iFGF14 Regulation of Cerebellar Neuron Excitability

 描述(申请人提供)：细胞内成纤维细胞生长因子14(IFGF14)是电压门控钠(NAV)通道9-11的一个新的辅助亚单位，与脊髓小脑性共济失调27(SCA27)3有关，这是一种与进行性共济失调和智力下降有关的衰弱疾病。以前在培养神经元和异源表达系统中的工作表明，iFGF14与NAV通道孔形成(α)亚单位的C末端结合，并调节动作电位5、13下的快速瞬时NAV电流的性质。iFGF14在中枢神经系统2、4、5的多种细胞类型中表达为两个N端剪接变体。最近发现，iFGF14的缺失或敲除可以减弱小脑颗粒和浦肯野神经元的兴奋性，然而，对iFGF14如何调节这些细胞类型的兴奋性或其对行为的影响尚缺乏了解。这项研究的目的是确定每个iFGF14剪接变异体在调节小脑神经元的内在兴奋性方面的效果和作用；并确定iFGF14在小脑神经元中的表达障碍如何导致有害表型。为此，我将利用病毒载体在不同类别的小鼠小脑神经元中急性表达或敲除iFGF14。我还将利用一个新产生的小鼠模型，该模型带有导致人类突变FGF14145S的敲击基因SCA27。利用这些实验系统，我将研究iFGF14对完整脑片上的小脑浦肯野和颗粒神经元NAV电流和内在兴奋性的影响。我将完成平行实验，以确定iFGF14对小鼠平衡和运动协调的影响。拟议的实验结果将推动我们对iFGF14功能的理解，并为SCA27病理生理学的机制提供新的见解。

 DESCRIPTION (provided by applicant): Intracellular Fibroblast Growth Factor 14 (iFGF14) is a novel accessory subunit of voltage gated sodium (Nav) channels9-11 that is linked to spinal cerebellar ataxia 27 (SCA27)3, a debilitating disease, associated with progressive ataxia and mental decline. Previous work in cultured neurons and heterologous expression systems demonstrate that iFGF14 binds to the C-termini of Nav channel pore forming (α) subunits and modulates the properties of the fast transient Nav currents underlying action potentials5,13. iFGF14 is expressed as two N-terminal splice variants in multiple cell types throughout the central nervous system2,4,5. Deletion or knock-down of iFGF14 has recently been shown to attenuate excitability in cerebellar granule and Purkinje neurons7-8, though, an understanding of how iFGF14 regulates excitability in these cell types or its effect on behavior is lacking. The goa of the proposed research is to determine the effect and role of each iFGF14 splice variant in regulating intrinsic excitability of cerebellar neurons; and, to define how dysfunction of iFGF14 expression in cerebellar neurons can result in deleterious phenotypes. To do this, I will utilize viral vectors for acute expression, or knock-down, of iFGF14 in distinct classes of mouse cerebellar neurons. I will also utilize a newly generated mouse model with a knockin SCA27 causing human mutation FGF14145S. With these experimental systems, I will investigate effects of iFGF14 on Nav currents and intrinsic excitability in cerebellar Purkinje and granule neurons from intact slices. I will complete parallel experiments to define the effects of iFGF14 on mouse balance and motor coordination. The results of the proposed experiments will move our understanding of iFGF14 function forward and provide new insights into the mechanisms underlying SCA27 pathophysiology.