The Implication of De Novo 21-Hydroxylase Mutation in Clinical and Prenatal Molecular Diagnoses

Abstract

We studied 37 unrelated families with a history of 21-hydroxylase deficiency (CYP21D) for eight common mutations and gene deletions in the 21-hydroxylase (CYP21) gene. We found de novo mutations in the CYP21 gene in two CYP21D patients. Analysis for eight common mutations in the 21-hydroxylase gene as well as large gene deletions was accomplished using polymerase chain reaction (PCR) followed by amplified created restriction site (ACRS) or restriction fragment length polymorphism (RFLP) and Southern blot followed by hybridization to a CYP21-specific probe. Linkage analysis was performed using microsatellite markers flanking the CYP21 gene. Ten short tandem repeat (STR) markers were used to confirm parentage in the two de novo mutation cases. In two prenatal diagnosis cases, an intron 2-13A/C>G mutation was identified in the proband, but not in the fetus, although the proband and fetus had identical linkage markers. Subsequently, the mutation was confirmed to be absent in the parents' genome and misparentage was ruled out. Our findings are consistent with previous studies showing a de novo mutation frequency of approximately 1.0-1.5% in the CYP21 gene. This new mutation rate is high relative to the rate of approximately one in one million for other autosomal recessive disorders. Thus, the de novo mutation rate in the CYP21 gene is not negligible. It must be considered and discussed in prenatal diagnosis and genetic counseling for this relatively common inherited disorder.

Fine-tuned characterization of RCCX copy number variants and their relationship with extended MHC haplotypes

“…Otherwise, no HLA-B, -DRB1 or -DQB1 allele in itself showed considerable correlation with an RCCX variant, indicating that disease associations of individual HLA alleles independent of ancestral MHC haplotypes are most probably independent of the RCCX as well. The fact that even rare RCCX structures occur in different genomic context is in accordance with the relatively frequent observations of de novo nonhomologous recombination events within the RCCX 28,35 and our recent results on the intraspecific genealogy of the RCCX. 14 Both RCCX structural variations and MHC haplotypes have long been studied for their effects on diverse physiological and pathological processes.…”

Guidelines for diagnosis and treatment of 21-hydroxylase deficiency (2014 revision)

“…Genetic diagnosis also provides important information for genetic counseling. However, the higher rates of de novo mutation in comparison with other autosomal recessive diseases require attention ( 64 , 65 , 66 ). The structures of the CYP21A2 gene and its pseudogene CYP21A1P are also complicated, and deletion or point mutations may not be detected.…”

Congenital adrenal hyperplasia: focus on the molecular basis of 21-hydroxylase deficiency

“…It is important to bear in mind that de novo mutations occur in the CYP21A2 gene with a considerable frequency of 1-1.5%, which can complicate molecular prenatal diagnosis of 21-0HD: the fetus might have a mutation that does not exist in the parents and that might not be screened on a first approach (Ref. 73). …”