Otx2 controls regional patterning within the MGE and regional identity of the septum [Agilent]

The Otx2 homeobox transcription factor is essential for gastrulation and early neural development. We generated Otx2 conditional knockout (cKO) mice to investigate its roles in telencephalon development after E9.0. We conducted transcriptional profiling and in situ hybridization to identify genes de-regulated in Otx2 cKO ventral forebrain. In parallel, we used ChIP-seq to identify enhancer elements, OTX2 binding motif, and which de-regulated genes are likely direct targets of Otx2 transcriptional regulation. We found that Otx2 was essential in septum specification; regulation of Fgf signaling in the rostral telencephalon; and medial ganglionic eminence (MGE) patterning, neurogenesis, and oligodendrogenesis. Within the MGE, Otx2 was required for ventral but not dorsal identity; this is the first demonstration of a transcription factor that contributes to regional patterning within the MGE. We used an Otx2flox (Otx2f) allele with RxCre, Cre-line, to abrogate Otx2 expression ~E8.5 and ~E10.0. RxCre mice express Cre throughout the forebrain, except in the caudal dorsomedial domain that includes the choroid plexus and cortical hem. We compared mRNA expression in the ganglionic eminences and septum of RxCre conditional knock out (cKO) and control mouse embryos at E12.5.

Otx2同源框转录因子（Otx2 homeobox transcription factor）在原肠胚形成与早期神经发育过程中发挥不可或缺的关键作用。本研究构建了Otx2条件性敲除（conditional knockout, cKO）小鼠模型，以探究其在胚胎发育第9.0天（E9.0）后端脑发育中的生物学功能。我们通过转录组分析（transcriptional profiling）与原位杂交（in situ hybridization）实验，鉴定了Otx2 cKO小鼠腹侧前脑中表达失调的基因。与此同时，我们采用染色质免疫共沉淀测序（ChIP-seq）技术，鉴定了增强子元件、OTX2结合基序，以及哪些表达失调的基因可能是OTX2转录调控的直接靶标。研究结果显示，Otx2在隔区特化、端脑前部成纤维细胞生长因子（Fibroblast Growth Factor, Fgf）信号通路调控，以及内侧神经节隆起（medial ganglionic eminence, MGE）的模式形成、神经发生与少突胶质发生过程中均具有核心调控作用。在内侧神经节隆起（MGE）中，Otx2对腹侧细胞身份的维持必不可少，但不参与背侧细胞身份的调控；本研究首次证实，存在一类转录因子可参与内侧神经节隆起内的区域模式形成。我们使用携带RxCre重组酶系（Cre-line）的Otx2 flox（Otx2f）等位基因，分别在约胚胎发育第8.5天（E8.5）与约第10.0天（E10.0）条件性敲除Otx2的表达。RxCre小鼠可在全前脑表达Cre重组酶，但在包含脉络丛与皮质缘区（cortical hem）的尾侧背内侧区域除外。我们对比了胚胎发育第12.5天（E12.5）时，RxCre条件性敲除小鼠与对照小鼠的神经节隆起及隔区的mRNA表达谱。