Temporal and spatial pattern of expression of cyclic nucleotide-gated channels in developing rat visual cortex

Cyclic nucleotide-gated channels, ligand-gated and highly permeable to calcium, are good candidates for transducing signals received by migrating cells, growth cones and developing synapses. The level of calcium in growth cones is important for axon guidance. Further, cyclic nucleotides, whose levels can be altered by nitric oxide and other transmitters, are known to alter growth cone motility. We use rat visual cortex as a model in our semi-quantitative RT-PCR and in situ hybridization studies to determine the developmental time course and localization of all three CNG family members (rod, olfactory and cone/testis). We demonstrate that in the cortex, the three channel subtypes are each expressed in a distinct temporal and spatial pattern in only sensorimotor and occipital regions of the cortex. Specifically, the rod and olfactory subtypes are present at the time of migration and rapid dendritic outgrowth, and the cone/testis subtype is highly expressed after eye opening. These results suggest CNG channels may play a role in both early and late events in visual cortical development.

The Jnk1 and Jnk2 protein kinases are required for regional specific apoptosis during early brain development

The c-Jun NH2-terminal kinase (Jnk) family is implicated in apoptosis, but its function in brain development is unclear. Here, we address this issue using mutant mice lacking different members of the family (Jnk1, Jnk2, and Jnk3). Mice deficient in Jnk1, Jnk2, Jnk3, and Jnk1/Jnk3 or Jnk2/Jnk3 double mutants all survived normally. Compound mutants lacking Jnk1 and Jnk2 genes were embryonic lethal and had severe dysregulation of apoptosis in brain. Specifically, there was a reduction of cell death in the lateral edges of hindbrain prior to neural tube closure. In contrast, increased apoptosis and caspase activation were found in the mutant forebrain, leading to precocious degeneration. These results suggest that Jnk1 and Jnk2 regulate region-specific apoptosis during early brain development.