Type: Interneuron
Male Wiring Project: MCML, MCMR
In Wormbase: MCM, MCML, MCMR
Lineage: AmsoL, AmsoR
Location: Anterior head
Description: Male specific interneurons (mystery cells of the male) that are born at the early L4 stage, when the male undergoes sexual maturation; Amso cells are born during embryogenesis from the same lineages in both sexes, but retain their plasticity only in males, re-entering the cell cycle during sexual maturation. Following Amso division, one daughter retains the Amso identity and the other becomes the MCM, which loses molecular and structural characteristics of a glia and acquires neuronal identity (Sammut et al., 2015.) Each MCM cell body sends a posteriorly

directed process within the same side amphid bundle. The process then leaves the bundle to enter the nerve ring, and from the nerve ring it extends into the ventral nerve cord (Sammut et al., 2015.) The bulk of the synaptic input to MCMs come from three interneuron classes, two of which are sex-shared (AVF, and PVQ), and one which is male-specific (EF). These interneurons receive extensive sensory input from the male copulatory circuits in the tail and extend processes through the ventral nerve cord into the nerve ring where they connect to the MCMs both directly and through RIF neurons. The largest synaptic output is onto the AVB command interneurons that drive forward locomotion and these outputs are both direct and indirect via RIF. There is a small amount of reciprocal interaction between the MCMs and the male-specific, pheromone-sensing CEM head sensory neurons (CEMV neurons are sisters of Amso) (Sammut et al., 2015.)
Neurotransmitter/ Neuropeptide:
- PDF-1; pigment dispersing factor homolog
Innexin expression:
- INX-3
Receptor expression:
Function:
- Required for a switch in chemosensory behavior induced by associative sexual conditioning; a normally attractive cue, salt becomes repulsive when worms are cultivated under conditions that couple salt with starvation (referred as starvation-dependent plasticity of chemotaxis). This aversive learning is suppressed in males in the presence of hermaphrodites during salt/starvation conditioning (Sakai et al., 2013.) In MCM-ablated males this switch fails to take place and salt remains repulsive. MCMs are not required for the sensory detection of hermaphrodite pheromone, salt or starvation but that they specifically regulate the integration of these sensory cues to produce the behavioral switch (Sammut et al., 2015.)