The chimeric CYP21P/CYP21 gene and 21-hydroxylase deficiency.
The chimeric CYP21P/CYP21 gene is a consequence of a 26- or 32-kb deletion in the C4-CYP21 repeat module of CYP21P, tenascin A ( XA), serine/threonine nuclear protein kinase ( RP2), and the C4B and CYP21 genes in congenital adrenal hyperplasia (CAH) with steroid 21-hydroxylase deficiency. To date, there have been three distinct chimeras found in CAH patients in ethnic Chinese. Initiation for production of these molecules is proposed to be chi-like sequences and a minisatellite consensus existing in several noncoding regions in CYP21 genes. These molecules have the 5' end of the CYP21P-specific sequence in common but differ in the 3' end of CYP21-specific genes. In addition, there appears to be a 3.2-kb fragment generated by Taq I digestion, which leads to allele dropout in PCR amplification for detecting the aberrant splicing site of the IVS2 -12A/C>G mutation at nucleotide (nt) 655 in the CYP21 gene. Therefore, the chimeric CYP21P/CYP21 cannot be detected by conventional methods. It has been demonstrated that a PCR product amplified with allele-specific primers covering tenascin B ( TNXB) to the 5' end of the CYP21 gene combined with Southern analysis by Ase I and Nde I digestion may be used for identifying the chimera in the CYP21 gene.
Lee
Hsien-Hsiung
HH
King Car Food Industrial Co., Yuan-Shan Research Institute, 326 Yuan-Shan Road, Sec. 2, Yuanshan, 264, Ilan, Taiwan, Republic of China. hhlee@ms2.kingcar.com.tw.
D000312:Adrenal Hyperplasia, Congenital / Q000235:genetics*; D001483:Base Sequence; D002681:China; D002896:Chromosomes, Human, Pair 6 / Q000235:genetics; D015935:Complement C4b / Q000235:genetics; D017931:DNA Primers; D005006:Ethnicity; D006801:Humans; D011544:Pseudogenes / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics; D011995:Recombination, Genetic / Q000235:genetics*; D017384:Sequence Deletion; D013255:Steroid 21-Hydroxylase / Q000235:genetics*
D017931:DNA Primers; D011993:Recombinant Fusion Proteins; D015935:Complement C4b; D013255:Steroid 21-Hydroxylase