National Centre for Adult Stem Cell Research, Eskitis Institute for Cell and Molecular Therapies, Griffith University, Nathan 4111, Brisbane, Australia.
Mol Cell Neurosci. 2011 Sep;48(1):9-19. doi: 10.1016/j.mcn.2011.05.011. Epub 2011 Jun 12.
Cell surface carbohydrates define subpopulations of primary olfactory neurons whose axons terminate in select glomeruli in the olfactory bulb. The combination of carbohydrates present on axon subpopulations has been proposed to confer a unique identity that contributes to the establishment of the olfactory topographic map. We have identified a novel subpopulation of primary olfactory neurons in mice that express blood group carbohydrates with GalNAc-ß1,4[NeuAcα 2,3]Galß1 residues recognised by the CT1 antibody. The CT1 carbohydrate has been shown to modulate adhesion of nerve terminals to the extracellular matrix and to synaptic proteins. The axons of the CT1-positive primary olfactory neurons terminate in a subpopulation of glomeruli in the olfactory bulb. Four lines of evidence support the view that CT1 glomeruli are topographically fixed. First, CT1 glomeruli were restricted predominantly to the dorsomedial olfactory bulb and were absent from large patches of the ventrolateral bulb. Second, similar distributions were observed for CT1 glomeruli on both the left and right olfactory bulbs of each animal, and between animals. Third, CT1 glomeruli were typically present as small clusters of 2-4 glomeruli. Fourth, a single CT1 glomerulus was always apposed to the glomeruli innervated by axons expressing the M72 odorant receptor. We also show that the CT1 carbohydrate is lost in gain-of-function transgenic mice over-expressing the blood group A glycosyltransferase in which there is aberrant targeting of M72 axons. Taken together, these results suggest that the CT1 carbohydrate, together with other carbohydrates, contributes to axon guidance during the establishment of the olfactory topographic map.
细胞表面碳水化合物定义了初级嗅觉神经元的亚群，其轴突终止于嗅球中特定的神经小球。存在于轴突亚群上的碳水化合物组合被认为赋予了独特的身份，有助于建立嗅觉拓扑图。我们在小鼠中鉴定出了一种新型的初级嗅觉神经元亚群，其表达的血型碳水化合物具有 CT1 抗体识别的 GalNAc-β1,4[NeuAcα 2,3]Galβ1 残基。CT1 碳水化合物已被证明能调节神经末梢与细胞外基质和突触蛋白的粘附。CT1 阳性初级嗅觉神经元的轴突终止于嗅球中神经小球的一个亚群。有四条证据支持 CT1 神经小球是拓扑固定的观点。首先，CT1 神经小球主要局限于嗅球的背内侧，而不存在于嗅球腹外侧的大片区域。其次，在每个动物的左右嗅球以及动物之间，都观察到了类似的 CT1 神经小球分布。第三，CT1 神经小球通常以 2-4 个神经小球的小簇出现。第四，单个 CT1 神经小球总是与表达 M72 气味受体的轴突支配的神经小球相邻。我们还表明，在过度表达血型 A 糖基转移酶的功能获得性转基因小鼠中，CT1 碳水化合物丢失，其中 M72 轴突的靶向异常。综上所述，这些结果表明，CT1 碳水化合物与其他碳水化合物一起，有助于在建立嗅觉拓扑图过程中的轴突导向。
