The multifaceted C. elegans major sperm protein: an ephrin signaling antagonist in oocyte maturation

ABSTRACTMany 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.

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The conserved molting/circadian rhythm regulator NHR-23/NR1F1 serves as an essential co-regulator of C. elegans spermatogenesis

Development ◽

10.1242/dev.193862 ◽

2020 ◽

Vol 147 (22) ◽

pp. dev193862

Author(s):

James Matthew Ragle ◽

Abigail L. Aita ◽

Kayleigh N. Morrison ◽

Raquel Martinez-Mendez ◽

Hannah N. Saeger ◽

...

Keyword(s):

Regulatory Network ◽

Nuclear Hormone Receptor ◽

Model Systems ◽

Residual Body ◽

Major Sperm Protein ◽

Sperm Protein ◽

C Elegans ◽

Gene Regulatory ◽

Established Role

ABSTRACTIn sexually reproducing metazoans, spermatogenesis is the process by which uncommitted germ cells give rise to haploid sperm. Work in model systems has revealed mechanisms controlling commitment to the sperm fate, but how this fate is subsequently executed remains less clear. While studying the well-established role of the conserved nuclear hormone receptor transcription factor, NHR-23/NR1F1, in regulating C. elegans molting, we discovered that NHR-23/NR1F1 is also constitutively expressed in developing primary spermatocytes and is a critical regulator of spermatogenesis. In this novel role, NHR-23/NR1F1 functions downstream of the canonical sex-determination pathway. Degron-mediated depletion of NHR-23/NR1F1 within hermaphrodite or male germlines causes sterility due to an absence of functional sperm, as depleted animals produce arrested primary spermatocytes rather than haploid sperm. These spermatocytes arrest in prometaphase I and fail to either progress to anaphase or attempt spermatid-residual body partitioning. They make sperm-specific membranous organelles but fail to assemble their major sperm protein into fibrous bodies. NHR-23/NR1F1 appears to function independently of the known SPE-44 gene regulatory network, revealing the existence of an NHR-23/NR1F1-mediated module that regulates the spermatogenesis program.

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Large P body-like RNPs form in C. elegans oocytes in response to arrested ovulation, heat shock, osmotic stress, and anoxia and are regulated by the major sperm protein pathway

Developmental Biology ◽

10.1016/j.ydbio.2008.02.059 ◽

2008 ◽

Vol 318 (1) ◽

pp. 38-51 ◽

Cited By ~ 65

Author(s):

Molly C. Jud ◽

Michael J. Czerwinski ◽

Megan P. Wood ◽

Rachel A. Young ◽

Christopher M. Gallo ◽

...

Keyword(s):

Heat Shock ◽

Osmotic Stress ◽

Major Sperm Protein ◽

Sperm Protein ◽

C Elegans

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Interactions between the WEE-1.3 kinase and the PAM-1 aminopeptidase in oocyte maturation and the early C. elegans embryo

G3 Genes|Genome|Genetics ◽

10.1093/g3journal/jkab063 ◽

2021 ◽

Author(s):

Dorothy Benton ◽

Eva C Jaeger ◽

Arielle Kilner ◽

Ashley Kimble ◽

Josh Lowry ◽

...

Keyword(s):

Missense Mutation ◽

Oocyte Maturation ◽

Protective Role ◽

C Elegans ◽

Direct Target ◽

The One ◽

Actomyosin Cytoskeleton ◽

Embryonic Viability ◽

Anterior Posterior

Abstract Puromycin-sensitive aminopeptidases are found across phyla and are known to regulate the cell-cycle and play a protective role in neurodegenerative disease. PAM-1 is a puromycin-sensitive aminopeptidase important for meiotic exit and polarity establishment in the one-cell Caenorhabditis elegans embryo. Despite conservation of this aminopeptidase, little is known about its targets during development. In order to identify novel interactors, we conducted a suppressor screen and isolated four suppressing mutations in three genes that partially rescued the maternal-effect lethality of pam-1 mutants. Suppressed strains show improved embryonic viability and polarization of the anterior-posterior axis. We identified a missense mutation in wee-1.3 in one of these suppressed strains. WEE-1.3 is an inhibitory kinase that regulates maturation promoting factor. While the missense mutation suppressed polarity phenotypes in pam-1, it does so without restoring centrosome-cortical contact or altering the cortical actomyosin cytoskeleton. To see if PAM-1 and WEE-1.3 interact in other processes, we examined oocyte maturation. While depletion of wee-1.3 causes sterility due to precocious oocyte maturation, this effect was lessened in pam-1 worms, suggesting that PAM-1 and WEE-1.3 interact in this process. Levels of WEE-1.3 were comparable between wild-type and pam-1 strains, suggesting that WEE-1.3 is not a direct target of the aminopeptidase. Thus, we have established an interaction between PAM-1 and WEE-1.3 in multiple developmental processes and have identified suppressors that are likely to further our understanding of the role of puromycin-sensitive aminopeptidases during development.

