Abstract：
The olfactory placode (OP) of vertebrates generates several classes of migrating cells, including hypothalamic gonadotropin-releasing hormone (GnRH)-producing neurons, which play essential roles in the reproduction system. Previous studies using OP cell labeling have demonstrated that OP-derived non-GnRH cells enter the developing forebrain; however, their final fates and phenotypes are less well understood. In chick embryos, a subpopulation of migratory cells from the OP that is distinct from GnRH neurons transiently expresses somatostatin (SS). We postulated that these cells are destined to develop into brain neurons. In this study, we examined the expression pattern of SS mRNA in the olfactory-forebrain region during development, as well as the destination of OP-derived migratory cells, including SS mRNA-expressing cells. Utilizing the Tol2 genomic integration system to induce long-term fluorescent protein expression in OP cells, we found that OP-derived migratory cells labeled at embryonic day (E) 3 resided in the olfactory nerve and medial forebrain at E17-19. A subpopulation of green fluorescent protein (GFP)-labeled GnRH neurons that remained in the olfactory nerve was considered to comprise terminal nerve neurons. In the forebrain, GFP-labeled cells showed a distribution pattern similar to that of GnRH neurons. A large proportion of GFP-labeled cells expressed the mature neuronal marker NeuN. Among the GFP-labeled cells, the percentage of GnRH neurons was low, while the remaining GnRH-negative neurons either expressed SS mRNA, neuropeptide Y, or calbindin D-28k or did not express any of them. These results indicate that a diverse population of OP-derived neuronal cells, other than GnRH neurons, integrates into the chick medial forebrain.
摘要：
脊椎动物的嗅觉placode（OP）产生几类迁移细胞，包括产生下丘脑促性腺激素释放激素（GnRH）的神经元，在生殖系统中起着至关重要的作用。以前使用OP细胞标记的研究表明，OP衍生的非GnRH细胞进入发育中的前脑；然而，他们的最终命运和表型不太清楚。在小鸡胚胎中，不同于GnRH神经元的OP的迁移细胞亚群瞬时表达生长抑素（SS）。我们推测这些细胞注定会发育成大脑神经元。在这项研究中,我们检查了发育过程中嗅觉-前脑区域SSmRNA的表达模式，以及OP衍生的迁移细胞的目的地，包括SSmRNA表达细胞。利用Tol2基因组整合系统在OP细胞中诱导长期荧光蛋白表达，我们发现在胚胎第3天（E）标记的OP衍生的迁移细胞在E17-19时位于嗅神经和内侧前脑。保留在嗅神经中的绿色荧光蛋白（GFP）标记的GnRH神经元亚群被认为包含末端神经神经元。在前脑，GFP标记的细胞显示出与GnRH神经元相似的分布模式。大部分GFP标记的细胞表达成熟的神经元标记物NeuN。在GFP标记的细胞中，GnRH神经元的百分比很低，而其余的GnRH阴性神经元要么表达SSmRNA，神经肽Y，或calbindinD-28k或没有表达它们中的任何一个。这些结果表明，OP衍生的神经元细胞的不同群体，除了GnRH神经元，整合到小鸡内侧前脑。
