Parentally imprinted allele typing at a short tandem repeat locus in intron 1a of imprinted gene KCNQ1.

A short tandem repeat (STR) in the intron 1a of paternally imprinted gene, KCNQ1, is evaluated as a new probe for use in parentally imprinting allele (PIA) typing. This typing can determine the inheritance of one allele from father by the methylation difference. Allelic and genotypic frequencies of the STR were determined using samples from 175 unrelated Japanese and 170 unrelated Germans. The polymorphism information contents were 0.652 and 0.634 for the Japanese and the Germans, respectively, indicating usefulness in individual identification. This method was applied to five Japanese families consisting of 19 individuals. Genomic DNA was digested by methylation-sensitive restriction endonucleases, HhaI and HapII, followed by PCR amplification using two-step sandwich primer sets and the products were analyzed on polyacrylamide gel electrophoresis. For all of the families, each child's paternal allele given by PIA typing corresponded to one of the two alleles from father, not the two from mother, that were determined by the STR genotyping. The results demonstrate that this STR probe is feasible for use in PIA typing and that its typing method can contribute to paternity testing.

Applicability of the parentally imprinted allele (PIA) typing of a VNTR upstream the H19 gene to forensic samples of different tissues.

The parentally imprinted allele (PIA) typing that we have recently developed determines parental alleles at a VNTR locus in the differentially methylated region upstream of the human H19 gene. The usefulness of this typing was demonstrated by its application to blood samples in paternity cases. However, its applicability to other tissue DNA remains to be tested. DNA samples from fifteen different postmortem tissues such as cerebrum, skeletal muscle and skin were examined, all of which were obtained from three autopsy cases 2-11h after death. DNA was digested with a methylation-sensitive HhaI enzyme and diluted solutions of the digests were subjected to the first PCR amplification, providing amplification of only the paternal H19 methylated allele. Subsequent VNTR typing was carried out for the amplified products to determine which allele was of paternal origin. No tissue-dependent difference was observed and all the samples examined, though degraded, were successfully used for determining the paternal allele. These results substantiate the usefulness of PIA typing in forensic examinations. Its application to two identity cases, a burned male body and a male body with adipocere formation, was also shown.

Novel paternity testing by distinguishing parental alleles at a VNTR locus in the differentially methylated region upstream of the human H19 gene.

Conventional PCR-based genotyping is useful for forensic testing but cannot be used to determine parental origins of alleles in DNA specimens. Here we describe a novel method of combined conventional genotyping and PIA typing (parentally imprinted allele typing) at a minisatellite region upstream from the H19 locus. The PIA typing uses two sets of primers and DNA digested with methylation-sensitive Hha I enzyme. The first amplification produces only the methylated fragment of paternal H19 allele, and the second detects polymorphism in the minisatellite. Hence, this distinguishes paternal and maternal alleles by difference in the DNA methylation. Furthermore, the polymorphism in this polymorphic locus was examined using 199 unrelated Japanese and 171 unrelated Germans, their polymorphism information content being 0.671 and 0.705, respectively. Feasibility of this typing is demonstrated for six families, and the usefulness is shown by application to paternity testing.