High-Throughput Screening for CYP21A1P-TNXA/TNXB Chimeric Genes Responsible for Ehlers Danlos Syndrome in Patients with Congenital Adrenal Hyperplasia.
Many patients with congenital adrenal hyperplasia (CAH) due to 21 hydroxylase deficiency have CAH-X syndrome, a connective tissue dysplasia consistent with hypermobility type Ehlers Danlos syndrome due to a contiguous gene deletion involving the adjacent CYP21A2 and TNXB genes. CAH-X syndrome is caused by carrying CYP21A1P-TNXA/TNXB chimeric genes (CAH-X CH-1 and CH-2) on one or more alleles. Genetic analysis is cumbersome due to pseudogene interference. We developed a PCR-based CAH-X high-throughput screening method to assess the copy numbers of TNXB exons 35 and 40 that is amenable to either quantitative PCR or droplet digital PCR. The assay was validated in a cohort of 278 subjects from 146 unrelated CAH families. Results were confirmed by a validated Sanger sequencing platform. A total of 44 CAH-X positive calls were made, with 42 (26 CH-1 and 16 CH-2) confirmed. The assay had 100% sensitivity (42 true/42 positives), 99.2% specificity (234 true/236 negatives), and an overall 99.3% accuracy (276/278). Calls made by qPCR and ddPCR were consistent (100%), and ddPCR offered easier data interpretation. The CAH-X prevalence was 15.6% (21/135 probands), higher than the previously estimated 8.5% and was particularly high (29.2% or 21/72) in those with a 30-kb deletion. This assay is suitable for high throughput CAH-X screening, especially for subjects testing positive for CAH in neonatal screening.
National Institutes of Health Clinical Center, Bethesda.,
National Institutes of Health Clinical Center, Bethesda.
National Institutes of Health Clinical Center, Bethesda; Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland. Electronic address: email@example.com.
Pub Type(s)Journal Article