The detectable time limit of intact STR profile for human tissues in unbuffered formalin / 中国法医学杂志

ABSTRACT

Objective To evaluate the STR profiling availability of formalin-fixed tissues and the detectable time limit of intact STR profile.Methods The different human tissues were fixed with 10-fold diluted commercial 40%formalin fixative for different duration under 15～20℃,and then DNA was extracted using the method of QIAamp~(R)DNA and IQ~(TM) DNA System.The extracted DNA was quantified with QuantifilerTM kit and amplified by both AmpFSTR identifiler kit and AmpFSTR MiniFiler kit.The STR profile was analyzed by GeneMapper ID v3.2 on 3100-Avant.Resuls The STR profiling availability of formalin-fixed tissues was relevant to the formalin fixing duration mainly.as well as the type of tissues and the template concentration and protocol of DNA extracting.The optimal ranges of template concentration is 1～3ng/μL and the QIAamp extracting method was preferable.There are differences in the degradation rate between various types of tissues in the unbuffered formalin fixative,and the lung tissue showed the slowest rate and liver and intestine tissues the fastest.Intact miniSTR profile of all the tissues detected could be obtained within 15 days duration of formalin fixing while intact STR profile could be obtained within 4 days.Conclusion The major factor that impact the availability of STR profiling of formalin-fixed tissues is the fixing duration in unbuffered formalin,as well as the type of tissues,method of extraction,concentration of PCR template and the kinds of STR loci.