DNA, PCR and formalinized animal tissue - a short review and protocols

Formaldehyde was first prepared in 1859, and since then has been in widespread use for fixing and preserving medical and biological specimens, The value of such archival material has increased considerably because several methods for extracting DNA from formaldehyde-fixed animal tissue have been developed. Most of these, however, either require large amounts of tissue (rarely available) or recover only short fragments of DNA. Here we summarize current knowledge of and experience with such published methods, look at some of the known problems, and develop an additional method based on embedding the tissue in agarose prior to treatment with proteinase-K and GeneReleaser(TM). With this method we have obtained mitochondrial DNA useful for PCR reactions from as little as 3 mg tissue of more than 30 years old formaldehyde-fixed aplacophoran molluscs. We examine the conditions under which obtaining relatively high-quality DNA from formaldehyde-fixed material is possible, making previously collected samples accessible for molecular studies in genetics, systematics and related fields. The purpose of this short review is to acquaint molecular systematists with some of the methodological advances and considerations in using formaldehyde-preserved material.