Fig. 4. Immunohistochemical analysis of Fxr1p expression in zebrafish embryos during embryonic development. (A) Longitudinal cryostat sections of 6 h.p.f. embryos, (B,C) head (B) and tail (C) of 1-day-old embryos, and (D,E) head (D) and tail (E) of 3 d.p.f. embryos stained for zebrafish Fxr1p using Affi5. Inset in D shows a higher magnification of the boxed region in the hindbrain from D. Note the nuclear staining in neurons from 3 d.p.f. embryos (D) and the very intense staining of myoblasts in muscle tissue within the somites (E). Y, yolk sac; M, myoseptum; N, neural tube. Arrows in C point to Fxr1p immunoreactive myoblasts in the developing somite. Scale bars, 15 µm (C); 30 µm (B); 35 µm (E); 70 µm (A); 100 µm (D).