Evolution and Nomenclature of the Zona Pellucida Gene Family

Abstract

Three subfamilies of genes are acknowledged within the zona pellucida (ZP) gene family. At present, these subfamilies each have two names that are used interchangeably: ZPA or ZP2, ZPB or ZP1, and ZPC or ZP3. The ZPA genes encode the longest protein sequences and the ZPC genes the shortest. Recently, several sequences, which have no clear relationship to the three subfamilies, have been identified. These sequences include two paralogous ZP genes from Xenopus laevis and a single gene from the fish Oryzias latipes. We have conducted extensive phylogenetic analyses of the known ZP genes. As well as establishing the evolutionary relationships among these genes, the analyses make it clear that the dual nomenclature system is no longer feasible, because major paralogous groups are present in the ZPB (ZP1) family of genes of amniotes. We propose a unified system of nomenclature for the ZP gene family that removes the existing ambiguities.

Gamete interactions in teleost fish: the egg envelope. Basic studies and perspectives as environmental biomonitor

“…While ZPB and ZPC were found in all vertebrates, ZPX was identifi ed in frogs, chicken and fi sh and ZPA has not been found so far in fi sh (Spargo and Hope, 2003).…”

“…Probably the fi rst step in ZP gene evolution was a gene duplication that might have originated both the ancestral ZPC gene and the precursor of the ZPA, ZPB and ZPX subfamilies. Because no ZPA gene has been found in fi sh, it has been assumed that it has been lost, probably through deletion events (Spargo and Hope, 2003). On the other hand the ZPX genes are present in fi sh, amphibians and birds, but not in mammals.…”

Rapidly evolving zona pellucida domain proteins are a major component of the vitelline envelope of abalone eggs

“…For example, the predominant model of mouse egg coat (zona pellucida) formation posits filaments of arrays of two ZP proteins (ZP2 and ZP3) crosslinked via a third (ZP1), resulting in a fibrous matrix completely enclosing the egg (1). Although orthologs of these mammalian proteins are known from egg coat structures across vertebrate lineages (6,7), non-vertebrate taxa are less well studied and it is not yet clear whether ZP proteins are similarly prominent features of egg coats across metazoans. For example, all known proteins comprising Drosophila egg coat structures lack ZP domains (8).…”

Testicular descent, sperm maturation and capacitation. Lessons from our most distant relatives, the monotremes

“…The platypus genes also share a high level of similarity with orthologous genes in the chicken (between 47 and 44% identity at the amino acid level). Further, the platypus genome encodes at least one ZP-associated gene (ZPAX ) that has only been found in birds, amphibians and fish and is thought to be lost from the eutherian lineage (Spargo and Hope 2003;Smith et al 2005;Warren et al 2008). For practical purposes we have successfully applied this knowledge of homologies between the platypus and chicken genes to develop an assay to test binding of monotreme spermatozoa to preparations of the perivitelline membrane of the chicken egg (which is analogous to the ZP of mammals).…”