Fig. 1.

MEKK4 expression during mouse development. (A) Northern blot analysis showed that MEKK4 mRNA is expressed in E7-E17 embryos. Actin was used as a loading control. (B) Whole-mount in situ hybridization for MEKK4 mRNA at E9. Three different views of the embryo surface are shown: dorsal view (Left Upper), anterior-horizontal view (Right Upper), and lateral view (Lower). Compared with the sense probe (S) control (Right Lower), the antisense (AS) probe revealed specific MEKK4 expression. More prominent signals were detected along the neuraxis, from the FB to HB regions and spanning the length of the spinal cord (SC). (C) Western blot analysis of E10.5 whole-head and E18.5 fetal-brain extracts showed that MEKK4-/- mice lack the expression of MEKK4 protein compared with MEKK4+/+ and MEKK4+/- mice. β-tubulin was used as a loading control.