A preliminary study on prenatal diagnosis of congenital malformations using chromosome-specific variable number of tandem repeats (VNTR).

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DNA samples from 30 cases of congenital malformations were analyzed by Southern blot hybridization by using pYNH24 (VNTR) as a probe. Abnormal bands were detected in 2 samples. Since the locus of pYNH24 was mapped in human chromosome 2, we further investigated the association of congenital malformations and Pst I-polymorphism of gamma-crystalline which was mapped on 2q33-36. The polymorphism was found in 2.1 and 1.7 kb bands. The frequency of these bands was as follows; 2.1/1.7 (53%) and 1.7/1.7 (27%) in normal controls, while 2.1/1.7 (7%) and 1.7/1.7 (73%) in severe congenital malformations. This result suggests that there may be a locus which is closely associated with congenital malformations. From the gene mapping data, we found that human homeobox 4 gene cluster is present in the proximity of gamma-cristalline gene. Therefore, we focused our investigation on Hox 4 genes.Homeobox gene are highly conserved genes and considered to encode programs for body plan during embryogenesis. As a first step to investigate mutations of homeobox genes, we isolated Hox 4A genomic DNA clone and determined the nucleotide sequence of about 6000 bp. Based on the sequence data, PCR primers were synthesized and PCR-SSCP analysis was carried out in 23DNA samples from severe congenital malformations. We failed to find abnormal bands in PCR-SSCP and now trying to detect Hox 4B gene abnormalities in human congenital malformations.