Identification of genes that are differentially expressed in extraocular and limb muscle

The extraocular muscles (EOM) are anatomically and physiologically distinct from other striated muscles in mammals. Among other differences, they can be driven to generate individual twitch contractions at an extremely high f requency and are resistant to [Ca2+]-induced myonecrosis. While EOM are pre ferentially targeted in some neuromuscular diseases such as myasthenia grav is and congenital fibrosis of the extraocular muscles, they are enigmatical ly spared in Duchenne's muscular dystrophy, despite the widespread damage s een in all other skeletal muscle groups during the course of this disease. To address the molecular mechanisms that specify the EOM-phenotype, we char acterized the transcriptional profile of genes expressed in rat EOM versus limb muscle using a differential display strategy. Ninety-five putative dif ferentially expressed cDNA tags were cloned, from which fourteen were confi rmed as being differentially expressed by RNA slot blot and Northern blot a nalysis. Ten of these cDNAs were homologous to known human or murine genes and ESTs, while four genes that were upregulated in EOM were novel, and hav e been named expressed in ocular muscle (eom) 1-4. The identification of th ese differentially expressed genes may provide mechanistic clues toward und erstanding the unique patho-physiological phenotype of EOM. (C) 2000 Elsevi er Science B.V. All rights reserved.