Pitx2 Function in Developing Mouse Brain Neurons

描述(由申请人提供)：这项工作与我们对大脑发育障碍的机制和潜在治疗方法的理解有关。PITX2是成对转录因子类中的一员，通过直接与DNA结合来调节多个其他基因的表达。在人类中，PITX2在Rieger综合征中发生突变，Rieger综合征是一种影响眼睛、脐部和牙齿的多发性先天性异常综合征，心脏、脑垂体和大脑有不同的异常。PITX2在胚胎和成年哺乳动物的脑神经元中产生，但其在这些细胞中的功能尚不清楚。在小鼠中，PITX2功能的丧失会导致丘脑底核和上丘神经元的异常发育，但对PITX2在神经前体细胞增殖和分化中的确切要求尚不清楚。由于胸部和腹部器官的严重缺陷，PITX2纯合缺失在中期是致命的，这限制了这些小鼠在以后的时间点上分析PITX2在大脑中的功能。PITX2在小鼠体内由两个不同的启动子以三种不同的亚型(a、b、c)表达，它们在心脏和颅面发育中具有独特的功能；这些不同的PITX2亚型对脑发育的相对贡献尚未确定。我们先前的研究证实了PITX2在发育中的小鼠脑中的离散神经元群体中的表达，并证实了丘脑底核和上丘神经元发育受阻并丧失了Pitx2的功能。我们的全球工作假说是，PITX2以脑区特异性和异构体特异性的方式调节神经元分化的一个或多个方面所需的基因的表达，包括迁移和轴突生长。拟议的研究将利用现有的PITX2cre和异构体特异的PITX2功能缺失等位基因和一种新的PITX2-TaulacZ敲入等位基因来研究发育中的PITX2突变神经元的产生、迁移、轴突形成和细胞命运。这些实验的结果将影响我们对PITX2介导的调控神经元分化和存活的转录机制的理解。拟议的研究还将揭示PITX2在小鼠大脑其他区域的神经元分化和生存中的功能，从而为PITX2在里格综合征和其他发育性大脑疾病中的潜在作用提供关键的见解(S)。这些结果将有助于指导未来旨在引导神经干细胞分化为特定神经细胞亚型的实验。

DESCRIPTION (provided by applicant): This work has relevance to our understanding of mechanisms and potential therapies for disorders of brain development. PITX2 is a member of the paired-like class of transcription factors that regulate expression of multiple other genes, through direct binding to DNA. In humans, PITX2 is mutated in Rieger syndrome, a multiple congenital anomaly syndrome affecting eyes, umbilicus, and teeth, with variable abnormalities in the heart, pituitary, and brain. PITX2 is produced in embryonic and adult mammalian brain neurons, but its function in these cells is unknown. In mice, loss of PITX2 function results in abnormal development of neurons in the subthalamic nucleus and superior colliculus, but the exact requirements for Pitx2 in neuronal progenitor proliferation and differentiation are not known. Homozygous loss of Pitx2 is lethal in midgestation due to severe defects of thoracic and abdominal organs, limiting the use of these mice for analysis of PITX2 function in the brain at later time points. PITX2 is expressed in mice from two different promoters as three separate isoforms (a, b, c) that exhibit unique functions in cardiac and craniofacial development; the relative contributions of these different PITX2 isoforms to brain development have not been determined. Our prior studies identified PITX2 expression in discrete neuronal populations in the developing mouse brain, and demonstrated disrupted neuronal development in the subthalamic nucleus and superior colliculus with loss of Pitx2 function. Our global working hypothesis is that PITX2 regulates expression of genes required for one or more aspects of neuronal differentiation, including migration and axon outgrowth, in a brain region-specific and isoform-specific manner. Proposed studies will examine the production, migration, axon formation, and cell fate of developing PITX2 mutant neurons, using existing PITX2cre and isoform specific PITX2 loss of function alleles and a novel PITX2-TaulacZ knock-in allele. Results obtained from these experiments will impact our understanding of PITX2- mediated transcriptional mechanisms that regulate neuronal differentiation and survival. Proposed studies will also uncover PITX2 functions in neuronal differentiation and survival in other regions of the mouse brain, thereby providing crucial insights into the potential role(s) for PITX2 in Rieger syndrome and other developmental brain disorders. These results will help guide future experiments aimed at directing neural stem cell differentiation toward specific neuronal cell subtypes.