Abstract
BACKGROUND
The retinoic acid (RA)โcatabolizing enzyme Cyp26a1 plays an important role in protecting tailbud tissues from inappropriate exposure to RA. Cyp26a1โnull animals exhibit caudal agenesis and spina bifida, imperforate anus, agenesis of the caudal portions of the digestive and urogenital tracts, and malformed lumbosacral skeletal elements. This phenotype closely resembles the most severe form of caudal agenesis in humans. In view of these findings, we investigated a potential involvement of the human CYP26A1 gene in the pathogenesis of caudal regression syndrome (CRS).
METHODS
Mutational screening of 49 CRS patients and 132 controls was performed using denaturing highโperformance liquid chromatography and sequencing. Differences in the genotype and allele frequency of each SNP were evaluated by ฯ^2^ analysis. The biological significance of the intronic variants was investigated by transfection assays of mutant constructs and by analysis of the splicing patterns with RTโPCR.
RESULTS
Mutational screening allowed us to identify 6 SNPs, 4 of which (447C>G, 1134G>A, IVS1+10G>C, and IVS4+8AG>GA) are new. In addition, we describe a novel 2โsite haplotype consisting of the 2 intronic SNPs. Both singleโlocus and haplotype analyses revealed no association with increased risk for CRS. The consequences of the 2 intronic polymorphisms on the mRNA splicing process were also investigated. Moreover, using functional and computational methods we demonstrated that both of these intronic polymorphisms affect the intron splicing efficiency.
CONCLUSIONS
Our research did not provide evidence that CYP26A1 has implications for the pathogenesis of human CRS. However, the relationship between CRS risk and the CYP26A1 genotype requires further study with a larger number of genotyped subjects. Birth Defects Research (Part A), 2006. ยฉ 2006 WileyโLiss, Inc.