Nematode sperm

Structure, development, and evolutive patterns of spermatozoa in rhabditid nematodes (Nematoda: Rhabditida)

Spermatogenesis of five rhabditid nematodes was studied using transmission electron microscopy and is described herein. Structure and development of nematode sperm in all available representatives of the extensive order Rhabditida have been analysed and the main characteristics of each infraorder are discussed. The ancestral sperm of the order Rhabditida was reconstructed using maximum likelihood and Bayesian methods based on 44 ultrastructural sperm characters. The hypothetical ancestral spermatogenesis of the order Rhabditida agrees with the previously suggested "rhabditid" pattern and appears to be conserved throughout the order Rhabditida. Despite the enormous variation of rhabditid nematodes, few groups deviate from the ancestral pattern. This conserved pattern can be informative within the phylum Nematoda at order level, but poses limitations when used in taxonomic and phylogenetic analysis within Rhabditida.

Evaluation of Brugia malayi sheath protein (Shp-1) as a diagnostic antigen for human lymphatic filariasis

Lymphatic filariasis is the second leading cause of permanent long-term disability globally and control of this disease needs efficient diagnostic methods. In this study, abundantly expressing microfilarial sheath protein (Shp-1) from Brugia malayi was characterized as a filarial diagnostic candidate using samples from different clinical population. Monoclonal antibodies were developed against E. coli expressed recombinant Shp-1 in order to assess its efficiency in filarial antigen detection assay system. Endemic Normal (EN, n = 170), asymptomatic microfilaeremics (MF, n = 65), symptomatic chronic pathology (CP, n = 45) and non endemic normal (NEN, n = 10) sera were analyzed by antigen capture enzyme-linked immunosorbent assay. Of the 290 individuals, all MF individuals (both brugian and bancroftian) were positive in this assay followed by CP and EN. When compared with SXP-1 and Og4C3 antigen assays, all assays detected Wb MF correctly, Bm MF was detected by Shp-1 and SXP-1 assays, and only Shp-1 was able to detect EN (12%) and CP (29%). Results showed that this assay may be useful for monitoring prior to mass drug administration.

Brugia malayi: in vitro effects of ivermectin and moxidectin on adults and microfilariae

The effect of ivermectin and moxidectin on the motility of Brugia malayi adults and microfilariae and on the fertility of B. malayi females was examined. Motility was reduced in adults after exposure to both drugs and worms were non-motile and dead within eight days. The motility of microfilariae was significantly reduced at all drug concentrations and ceased at concentrations of 2500 and 5000mug/mL. The motility of microfilariae released by females was reduced after exposure to both drugs, however ivermectin had a greater effect at concentrations between 170 and 5000mug/mL. Both drugs reduced the number of microfilariae released by females and within four days their release was inhibited. The presence of the bacterial endosymbiont Wolbachia was examined in adults and microfilariae after exposure to increasing concentrations of ivermectin and moxidectin. A decrease in wsp expression was correlated with increasing drug concentration.

The genome of Brugia malayi - all worms are not created equal

Filarial nematode parasites, the causative agents of elephantiasis and river blindness, undermine the livelihoods of over one hundred million people in the developing world. Recently, the Filarial Genome Project reported the draft sequence of the ~95 Mb genome of the human filarial parasite Brugia malayi - the first parasitic nematode genome to be sequenced. Comparative genome analysis with the prevailing model nematode Caenorhabditis elegans revealed similarities and differences in genome structure and organization that will prove useful as additional nematode genomes are completed. The Brugia genome provides the first opportunity to comprehensively compare the full gene repertoire of a free-living nematode species and one that has evolved as a human pathogen. The Brugia genome also provides an opportunity to gain insight into genetic basis for mutualism, as Brugia, like a majority of filarial species, harbors an endosybiotic bacterium (Wolbachia). The goal of this review is to provide an overview of the results of genomic analysis and how these observations provide new insights into the biology of filarial species.

