A method for the extraction of genomic DNA from human brain tissue fixed and stored in formalin for many years

We report a method providing access to high molecular weight, polymerase chain reaction (PCR)-amplifiable genomic DNA from brains stored in formalin for many years. It consists mainly of an intensive proteinase K treatment of ground tissue previously embedded in agarose plugs, followed by a washing and an elution step. The method was tested on brains fixed and stored in formalin for up to 46 years. All extracted DNA show an identical pattern of degradation ranging from well-preserved (more than 20 kb) to 400-bp-long fragments. This was demonstrated for DNA extracted from the cerebellums of elderly psychiatric and geriatric patients (of more than 60 years of age), male and female, demented or not, with postmortem delays longer than 1 h and shorter than 1 day. In all these cases PCR amplification of a 838-bp-long beta-actin product was successfully performed when proteinase K treatment was sufficiently effective to generate pure DNA. Thus, high molecular weight, PCR-amplifiable genomic DNA can be extracted from brains stored in formalin for almost half a century.