Department of Developmental Neurobiology, Faculty of Life Science, Kumamoto University

1) Xiaohong Song (DC4)
Equarin is involved as an FGF signaling modulator in chick lens differentiation
Lens growth involves the proliferation of epithelial cells, followed by their migration to the equator region and differentiation into secondary fiber cells. It is widely accepted that fibroblast growth factor (FGF) signaling is required for the differentiation of lens epithelial cells into crystallin-rich fibers, but this signaling is insufficient to induce full differentiation. To better understand lens development, investigatory and functional analyses of novel molecules are required. Here, we demonstrate that Equarin, which is a novel secreted molecule, was expressed exclusively in the lens equator region during chick lens development. Equarin upregulated the expression of fiber markers, as demonstrated using in ovo electroporation. In a primary lens cell culture, Equarin promoted the biochemical and morphological changes associated with the differentiation of lens epithelial cells to fibers. A loss-of-function analysis was performed using zinc-finger nuclease s targeting the Equarin gene. L ens cell differentiation wa s markedly inhibited wh en endogenous Equarin was blocked, indicating that Equarin wa s essential for normal chick lens differentiation. Furthermore, biochemical analysis showed that Equarin directly bound to FGFs and heparan sulfate proteoglycan and thereby upregulate d the expression of phospho-ERK1/2 (ERK- P ) proteins , the downstream of the FGF signaling pathway , in vivo and in vitro . Conversely, the absence of endogenous Equarin clearly diminished FGF-induced fiber differentiation. Taken together, our results suggest that Equarin is involved as an FGF modulator in chick lens differentiation . (DB in press)

2) Mahmud Hossain (DC4)
The combinatorial guidance activities of Draxin and Tsukushi are essential for forebrain commissure formation

 3) M. Asrafuzzaman Riyadh (DC2)
Draxin, a repulsive cue for cortical interneuron migration
Majority of the cortical GABAergic interneurons originate in the ganglionic eminences, migrate tangentially into the cortex using distinct trajectories. This process requires the coordinated action of many intrinsic and extrinsic factors. Several classes of axon guidance molecules influence the migration of cortical interneuron. Draxin, a recently identified novel class of repulsive axon guidance protein, is essential for the formation of forebrain commissures and can mediate repulsion of diverse classes of neurons from chickens and mice. Here we show that Draxin is dynamically expressed throughout the period of corticogenesis suggesting that it play a role in the migration of these cells. Draxin inhibits interneuron migration from the matrigel culture of medial ganglionic eminence (MGE) region which is the major source of cortical interneuron . Using glutamate decarboxylase (GAD)67-green fluorescence protein (GFP) knock-in embryonic mice we don’t find significant difference in interneuron migration between wild type and Draxin knockout mice. These results suggest that draxin functions as an inhibitory guidance cue for cortical interneuron migration.