Major sperm protein as a diagnostic antigen for onchocerciasis

Onchocerciasis, also known as river blindness, is the second leading infectious cause of blindness worldwide. In order to successfully control this disease, the development of efficient diagnostic tools as well as effective treatments is imperative. A number of proteins have been proposed as vaccine and diagnostic candidates, yet none have been successfully advanced to the point of general clinical use. We have prepared major sperm protein 2 (MSP2) from Onchocerca volvulus as a possible diagnostic antigen for onchocerciasis. Importantly, recombinant MSP2 is dimeric in solution, identical to alpha-MSP from the roundworm, Ascaris suum. A panel of sera obtained from Cameroonian individuals afflicted with onchocerciasis positively responded to the recombinant MSP2. Our data suggest that MSP2, like the previously described antigen Ov16, can be utilized as a diagnostic onchocerciasis antigen for monitoring the interruption of transmission.

Molecular cloning and characterization of a C-type lectin from Ancylostoma ceylanicum: evidence for a role in hookworm reproductive physiology

Lectins comprise a family of related proteins that mediate essential cell functions through binding to carbohydrates. Within this protein family, C-type lectins are defined by the requirement of calcium for optimal biologic activity. Using reverse transcription PCR, a cDNA corresponding to a putative C-type lectin has been amplified from the hookworm parasite Ancylostoma ceylanicum. The 550 nucleotide open reading frame of the A. ceylanicum C-type Lectin-1 (AceCTL-1) cDNA corresponds to a 167 amino acid mature protein (18,706 Da) preceded by a 17 amino acid secretory signal sequence. The recombinant protein (rAceCTL-1) was expressed in Drosophila S2 cells and purified using a combination of affinity chromatography and reverse phase HPLC. Using in vitro carbohydrate binding studies, it was determined that rAceCTL-1 binds N-acetyl-d-glucosamine, a common component of eukaryotic egg cell membranes. Using a polyclonal IgG raised against the recombinant protein, the native AceCTL-1 was identified in sperm and soluble protein extracts of adult male A. ceylanicum by immunoblot. Probing of adult hookworm sections with the polyclonal IgG demonstrated localization to the testes in males, as well as the spermatheca and developing embryos in females, consistent with its role as a sperm protein. Together, these data strongly suggest that AceCTL-1 is a male gender-specific C-type lectin with a function in hookworm reproductive physiology.

MSP domain proteins show enhanced expression in male germ line cells

Nematode sperm utilize a crawling motility based on polymerization--depolymerization of a nematode-specific cytoskeletal molecule-major sperm protein (MSP). While several proteins that interact with and regulate MSP filament formation have been identified using in vitro approaches, it is likely that additional molecules participate in vivo in the regulation of MSP cytoskeletal dynamics. By comparing EST data generated from an Ascaris suum testis germinal zone cDNA library with EST data from other tissue- and stage-specific A. suum cDNA libraries and with expression profile data from Caenorhabditis elegans, 42 genes were selected with exclusive or enhanced expression in male germ line cells. In addition to 11 protein kinases and seven protein phosphatases, 10 genes encoding proteins with protein-protein interaction domains were identified. These potential cytoskeletal modifiers included five novel MSP-domain proteins (As-MDPs). All five As-mdps were highly expressed in male germ line cells, but only As-mdp-2, 3 and 5 were transcribed exclusively in the testis. The prediction that As-MDP-1, 2 and 3 were cytosolic components and that As-MDP-4 and 5 were associated with the sperm cell membrane proteins was supported by the results of immunoblotting experiments. The 23 members of the MDP family of proteins from C. elegans were predicted to be transcribed in the testis. The findings provide additional candidates to the growing list of molecules that regulate MSP cytoskeletal dynamics.

