Figure 1. Overview of sex hierarchy and experimental design.
(A) The Drosophila somatic sex determination hierarchy is an alternative pre-mRNA splicing cascade (reviewed in Andrew et al., 2019). The presence of two X chromosomes in females results in splicing of Sxl pre-mRNA, such that functional Sxl is produced. Sxl regulates Sxl and tra pre-mRNA splicing, resulting in continued production of functional Sxl and Tra in females. Tra and Tra-2 regulate the pre-mRNA splicing of dsx and fru P1 in females, whereas in males dsx and fru P1 are spliced by the default pre-mRNA splicing pathway. The sex-specific splicing results in production of sex-specific Dsx and Fru transcription factors (Burtis and Baker, 1989; Ito et al., 1996; Ryner et al., 1996). dsx regulates sex differences that lead to both dimorphic behavior and gross anatomical morphological differences, whereas fru P1 regulates sex differences that lead to dimorphic behaviors. (B) Previous genome-wide studies found that dpr/DIPs are regulated downstream of fru P1, FruM, and/or are expressed in fru P1 neurons (Goldman and Arbeitman, 2007; Dalton et al., 2013; Neville et al., 2014; Vernes, 2015; Newell et al., 2016). (C) A genetic intersectional strategy was used to express marker or effector genes in fru P1 ∩ dpr/DIP neurons. This strategy takes advantage of the two-component Gal4/UAS expression system, and Flippase-mediated removal of a stop cassette within an expression vector. Expression of the marker/effector gene requires both removal of the stop cassette via fru P1-flippase (flp) expression and expression of Gal4 via dpr/DIP regulation. Therefore, only neurons that express both fru P1 and one of the dpr/DIPs have expression of the effector or marker (shown on right).