Extended Data Fig. 6: Regulation and neuronal migration effects of serotonin signalling.

a, Effects of L1 starvation on male-specific synaptic pruning can also be rescued by exogenous serotonin during L3 (while animals are feeding). Each dot represents one adult male animal (n = number of animals, shown in each column), blue bar represents median, black box represents quartiles, vertical black bars represent range (a, b, e). P values calculated by two-sided Wilcoxon rank-sum test (a, b, e). b, tph-1 overexpression in NSM does not rescue starvation effects on pruning. Quantification of PHB > AVA and PHA > AVG synaptic connectivity in L1-starved adult males overexpressing tph-1 in NSM. Two independent transgenic lines were tested for each experiment; L1-starved animals without transgenic lines are siblings of transgenic animals; controls are non-starved adult males with transgenic arrays. None of the transgenic lines resulted in partial or complete rescue. c, Overexpression of tph-1 under an ADF-specific promoter during L1 starvation rescues the male-specific pruning of the PHB > AVA and PHA > AVG synaptic connections. Representative images shown; for quantification and replication, see Fig. 3e and Methods. d, tph-1 (n4622) and ttx-3 (ot22); unc-86 (n846) mutants (in which the NSM neuron does not express tph-1 or produce serotonin²⁹) have cell body displacement, dendrite, and axon fasciculation defects in the phasmids. Overexpression of tph-1 under an NSM-specific promoter in the tph-1 (n4622) mutant background rescues the severity and penetrance of these defects. Representative images of defects in the PHB neuron are shown here as inverted black and white fluorescence images. Asterisk indicates dendrite defect, arrow shows anteriorly shifted cell body, arrowhead shows fasciculation defect. Scale bars, 10 µm. Per cent of animals with visible defects categorized and quantified to the right, n = number of animals, shown in each column. P values calculated by Freeman–Halton extension of one-sided Fisher exact test. e, Overexpression of tph-1 under an NSM-specific promoter in the tph-1 (n4622) mutant background (essentially, an ADF-specific tph-1 null) results in male-specific PHB > AVA pruning defects. Of two independent NSM::tph-1 transgenic lines, one resulted in a slight but insignificant defect in pruning, and one resulted in a substantial defect in pruning.