The Caenorhabditis elegans orthologue of mammalian puromycin-sensitive aminopeptidase has roles in embryogenesis and reproduction

Mammals possess membrane-associated and cytosolic forms of the puromycin-sensitive aminopeptidase (PSA; EC 3.4.11.14). Increasing evidence suggests the membrane PSA is involved in neuromodulation within the central nervous system and in reproductive biology. The functional roles of the cytosolic PSA are less clear. The genome of the nematode Caenorhabditis elegans encodes an aminopeptidase, F49E8.3 (PAM-1), that is orthologous to PSA, and sequence analysis predicts it to be cytosolic. We have determined the spatio/temporal gene expression pattern of pam-1 by using the promoter region of F49E8.3 to control expression in the nematode of a second exon translational fusion of the aminopeptidase to green fluorescent protein. Cytosolic fluorescence was observed throughout development in the intestine and nerve cells of the head. Neuronal expression was also observed in the tail of adult males. Recombinant PAM-1, expressed and purified from Escherichia coli, hydrolyzed the N-terminal amino acid from peptide substrates. Favored substrates had positively charged or small neutral amino acids in the N-terminal position. Peptide hydrolysis was inhibited by the metal-chelating agent 1,10-phenanthroline and by the aminopeptidase inhibitors actinonin, amastatin, and leuhistin. However, the enzyme was approximately 100-fold less sensitive toward puromycin (IC50, 135 mum) than other PSA homologues. Following inactivation of the enzyme, aminopeptidase activity was recovered with Zn2+, Co2+, and Ni2+. Silencing expression of pam-1 by RNA interference resulted in 30% embryonic lethality. Surviving adult hermaphrodites deposited large numbers of oocytes throughout the self-fertile period. The overall brood size was, however, unaffected. We conclude that pam-1 encodes an aminopeptidase that clusters phylogenetically with the PSAs, despite attenuated sensitivity toward puromycin, and that it functions in embryo development and reproduction of the nematode.

How the assembly dynamics of the nematode major sperm protein generate amoeboid cell motility

Nematode sperm are amoeboid cells that use a major sperm protein (MSP) cytoskeleton in place of a conventional actin cytoskeleton to power their amoeboid motility. In these simple, specialized cells cytoskeletal dynamics is tightly coupled to locomotion. Studies have capitalized on this feature to explore the key structural properties of MSP and to reconstitute motility both in vivo and in vitro. This review discusses how the mechanistic properties shared by the MSP machinery and actin-based motility systems lead to a "push-pull" mechanism for amoeboid cell motility in which cytoskeletal assembly and disassembly at opposite ends of the lamellipodium are associated with independent forces for protrusion of the leading edge and retraction of the cell body.

Every sperm is sacred: fertilization in Caenorhabditis elegans

The nematode Caenorhabditis elegans is an attractive model system for the study of fertilization. C. elegans exists as a self-fertilizing hermaphrodite or as a male. This unusual situation provides an excellent opportunity to identify and maintain sterile mutants that affect sperm and no other cells. Analysis of these mutants can identify genes that encode proteins required for gamete recognition, adhesion, signaling, fusion, and/or activation at fertilization. These genes can also provide a starting point for the identification of additional molecules required for fertility. This review describes progress in the genetic and molecular dissection of fertilization in C. elegans and related studies on sperm competition.

The microtubular system and posttranslationally modified tubulin during spermatogenesis in a parasitic nematode with amoeboid and aflagellate spermatozoa

Using transmission electron microscopy and immunologic approaches with various antibodies against general tubulin and posttranslationally modified tubulin, we investigated microtubule organization during spermatogenesis in Heligmosomoides polygyrus, a species in which a conspicuous but transient microtubular system exists in several forms: a cytoplasmic network in the spermatocyte, the meiotic spindle, a perinuclear network and a longitudinal bundle of microtubules in the spermatid. This pattern differs from most nematodes including Caenorhabditis elegans, in which spermatids have not microtubules. In the spermatozoon of H. polygyrus, immunocytochemistry does not detect tubulin, but electron microscopy reveals two centrioles with a unique structure of 10 singlets. In male germ cells, microtubules are probably involved in cell shaping and positioning of organelles but not in cell motility. In all transient tubulin structures described in spermatocytes and spermatids of H. polygyrus, detyrosination, tyrosination, and polyglutamylation were detected, but acetylation and polyglycylation were not. The presence/absence of these posttranslational modifications is apparently not stage dependent. This is the first study of posttranslationally modified tubulin in nematode spermatogenesis.