Time-lapse imaging revealed that the precursors migrate in the dorsolateral Selleck ABT-737 direction soon after they were born in the WT embryos ( Figure 1B and Movie S1, available online). However, in the rw306 embryos, the precursors migrated in uncoordinated directions, deviating from the normal migratory pathways ( Figure 1B and Movie S2). The overall patterning and differentiation of neurons other than the vagus motor neurons in the posterior hindbrain were unaffected by the rw306 mutation ( Figures S1A–S1J). By positional cloning based on 918 meioses, we identified a T-to-G mutation in the 9th exon

of the moe gene of the rw306 embryos. This resulted in an amino acid substitution from Leu221 to Arg ( Figure 1Ca). Moe is a putative adaptor protein that contains a FERM domain and a putative PSD-95, DLG1 and ZO-1 (PDZ)-binding domain (PB), both of which are required for protein-protein interactions ( Figure 1Cb) ( Bulgakova and Knust, 2009). Leu221 was identified Lonafarnib in the FERM domain and was conserved across various species, from humans to flies ( Figures 1Cb and 1Cc). Hereafter, the rw306 mutant allele will be referred to as moerw306, since the repression of moe induced by the injection of antisense morpholino oligonucleotide (MO) phenocopied the rw306 defect with respect to the formation of the vagus motor

nuclei ( Figure 1Cd), and injection of the WT moe mRNA, but not the rw306-type (L221R-type) moe mRNA, rescued the rw306 defect ( Figures 1Ce and 1Cf). High-level expression of moe mRNA was observed in the ventricular zone of the caudal hindbrain ( Figure 1Cg). The expression level of Moe protein in the moerw306 mutant was comparable to that in the WT ( Figure 1Ch). These results raised the possibility

that the L221R mutation in the FERM domain of Moe affects protein-protein interactions with its specific binding factors rather than the stability of Moe in neuroepithelial cells. Moe forms a complex with the transmembrane protein Crb through its FERM domain, and controls its localization secondly in the developing zebrafish retina and brain (Hsu et al., 2006). Since the moerw306 mutant had a missense mutation in the FERM domain, we investigated the interaction between Moe and Crb. Plasmids that encode FLAG-tagged Moe and HA-tagged Crb family proteins were transfected into 293T cells. The WT Moe coimmunoprecipitated with the Crb family proteins (Crb1, Crb2, and Crb2l), which are expressed in the zebrafish hindbrain ( Hsu et al., 2006 and Omori and Malicki, 2006), whereas the L221R-type Moe did not exhibit this pattern of coimmunoprecipitation ( Figure 2Aa). Both the WT Moe and L221R-type Moe interacted with another molecule, Mind bomb ( Figure 2Ab) (A.B. Chitnis, personal communication). These results indicate that the L221R mutation specifically affects formation of the Crb⋅Moe complex.