PORCINE AND BOVINE STEROIDOGENIC ACUTE REGULATORY PROTEIN (STAR) GENE-EXPRESSION DURING GESTATION

We have generated complete complementary DNA (cDNA) sequences for the porcine steroidogenic acute regulatory protein (StAR) gene, using a co mbination of genomic PCR amplification and reverse transcription-PCR a mplification of pig ovarian cDNA. Porcine StAR cDNA consists of 855 bp and shares 90.2%, 87.3%, 84.3%, and 83.9% homologies with bovine, hum an, mouse, and rat StAR cDNA at the nucleotide level, and 89.1%, 88.8% , 86.7%, and 86.3% homologies with bovine, human, mouse, and rat StAR protein at the deduced amino acid level. Northern analysis of porcine StAR showed that it is expressed in adult and fetal steroidogenic tiss ues, including adult testes and ovaries and adult adrenal glands as we ll as steroidogenic tissues of pregnancy, including developing fetal t estes, corpus luteum, and pregnancy, but not the fetal ovary. Major hy bridizing bands of 1.8 and 1.1 kilobases were demonstrated. In contras t to human StAR, porcine StAR was not expressed in adult or fetal kidn eys. Expression of porcine StAR by the pig placenta is in contrast to human StAR, which is not expressed by the human placenta. Northern ana lysis of bovine cotyledons using a homologous probe for bovine StAR sh owed that StAR is also expressed by the placenta in the bovine animal. With respect to placental expression of StAR, variations may exist am ong mammalian species.