A new CYP21A1P/CYP21A2 chimeric gene identified in an Italian woman suffering from classical congenital adrenal hyperplasia form.
BACKGROUND
More than 90% of Congenital Adrenal Hyperplasia (CAH) cases are associated with mutations in the 21-hydroxylase gene (CYP21A2) in the HLA class III area on the short arm of chromosome 6p21.3. In this region, a 30 kb deletion produces a non functional chimeric gene with its 5' and 3' ends corresponding to CYP21A1P pseudogene and CYP21A2, respectively. To date, five different CYP21A1P/CYP21A2 chimeric genes have been found and characterized in recent studies. In this paper, we describe a new CYP21A1P/CYP21A2 chimera (CH-6) found in an Italian CAH patient.


METHODS
Southern blot analysis and CYP21A2 sequencing were performed on the patient. In addition, in order to isolate the new CH-6 chimeric gene, two different strategies were used.


RESULTS
The CYP21A2 sequencing analysis showed that the patient was homozygote for the g.655C/A>G mutation and heterozygote for the p.P30L missense mutation. In addition, the promoter sequence revealed the presence, in heterozygosis, of 13 SNPs generally produced by microconversion events between gene and pseudogene. Southern blot analysis showed that the woman was heterozygote for the classic 30-kb deletion producing a new CYP21A1P/CYP21A2 chimeric gene (CH-6). The hybrid junction site was located between the end of intron 2 pseudogene, after the g.656C/A>G mutation, and the beginning of exon 3, before the 8 bp deletion. Consequently, CH-6 carries three mutations: the weak pseudogene promoter region, the p.P30L and the g.655C/A>G splice mutation.


CONCLUSIONS
We describe a new CYP21A1P/CYP21A2 chimera (CH-6), associated with the HLA-B15, DR13 haplotype, in a young Italian CAH patient.
Concolino
Paola
P
Laboratory of Molecular Biology, Institute of Biochemistry and Clinical Biochemistry, Catholic University, Largo A, Gemelli 8, 00168 Rome, Italy. paolaconcolino78@libero.it
Mello
Enrica
E
Minucci
Angelo
A
Giardina
Emiliano
E
Zuppi
Cecilia
C
Toscano
Vincenzo
V
Capoluongo
Ettore
E
D000312:Adrenal Hyperplasia, Congenital / Q000201:enzymology / Q000235:genetics*; D000328:Adult; D000483:Alleles; D015139:Blotting, Southern; D002678:Chimera / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D015235:HLA-B Antigens / Q000235:genetics; D059910:HLA-B15 Antigen; D006684:HLA-DR Antigens / Q000235:genetics; D059810:HLA-DR Serological Subtypes; D006239:Haplotypes; D006801:Humans; D007438:Introns; D007558:Italy; D009154:Mutation; D016133:Polymerase Chain Reaction; D011544:Pseudogenes; D013255:Steroid 21-Hydroxylase / Q000235:genetics*; D044465:White People
D015235:HLA-B Antigens; D059910:HLA-B15 Antigen; D006684:HLA-DR Antigens; D059810:HLA-DR Serological Subtypes; C097337:HLA-DR13 antigen; C531510:CYP21A2 protein, human; D013255:Steroid 21-Hydroxylase