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Isolation of Sperm DNA Through Protamine Capture

NCJ Number
Date Published
June 2017
11 pages
Findings, methodology and implications for the forensic community are presented for a research project that focused on the adaptation of conventional chromatin immunoprecipitation (Chip) to an optimized, sample-specific method for use on mixed samples from sexual assault casework.

The SpermDNA Capture method used takes advantage of the uniqueness of sperm chromatin, wherein the majority of histone proteins have been replaced by a class of protein called protamines. Protamines facilitate the packaging of the sperm genome into a highly condensed state in which approximately 85 percent of the sperm genome is protamine bound. The DNA/protamine complex is targeted, using monoclonal antibodies to completely separate the sperm DNA from other DNAs in the mixture. Throughout the project, the key performance evaluations have been DNA yield, clean separation of the DNAs in mixed samples, and the method's sample-to-purified-DNA time commitment benchmarked against current differential extraction methods. The project overcame technical risk to deliver a novel streamlined method with many benefits over differential extraction. Sperm's unique chromatin structure proved to be an ideal target for immunocapture using Chip. This method has been de-risked of any technical bottlenecks and should result in a new commercial offering for the forensics community. This method will enable the isolation of sperm DNA from samples that have up until now been unsuitable for differential extraction. This should result in more full autonomic STR profiles, reduced backlogs of untested sexual assault kits, and compliance with sample processing regulations. Work is being done to achieve full automation of the method. Project design and methods are described. 6 figures and 30 bibliographic/reference listings

Date Published: June 1, 2017