In addition, the RMG interneuron pair modulates signaling from the ASKs via gap junctions ( Macosko et al., 2009). A subset that should masculinize all of the AIA, AIB, AIY, and AIZ neurons but not the RMG interneurons (Pglr-2 + Pser-2b) fully expressed sexual attraction, comparable to broad masculinization (Pglr-2 + Pglr-5 + Pser-2b). That is, repression was not engaged. Subsets that should masculinize only some of the AIA, AIB, AIY, and AIZ neurons and include the RMG neurons also fully expressed sexual attraction

(the Pglr-5 + Panobinostat purchase Pglr-2 and Pglr-2 + Pser-2b combinations). In contrast, subsets that should masculinize only some of the AIA, AIB, AIY, and AIZ neurons but do not include RMG expressed sexual attraction less frequently (Pglr-2) or not at all (Pser-2b). Conversely, a subset that should masculinize RMG, but not AIA, AIY, and AIZ (and possibly not AIB; Pglr-5), did not exhibit sexual attraction. Within the framework provided by the hermaphrodite wiring diagram ( White et al., 1986; Chen et al., 2006), a straightforward interpretation of these results is that sexual

differences in AIA and AIB are most important for sexual attraction, with contributions from AIY and AIZ and possibly modulation by RMG. Independent of the hermaphrodite wiring, it appears unlikely that pheromone sensory input converges on a single interneuron class but instead remains distributed. Taken together, the neuron-selective masculinization PD-0332991 cost experiments suggest that the AWA, AWC, Levetiracetam and ASK sensory neurons and their interneuron partners—most likely the AIA, AIB, AIY, and AIZ neurons—must be male for the animal to

display male behavior. A simple model based on these data is that a male-specific constellation of connections among these sensory neurons and interneurons forms during development to generate male-specific sexual attraction (Figure 4D). In this model, hermaphrodites are also capable of developing these connections, but repression either prevents them from being established or subsequently disables them. In general, sex-specific behaviors may be generated by extra circuitry entirely present only in one sex or by modification of circuitry present in both sexes (Stowers and Logan, 2010). In C. elegans, there are no additional male-specific neurons in the sex pheromone processing circuitry to account for male-specific sexual attraction, based on two facts. First, the nervous system is fully cataloged in males and hermaphrodites, establishing that there is a core nervous system common to both sexes ( White et al., 1986; Sulston, 1983; Sulston et al., 1980; Sulston and Horvitz, 1977). Second, this core nervous system is sufficient for male-specific sexual attraction behavior ( White et al., 2007).