Endocrine Abstracts

Prolactin (PRL) exerts pleiotropic physiological effects in various cells and tissues, and is mainly considered as a regulator of reproduction and cell growth. Null mutation of the PRL receptor (R) gene leads to female sterility due to a complete failure of embryo implantation. Pre-implantatory egg development, implantation and decidualization in the mouse appear to be dependent on ovarian rather than uterine PRLR expression, since progesterone replacement permits the rescue of normal implantation and early pregnancy. To better understand PRL receptor deficiency, we analyzed in details ovarian development, ovulation and the subsequent expression of specific mRNAs of enzymes involved in steroid production using RT-PCR and in situ hybridization techniques in a time-dependent manner, during the first stages of early pregnancy of PRLR null females. The present study provides informative insights into the molecular events during the granulosa to luteal transition. Using the mRNA differential display method, we identified PRL target genes during the peri-implantation period. Among several isolated cDNAs, we characterized two which are regulated in the female reproductive tract during pregnancy. One gene encodes decysin, a new member of metalloproteinases and the other gene corresponds to a P311 mouse cDNA originally identified for its high expression in late-stage embryonic brain and adult cerebellum. Their respective expression was analyzed, and using in situ hybridization their localization was determined from implantation until mid-gestation.