Figure 3.

Defects in development of the mid-hindbrain region in Pax2^1Neu mutant embryos. Wild-type (A, C, and E) and mutant (B, D, and F) embryos. (A and B) Overview of head region of TS21 embryos. The mid-hindbrain junction (isthmus) is clearly visible in wild-type (A) (arrow) but absent in mutant (B) embryos. (C and D) Sagittal sections through head regions of TS23 embryos. The anlagen of the cerebellum and most parts of the mesencephalon are missing in mutant embryos whereas the pons appears to be unaffected (D). (E and F) TS15 whole-mount embryos hybridized with an En2-specific RNA probe. In wild-type, En2 is expressed in a broad band across the mid-hindbrain region (E) (arrowheads). In mutants (F), En2 expression was greatly reduced to a small region in the dorsal neural tube. IV, fourth ventricle; CB, cerebellum; CP, choroid plexus; ME, mesencephalon; MY, myelencephalon; P, pons; TE, telencephalon. (C and D, bars = 500 μm.)