Keeney D S, Ikeda Y, Waterman M R, Parker K L
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
Mol Endocrinol. 1995 Aug;9(8):1091-8. doi: 10.1210/mend.9.8.7476982.
In situ hybridization studies reveal novel sites of expression of cholesterol side-chain cleavage cytochrome P450 (P450scc) during murine embryonic development. In addition to fetal adrenals and testes, P450scc transcripts localize in situ to the primitive gut and to a subset of unidentified cells in the dermal mesenchyme of embryonic skin. In the gut, transcripts are most abundant in luminal epithelia of the hindgut, which will form the colon. P450scc transcript abundance at these novel sites is a fraction of that in fetal adrenals or testes, suggesting a local rather than an endocrine function. Immunocytochemical analyses localize P450scc protein to the fetal hindgut, indicating that the transcripts are translated in vivo. RNA isolated from microdissected embryonic hindgut and skin was reverse transcribed and amplified by polymerase chain reaction. DNA sequence analyses of polymerase chain reaction products confirmed that specific hybridization in situ represents authentic P450scc gene (Cyp11A) transcripts and that 3 beta-hydroxysteroid dehydrogenase/delta 5-->delta 4-isomerase transcripts are also present, demonstrating the potential of these fetal tissues to produce pregnenolone and progesterone. P450scc transcripts are also detectable by in situ hybridization in primitive gut and skin of Fushi tarazu factor 1 null mice, which lack the nuclear receptor steroidogenic factor 1, proving that steroidogenic factor 1 is not required for steroid hydroxylase gene expression at these sites. The capacity for C21 steroid biosynthesis in primitive gut and skin during organogenesis raises the question whether local production of steroid hormones may be required for normal cellular growth and differentiation of these tissues during embryogenesis.
原位杂交研究揭示了胆固醇侧链裂解细胞色素P450（P450scc）在小鼠胚胎发育过程中的新表达位点。除了胎儿肾上腺和睾丸外，P450scc转录本原位定位于原始肠道以及胚胎皮肤真皮间充质中一部分未识别的细胞。在肠道中，转录本在后肠的腔上皮中最为丰富，后肠将形成结肠。这些新位点处的P450scc转录本丰度仅为胎儿肾上腺或睾丸中的一小部分，提示其具有局部而非内分泌功能。免疫细胞化学分析将P450scc蛋白定位于胎儿后肠，表明这些转录本在体内被翻译。从显微切割的胚胎后肠和皮肤中分离的RNA经逆转录后通过聚合酶链反应进行扩增。聚合酶链反应产物的DNA序列分析证实原位特异性杂交代表真实的P450scc基因（Cyp11A）转录本，并且3β-羟基类固醇脱氢酶/δ5→δ4-异构酶转录本也存在，证明这些胎儿组织具有产生孕烯醇酮和孕酮的潜力。在缺乏核受体类固醇生成因子1的Fushi tarazu因子1缺失小鼠的原始肠道和皮肤中，通过原位杂交也可检测到P450scc转录本，证明在这些位点类固醇生成因子1并非类固醇羟化酶基因表达所必需。器官发生过程中原始肠道和皮肤中C21类固醇生物合成的能力提出了一个问题，即在胚胎发育过程中这些组织的正常细胞生长和分化是否可能需要局部产生类固醇激素。
