Feasibility of a cost-effective approach to evaluate short tandem repeat markers suitable for chimerism follow-up.
BACKGROUND
Precise chimerism monitoring is important for the prediction of the success of allogeneic bone marrow transplantation (BMT). Most of the current procedures employed for chimerism follow-up with short tandem repeat (STR) markers are either time-consuming, labor-intensive, or use expensive assays, making it burdensome to perform large-scale studies of transplanted patients.


OBJECTIVE
To set-up a simple nonradioactive method to investigate a set of STR markers that could be used in the evaluation of chimerism status after allogeneic BMT.


METHODS
Six dinucleotide STRs (D2S123, D5S107, CRTL1, D7S500, D11S1356, and TP53) were analyzed by touchdown (TD)-PCR followed by medium size non-denaturing polyacrylamide gel electrophoresis and silver staining. The sensitivity of the approach was evaluated by dilution competition assays. Peripheral blood samples were taken from a group of 50 healthy Argentinean donors, two transplanted patients, and their respective bone marrow donors. Buccal mucosa samples were also obtained from the BMT recipients.


RESULTS
Four markers, D2S123, D7S500, D11S1356, and TP53, presented the highest heterozygosities (0.67-0.88) under our experimental system. A sensitivity of 0.8-1.6% for chimerism detection was consistently found for the different STR. The usefulness of these STR in chimerism analysis was illustrated with the screening of related siblings analyzing two transplanted patients with persistent mixed chimerism, which were previously studied by fluorescence in situ hybridization (FISH). Similar proportions of mixed chimerism were obtained with STR analysis compared with those estimated by FISH.


CONCLUSIONS
To our knowledge, this was the first study of mixed chimerism using TD-PCR to achieve a highly specific STR amplification. This approach allows simple and accurate chimerism quantification because it avoids slippage of Taq polymerase on repeat stretches and prevents the differential amplification of the shorter allele. STR heterozygosities and the high level of sensitivity of this method demonstrated that this approach is not only very informative in this population, but is also rapid (taking less than 14 hours) and cost-efficient.


CONCLUSIONS
The data confirms that this method is a useful tool applicable to routine large-scale STR genotyping and mixed chimerism analysis in low-complexity laboratories worldwide.
Fundia
Ariela F
AF
Department of Genetics, Institute of Hematological Research, Mariano R Castex, National Medicine Academy of Buenos Aires, Argentina. affundia@hematologia.anm.edu.ar
De Brasi
Carlos
C
Larripa
Irene
I
D016026:Bone Marrow Transplantation / Q000502:physiology; D002648:Child; D046528:Chimerism; D003362:Cost-Benefit Analysis; D005260:Female; D005819:Genetic Markers; D006801:Humans; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction / Q000191:economics* / Q000379:methods*; D012680:Sensitivity and Specificity; D020080:Tandem Repeat Sequences / Q000235:genetics*; D018183:Transplantation Chimera / Q000235:genetics*
D005819:Genetic Markers