Fueshko S, Wray S
Laboratory of Neurochemistry, National Institute of Neurological Disease and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Dev Biol. 1994 Nov;166(1):331-48. doi: 10.1006/dbio.1994.1319.
Luteinizing hormone releasing hormone (LHRH) neurons arise from progenitor cells in the olfactory placode. During prenatal development, these cells migrate via neurophilic interactions, in track-like arrangements along axons of the olfactory complex. The mechanisms by which these cells attain an adult-like distribution are unknown. In this study, we established an in vitro, embryonic mouse olfactory explant model to examine the factors directing LHRH cell migration. Cultures were generated from E11.5 embryos and maintained for up to 3 weeks. Typically 20-50% (160-400 LHRH cells) of the total LHRH neuronal population survived and maintained gene expression in these explants. Fibronectin and laminin staining delineated substratum producing cells which concentrically spread, from Days 1-7, from the periphery of the entire explanted tissue. In contrast, LHRH cells emigrated exclusively from inside olfactory pit areas to the surface of the culture after 3 days. The relationship between groups of LHRH cells emerging from bilateral olfactory pits was not random, but highly organized; in 93% of the cultures examined, the angular relationship between these groups was 180-270 degrees. After 5 or more days in vitro, LHRH cells were found in directional tracks similar to those observed in vivo forming a continuum from the olfactory pit out onto the substratum, where many bipolar LHRH cells were discretely located. The maximum distance away from the olfactory pit that LHRH cells were detected was 0.9 mm, which is compatible with the distance traversed by LHRH cells through the nasal region in vivo. The reproducible spatiotemporal appearance of LHRH cells was unrelated to the concentric spread of the fibronectin and laminin producing cells of the explant. Taken together, these data indicate that LHRH cells migrated directionally in these explants and that the molecular cues governing the initial migration of these neurons remained intact in this system in the absence of brain tissue. Double-label immunocytochemistry indicated that at least three populations of neuronal fibers existed in the explants: N-CAM-positive, peripherin-positive, and N-CAM/peripherin-positive. Although all three fibers groups showed highly organized spatiotemporal distribution patterns, only peripherin-positive fibers correlated with the location of LHRH cells. LHRH cells were always preceded by, and in close association with, peripherin-positive fibers. We hypothesize that signals arising from the peripherin-positive axons provide the appropriate guidance cues to LHRH cells as they emigrate from the olfactory pit.
促黄体生成素释放激素（LHRH）神经元起源于嗅基板中的祖细胞。在产前发育期间，这些细胞通过嗜神经相互作用，沿着嗅觉复合体的轴突以轨道状排列迁移。这些细胞如何获得类似成年期的分布机制尚不清楚。在本研究中，我们建立了一个体外胚胎小鼠嗅觉外植体模型，以研究指导LHRH细胞迁移的因素。培养物取自E11.5胚胎，并维持长达3周。在这些外植体中，通常20 - 50%（160 - 400个LHRH细胞）的LHRH神经元群体存活并维持基因表达。纤连蛋白和层粘连蛋白染色勾勒出从第1天到第7天从整个外植组织周边同心扩散的基质产生细胞。相比之下，LHRH细胞在3天后仅从嗅凹区域内部迁移到培养物表面。从双侧嗅凹出现的LHRH细胞群之间的关系并非随机，而是高度有序的；在93%的检测培养物中，这些细胞群之间的角度关系为180 - 270度。在体外培养5天或更长时间后，发现LHRH细胞位于与体内观察到的类似的定向轨道中，形成从嗅凹到基质的连续体，许多双极LHRH细胞离散地位于基质上。检测到LHRH细胞离嗅凹的最大距离为0.9毫米，这与LHRH细胞在体内穿过鼻腔区域的距离相符。LHRH细胞可重复的时空出现与外植体中纤连蛋白和层粘连蛋白产生细胞的同心扩散无关。综上所述，这些数据表明LHRH细胞在这些外植体中定向迁移，并且在没有脑组织的情况下，控制这些神经元初始迁移的分子线索在该系统中保持完整。双重标记免疫细胞化学表明外植体中至少存在三种神经元纤维群体：N-CAM阳性、外周蛋白阳性和N-CAM/外周蛋白阳性。尽管所有三种纤维群体都显示出高度有序的时空分布模式，但只有外周蛋白阳性纤维与LHRH细胞的位置相关。LHRH细胞总是先于外周蛋白阳性纤维出现，并与之紧密相关。我们假设，当LHRH细胞从嗅凹迁移时，外周蛋白阳性轴突产生的信号为它们提供了适当的引导线索。
