Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, Maryland 21202, USA.
Endocrinology. 2010 Jan;151(1):332-40. doi: 10.1210/en.2009-0548. Epub 2009 Oct 27.
Hypophysiotropic GnRH neurons are located in the preoptic area and ventral hypothalamus of sexually mature vertebrates. In several species, the embryonic origin of hypophysiotropic GnRH neurons remains unclear. Using the Tg(GnRH3:EGFP) zebrafish line, in which GnRH3 neurons express EGFP, GnRH3 neurons in the olfactory region were specifically and individually ablated during early development using laser pulses. After ablation, the olfactory region maintained the capacity to regenerate GnRH3 neurons. However, this capacity was time-limited. When ablation of GnRH3 cells was conducted at 2 d after fertilization, high regeneration rates were observed, but regeneration capacity significantly decreased when ablation was performed at 4 or 6 d after fertilization. Unilateral GnRH3 neuron ablation results in unilateral soma presence. These unilateral somata are capable of projecting fiber extensions bilaterally. Successful bilateral GnRH3 soma ablation during development resulted in complete lack of olfactory, terminal nerve, preoptic area, and hypothalamic GnRH3 neurons and fibers in 12-wk-old animals. Mature animals lacking GnRH3 neurons exhibited arrested oocyte development and reduced average oocyte diameter. Animals in which GnRH3 neurons were partially ablated exhibited normal oocyte development; however, their fecundity was significantly reduced. These findings demonstrate that the hypophysiotropic GnRH3 populations in zebrafish consist of neurons that originate in the olfactory region during early development. The presence of GnRH3 neurons of olfactory region origin in reproductively mature zebrafish is a prerequisite for normal oocyte development and reproduction.
促性腺激素释放激素神经元位于性成熟脊椎动物的视前区和下丘脑腹侧。在一些物种中，促性腺激素释放激素神经元的胚胎起源仍不清楚。利用 Tg(GnRH3:EGFP)斑马鱼系，其中 GnRH3 神经元表达 EGFP，在早期发育过程中使用激光脉冲特异性和单独消融嗅觉区域中的 GnRH3 神经元。消融后，嗅觉区域仍有再生 GnRH3 神经元的能力。然而，这种能力是有限的。当在受精后 2 天进行 GnRH3 细胞消融时，观察到高再生率，但当在受精后 4 天或 6 天进行消融时，再生能力显著下降。单侧 GnRH3 神经元消融导致单侧体细胞存在。这些单侧体细胞能够双侧投射纤维延伸。在发育过程中成功进行双侧 GnRH3 体细胞消融会导致 12 周龄动物中嗅觉、终丝、视前区和下丘脑 GnRH3 神经元和纤维完全缺失。缺乏 GnRH3 神经元的成熟动物表现出卵母细胞发育停滞和平均卵母细胞直径减小。部分消融 GnRH3 神经元的动物表现出正常的卵母细胞发育；然而，它们的繁殖力显著降低。这些发现表明，斑马鱼的促性腺激素释放激素神经元群由在早期发育过程中起源于嗅觉区域的神经元组成。具有嗅觉区域起源的 GnRH3 神经元存在于生殖成熟的斑马鱼中是正常卵母细胞发育和繁殖的先决条件。
