CONTROL OF NEURONAL PATHWAY SELECTION BY THE DROSOPHILA LIM-HOMEODOMAIN GENE APTEROUS

The Drosophila apterous gene encodes a LIM homeodomain protein express ed embryonically in a small subset of differentiating neurons. To esta blish the identity of these neurons and to study the role of apterous in their development, we made apterous promoter fusions to an axon-tar geted reporter gene. We found that all apterous-expressing neurons are interneurons that choose a single pathway within the developing centr al nervous system. In apterous mutants, these neurons choose incorrect pathways and fail to fasciculate with one another. Our results indica te that apterous functions to control neuronal pathway selection and s uggest that other vertebrate and invertebrate members of the LIM homeo domain class of proteins may serve similar functions.