Fig. 2. Identification of early Cnbp-expression pattern and Cnbp-transgene rescue of forebrain defects in Cnbp mutants. (A-D) Cnbp expression was analyzed at pre-gastrulation, gastrulation and post-gastrulation stages by whole-mount in situ hybridization. (A) Cnbp is expressed at the visceral endoderm, anterior to the distal tip of the early embryo at early gastrulation (E6.0; arrow). (B) During primitive streak formation, at E7.0, Cnbp expression localizes to the AVE in the anterior midline from the proximal to the distal region. (C) Cnbp is expressed in anterior axial mesendoderm, ADE and ANE at late-primitive streak stage (E7.5). (D) Sagittal section of an embryo at an approximately similar stage to that shown in C, showing Cnbp expression in the anterior axial mesendoderm, ADE and ANE. (E-G) Cnbp is expressed in the anterior neural folds at 8-10 somite stages. (F) Sagittal section of an embryo at an approximately a similar stage to that shown in E, showing Cnbp expression in the ANE (forebrain) and head mesenchyme. (G) Cnbp continues to be expressed in the headfolds. (H) Cnbp is expressed in the forebrain at E9.25. Transcripts were also detected in the early facial prominences, including the first branchial arch, primitive maxillary region and early frontonasal area. Regions of expression other than the head include the limb bud and tail. (I) The Cnbp transgene comprising the 10 kb mouse Cnbp promoter, the entire Cnbp gene (11 kb) and a 300 bp vector DNA fragment (shaded region on left side) as a tag for genotyping. (J) Transgenic genotyping by PCR analysis using primers P1 and P2, described in I. Lane 5 shows control DNA from wild-type mice. The 300 bp fragment in lanes 1-4 represents recovery of transgenic embryos. (K) Transgenic genotyping by Southern blot analysis using the 300 bp vector DNA as probe. Wild-type embryos are represented in lanes 1, 3 and 5. Genomic DNA from transgenic embryos hybridizes to probe (lanes 2, 4 and 6). (L-M) Transgenic rescue of forebrain defects in Cnbp mutants. Cnbp expression in Cnbp^+/+ wild-type embryo (L), Cnbp^-/- mutant (M) and TG/Cnbp^-/- (n=7) (N) embryos at E9.5. Embryo in M shows forebrain truncation, whereas the transgenic rescued embryo has a normal phenotype and a nearly identical expression pattern as the wild-type embryo (L,N). Cnbp begins to also be expressed in the midbrain shortly before E9.5 (L).

Return to article