Mutation in LBX1/Lbx1 precludes transcription factor cooperativity and causes congenital hypoventilation in humans and mice

The respiratory rhythm is generated by the preBötzinger complex in the medulla oblongata, and is modulated by neurons in the retrotrapezoid nucleus (RTN), which are essential for accelerating respiration in response to high CO2. Here we identify a LBX1 frameshift (LBX1FS) mutation in patients with congenital central hypoventilation. The mutation alters the C-terminal but not the DNA-binding domain of LBX1. Mice with the analogous mutation recapitulate the breathing deficits found in humans. Furthermore, the mutation only interferes with a small subset of Lbx1 functions, and in particular with development of RTN neurons that coexpress Lbx1 and Phox2b. Genome-wide analyses in a cell culture model show that Lbx1FS and wild-type Lbx1 proteins are mostly bound to similar sites, but that Lbx1FS is unable to cooperate with Phox2b. Thus, our analyses on Lbx1FS (dys)function reveals an unusual pathomechanism; that is, a mutation that selectively interferes with the ability of Lbx1 to cooperate with Phox2b, and thus impairs the development of a small subpopulation of neurons essential for respiratory control. Overall design: ChIP-seq of retinoic acid induced P19 cells expressing virally expressed Lbx1wt or Lbx1-frameshift constructs

呼吸节律由延髓中的前包钦格复合体（preBötzinger Complex）产生，并受后斜方核（retrotrapezoid nucleus, RTN）内神经元的调控，后者对于机体响应高二氧化碳浓度时加速呼吸至关重要。本研究在先天性中枢性低通气综合征患者中鉴定出一种LBX1移码突变（LBX1FS）。该突变仅改变LBX1的C端，而非其DNA结合结构域。携带该同源突变的小鼠重现了人类患者中观察到的呼吸缺陷。进一步研究表明，该突变仅干扰Lbx1的部分功能，尤其影响共表达Lbx1与Phox2b的后斜方核神经元的发育。细胞培养模型中的全基因组分析显示，Lbx1FS与野生型Lbx1蛋白大多结合相似的基因组位点，但Lbx1FS无法与Phox2b产生协同作用。综上，我们针对Lbx1FS功能异常的研究揭示了一种罕见的致病机制：该突变选择性干扰Lbx1与Phox2b的协同能力，进而损害了对呼吸调控至关重要的一小部分神经元亚群的发育。实验设计：对经视黄酸诱导、并通过病毒介导表达野生型Lbx1（Lbx1wt）或Lbx1移码突变构建体的P19细胞开展染色质免疫共沉淀测序（ChIP-seq）