Antp enhances fasII expression and controls axonal pattern in Drosophila mushroom body and ventral nerve cord. K. Fushima, Y. Hatatani, H. Tsujimura. Developmental Biol, Tokyo Univ Agri Tech, Tokyo, Japan.

   Homeotic genes are expressed in a region specific pattern in the developing CNS and supposed to control regional identity of the CNS. However, there have been only a few reports about it. abd-A controls the regional specific NB division pattern during larval development (Bello et al., 2003). In this study, we demonstrate that Antp controls axonal pattern by enhancing FASII in the adult mushroom body and the larval ventral nerve cord. When Antp was ectopically expressed in the developing adult mushroom body, adult /-lobes pattern was defected. -lobe was often misdirected horizontally to the -lobe position and in a few cases -lobe misdirected dorsally to the -lobe position. This phenotype was first observed at 24 hours APF, and was likely caused through induction of FASII expression in '-lobe. Normally, FASII is never expressed in '-lobe. But, when Antp was mis-expressed, ectopic FASII expression was induced in '-lobe on the pupal stages, and '-lobe was often reduced or lost. This idea was confirmed by the following two facts. If fasII, not Antp, was over-expressed in the mushroom body, the same lobe misdirection phenotype took place. fasII loss of the function mutantion suppressed the lobe misdirection phenotype caused by Antp. The same genetic cascade in which Antp controls axonal pattern through fasII enhancement was observed in the larval ventral nerve cord. There are many FASII expressing longitudinal fascicles in the thoracic ganglia, where Antp is normally expressed. These fascicles showed axonal defects such as defasciculation and mis-routing in trans-heterozygous mutants for Antp and fasII.