Otp paralogs regulate neuropeptide switching in OXT neurons.
(A–F) In situ hybridization of crh mRNA in wild type, otpa−/− and otpb−/− on the background of a transgenic OXT reporter [Tg(oxt:egfp)]. The image panels show representative single confocal planes (dorsal view, anterior to the top) of OXT neurons in either the neurosecretory preoptic area (NPO; A–C) or the posterior tuberculum (PT; D–F). OXT neurons expressing crh mRNA are indicated by arrowheads. Scale bar, 20 µm. (G,H) Bar histogram showing the percentage (%) and cell count (upper right insets) of OXT cells co-expressing crh in the NPO (G) and PT (H). wild type (n = 40), otpa−/− (n = 30) and otpb−/− (n = 20). Kruskal-Wallis indicated a significant main effects for ‘genotype’ on the percentage of crh-positive OXT neurons in both the NPO [X2(2)=29.284; p=0.000] and PT [X2(2)=27.174; p=0.000]; Dunn’s corrected pair-wise comparisons indicated that in both the NPO and PT, wild type differed significantly from otpa−/− (p=0.000). Notably, otpb−/− mutants exhibit a trend for decreased (p=0.077) crh-positive OXT neurons when compared to WT. (I) A model summarizing the suggested effects of otp paralogs on neuropeptide switching in OXT neuronal clusters in NPO and PT based on the results presented in Figures 4 and 5 (see text). Arrows and T-bars indicated a positive and negative effect, respectively. Dotted arrows indicate a trend for a positive effect of otpb on crh expression.