Cloning of gonadotropin-releasing hormone I complementary DNAs in songbirds facilitates dissection of mechanisms mediating seasonal changes in reproduction.
Cloning of gonadotropin-releasing hormone I complementary DNAs in songbirds facilitates dissection of mechanisms mediating seasonal changes in reproduction.
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DOI：
10.1210/en.2008-1435
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发表时间：
2009-04
期刊：
影响因子：
4.8
通讯作者：
T. J. Stevenson;K. Lynch;P. Lamba;Gregory F Ball;D. Bernard
中科院分区：
文献类型：
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作者：
T. J. Stevenson;K. Lynch;P. Lamba;Gregory F Ball;D. Bernard
温带动物的生殖生理表现出季节性变化。在大多数情况下，生殖状态的季节性变化是由视前区（POA）/下丘脑前部的GnRH 1分泌而不是合成的变化来调节的。一个重要的例外发生在一些鸣禽，成为photorefractory长日的刺激作用，并表现出深刻的下降，脑GnRH 1蛋白质含量。这种下降是否反映了基因表达的变化是未知的，因为过去的失败来衡量GNRH 1 mRNA水平，在很大程度上是由于没有可用的GNRH 1基因序列在此taxon. Here，我们报告的第一个克隆的GNRH 1 cDNA在两个鸣禽：欧洲椋鸟和斑胸草雀。与其他鸟类和非鸟类物种中激素前体的大小一致，开放阅读框分别预测91和92个氨基酸的蛋白质。而在这两个物种的十肽是完全保守的鸡GnRH 1，在信号肽和GnRH相关的肽亚结构域的氨基酸的身份是显着不太保守。在核苷酸水平上，椋鸟和斑胸草雀的编码序列彼此大约88%相同，但与鸡的GNRH 1只有大约70%相同。使用放射性标记的cRNA探针原位杂交表明，GNRH 1 mRNA的表达主要在POA，与以前的研究一致的GnRH 1免疫反应细胞体的分布。此外，我们还为雄性椋鸟GNRH 1 mRNA的光周期依赖性调节提供了证据。GNRH 1 mRNA水平的下降与睾丸退化平行发生。因此，光不应性与内侧POA中GNRH 1基因表达的减少有关。
Temperate zone animals exhibit seasonal variation in reproductive physiology. In most cases, seasonal changes in reproductive states are regulated by changes in GnRH1 secretion, rather than synthesis, from the preoptic area (POA)/anterior hypothalamus. An important exception occurs in some songbirds that become photorefractory to the stimulatory effects of long days and show profound decreases in brain GnRH1 protein content. Whether this decline reflects changes in gene expression is unknown because of past failures to measure GNRH1 mRNA levels, due in large part to the absence of available GNRH1 gene sequence in this taxon. Here, we report the first cloning of GNRH1 cDNAs in two songbirds: European starlings and zebra finches. Consistent with the size of the prepro-hormone in other avian and non-avian species, the open-reading frames predict proteins of 91 and 92 amino acids, respectively. Whereas the decapeptide in both species is perfectly conserved with chicken GnRH1, the amino acid identity in the signal peptide and GNRH associated peptide subdomains are significantly less well conserved. At the nucleotide level, the starling and zebra finch coding sequences are approximately 88% identical to each other but only approximately 70% identical to chicken GNRH1. In situ hybridization using radiolabeled cRNA probes demonstrated GNRH1 mRNA expression primarily in the POA, consistent with previous studies on the distribution of the GnRH1-immunoreactive cell bodies. Furthermore, we provide evidence for photoperiod-dependent regulation of GNRH1 mRNA in male starlings. Declines in GNRH1 mRNA levels occur in parallel with testicular involution. Thus, photorefractoriness is associated with decreases in GNRH1 gene expression in the medial POA.