A DROSOPHILA DYSTROPHIN-RELATED PROTEIN, MSP-300, IS REQUIRED FOR EMBRYONIC MUSCLE MORPHOGENESIS

Proteins from the spectrin superfamily contribute to cell polarity and shape during the morphogenetic movements that accompany embryogenesis . Drosophila MSP-300, a member of the spectrin superfamily, is express ed in somatic, visceral and heart embryonic muscles. Cloning and seque nce analysis of various spliced forms of MSP-300 reveals functional an d structural similarities between MSP-300 and vertebrate Dystrophin, t he product of the Duchenne Muscular Dystrophy gene. The identification of a strain mutant for the MSP-300 gene is described. Analysis of the somatic muscle phenotype in MSP-300 mutant embryos suggests that the protein contributes to the integrity of the somatic and visceral muscl e tissue during periods of significant morphogenetic change. Functiona l synergism between MSP-300 and laminin is demonstrated by the analysi s of the phenotype of embryos mutant for both genes. The enhancement o f aberrant muscle phenotype in the double mutants suggests a link betw een MSP-300 and laminin function in mediating proper extension of the myotube towards the epidermal muscle attachment site. In addition, bot h genes function to establish gut integrity. In view of the functional and structural similarities between MSP-300 and Dystrophin, it is pos tulated that Dystrophin is not only required for proper muscle functio n in adult life but also contributes to muscle morphogenesis during th e development of the vertebrate embryo.