MYOTONIC PROTEIN-KINASE EXPRESSION IN HUMAN AND BOVINE LENSES

Myotonic dystrophy (DM) is an autosomal dominant trait closely associa ted with CGT repeat expansions in the same locus on human chromosome 1 9q13.3. The expansions occur in the 3' untranslated region of a transc ription unit encoding a serine-threonine kinase (DM kinase) of a new c lass based upon structure and function. Lens cataracts are a prominent finding in myotonic dystrophy. DM kinase was shown to be expressed in human and bovine lenses at the RNA level and in human lenses at the p rotein level. Sequencing of PCR products of RNA extracted from normal human lenses demonstrated an exact match to published genomic and cDNA 3' UTR sequences. Northern blots of bovine lens RNA showed that the t ranscript is similar in size to the transcript detected in other tissu es that are affected in myotonic dystrophy. A polyclonal antibody (DM- 2) was produced against recombinant DM protein kinase in rabbits. Deve lopment of Western blots with DM-2 showed a single reactive band of 67 kDa. Immunofluorescent studies of formalin-fixed human lens sections detected the DM kinase in the perinuclear cytoplasm of normal human le ns epithelial cells and more diffusely in superficial subcapsular cort ical fibers. In contrast, the same antibody labeled the nucleus most p rominently in a single DM lens. (C) 1996 Academic Press, Inc.