A forward genetic screen with a thalamocortical axon reporter mouse yields novel neurodevelopment mutants and a distinct emx2 mutant phenotype
A forward genetic screen with a thalamocortical axon reporter mouse yields novel neurodevelopment mutants and a distinct emx2 mutant phenotype
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DOI：
10.1186/1749-8104-6-3
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发表时间：
2011-01-07
影响因子：
3.6
通讯作者：
Beier, David R.
中科院分区：
文献类型：
--
作者：
Dwyer, Noelle D.;Manning, Danielle K.;Beier, David R.
背景：背侧丘脑充当大脑皮层信息进出的网关和调节器。这种活动需要丘脑和皮质之间形成相互的地形轴突连接。轴突沿着复杂的多步路径生长，急转弯，跨越表达边界，并遇到中间目标。然而，介导这些步骤的细胞和分子成分仍然知之甚少。结果：为了进一步阐明丘脑皮质系统的发育，我们首先创建了丘脑皮质轴突报告系，用作突变小鼠表型的灵敏分析的遗传工具。 TCA-tau-lacZ 报告小鼠在发育过程中显示丘脑皮质轴突 (TCA) 的特异性、稳健且可重复的标记，但不显示重叠的皮质丘脑轴突。此外，它很容易揭示已知皮质突变体（例如 reeler）中的 TCA 寻路异常。接下来，我们使用 TCA 报告基因进行随机诱变，对参与丘脑皮质发育的基因进行了公正的筛选。六个独立的突变系在该途径的不同步骤显示出异常的 TCA 表型。这些包括腹侧错误路由、过度束震、皮质纹状体边界停滞以及异位皮质细胞簇的侵入。异型杂交育种策略与单核苷酸多态性基因组相结合，促进了少量突变小鼠的遗传图谱绘制。我们将腹侧错误路由突变体映射到 Emx2 基因，并发现一些 TCA 延伸到该突变体的嗅球。绘图数据表明，其他细胞系携带以前未知的在丘脑皮质发育中的作用的基因突变。结论：这些数据证明了用正向遗传方法来理解哺乳动物大脑形态发生和接线的可行性。强大的轴突报告基因能够对小鼠大脑内的特定轴突束进行灵敏分析，识别该通路多个步骤的突变表型，并揭示 Emx2 突变体的新方面。这些表型突出了 TCA 的脆弱选择点和潜在趋势，并将导致对形成丘脑皮质系统所需的元素和相互作用的深入理解。参见评论：http://www.biomedcentral.com/1741-7007/9/1
Background: The dorsal thalamus acts as a gateway and modulator for information going to and from the cerebral cortex. This activity requires the formation of reciprocal topographic axon connections between thalamus and cortex. The axons grow along a complex multistep pathway, making sharp turns, crossing expression boundaries, and encountering intermediate targets. However, the cellular and molecular components mediating these steps remain poorly understood.Results: To further elucidate the development of the thalamocortical system, we first created a thalamocortical axon reporter line to use as a genetic tool for sensitive analysis of mutant mouse phenotypes. The TCA-tau-lacZ reporter mouse shows specific, robust, and reproducible labeling of thalamocortical axons (TCAs), but not the overlapping corticothalamic axons, during development. Moreover, it readily reveals TCA pathfinding abnormalities in known cortical mutants such as reeler. Next, we performed an unbiased screen for genes involved in thalamocortical development using random mutagenesis with the TCA reporter. Six independent mutant lines show aberrant TCA phenotypes at different steps of the pathway. These include ventral misrouting, overfasciculation, stalling at the corticostriatal boundary, and invasion of ectopic cortical cell clusters. An outcross breeding strategy coupled with a genomic panel of single nucleotide polymorphisms facilitated genetic mapping with small numbers of mutant mice. We mapped a ventral misrouting mutant to the Emx2 gene, and discovered that some TCAs extend to the olfactory bulbs in this mutant. Mapping data suggest that other lines carry mutations in genes not previously known for roles in thalamocortical development.Conclusions: These data demonstrate the feasibility of a forward genetic approach to understanding mammalian brain morphogenesis and wiring. A robust axonal reporter enabled sensitive analysis of a specific axon tract inside the mouse brain, identifying mutant phenotypes at multiple steps of the pathway, and revealing a new aspect of the Emx2 mutant. The phenotypes highlight vulnerable choice points and latent tendencies of TCAs, and will lead to a refined understanding of the elements and interactions required to form the thalamocortical system. See Commentary: http://www.biomedcentral.com/1741-7007/9/1