Neuro-muscular innervation in neonatal intestinal development

我们观察了新生哺乳动物肠道神经肌肉层的发育，在达到成年大小之前，肠道将延长数倍。这涉及到平滑肌细胞的广泛生长，以形成成体。然而，出生时都存在的肠道神经系统(ENS)的神经元必须与此相协调，并发展成成人的神经模式，因为ENS最终将调节允许正常消化的平滑肌的及时收缩和放松。我们的目标是了解神经元在出生时如何保持存活并适应其目标细胞的快速生长，从而创建成人中所见的复杂、稳定的关系。*目前的支持向我们表明，单一因素(GDNF；神经营养因子)负责ENS神经元在出生后的存活，GDNF由肠道平滑肌细胞制造。重要的是，这些细胞的生长是GDNF表达增加所必需的，GDNF的表达导致神经元存活和轴突生长。我们认为，GDNF与其受体RET的结合导致两种结果：最初是存活，然后是轴突延伸，可能是每种结果都需要不同水平的GDNF。我们拥有解决这一问题所需的细胞和分子技术，以及一种涉及新生儿肠道神经元和平滑肌细胞的独特组织培养模型。我们将用药物抑制剂分离GDNF信号转导的结果，这些药物可以阻断神经元(唯一表达GDNF受体的细胞)中的不同路径，然后测量细胞存活的结果或轴突生长的程度。然后，当生长完成时，我们将研究神经元对GDNF的需求--非常低的水平是否能维持存活？这一信号是如何实现的？*成年肠道中似乎没有轴突生长，但当轴突生长促进修复时，神经元功能不佳，这在其他神经受损的地方也可以看到。我们现在认为，新生儿ENS中的轴突生长和神经功能(即动作电位和神经递质释放)往往不是同时发生的。因此，随着神经功能方案在神经递质的合成、储存和释放方面获得优势，结构方案变得更加完整。对相关步骤的定量测量，如mRNA和蛋白质，将测量属于这两个程序中的任何一个的关键蛋白质，这将与神经元显示成熟信号特性的能力相关。这将帮助我们了解新生儿肠道是如何发育的，这是一个知之甚少的领域。*我将与受训人员合作，他们将主要是研究生和大四的本科生。他们将获得技术专长以及科学思维和批判性评估方面的教育。到目前为止，我们的毕业生非常成功，在这一领域发表了大量的论文，并在职业生涯中取得了非常好的成就。

We look at the development of the neuromuscular layer of the newborn mammalian intestine, which will lengthen many-fold before reaching its adult size. This involves extensive growth of the smooth muscle cells to create the adult form. However, the neurons of the enteric nervous system (ENS), which are all present at birth, must coordinate with this and develop the adult pattern of innervation, as the ENS will eventually regulate the timely contraction and relaxation of the smooth muscle that allows normal digestion. Our goal is to understand how neurons at birth stay alive and adapt to the rapid growth of their target cells, creating the complex, stable relationship seen in the adult.****Current support showed us that a single factor (GDNF; a neurotrophin) is responsible for survival of the ENS neurons after birth, and that GDNF is made by the intestinal smooth muscle cells. Critically, growth of these cells is required for increased GDNF expression that leads to neuron survival and axon outgrowth. We propose that the binding of GDNF to its receptor, RET, causes two outcomes: initially, survival and then axonal extension, and it may be that different levels of GDNF are required for each. We have the cellular and molecular techniques needed to address this, and a unique tissue culture model involving both neonatal intestinal neurons and smooth muscle cells. We will separate the outcomes of GDNF signalling with pharmacological inhibitors that block distinct pathways in the neurons (the only cells expressing GDNF receptors) , and then measure cellular outcomes of survival or the degree of axonal outgrowth. We will then examine the requirements of neurons for GDNF when growth is complete - do very low levels maintain survival? How is this signalling achieved?****Axonal outgrowth seems absent in the adult intestine, but when it arises to facilitate repair, the neurons do not function well, and this is seen elsewhere with nerve damage. We now think that axon outgrowth and nerve function in the neonatal ENS (ie, action potentials and neurotransmitter release) tend not to occur at the same time. Therefore, the structural programme becomes complete as the functional programme gains ascendancy, with synthesis, storage and release of neurotransmitters. Quantitative measurement of the steps involved, such as mRNA and protein, will measure key proteins that belong in either one of these programmes, and this will be correlated with the ability of the neurons to display mature signalling properties. This will help us to understand how the intestine develops in the neonate, a field where little is known.****I will work with trainees, who will mainly be graduate students as well as senior undergraduates. They will gain both technical expertise as well as education in scientific thinking and critical evaluation. To date, our graduates are highly successful, with significant publications in this field, and very good career achievements.**********