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Localized Depolymerization of the Major Sperm Protein Cytoskeleton Correlates with the Forward Movement of the Cell Body in the Amoeboid Movement of Nematode Sperm

The Journal of Cell Biology ◽

10.1083/jcb.146.5.1087 ◽

1999 ◽

Vol 146 (5) ◽

pp. 1087-1096 ◽

Cited By ~ 40

Author(s):

Joseph E. Italiano ◽

Murray Stewart ◽

Thomas M. Roberts

Keyword(s):

Cell Body ◽

Body Movement ◽

Leading Edge ◽

Amoeboid Movement ◽

Major Sperm Protein ◽

Membrane Protrusion ◽

Forward Movement ◽

Sperm Protein ◽

Amoeboid Motility ◽

Tightly Coupled

The major sperm protein (MSP)-based amoeboid motility of Ascaris suum sperm requires coordinated lamellipodial protrusion and cell body retraction. In these cells, protrusion and retraction are tightly coupled to the assembly and disassembly of the cytoskeleton at opposite ends of the lamellipodium. Although polymerization along the leading edge appears to drive protrusion, the behavior of sperm tethered to the substrate showed that an additional force is required to pull the cell body forward. To examine the mechanism of cell body movement, we used pH to uncouple cytoskeletal polymerization and depolymerization. In sperm treated with pH 6.75 buffer, protrusion of the leading edge slowed dramatically while both cytoskeletal disassembly at the base of the lamellipodium and cell body retraction continued. At pH 6.35, the cytoskeleton pulled away from the leading edge and receded through the lamellipodium as its disassembly at the cell body continued. The cytoskeleton disassembled rapidly and completely in cells treated at pH 5.5, but reformed when the cells were washed with physiological buffer. Cytoskeletal reassembly occurred at the lamellipodial margin and caused membrane protrusion, but the cell body did not move until the cytoskeleton was rebuilt and depolymerization resumed. These results indicate that cell body retraction is mediated by tension in the cytoskeleton, correlated with MSP depolymerization at the base of the lamellipodium.

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Supramolecular assemblies of the Ascaris suum major sperm protein (MSP) associated with amoeboid cell motility

Journal of Cell Science ◽

10.1242/jcs.107.10.2941 ◽

1994 ◽

Vol 107 (10) ◽

pp. 2941-2949

Author(s):

K.L. King ◽

M. Stewart ◽

T.M. Roberts

Keyword(s):

Ascaris Suum ◽

Leading Edge ◽

Intrinsic Property ◽

Basic Unit ◽

Major Sperm Protein ◽

Sperm Protein ◽

Amoeboid Cell ◽

Left Handed ◽

Self Association

Sperm of the nematode, Ascaris suum, are amoeboid cells that do not require actin or myosin to crawl over solid substrata. In these cells, the role usually played by actin has been taken over by major sperm protein (MSP), which assembles into filaments that pack the sperm pseudopod. These MSP filaments are organized into multi-filament arrays called fiber complexes that flow centripetally from the leading edge of the pseudopod to the cell body in a pattern that is intimately associated with motility. We have characterized structurally a hierarchy of helical assemblies formed by MSP. The basic unit of the MSP cytoskeleton is a filament formed by two subfilaments coiled around one another along right-handed helical tracks. In vitro, higher-order assemblies (macrofibers) are formed by MSP filaments that coil around one another in a left-handed helical sense. The multi-filament assemblies formed by MSP in vitro are strikingly similar to the fiber complexes that characterize the sperm cytoskeleton. Thus, self-association is an intrinsic property of MSP filaments that distinguishes these fibers from actin filaments. The results obtained with MSP help clarify the roles of different aspects of the actin cytoskeleton in the generation of locomotion and, in particular, emphasize the contributions made by vectorial assembly and filament bundling.

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