Tanaka H, Fukushima M, Ohta K, Kimura Y, Sudo A, Shirabe K, Takeshita M
Division of Developmental Neurobiology, Kumamoto University, Graduate School of Medical Sciences, Japan.
Dev Neurosci. 1997;19(1):106-11. doi: 10.1159/000111193.
To identify molecules that might be involved in the early development of motoneurons, we performed RT-PCR for receptor tyrosine kinases (RTKs) and mRNA differential display with embryonic day 5 (E5) chick motoneurons enriched by panning. In situ hybridization revealed that Cek88 RTK among the cloned molecules was specifically expressed on motoneurons at the brachial and lumbar segments of the spinal cord which innervate limb muscles. We found that the expression of Cek8 in limb motoneurons was already intrinsically determined at E2. To analyze how motoneurons acquire regional specification along the anterior-posterior (A-P) axis and in the transverse plane, we observed the expression of Cek8, Islet-1, SC1 and low-affinity NGF receptor on ectopic motoneurons induced by implanting a supernumerary notochord or floor plate. The ectopic motoneurons induced by the graft obtained from either the thoracic or lumbar segments had the same expression profile as the in situ motoneurons at each A-P level. These findings suggest that regional specification of motoneurons is independent of the notochord and the floor plate and that the whole neural tube is committed to differentiate into the motoneuron subtypes along the A-P axis at the operative stages.
为了鉴定可能参与运动神经元早期发育的分子，我们对通过淘选富集的胚胎第5天（E5）鸡运动神经元进行了受体酪氨酸激酶（RTK）的逆转录聚合酶链反应（RT-PCR）和mRNA差异显示。原位杂交显示，在克隆的分子中，Cek88 RTK在脊髓臂段和腰段支配肢体肌肉的运动神经元上特异性表达。我们发现，E2时肢体运动神经元中Cek8的表达就已由内在因素决定。为了分析运动神经元如何沿前后（A-P）轴和在横平面上获得区域特异性，我们观察了通过植入多余脊索或底板诱导的异位运动神经元上Cek8、胰岛-1、SC1和低亲和力神经生长因子受体的表达。由胸段或腰段移植诱导的异位运动神经元在每个A-P水平上具有与原位运动神经元相同的表达谱。这些发现表明，运动神经元的区域特异性独立于脊索和底板，并且在手术阶段整个神经管已注定沿A-P轴分化为运动神经元亚型。
