Expression Analysis of the Steroidogenic Acute Regulatory Protein (STAR) Gene in Developing Porcine Conceptuses

• Published in: Molecular reproduction and development 2005-12, Vol.72 (4), p.419-429
• Main Authors: Blomberg, L.A, Zuelke, K.A
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Biological Transport, Active - physiology; Blastocyst - physiology; Cholesterol - metabolism; conceptus; conceptus elongation; corpus luteum; Corpus Luteum - metabolism; differential gene expression; embryo development; Embryology: invertebrates and vertebrates. Teratology; Female; Fundamental and applied biological sciences. Psychology; gene expression; gene expression regulation; Gene Expression Regulation, Developmental - physiology; General aspects; General aspects. Development. Fetal membranes; gestational age; Homeodomain Proteins - biosynthesis; Homeodomain Proteins - genetics; messenger RNA; Mitochondria - metabolism; Phosphoproteins - biosynthesis; Phosphoproteins - genetics; preimplantation; protein synthesis; Receptors, Cytoplasmic and Nuclear - biosynthesis; Receptors, Cytoplasmic and Nuclear - genetics; regulatory proteins; STAR; steroidogenesis; Steroidogenic Factor 1; Sus scrofa; Swine; temporal variation; transcription (genetics); transcription factors; Transcription Factors - biosynthesis; Transcription Factors - genetics; X Chromosome - physiology
• ISSN: 1098-2795; 1040-452X; 1098-2795
• DOI: 10.1002/mrd.20369

Steroidogenesis in porcine non-conceptus tissue is regulated by the STAR-dependent transport of cholesterol from the outer to inner mitochondrial membrane. Previous serial analysis of gene expression (SAGE) identified a STAR mRNA transcript in the porcine peri-implantation conceptus during trophectoderm elongation and increased conceptus estrogen synthesis between gestational day 11 and 12. To assess a potential role for STAR in the modulation of conceptus steroidogenesis via cholesterol transport, the conceptus STAR transcript was PCR cloned and temporal expression of mRNA and protein were examined. Northern analysis of day 12 corpora lutea and pig conceptus RNA detected multiple STAR transcripts in both tissues and identified the cloned transcript as the longest variant. The transcript had a 99% similarity to a truncated ovarian STAR transcript. The conceptus STAR transcript was temporally regulated during elongation but trace expression was present in day 6 blastocysts and day 25 conceptuses. Differential regulation of STAR mRNA was concomitant with the presence of the stimulatory transcription factor steroidogenic factor 1, and absence of the inhibitory transcription factor dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene-1, transcripts. In contrast to peak STAR mRNA expression at the filamentous stage, Western blot analyses revealed STAR protein levels were highest in tubular conceptuses. These data confirm the presence of STAR mRNA and protein during porcine conceptus elongation and suggest regulation of STAR at two levels, transcriptionally, in part, through differential regulation of transcription factors, and post-transcriptionally, evidenced by the disparity of protein to RNA in filamentous conceptuses.