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Fig. S2 lib mutant morphology and nephron segmentation are rescued by treatment with exogenous retinoic acid (RA) or overexpression of aldh1a2. A: Lateral views of living 28 somite wild-type and lib embryos compared with embryos injected with aldh1a2 cRNA transcripts. lib embryos formed a normal body trunk without curvature and a kink between the head and trunk, although mild pericardial edema still developed. B: Table of rescue percentages in offspring from nls, nls/lib, and lib heterozygous crosses after treatment with dimethyl sulfoxide (DMSO; vehicle alone), all-trans RA at 1 × 10-9M, all-trans RA at 1 × 10-8M, and wild-type aldh1a2 cRNA injection. Rescue evaluation was determined by presence of pectoral fins in mutant embryos. lib homozygote embryos were rescued only by higher RA or aldh1a2 overexpression, while nls homozygotes and nls/lib compound heterozygotes were rescued at the lower RA dosage. C: Whole-mount in situ hybridization analysis for nephron segment markers (purple) and mhc (red) at the 28 somite stage in wild-type and lib mutants after exogenous treatment with all-trans RA at 1 × 10-9M. Embryos are shown in lateral views with anterior to the left, with the exception of dorsal views to show podocytes. Black brackets and arrows indicated expression domains, and numbers correspond to somite position. RA treatment restored the podocyte population in lib, and expanded proximal tubule fates (proximal convoluted tubule [PCT] and proximal straight tubule [PST]), while the distal fates (distal early [DE], distal late [DL], pronephric duct [PD]) were all reduced, showing pronephros progenitors were competent to respond to elevated exogenous RA. Similar phenotype trends were observed in wild-types exposed to this dosage of RA. D: Summary of nephron segmentation with respect to embryo somite number in wild-type and lib with DMSO or all-trans RA 1 × 10-9M exposure.