Identification of a novel testis-specific leucine-rich protein in humans and mice

A novel testis-specific protein, termed LRTP, was identified by screening b oth human and mouse testis and mouse pachytene spermatocyte cDNA libraries. Sequence analyses (GenBank accession number: AF092208) revealed that LRTP contains an amino terminus leucine-rich repeat domain. There are several ac idic regions rich in glutamic acid in the C-terminus. The sequence, by GenB ank search, shows similarities to LANP and SDS22+, leucine-rich repeat prot eins localized to the nucleus and involved in the regulation of protein pho sphatases. In mouse, the mRNA is first detected at about Day 14 postpartum, presumably when mid-pachytene spermatocytes are first seen. In situ hybrid ization confirmed the expression of the LRTP mRNA at this stage of spermato genesis. Immunohistochemical analysis revealed that the protein is most abu ndant in the cytoplasm of pachytene and diplotene cells, corresponding to l ate prophase of meiosis I. immunohistochemical localization is markedly red uced in secondary spermatocytes, suggesting a functional association of LRT P with meiosis. An LRTP cDNA probe did not bind to mouse ovary RNA in a dot blot assay.