Does sex-specific neurite patterning involve cell-cell interactions in Drosophila central neurons?

Takahiro Kato, Kosei Sato and Daisuke Yamamoto
Division of Neurogenetics, Tohoku University Graduate School of Life Sciences, Sendai, Japan

Sex differences in the neural number and structure are prevalent in the brain. This has been particularly well documented in the brain of a genetic model organism, Drosophila melanogaster. In this organism, circulating sex hormones are nonexistent. Instead, the genetic code determines the sex of each cell. Transformer (Tra), a female determinant protein, plays a key role here. Tra is a female-specific splicing factor which, depending on the sex, produces different mRNA species in two target genes, fruitless (fru) and doublesex (dsx), both encoding transcription factors that orchestrate transcription of genes for the neural sex differentiation. In this study, we focus on a group of fru-expressing neurons, mcALa cluster neurons, as they show a striking sex difference in the neurite structure. The mcALa neurons have been implicated in ordered execution of distinct courtship motor actions. The mcALa male-specific arbors form in females that are homozygous for tra¹, a loss-of-function tra allele, which is known to completely masculinize a female fly. Next, we generated tra¹-mutant mcALa clones in the otherwise female brain, with the expectation that these tra¹ mutant clones of mcALa develop the male-specific arborizations. Surprisingly, the tra¹-mutant mcALa neurons did not form the male-specific arborizations. Our finding indicates that mcALa neurons require some inductive actions from neighbors to develop the male-specific arbors, representing a non-cell autonomous mechanism for neural sex differentiation in Drosophila.

JSPS Research Fellow