A novel function for the presenilin family member spe-4: inhibition of spermatid activation in Caenorhabditis elegans.

<p>Abstract</p> <p>Background</p> <p>Sperm cells must regulate the timing and location of activation to maximize the likelihood of fertilization. Sperm from most species, including the nematode <it>Caenorhabditis elegans</it>, activate upon encountering an external signal. Activation for <it>C. elegans </it>sperm occurs as spermatids undergo spermiogenesis, a profound cellular reorganization that produces a pseudopod. Spermiogenesis is initiated by an activation signal that is transduced through a series of gene products. It is now clear that an inhibitory pathway also operates in spermatids, preventing their premature progression to spermatozoa and resulting in fine-scale control over the timing of activation. Here, we describe the involvement of a newly assigned member of the inhibitory pathway: <it>spe-4</it>, a homolog of the human presenilin gene PS1. The <it>spe-4(hc196) </it>allele investigated here was isolated as a suppressor of sterility of mutations in the spermiogenesis signal transduction gene <it>spe-27</it>.</p> <p>Results</p> <p>Through mapping, complementation tests, DNA sequencing, and transformation rescue, we determined that allele <it>hc196 </it>is a mutation in the <it>spe-4 </it>gene. Our data show that <it>spe-4(hc196) </it>is a bypass suppressor that eliminates the need for the spermiogenesis signal transduction. On its own, <it>spe-4(hc196) </it>has a recessive, temperature sensitive spermatogenesis-defective phenotype, with mutants exhibiting (i) defective spermatocytes, (ii) defective spermatids, (iii) premature spermatid activation, and (iv) spermatozoa defective in fertilization, in addition to a small number of functional sperm which appear normal microscopically.</p> <p>Conclusion</p> <p>A fraction of the sperm from <it>spe-4(hc196) </it>mutant males progress directly to functional spermatozoa without the need for an activation signal, suggesting that <it>spe-4 </it>plays a role in preventing spermatid activation. Another fraction of spermatozoa from <it>spe-4(hc196) </it>mutants are defective in fertilization. Therefore, prematurely activated spermatozoa may have several defects: we show that they may be defective in fertilization, and earlier work showed that they obstruct sperm transfer from males at mating. <it>hc196 </it>is a hypomorphic allele of <it>spe-4</it>, and its newly-discovered role inhibiting spermiogenesis may involve known proteolytic and/or calcium regulatory aspects of presenilin function, or it may involve yet-to-be discovered functions.</p

A persistent mitochondrial deletion reduces fitness and sperm performance in heteroplasmic populations of C. elegans

BACKGROUND: Mitochondrial DNA (mtDNA) mutations are of increasing interest due to their involvement in aging, disease, fertility, and their role in the evolution of the mitochondrial genome. The presence of reactive oxygen species and the near lack of repair mechanisms cause mtDNA to mutate at a faster rate than nuclear DNA, and mtDNA deletions are not uncommon in the tissues of individuals, although germ-line mtDNA is largely lesion-free. Large-scale deletions in mtDNA may disrupt multiple genes, and curiously, some large-scale deletions persist over many generations in a heteroplasmic state. Here we examine the phenotypic effects of one such deletion, uaDf5, in Caenorhabditis elegans (C. elegans). Our study investigates the phenotypic effects of this 3 kbp deletion. RESULTS: The proportion of uaDf5 chromosomes in worms was highly heritable, although uaDf5 content varied from worm to worm and within tissues of individual worms. We also found an impact of the uaDf5 deletion on metabolism. The deletion significantly reduced egg laying rate, defecation rate, and lifespan. Examination of sperm bearing the uaDf5 deletion revealed that sperm crawled more slowly, both in vitro and in vivo. CONCLUSION: Worms harboring uaDf5 are at a selective disadvantage compared to worms with wild-type mtDNA. These effects should lead to the rapid extinction of the deleted chromosome, but it persists indefinitely. We discuss both the implications of this phenomenon and the possible causes of a shortened lifespan for uaDf5 mutant worms

Knockout of the folate transporter folt-1 causes germline and somatic defects in C. elegans

