Molecular determinants specifying diversity of neurons in the visual system during development

视觉信息由视网膜检测，并通过外侧膝状核（LGN）传递到初级视觉皮层，这是丘脑核之一。这条初级视觉通路包含多种神经元，它们选择性地对特定类型的视觉刺激作出反应，如M细胞和P细胞分别对视觉刺激的空间信息和颜色/形状信息作出反应。这些神经元在视觉系统中形成柱状结构或分层结构。神经元的多样性和这些神经元的三维结构被认为是有效的视觉处理的重要因素。然而，神经元身份和三维结构形成的分子机制在很大程度上仍然未知。我们研究了LGN中M细胞分化的机制。在此之前，我们已经发现PCP4/PEP-19在M细胞中表达，并使用PCP4作为M细胞标记物，我们研究了自发视网膜活性在M细胞分化中的重要性。我们在出生后双眼注射抑制自发视网膜活性的依比替丁，并采用原位杂交技术检测llgn中PCP4的表达。我们发现PCP4的表达在经依比替定处理的动物中没有受到影响，这表明M细胞分化不需要自发的视网膜活动。此外，PCP4在去核动物中表达正常。这些结果表明，M细胞分化不仅需要自发的视网膜活动，还需要各种视网膜输入。LGN不仅接受来自视网膜的输入，还接受来自视觉皮层和脑干的输入，这可能驱动M细胞分化。因此，我们分离LGN并进行体外培养。有趣的是，我们发现M细胞分化发生在培养的LGN中，这表明LGN分化可以在没有其他脑区输入的情况下进行。值得注意的是，我们的实验只使用了一种M细胞标记物。我们需要使用额外的M细胞标记物来确认我们的结果。少

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 … More 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