Fig. 4. Scanning electron microscopy reveals defects in monocilium formation in mD2LIC^–/– mouse embryos. (A) The distal tip of a wild-type embryo at 7.5-8.0 dpc (1-2 somite stage) viewed at low power. (C,E) The gross morphology of the node of homozygous mutant embryos is normal. Conditions and magnification are identical in A and C, and E is at twice the magnification. (B,G) Higher-power view of a wild-type embryo reveals rounded cells bearing monocilia (arrowheads). (D,H,F,I) Ventral node cells in mD2LIC^–/– embryos are flatter than their wild-type counterparts and they lack normal monocilia. In some cases stunted structures are formed in the place of monocilia (arrows). G-I are at the same magnification. White boxes in B,D,F indicate regions of the node shown at higher magnification in G-I respectively. (F) Cells in the anterior region of the node and notochordal plate have the most extreme phenotype.