Figure 4.

GAP43 can functionally substitute for CAP23. (A) Generation of CAP23^gap43/gap43 knockin mice. (top) Targeting construct for gene replacement, (bottom) genomic Southern blot (left), and Northern blot of adult brain mRNA. The signs (+) and (−) refer to a wild-type or mutated CAP23 allele. (B) Enhanced mortality of CAP23^+/− and CAP23^−/− mice, and its rescue by GAP43. (g/g) CAP23^gap43/gap43 background. (C) Correction by GAP43 of an nmj morphology phenotype because of the absence of CAP23. Combined silver esterase stains of fast-type medial gastrocnemius nmjs at 2 mo. Note the irregular diameter and blobs at nerve terminal branches of CAP23^−/− mice. In the presence of GAP43, instead of CAP23, nerve terminal branches at the nmj were slightly broader than in a wild-type background, but regular in size, and without blobs. (D) Rescue of BotA-induced nerve sprouting at the soleus nmj of CAP23^gap43/gap43 mice. Combined silver esterase stains and quantitative analysis of sprouting of soleus nmj's, 7 d after BotA injection; sprouts are indicated by arrows. Sprouts in the presence of GAP43, instead of CAP23, were shorter and more branched. Bar, 50 μm.