| Budget Amount *help |
¥4,020,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥420,000)
Fiscal Year 2007: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Fiscal Year 2006: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
Visual information is detected by the retina, and transferred to the primary visual cortex via the lateral geniculate nucleus (LGN), which is one of thalamic nuclei. This primary visual pathway contains a variety of neurons, which selectively respond to specific types of visual stimuli, such as M cells and P cells which respond to spatial information and color/shape information of visual stimuli, respectively. These neurons form column-like structures or layered structures in the visual system. The variety of neurons and 3D structures of these neurons are considered to be important for efficient visual processing. However, molecular mechanisms underlying specification of neuronal identities and formation of 3D structures are still largely unknown.
We have examined the mechanisms of M cell differentiation in the LGN. Previously, we have found that PCP4/PEP-19 is expressed in M cells, and using PCP4 as an M cell marker, we examined the importance of spontaneous retinal activity in M cell
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differentiation. We binocularly injected epibatidine, which suppresses spontaneous retinal activity, into the two eyes just after birth, and examined the expression of PCP4 in the LGN using in situ hybridization. We found that the expression of PCP4 was not affected in epibatidine-treated animals, suggesting that M cell differentiation does not require spontaneous retinal activity. Moreover, PCP4 expression was normal in enucleated animals. These results suggest that M cell differentiation does not require not only spontaneous retinal activity, but also all kinds of retinal inputs.
LGN receives inputs not only from the retina but also from the visual cortex and the brainstem, which may drive M cell differentiation. We therefore isolated LGN and cultured it in vitro. Interestingly, we found that M cell differentiation occurred in the cultured LGN, suggesting that LGN differentiation can proceed without inputs from other brain regions. It should be noted that we have performed our experiments using only one kind of M cell marker. We need to confirm our results using additional M cell markers. Less
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