| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2004: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
Group B1 Sox genes including Sox2 encode HMG domain transcription factors that play major roles in neural and placodal development, but little is known about gene regulatory networks involving the group B1 SOX proteins. In this project, we aimed to understand these networks.
Neural plate and sensory placodes share the expression of N-cadherin and Group B1 Sox genes, represented by Sox2. A 219-kb region of the chicken genome centered by the N-cadherin gene was scanned for neural and placodal enhancers. Random subfragments of 4.5 kb average length were prepared and inserted into tkEGFP reporter vector to construct a library with three-fold coverage of the region. Each clone was then transfected into N-cadherin-positive (lens, retina and forebrain) or -negative embryonic cells, or electroporated into early chicken embryos to examine enhancer activity. Enhancers 1 to 4 active in the CNS/placode derivatives, and non-specific enhancer 5 were identified by transfection, while electroporation of early embryos confirmed enhancers 2 to 4 as having activity in the early CNS and/or sensory placodes but with unique spatio-temporal specificities. Enhancers 2 to 4 are dependent on SOX binding sites, and mis-expression of Group B1 Sox genes in the head ectoderm caused ectopic development of placodes expressing N-cadherin, indicating the involvement of Group B1 Sox functions in N-cadherin regulation. Enhancers 1,2 and 4 correspond to sequence blocks conserved between the chicken and mammalian genomes, but enhancer 3 and 5 are unique to the chicken.
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