Fig. 1. Morphology of the Raldh2^–/– forelimbs. (A-C) Scanning electron micrographs of wild-type (A) and Raldh2^–/– (B,C) embryos collected at E13.5 after RA supplementation by oral gavage from E6.75 to E9.25. (C) A close-up of the left mutant forelimb. (D) Raldh2^–/– fetus collected at E18.5 after RA supplementation via the maternal food supply (100 µg/g food) from E7.5 to 8.5. An enlargement of the forelimb rudiment is shown (inset). (E) Raldh2^–/– fetus collected at E18.5 after RA supplementation via maternal food (100 µg/g food from E7.5 to 8.5 and 250 µg/g food from E8.5 to E14.5). The left forelimb shows mirror-image digit duplications and the right forelimb has an abnormal digital cleft (arrowhead). (F,G) Abnormal digit patterning in two Raldh2^–/– fetuses collected at E18.5 after the same conditions of supplementation. The arrowhead in G points to the enlarged first digit. hl, hindlimb; fl, forelimb.

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