Virilizing congenital adrenal hyperplasia (CAH) describes a group of disorders of steroidogenesis involving the pathway from cholesterol to cortisol. Ninety-five percent of CAH results from alteration of the CYP21 gene. The salt wasting form of CAH may be fatal in the neonatal period while non-classical forms cause health problems late in life. Screening for CAH involves measuring 17-hydroxyprogesterone. In screening for CAH, cut-off levels for 17-OHP are held so high that many treatable forms of CAH are not detected. These cases of CAH would be identified if cut-off levels were lowered and a molecular assay for CYP21 mutations was performed. Molecular analysis eliminates false positives while identifying affected individuals. Rapid cycle PCR with analysis of fluorescence resonance energy transfer (FRET) probes is an innovative approach to mutation and gene dosage analysis. Rapid cycle PCR and FRET analysis will be used to detect CYP21 mutations I172N, I2, and 8 bp del 706-713 plus deletion/duplication events. Comprehensive CYP21 analysis is performed using Peptide Mass-Signature Genotyping (PSMG). PSMG involves expression of amplification products, mass determination of expression peptides by MALDI-TOF, and computational deconvolution of mass data to determine genetic changes. CYP21 exon 8 is the model system. The model systems for mutational, gene dosage, and PSMG analysis will demonstrate feasibility of a CYP21 genotyping service.
Rapid CYP21 dosage and mutation analysis allows for an improved CAH screening program. This service will be used in-house and offered to other screening programs, pediatricians, and pediatric endocrinologists. CYP21 genotyping will find a large market to endocrinologists seeing patients with the often enigmatic mild 17-OHP elevations and putative late-onset non-classical forms of CAH which are common in the general population.
| Zeng, Xuemei; Witchel, Selma F; Dobrowolski, Steven F et al. (2004) Detection and assignment of CYP21 mutations using peptide mass signature genotyping. Mol Genet Metab 82:38-47 |
