THE MUTANT NOT ENOUGH MUSCLES (NEM) REVEALS REDUCTION OF THE DROSOPHILA EMBRYONIC MUSCLE PATTERN

In a search for mutations affecting embryonic muscle development in Dr osophila we identified a mutation caused by the insertion of a P-eleme nt, which we called not enough muscles (item), The phenotype of the P- element mutation of the item gene suggests that it may be required for the development of the somatic musculature and the chordotonal organs of the PNS, while it is not involved in the development of the viscer al mesoderm and the dorsal vessel, Mutant embryos are characterized by partial absence of muscles, monitored by immunostainings with mesoder m-specific anti-beta 3 tubulin and anti-myosin heavy chain antibodies. Besides these muscle distortions, defects in the peripheral nervous s ystem were found, indicating a dual function of the nem gene product. Ethyl methane sulfonate-induced alleles for the P-element mutation wer e created for a detailed analysis, One of these alleles is characteriz ed by unfused myoblasts which express beta 3 tubulin and myosin heavy chain, indicating the state of cell differentiation.