Brain tissue identification based on myosin heavy chain isoforms.

Non-muscle tissues contain 3 myosin heavy chain (MHC) isoforms; MIIA, MIIB1 and MIIB2. MIIA is a non-muscle type isoform distributed in all non-muscle tissues and smooth-muscle, while MIIB1 and MIIB2 are brain-type isoforms distributed mainly in neuronal tissues. The ratio of MIIA and MIIB (A/B ratio) differs between tissues, suggesting that this ratio may be a useful marker for tissue identification. To apply the A/B ratio for tissue identification in forensic practice, we developed a highly sensitive ELISA for quantification of each MHC isoform. At least 100 pg of both MHC isoforms could be detected by the present method. Analysis of the A/B ratio of the cerebrum, cerebellum, liver, kidney, spleen and andrenal gland by the present method indicated that the A/B ratio of the brain tissue (< 0.5) was quite different from other tissues (> 3.0). The A/B ratio could be determined from at least 8 micrograms of fresh tissue sample and 0.1 mg of dried tissue sample stored for 1 month at room temperature. Therefore, the A/B ratio seems to be an excellent marker for identification of the brain tissue.