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. 2019 Jan 1;8:e42078. doi: 10.7554/eLife.42078

Figure 2. Temporal expression pattern of heterochronic pathway genes in the nervous system.

Figure 2.

(A) mab-10::mCherry expression pattern during larval development in both sexes. An endogenously tagged mab-10 allele (xe75) showed ubiquitous expression starting in the L4 stage, including in the nervous system. Reporter expression was maintained in the adult. No sexually dimorphic differences were observed for mab-10 expression. A cartoon for the mab-10 locus is shown below the images. (B) lin-28::gfp expression pattern during early larval development. A lin-28::gfp fosmid-based reporter (wgIs535) showed ubiquitous expression at the L2 stage, including in the nervous system. Reporter expression was broadly downregulated at the L3 and L4 stages. The fosmid-based cho-1/CHT reporter (otIs544) was used to label cholinergic neurons. No sexually dimorphic differences were observed for lin-28 expression. (C) lin-41 expression pattern during larval development in both sexes. An endogenously tagged lin-41 allele (tn1541) showed ubiquitous expression at the L3 stage, including in the nervous system. Reporter expression is broadly downregulated at the L4 stage. Expression of lin-41::gfp was maintained in two neuronal pairs in the head (black arrows). No sexually dimorphic differences were observed for lin-41 expression. A cartoon for the lin-41 locus is shown below the images. (D) let-7 activity sensor and control sensor expression during larval development in both sexes. A lin-41 promoter fusion driving gfp and fused to the lin-41 3’UTR (xeSi182), which is directly targeted by let-7 miRNA, showed ubiquitous expression of gfp in the nervous system from the L1 to the L3 stage. At the L4 stage, reporter expression is broadly downregulated and only a few cells are labeled by GFP in the adult head, recapitulating the lin-41::gfp expression. The same lin-41 promoter fusion driving gfp and fused to the unc-54 3’ UTR (xeSi202) failed to be normally downregulated at the L4 stage showing that lin-41 downregulation requires its 3’UTR being bound by miRNA let-7. Cholinergic neurons were labeled by a cho-1/CHT fosmid reporter (otIs544) driving mCherry allowing us to correlate the lin-41 downregulation with AIM neurotransmitter switch in males at the L4 stage. No sexually dimorphic differences in gfp expression were observed for the let-7 sensor and its control. Cartoons for each construct are shown above the images.