Biosynthesis of avian perivitelline membrane ZPC protein and regulation of sperm receptor activity

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Avian perivitelline membrane, an oocyte extracellular matrix homologous to the zona pellucida in mammals or chorion in fish, is composed of ZPC and ZP1. Previous studies have indicated that one of the components, a glycoprotein homologous to mammalian ZPC, is produced in the granulosa cells of the developing follicles of quail ovary on stimulation with testosterone.However, little is known about the molecular biology of the other component of the avian perivitelline membrane, ZP1, and information about gene expression is particularly lacking. We have cloned the ZP1 in Japanese quail and examined its gene expression. A cDNA encoding quail ZP1 was isolated from the livers of mature females using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends. It encoded a 934-amino acid protein that showed greatest homology (87% identity) with the chicken ZP1. From 128 to 571 amino acid from its N-terminal is unique, so only less than 40% identity with other mammals. RT-PCR amplification of 880 bases indicated that the ZP1 mRNA in the liver was restricted to mature laying females. The expression of ZP1 mRNA was stimulated by in-vivo treatment with diethylstilbestrol in immature females as well as males. These results suggested that androgens and estrogens coordinately regulate the formation of quail perivitelline membrane proteins. In addition, the use of ZP1 transcriptional induction in males or immature females as a biological marker of environmental estrogens is discussed.