The phenotype of <i>Ttbk2</i>^{<i>sca11/sca11</i>} embryos is identical to that of the null allele.

(A) Representative wild-type, Ttbk2null/null, and Ttbk2sca11/sca11 E10.5 embryos, as indicated. Scale bar = 1mm. Arrowheads point out the forebrain, which in Ttbk2null/nul and Ttbk2sca11/sca11 fails to form two distinct hemispheres (holoprosencephaly). * Indicates the midbrain flexure which in both mutants is narrowed and takes on a pointed appearance, similar to other mutants with disrupted cilia and SHH signaling. (B-C, E-F) Transverse sections through neural tubes of wild-type (B-C) and Ttbk2sca11/sca11 (E-F) E10.5 embryos. Sections were taken at the level of the forelimbs and immunostained for ISL1 (B, E) to label differentiated motor neurons or NKX2.2 and OLIG2 (C, F) to label V3 interneuron progenitors and motor neuron progenitors, respectively. Scale bar = 100μm. (D, G) Mesenchymal cells surrounding neural tube of E10.5 WT and Ttbk2sca11/sca11 embryos, immunostained for ARL13B to label cilia (green) and γ-Tubulin (red). Scale bar = 13μm.