T-]A TRANSVERSION 11 BP FROM A SPLICE ACCEPTOR SITE IN THE HUMAN GENEFOR STEROIDOGENIC ACUTE REGULATORY PROTEIN CAUSES CONGENITAL LIPOID ADRENAL-HYPERPLASIA

Congenital lipoid adrenal hyperplasia (lipoid CAH) is the most severe form of CAH. Affected individuals can make no adrenal or gonadal stero ids, All affected individuals are phenotypic females irrespective of g onadal sex, and frequently die in infancy if mineralocorticoid and glu cocorticoid replacements are not instituted. Recent data implicate the steroidogenic acute regulatory (StAR) protein in this disorder. We no w describe a 46,XY patient of Vietnamese ancestry with lipoid CAH who had a somewhat milder form of the disease, Diagnosis was at 10 weeks o f age, and low levels of plasma progesterone, corticosterone, 18OH-cor ticosterone and androstenedione were detectable, Testicular RNA for St AR was reverse transcribed, amplified, cloned and sequenced, revealing a 185 bp deletion corresponding to all of exon 5, The corresponding m RNA did not encode active protein in transfected cells. Cloned genomic DNA from the patient revealed only a T-->A transversion in intron 4, 11 bp from the splice acceptor site of exon 5, This transversion destr oys an Ncol site; digestion of PCR-amplified genomic DNA from the pati ent and both parents confirmed that the patient was homozygous and the parents were heterozygous. Expression vectors for StAR minigenes were constructed containing all StAR exons plus introns 4, 5 and 6 either with or without the T-->A mutation in intron 4, RNase protection assay s showed that expression of the vector with normal intron 4 yielded co rrectly spliced StAR mRNA in transfected COS-1 cells, while most, but not all StAR mRNA from the vector with the T-->A transversion in intro n 4 was abnormally spliced. RNase protection of the patient's testicul ar RNA confirmed that most, but not all StAR mRNA was similarly splice d abnormally. Splicing errors appear to be a rare cause of genetic dis eases, but subtle intronic mutations may be missed when genomic DNA is the only material available for study, The low level of normal StAR m RNA produced may account for the later clinical presentation and low l evels of steroid hormones detected in this patient.