title: A nematode gene required for sperm vesicle fusion.
abstract: During maturation of spermatids to motile spermatozoa in Caenorhabditis elegans, large vesicles called membranous organelles (MOs) fuse with the spermatid plasma membrane. Mutations in the gene fer-1 cause abnormal spermatozoa in which the MOs do not fuse, although they abut the plasma membrane normally. Here we describe the fer-1 gene, which we found to be approximately 8.6 kb in length and to encode a 6.2 kb transcript whose expression is limited to the primary spermatocytes, the cells in which the MOs form. fer-1 is predicted to encode a 235 kDa protein which is highly charged except for a putative transmembrane domain near the C terminus. We identified the mutations associated with five fer-1 alleles, all of which are missense mutations causing single amino acid changes. FER-1 is not similar to any characterized proteins in sequence databases, nor does it contain known functional motifs other than the predicted transmembrane domain. The C-terminal transmembrane domain makes FER-1 resemble some viral fusion proteins, suggesting it may play a direct role in MO-plasma membrane fusion. FER-1 does show significant sequence similarity to several predicted human proteins of unknown function. Two of the identified fer-1 mutations are located in regions of similarity between FER-1 and two of these predicted proteins. This strengthens the biological significance of these similarities and suggests these regions of similarity represent functionally important domains of FER-1 and the human proteins.
authors.affiliation: Department of Molecular and Cellular Biology, The University of Arizona, Tucson 85721, USA.
authors.forename: W E
authors.initials: WE
authors.lastname: Achanzar
authors.forename: S
authors.initials: S
authors.lastname: Ward
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology; D003001:Cloning, Molecular; D005306:Fertilization / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology; D017238:Genes, Helminth / Q000502:physiology; D016678:Genome; D015801:Helminth Proteins / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D008297:Male; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D013091:Spermatogenesis / Q000502:physiology; D013094:Spermatozoa / Q000502:physiology* / Q000648:ultrastructure*; D013737:Testis / Q000737:chemistry / Q000502:physiology
chemical_list: D029742:Caenorhabditis elegans Proteins; C106933:FER-1 protein, C elegans; D015801:Helminth Proteins; D008565:Membrane Proteins; D012333:RNA, Messenger