MOUSE LEYDIG INSULIN-LIKE (LEY I-L) GENE - STRUCTURE AND EXPRESSION DURING TESTIS AND OVARY DEVELOPMENT

Leydig insulin-like protein (Ley I-L) is a novel member of the insulin -like hormone superfamily. We report here the isolation and expression of the mouse Ley I-L gene. The gene encodes a polypeptide of 122 amin o acids that shows a relatively weak homology (54%) to human and porci ne prepro-Ley I-L. However, the predicted B and A chain of the mature mouse Ley I-L exhibit similarities of 73% and 71% with human and porci ne Ley I-L, respectively, Alignment of the 5' flanking region of the m ouse gene with those of human and porcine did not exhibit any signific ant sequence homology. However, it contains the conserved sequence of the Ad4 binding site that is present in all promoter regions of steroi dogenic P-450 genes and the Mullerian inhibitor substance gene and is recognized by steroidogenic factor 1. The Ley I-L gene is expressed at a high level in the testis and at a much lower level in the ovary. No transcripts could be detected in placenta prepared between days 10 an d 19 of pregnancy. Ley I-L transcripts were first detected in fetal te stis at 13.5 dpc. After birth, transcript levels remain constant durin g the following 3 weeks, increasing at the stage in which the first wa ve of round spermatids undergo spermiogenesis suggesting a functional role of the Ley I-L in early stages of spermatogenesis and germ-cell m aturation. In the ovary, the expression of Ley I-L was first detected at day 6 after birth. The pattern of Ley I-L expression at various sta ges of the estrous cycle and during pregnancy showed a correlation wit h follicle development. (C) 1997 Wiley-Liss, Inc.