Involved in the normal targeting of ventral muscle, muscle 12, by motoneurons. May function as an axon guidance molecule involved in neuromuscular specificity. Expressed strongly throughout the yolk. Later, zygotic expression is confined to the presumptive neurogenic regions. In the CNS, expressed in the ventral nerve cord. Expressed in the PNS including in the lateral chordotonal organs at stages 16-17, expressed in epidermal cells at stages 13-15, and expressed in heart cells at stages 13-17. Homozygotes are viable and fertile, display no obvious abnormalities in the development of the CNS, PNS or muscles. However, they exhibit highly specific defects in the innervation pattern of muscle 12, but no obvious defects in the innervation of other muscles. Both loss and gain of function mutants display altered neuromuscular specificity.