Identification of Phox2b-regulated genes by expression profiling of cranial motoneuron precursors on NeuroDev microarray

Branchiomotor neurons are an important class of cranial motor neurons that innervate the branchial-arch-derived muscles of the face, jaw and neck. They arise in the ventralmost progenitor domain of the rhombencephalon characterized by expression of the homeodomain transcription factors Nkx2.2 and Phox2b. Phox2b in particular plays a key role in the specification of branchiomotor neurons. In its absence, generic neuronal differentiation is defective in the progenitor domain, and no branchiomotor neurons are produced. Conversely, ectopic expression of Phox2b in spinal regions of the neural tube promotes cell cycle exit and neuronal differentiation and at the same time induces genes and an axonal phenotype characteristic for branchiomotor neurons. How Phox2b exerts its pleiotropic functions, both as a proneural gene and a neuronal subtype determinant, has remained unknown. To gain further insight into the genetic programme downstream of Phox2b we searched for novel Phox2b-regulated genes by cDNA microarray (here NeuroDev slides) analysis of facial branchiomotor neuron precursors from heterozygous and homozygous Phox2b mutant embryos. Keywords: Phox2b-regulated genes identification Four biological replicates each in dye swap鳃运动神经元（Branchiomotor neurons）是一类重要的颅运动神经元，可支配源自鳃弓的面部、颌部与颈部肌肉。该类神经元起源于菱脑（rhombencephalon）最腹侧的祖细胞结构域，该结构域以表达同源域转录因子（homeodomain transcription factors）Nkx2.2与Phox2b为特征。其中，Phox2b在鳃运动神经元的特化过程中发挥核心调控作用：当Phox2b缺失时，该祖细胞结构域内的一般性神经元分化程序出现缺陷，无法产生鳃运动神经元。反之，在神经管脊髓区域异位表达Phox2b，可促进细胞周期退出与神经元分化，同时诱导鳃运动神经元特有的基因表达谱与轴突表型。然而，Phox2b同时作为神经前基因与神经元亚型决定因子发挥多效性功能的具体机制，至今仍未阐明。为进一步解析Phox2b下游的遗传调控程序，本研究通过cDNA微阵列（cDNA microarray，即NeuroDev芯片（NeuroDev slides））分析杂合与纯合Phox2b突变胚胎的面鳃运动神经元前体细胞，以筛选受Phox2b调控的新基因。关键词：Phox2b调控基因鉴定；各染料交换（dye swap）组均设置4次生物学重复。