American Journal of Medical Genetics 122A:193–200 (2003) Mutations in CYP11B1 Gene: Phenotype–Genotype Correlations Yuan-Shan Zhu, 1 Juan J. Cordero, 1 Selcuk Can, 2 Li-Qun Cai, 1 Xueke You, 1 Cecilia Herrera, 3 Mariano DeFillo-Ricart, 3 Cedric Shackleton, 4 and Julianne Imperato-McGinley 1 * 1 Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, Weill Medical College of Cornell University, New York, New York 2 American Hospital, Istanbul, Turkey 3 University of National Pedro Henriquez Urena, Santo Domingo, The Dominican Republic 4 Children’s Hospital Medical Center of Northern California, Oakland, California 11b-hydroxylase deficiency, an autosomal recessive disorder, is the second most com- mon cause of congenital adrenal hyper- plasia. We studied four subjects with classic 11b-hydroxylase deficiency and severe hy- pertension: a 46,XX affected subject from a Turkish family with severe ambiguity of the external genitalia and hypertension, and three affected 46,XY subjects from a Domin- ican kindred with isosexual precocious pub- erty and severe hypertension. The affected subjects had significantly elevated plasma 11-desoxycortisol, 11-desoxycorticosterone, D4-androstenedione, and testosterone. To determine the molecular genetic defects, genomic DNA was isolated from the leuko- cytes of affected subjects and their family members. The encoding region of the 11b- hydroxylase gene (CYP11B1) was amplified by PCR with specific primers. Using single- stranded DNA conformational polymorph- ism (SSCP) and DNA sequencing, a nonsense mutation in exon 6 of CYP11B1 in the af- fected 46,XX subject from the Turkish family was identified, where a cytosine was sub- stituted by a thymidine, resulting in the replacement of glutamine (CAG) by a stop codon (TAG) at amino acid position 338 (Q338X). In the three 46,XY Dominican boys, the mutation was also a nonsense mutation in exon 6 of CYP11B1, where a cytosine was substituted by a thymidine, resulting in the replacement of glutamine (CAG) by a stop codon (TAG) at amino acid position 356 (Q356X). Both mutations result in the biosynthesis of a truncated 11b-hydroxylase protein with loss of enzymatic activity. Heterozygosity was determined in family members of both probands including par- ents and siblings. These results indicate that mutations of CYP11B1 in these subjects are responsible for their clinical syndromes. ß 2003 Wiley-Liss, Inc. KEY WORDS: 11b-hydroxylase; mutation; hypertension; congenital ad- renal hyperplasia INTRODUCTION Steroid 11b-hydroxylase deficiency due to mutations of 11b-hydroxylase gene (CYP11B1) represents 5 – 8% of the cases of congenital adrenal hyperplasia [Curnow et al., 1993; White et al., 1994]. A deficiency of steroid 11b-hydroxylase activity results in a reduction of cortisol biosynthesis, which leads to an increased secretion of corticotropin and overproduction of steroid precursors. These steroid precursors are shunted to the pathways of androgen and mineralocorticoid biosynthesis. Thus, steroid 11b-hydroxylase deficiency is characterized by decreased plasma cortisol (F) with elevated plasma levels of 11-deoxycortisol (S), 11-deoxycorticosterone (DOC), and androgens. Elevated DOC and its metabo- lites causes hypertension in approximately two thirds of the patients, often presenting early in life [Mimouni et al., 1985; Rosler et al., 1992; White et al., 1994]. Females with this disorder are born with masculi- nized external genitalia, while male patients develop isosexual precocious puberty. All patients undergo rapid somatic growth with premature epiphyseal closure, Yuan-Shan Zhu and Juan J. Cordero have contributed equally to this project. Grant sponsor: NIHM01-RR-00047 (General Clinical Research Center); Grant sponsor: Merck Foundation. *Correspondence to: Dr. Julianne Imperato-McGinley, Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, New York Hospital-Cornell Medical Center, 1300 York Avenue, Box-149, Rm. F-263, New York, NY 10021. E-mail: jimperat@mail.med.cornell.edu Received 14 November 2001; Accepted 16 December 2002 DOI 10.1002/ajmg.a.20108 ß 2003 Wiley-Liss, Inc.