<p>Abstract</p> <p>Background</p> <p>The <it>C. elegans </it>gene <it>folt-1 </it>is an ortholog of the human reduced folate carrier gene. The FOLT-1 protein has been shown to transport folate and to be involved in uptake of exogenous folate by worms. A knockout mutation of the gene, <it>folt-1(ok1460)</it>, was shown to cause sterility, and here we investigate the source of the sterility and the effect of the <it>folt-1 </it>knockout on somatic function.</p> <p>Results</p> <p>Our results show that <it>folt-1(ok1460) </it>knockout hermaphrodites have a substantially reduced germline, generate a small number of functional sperm, and only rarely produce a functional oocyte. We found no evidence of increased apoptosis in the germline of <it>folt-1 </it>knockout mutants, suggesting that germline proliferation is defective. While <it>folt-1 </it>knockout males are fertile, their rate of spermatogenesis was severely diminished, and the males were very poor maters. The mating defect is likely due to compromised metabolism and/or other somatic functions, as <it>folt-1 </it>knockout hermaphrodites displayed a shortened lifespan and elongated defecation intervals.</p> <p>Conclusions</p> <p>The FOLT-1 protein function affects both the soma and the germline. <it>folt-1(ok1460) </it>hermaphrodites suffer severely diminished lifespan and germline defects that result in sterility. Germline defects associated with folate deficiency appear widespread in animals, being found in humans, mice, fruit flies, and here, nematodes.</p

Molecular evolution in Panagrolaimus nematodes: origins of parthenogenesis, hermaphroditism and the Antarctic species P. davidi

10.1186/1471-2148-9-15BMC Evolutionary Biology911

Premature sperm activation and defective spermatogenesis caused by loss of spe-46 function in Caenorhabditis elegans.

Given limited resources for motility, sperm cell activation must be precisely timed to ensure the greatest likelihood of fertilization. Like those of most species, the sperm of C. elegans become active only after encountering an external signaling molecule. Activation coincides with spermiogenesis, the final step in spermatogenesis, when the spherical spermatid undergoes wholesale reorganization to produce a pseudopod. Here, we describe a gene involved in sperm activation, spe-46. This gene was identified in a suppressor screen of spe-27(it132ts), a sperm-expressed gene whose product functions in the transduction of the spermatid activation signal. While spe-27(it132ts) worms are sterile at 25°C, the spe-46(hc197)I; spe-27(it132ts)IV double mutants regain partial fertility. Single nucleotide polymorphism mapping, whole genome sequencing, and transformation rescue were employed to identify the spe-46 coding sequence. It encodes a protein with seven predicted transmembrane domains but with no other predicted functional domains or homology outside of nematodes. Expression is limited to spermatogenic tissue, and a transcriptional GFP fusion shows expression corresponds with the onset of the pachytene stage of meiosis. The spe-46(hc197) mutation bypasses the need for the activation signal; mutant sperm activate prematurely without an activation signal in males, and mutant males are sterile. In an otherwise wild-type genome, the spe-46(hc197) mutation induces a sperm defective phenotype. In addition to premature activation, spe-46(hc197) sperm exhibit numerous defects including aneuploidy, vacuolization, protruding spikes, and precocious fusion of membranous organelles. Hemizygous worms [spe-46(hc197)/mnDf111] are effectively sterile. Thus, spe-46 appears to be involved in the regulation of spermatid activation during spermiogenesis, with the null phenotype being an absence of functional sperm and hypomorphic phenotypes being premature spermatid activation and numerous sperm cell defects

A novel function for the presenilin family member : inhibition of spermatid activation in .-4

Atched unmated hermaphrodite showing the absence of sperm nuclei. SN indicates the characteristically compact DAPI labeled nuclei from the male's sperm [43], which appear localized to the spermatheca. OC indicates the oocyte chromosomes that are nearly the same size as sperm nuclei but occur in groups of 6 and are not as brightly fluorescent.<p><b>Copyright information:</b></p><p>Taken from "A novel function for the presenilin family member : inhibition of spermatid activation in ."</p><p>http://www.biomedcentral.com/1471-213X/8/44</p><p>BMC Developmental Biology 2008;8():44-44.</p><p>Published online 22 Apr 2008</p><p>PMCID:PMC2383881.</p><p></p

A novel function for the presenilin family member : inhibition of spermatid activation in .-3

in sperm medium containing the protease Pronase, which activates spermatids to spermatozoa .<p><b>Copyright information:</b></p><p>Taken from "A novel function for the presenilin family member : inhibition of spermatid activation in ."</p><p>http://www.biomedcentral.com/1471-213X/8/44</p><p>BMC Developmental Biology 2008;8():44-44.</p><p>Published online 22 Apr 2008</p><p>PMCID:PMC2383881.</p><p></p

A novel function for the presenilin family member : inhibition of spermatid activation in .-1

N is shown below the third exon. The arrows represent oligonucleotides used for PCR amplification and DNA sequencing. B. The sequence of the oligonucleotides.<p><b>Copyright information:</b></p><p>Taken from "A novel function for the presenilin family member : inhibition of spermatid activation in ."</p><p>http://www.biomedcentral.com/1471-213X/8/44</p><p>BMC Developmental Biology 2008;8():44-44.</p><p>Published online 22 Apr 2008</p><p>PMCID:PMC2383881.</p><p></p