Neurons acquire distinct cell identities and implement differential gene programs to generate their appropriate neuronal attributes. On the basis of position, axonal structure and synaptic connectivity, the 302 neurons of the nematode Ceanorhabditis elegans are divided into 118 classes. The development and differentiation of many neurons require the gene zag-1, which encodes a δEF1/ZFH-1 Zn-finger-homeodomain protein. zag-1 mutations cause misexpression of neuron-specific genes, block formation of stereotypic axon branches, perturb neuronal migrations, and induce various axon-guidance, fasciculation and branching errors. A zag-1-GFP translational reporter is expressed transiently in most or all neurons during embryogenesis and in select neurons during the first larval stage. Analysis of the zag-1 promoter reveals that zag-1 is expressed in neurons and specific muscles, and that ZAG-1 directly represses its own expression. zag-1 activity also downregulates expression of genes involved in either the synthesis or reuptake of serotonin, dopamine and GABA. We propose that ZAG-1 acts as a transcriptional repressor to regulate multiple, discrete, neuron-specific aspects of terminal differentiation, including cell migration, axonal development and gene expression.

The kinesin KIF14 associates with the PDZ domain of Radil and negatively regulates Rap1-mediated inside-out integrin activation by tethering Radil on microtubules.

Control of cell-division orientation is integral to epithelial morphogenesis and asymmetric cell division. Proper spatiotemporal localization of the evolutionarily conserved Gαi-LGN-NuMA protein complex is critical for mitotic spindle orientation, but how this is achieved remains unclear. Here we identify Suppressor APC domain containing 2 (SAPCD2) as a previously unreported LGN-interacting protein. We show that SAPCD2 is essential to instruct planar mitotic spindle orientation in both epithelial cell cultures and mouse retinal progenitor cells in vivo. Loss of SAPCD2 randomizes spindle orientation, which in turn disrupts cyst morphogenesis in three-dimensional cultures, and triples the number of terminal asymmetric cell divisions in the developing retina. Mechanistically, we show that SAPCD2 negatively regulates the localization of LGN at the cell cortex, likely by competing with NuMA for its binding. These results uncover SAPCD2 as a key regulator of the ternary complex controlling spindle orientation during morphogenesis and asymmetric cell divisions.