Microsatellite stability in human post-mortem tissues

Human identification and forensic criminal casework may involve DNA profili ng of decomposed material. Somatic microsatellite (STR) instability may lea d to false exclusions and theoretically to false inclusions, both in crimin al cases and in human identification. Hence, the somatic and postmortal sta bility of the actual sequences is crucial to the reliability of such analys es. Somatic STR stability in human tissues has been documented in small ser ies only and the effect of postmortal tissue decomposition on microsatellit e stability remains to be elucidated. On this basis, we have systematically searched for somatic STR mutations in 26 deceased humans without signs of decomposition at autopsy and 25 autopsy cases with obvious signs of postmor tal decomposition. A blood sample and six tissue samples were collected fro m each case. Seven STRs were chosen for study, the tetranucleotides HUMVWA31/A, HUMTH01, HUMF13A1, and HUMFES/FPS, and the hyperpolymorphic markers HUMAPOAI1, D11S 554 and HUMACTBP2. Denaturing gel electrophoresis was performed on an ABD P rism (TM) 377 gene sequencer with Genescan 672 software (Applied Biosystems , Inc.). The bone DNA profile of each case was chosen as the standard DNA profile. A ll cases gave profiles from additional tissues. By intraindividual comparis on of DNA profiles in the cases without signs of degradation we find that t he short repetitive sequences under study are stable, that is without evide nce of somatic mutations. The cases with varying degree of decomposition di splay postmortal microsatellite stability, we detect no somatic mutations o r other possible postmortal changes that could lead to between-organ non-ma tches. In conclusion, PCR-based STR analyses are suitable in human identification and forensic casework dealing with different tissues, even when the substra te is heavily decomposed. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.