Friese Andreas, Kaltschmidt Julia A, Ladle David R, Sigrist Markus, Jessell Thomas M, Arber Silvia
Biozentrum, Department of Cell Biology, University of Basel and Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland.
Proc Natl Acad Sci U S A. 2009 Aug 11;106(32):13588-93. doi: 10.1073/pnas.0906809106. Epub 2009 Jul 27.
Spinal motor neurons are specified to innervate different muscle targets through combinatorial programs of transcription factor expression. Whether transcriptional programs also establish finer aspects of motor neuron subtype identity, notably the prominent functional distinction between alpha and gamma motor neurons, remains unclear. In this study, we identify DNA binding proteins with complementary expression profiles in alpha and gamma motor neurons, providing evidence for molecular distinctions in these two motor neuron subtypes. The transcription factor Err3 is expressed at high levels in gamma but not alpha motor neurons, whereas the neuronal DNA binding protein NeuN marks alpha but not gamma motor neurons. Signals from muscle spindles are needed to support the differentiation of Err3(on)/NeuN(off) presumptive gamma motor neurons, whereas direct proprioceptive sensory input to a motor neuron pool is apparently dispensable. Together, these findings provide evidence that transcriptional programs define functionally distinct motor neuron subpopulations, even within anatomically defined motor pools.
脊髓运动神经元通过转录因子表达的组合程序被指定支配不同的肌肉靶点。转录程序是否也能建立运动神经元亚型身份的更细微方面，特别是α运动神经元和γ运动神经元之间显著的功能差异，仍不清楚。在本研究中，我们鉴定出在α和γ运动神经元中具有互补表达谱的DNA结合蛋白，为这两种运动神经元亚型的分子差异提供了证据。转录因子Err3在γ运动神经元中高水平表达，而在α运动神经元中不表达，而神经元DNA结合蛋白NeuN标记α运动神经元而非γ运动神经元。肌肉纺锤体发出的信号对于支持Err3（开启）/NeuN（关闭）假定γ运动神经元的分化是必需的，而对运动神经元池的直接本体感觉输入显然是可有可无的。总之，这些发现提供了证据，表明转录程序定义了功能上不同的运动神经元亚群，即使是在解剖学定义的运动池中也是如此。
