakes, D.

Publications and source records attributed to Shakes, D..

3 recordsLinked to original sources

bioRxiv2022

The X chromosome is a potential polarising signal for asymmetric cell divisions in meiotic cells of a nematode

The unequal partition of molecules and organelles during cell division results in daughter cells with different fates. Asymmetric cell divisions have been best characterised in systems in which extrinsic signals polarise the mother cell during cell division. However, the mechanisms of asymmetric cell division mediated by intrinsic signals, and the nature of these signals, are mostly unknown. Here we report an asymmetric cell division in the nematode Auanema rhodensis that may be cued by the X chromosome. In the wildtype XO male, the spermatocyte divides asymmetrically to generate X-bearing spermatids that inherit components necessary for sperm viability, and nullo-spermatids that inherits components to be discarded. We found that in XX mutant pseudomales, sperm components co-segregate with the X chromosome, supporting the hypothesis that the X chromosome is employed as a polarising signal for partitioning essential cytoplasmic components for sperm function.

developmental biology↗

bioRxiv2020

The intrinsically disordered protein SPE-18 promotes localized assembly of the major sperm protein in C. elegans spermatocytes

Many specialized cells use unconventional strategies of cytoskeletal control. Nematode spermatocytes discard their actin and tubulin following meiosis, and instead employ the regulated assembly/disassembly of the Major Sperm Protein (MSP) to drive sperm motility. However prior to the meiotic divisions, MSP is effectively sequestered as it exclusively assembles into paracrystalline structures called fibrous bodies (FBs). The accessory proteins that direct this sequestration process have remained mysterious. This study reveals SPE-18 as an intrinsically disordered protein that that is essential for MSP assembly within FBs. In spe-18 mutant spermatocytes, MSP remains cytosolic, and the cells arrest in meiosis. In wildtype spermatocytes, SPE-18 localizes to pre-FB complexes and functions with the kinase SPE-6 to recruit MSP. Changing patterns of SPE-18 localization revealed unappreciated complexities in FB maturation. Later, within newly individualized spermatids, SPE -18 is rapidly lost, yet SPE-18 loss alone is insufficient for MSP disassembly. Our findings reveal an alternative strategy for sequestering cytoskeletal elements, not as monomers but in localized, bundled polymers. Additionally, these studies provide an important example of disordered proteins promoting ordered cellular structures. Summary StatementIntrinsically disordered proteins are increasingly recognized as key regulators of localized cytoskeletal assembly. Expanding that paradigm, SPE-18 localizes MSP assembly within C. elegans spermatocytes.

developmental biology↗

bioRxiv2017

Gender- and gamete-specific patterns of X chromosome segregation in a three-gendered nematode

Meiosis is at the core of sexual reproduction and alterations to its program can have dramatic effects. In this study, we investigate the segregation pattern of the X chromosome in Auanema rhodensis, a three-gendered nematode. This species has an atypical pattern of X chromosome segregation during male spermatogenesis that results in the exclusive production of haplo-X sperm. Here we use a combination of genetic and cytological approaches to show that while XX females undergo conventional meiosis to produce mostly haplo-X oocytes, hermaphrodites undergo atypical meiosis to produce nullo-X oocytes and mostly diplo-X sperm. Gender- and gamete-specific alterations of the normal meiotic program include non-pairing of the X homologs and precocious separation of X chromatids. Given these intra-species, intra-individual and intra-gametogenesis variations in meiotic program of A. rhodensis, we argue that it is an ideal model to study the plasticity of meiosis and how it can be modulated.\n\nHighlights- Matings between A. rhodensis hermaphrodites and males generate only male crossprogeny.\n- Hermaphrodites generate mostly nullo-X oocytes and diplo-X sperm.\n- Following normal Mendelian genetics, XX females produce haplo-X oocytes.\n- In cross-progeny, sons always inherit the X chromosome from the father.

genetics↗