Prin Fabrice, Ng Keat-Eng, Thaker Uma, Drescher Uwe, Guthrie Sarah
MRC Centre for Developmental Neurobiology, 4th Floor New Hunt's House, King's College, Guy's Campus, London SE1 1UL, United Kingdom.
Dev Biol. 2005 Mar 15;279(2):402-19. doi: 10.1016/j.ydbio.2004.12.030.
In this study, we investigate the possible role of ephrin-Eph signaling in trigeminal motor axon projections. We find that EphA receptors are expressed at higher levels by rhombomere 2 (r2) trigeminal motor neurons than by r3 trigeminal motor neurons in the chick embryo. Mapping of rhombomere-specific axon projections shows that r2 and r3 trigeminal motor neurons project to different muscle targets, including the mandibular adductor and the intermandibularis muscles respectively. Ephrin-A5 is expressed in these muscles, especially in some regions of the intermandibularis muscle, and can cause growth cone collapse of both r2 and r3 motor axons in vitro. We demonstrate that in vivo overexpression of ephrin-A5 in the intermandibularis muscle, or overexpression of dominant-negative EphA receptors in trigeminal motor neurons leads to a reduction in branching of r3-derived motor axons specifically. Overexpression of full-length EphA receptors impairs the formation of r3 projections to the intermandibularis muscle. These findings indicate that ephrins and their Eph receptors play a role in trigeminal motor axon topographic mapping and in rhombomere 3-derived projections in particular.
在本研究中，我们调查了ephrin-Eph信号在三叉神经运动轴突投射中的可能作用。我们发现，在鸡胚中，菱脑节2（r2）三叉神经运动神经元表达EphA受体的水平高于r3三叉神经运动神经元。对菱脑节特异性轴突投射的绘图显示，r2和r3三叉神经运动神经元分别投射到不同的肌肉靶点，包括下颌内收肌和下颌间肌。Ephrin-A5在这些肌肉中表达，尤其是在下颌间肌的某些区域，并且在体外可导致r2和r3运动轴突的生长锥塌陷。我们证明，在体内下颌间肌中过表达ephrin-A5，或在三叉神经运动神经元中过表达显性负性EphA受体会特异性导致r3来源的运动轴突分支减少。全长EphA受体的过表达会损害r3向下颌间肌的投射形成。这些发现表明，ephrin及其Eph受体在三叉神经运动轴突拓扑映射中发挥作用，尤其是在菱脑节3来源的投射中。
