Detection and functional characterization of the novel missense mutation Y254D in type II 3{beta}-hydroxysteroid dehydrogenase (3{beta}HSD) gene of a female patient with nonsalt-losing 3{beta}HSD deficiency
- Laval Univ., Quebec (Canada)
- Univ. of Chicago, IL (United States)
Three {beta}-hydroxysteroid dehydrogenase/{Delta}{sup 5}-{Delta}{sup 4}-isomerase (3{beta}HSD) deficiency is a form of congenital adrenal hyperplasia characterized by severe impairment of steroid biosynthesis in the adrenals and gonads. To better understand the molecular basis of the phenotypic heterogeneity found in 3{beta}HSD deficiency, the authors analyzed the structure of type I and II 3{beta}HSD genes in a female patient with nonsalt-losing 3{beta}HSD deficiency diagnosed at puberty. They directly sequenced DNA fragments generated by polymerase chain reaction amplification of the four exons, the exon-intron boundaries, and the 5{prime}-flanking regions of each gene. No mutation was detected in the type I 3{beta}HSD gene, which is the predominant species expressed in the placenta and peripheral tissues. They detected a novel missense mutation, Y254D, in one allele of the patient`s type II 3{beta}HSD gene, which is the almost exclusive type expressed in the adrenals and gonads. The influence of the Y254D mutation on enzymatic activity was assessed by analyzing the recombinant mutant enzyme generated by site-directed mutagenesis after its transient expression in COS-1 monkey kidney cells. Recombinant mutant type II 3{beta}HSD enzyme carrying the Y254D substitution exhibits no detectable activity with C{sub 21} {Delta}{sup 5}-steroid pregnenolone or C{sub 19} {Delta}{sup 5}-steroid hydroepiandrosterone used as substrate. The absence of restriction fragment length polymorphism by Southern blot analysis and the finding that all of the amplified DNA fragments possess the expected length suggest the absence of deletions, duplications, or rearrangements in the other allele. A putative second mutation could be located farther than 1427 basepairs upstream of the initiation codon, thus potentially affecting the normal expression of this gene or within intronic regions, generating an alternative aberrant splicing site. 43 refs., 5 figs., 1 tab.
- OSTI ID:
- 39420
- Journal Information:
- Journal of Clinical Endocrinology and Metabolism, Vol. 78, Issue 3; Other Information: PBD: Mar 1994
- Country of Publication:
- United States
- Language:
- English
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