Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
Neuron. 2011 Sep 8;71(5):820-32. doi: 10.1016/j.neuron.2011.06.026.
Neurons receive signals through dendrites that vary widely in number and organization, ranging from one primary dendrite to multiple complex dendritic trees. For example, retinal amacrine cells (ACs) project primary dendrites into a discrete synaptic layer called the inner plexiform layer (IPL) and only rarely extend processes into other retinal layers. Here, we show that the atypical cadherin Fat3 ensures that ACs develop this unipolar morphology. AC precursors are initially multipolar but lose neurites as they migrate through the neuroblastic layer. In fat3 mutants, pruning is unreliable and ACs elaborate two dendritic trees: one in the IPL and a second projecting away from the IPL that stratifies to form an additional synaptic layer. Since complex nervous systems are characterized by the addition of layers, these results demonstrate that mutations in a single gene can cause fundamental changes in circuit organization that may drive nervous system evolution.
神经元通过树突接收信号，树突的数量和结构差异很大，从一个主树突到多个复杂的树突树不等。例如，视网膜无长突细胞 (ACs) 将主树突投射到一个称为内丛状层 (IPL) 的离散突触层中，很少有突起延伸到其他视网膜层。在这里，我们表明，非典型钙黏蛋白 Fat3 确保 ACs 具有这种单极形态。AC 前体最初是多极的，但在它们通过神经母细胞层迁移时会失去神经突。在 fat3 突变体中，修剪不可靠，ACs 会形成两个树突树：一个在 IPL 中，另一个从 IPL 向外投射并分层形成另一个突触层。由于复杂的神经系统的特征是增加了层，这些结果表明，单个基因突变可能导致电路组织的根本变化，从而可能推动神经系统的进化。
