Chimerism detection by short tandem repeat analysis when donor and recipient genotypes are not known

BackgroundsThe analysis of chimerism after bone marrow transplantation by STR–PCR is frequently carried out with commercial kits designed for forensic purposes and including too many non informative STR. Furthermore, in routine clinical practice it is not uncommon to lack the pre-transplant genotype of the recipient or the donor, thus making it difficult to identify both components in the post-transplant genotype. The objective of this paper is to overcome these drawbacks by analyzing the informativity of STR markers from a perspective which can be applied whether the pretransplant genotypes are available or not, and selecting a minimum STR panel that allows an effective direct detection of chimerism.MethodsDNA extraction, STR–PCR and fragment analysis of 15 STR in 90 donor-recipient pairs, 60 of which were part of the discovery set and 30 in a validation set. Loci were considered as informative when there were 3 or 4 different alleles in the combined genotypes of the recipient and the donor.ResultsThe informativity varied between 41.6 and 76.6. The 4 most informative loci were D2S1338, D21S11, D18S51 and FGA. We could select a minimum set of 8 markers (D2S1338, D21S11, D18S51, FGA, VWA, D19S433, TH01 and D3S1358) that provided at least 3 informative loci in 95% of cases.ConclusionThis minimum STR panel may be an efficient way to detect and quantitate donor–recipient chimerism after transplantation.

► The objective of this paper is to analyze the informativity of STR markers from a perspective which can be applied whether the pretransplant genotypes are available or not, and selecting a minimum STR panel what allows an effective direct detection of chimerism.
► We could select a minimum set of 8 markers that provided at least 3 informative loci in 95% of cases.
► This may be an efficient way to detect and quantitate donor–recipient chimerism after trasplantation.