Purification of Mycobacterium leprae RNA for gene expression analysis from leprosy biopsy specimens.

Gene expression analysis in Mycobacterium leprae, an obligate intracellular pathogen and the etiologic agent of leprosy, has been hampered by the lack of an efficient method to purify RNA from leprosy lesions. Therefore to date, transcripts for only a few genes have been identified. We report the use of a single-tube homogenization/RNA extraction method that produces enough RNA to study the expression of 30 genes from a single skin biopsy specimen of a multibacillary leprosy patient and demonstrate that RNA can be purified after fixation of biopsies in 70% ethanol for up to a year. This represents a major advancement in the ability to study M. leprae gene expression directly from biopsy material and should help to define genes that are associated with intracellular survival of this human pathogen.