Sahakitrungruang, T.; Soccio, R. E.; Lang-Muritano, M.; Walker, J. M.; Achermann, J. C.; Miller, W. L.; (2010) Clinical, genetic, and functional characterization of four patients carrying partial loss-of-function mutations in the steroidogenic acute regulatory protein (StAR). Journal of Clinical Endocrinology and Metabolism , 95 (7) pp. 3352-3359. 10.1210/jc.2010-0437.

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Abstract

Context: Nonclassic congenital lipoid adrenal hyperplasia (lipoid CAH) is a recently recognized disorder caused by mutations in the steroidogenic acute regulatory protein (StAR) that retain partial function. Affected individuals can present with a phenotype of late onset adrenal insufficiency with only mild or minimally disordered sexual development. Objectives: The aim was to delineate the clinical spectrum of StAR mutations and correlate phenotype with StAR activity. Patients: Four patients had nonclassic/atypical lipoid CAH. Adrenal insufficiency was manifested at birth in two patients and at 11 months and 4 yr in the other two. Three were 46,XY with underdeveloped genitalia. Methods: The StAR gene was sequenced, mutations were recreated in expression vectors, and StAR activity was measured as pregnenolone production in COS-1 cells cotransfected with the cholesterol side-chain cleavage system. StAR mutants were expressed as N-62 StAR in bacteria, and purified proteins were tested for activity with isolated steroidogenic mitochondria and for cholesterol-binding capacity. Results: DNA sequencing identified mutations on all alleles. Missense mutations were R188C, G221D, L260P, and F267S; we also tested R192C described by others. The respective activities of R188C, R192C, G221D, L260P, and F267S were 8.0, 39.4, 2.4, 3.1, and 6.1% of wild-type in transfected cells, and 12.8, 54.8, 6.3, 1.8, and 9.5% with isolated mitochondria. Cholesterol binding capacities of R188C, R192C, G221D, L260P, and F267S were 6.7, 55.3, 10.2, 4.6, and 20.9%. These data are correlated to the three-dimensional structure of StAR. Conclusions: There is a broad clinical spectrum of StAR mutations; StAR activities in vitro correlate well with clinical phenotypes.

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