Summary:Variable number tandem repeats (VNTRs) were among the first genetic markers used to quantitate bone marrow transplant engraftment. STRs, which are standard tools for genotyping in parentage testing 6 and forensic human identity testing, 7 have recently been used for the quantitative analysis of BMT engraftment. [8][9][10][11] STRs provide an excellent tool for this purpose because of their high degree of polymorphism and relatively short length. Furthermore, STR-based human identity kits are commercially available, which eliminates the need for developing the methodology in each individual laboratory. Several of the commercial STR human identity kits have been optimized for automated DNA sequencers which enables data collection and analysis by sophisticated software. Commercial kits for VNTR analysis currently are not available. Although STRs are now widely used in BMT testing, only one direct comparison of VNTR and STR engraftment results has been published. 11 The purpose of this study is to validate STRs in BMT engraftment analysis by comparing VNTR and STR results for the same sets of post-transplant samples from patients who had undergone allogeneic BMT. Sixteen post-transplant samples from four allogeneic BMT patients are included in this correlation study. Patient samples previously analyzed by the VNTR method at the FairviewUniversity Medical Center Molecular Diagnostics Laboratory were chosen to cover the full range of engraftment from near 0% to 100%. STR analysis was then performed on the same samples in a blinded fashion at the Central Arkansas Veterans Healthcare System Molecular Diagnostics Laboratory. Good quantitative correlation was found between STR and VNTR results in samples from all four patients. STR markers were informative in one patient for whom PCR-based VNTR markers were not available. This study demonstrates that STR-based human identity testing kits are well suited for engraftment analysis.

We used single-strand conformational polymorphism (SSCP) to determine apolipoprotein E (Apo E) genotypes in 47 individuals. A 295-base-pair (bp) DNA fragment coding for amino acid residues 80-178 of the Apo E protein gave distinct patterns for the three alleles. When we used SSCP to determine the Apo E polymorphism of five individuals whose phenotyping results differed from those of genotyping, the SSCP results agreed with the genotyping results obtained by the PCR-based amplification refractory mutation system (ARMS). Because most of the reported rare alleles of the Apo E gene involve mutations of amino acid residues in positions 120-160, our SSCP method is useful for determining rare as well as common alleles.

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