84 STUDY OF THE HUMAN GENE FOR THE CHOLESTEROL SIDE- CHAIN CLEAVAGE ENZYME, P450SCC (20,22 DESMOLASE) IN CONGENITAL LIPOID ADRENAL HYPERPLASIA

摘要

Conversion of cholesterol to pregnenolone is mediated by the single mitochondrial cholesterol side-chain cleavage (SCC) enzyme P450scc, formerly termed 20,22 desmolase. SCC activity is absent in patients with congenital lipoid adrenal hyperplasia (lipoid CAH) and direct evidence for absent P450scc protein his been reported in one case. To determine if SCC deficiency is caused by deletion of the P450scc gene, we obtained leukocytes from 3 of the 10 reported living patients with lipoid CAH. Leukocyte DNA was cleaved with restriction endonucleases and analyzed on Southern blots. Blots were probed with long chemically synthesized oligonucleotides containing 63 to 72 bases of the bovine P450scc cDNA sequence, and with a 1 kb human P450scc cDNA cloned in our laboratory. Analysis of Northern blots of human and bovine adrenal mRNA indicate the P450scc mRNA is 2.0 kb long and arises from precursors ~6 kb long in both species, indicating the P450scc gene is about 6 kb. Analysis of Southern blots of DNA from the 3 patients and 8 controls showed no deletion in the human P450scc gene, and no detectable restriction fragment length polymorphisms with the following enzymes: BamHI, EcoRI, HindIII, PstI, PvuII, and TagI. We conclude that the absent SCC activity in the adrenals and gonads of patients with lipoid CAH is not due to a large deletion in the P450scc gene.