UMR 0083 BOA, INRAE, Centre Val de Loire, 37380 Nouzilly, France.
Teagasc, Animal & Grassland Research and Innovation Centre, Grange, Dunsany, Co. Meath. C15 PW93, Ireland.
Animal. 2023 May;17 Suppl 1:100812. doi: 10.1016/j.animal.2023.100812.
This article reviews the scientific literature on puberty with a focus on ruminants and draws inference, where appropriate, from recent findings in transgenic mouse models and human pathology. Early genetic determinants of puberty have been discovered in humans suffering from hypogonadotropic hypogonadism or central precocious puberty. Transgenic mouse models selected on the basis of the causative defective genes helped in discovering the cellular and molecular mechanisms involved. Most of the genes found are involved in the development of neuroendocrine networks during embryo development and early postnatal life. Notwithstanding that the development of neuroendocrine networks takes place early in puberty, a delay or acceleration in the development of Gonadotropin Releasing Hormone (GnRH) neurons has an impact on puberty onset inducing a delay or an advance, respectively. Among the genes discovered in humans and laboratory models, only a few of them displayed polymorphisms associated with advanced sexual maturity, but also marbling, growth traits and callipygian conformation. This could be related to the fact that rather than puberty onset, most research monitored sexual maturity. Sexual maturity occurs after puberty onset and involves factors regulating the maturation of gonads and in the expression of sexual behaviour. The association with growth and metabolic traits is not surprising since nutrition is the major environmental factor that will act on late genetic determinants of puberty onset. However, a recent hypothesis emerged suggesting that it is the postnatal activation of the GnRH neuronal network that induces the acceleration of growth and weight gain. Hence, nutritional factors need the activation of GnRH neurons first before acting on late genetic determinants. Moreover, nutritional factors can also affect the epigenetic landscape of parental gamete's genome with the consequence of specific methylation of genes involved in GnRH neuron development in the embryo. Season is another important regulator of puberty onset in seasonal small ruminants and appears to involve the same mechanisms that are involved in seasonal transition in adults. The social environment is also an underestimated factor affecting puberty onset in domestic ruminants, most research studies focused on olfactory cues, but the genetic basis has not heretofore been adequately tackled by the scientific community. Additionally, there is some evidence to suggest transgenerational effects exist, in that nutritional and social cues to which parents were exposed, could affect the epigenetic landscape of parental gametes resulting in the epigenetic regulation of early genetic determinants of puberty onset in their offspring.
本文回顾了有关青春期的科学文献，重点关注反刍动物，并在适当情况下从最近的转基因小鼠模型和人类病理学发现中进行推断。在患有促性腺激素低下性性腺功能减退症或中枢性性早熟的患者中，已经发现了青春期的早期遗传决定因素。基于致病缺陷基因选择的转基因小鼠模型有助于发现所涉及的细胞和分子机制。大多数发现的基因都参与了胚胎发育和出生后早期神经内分泌网络的发育。尽管神经内分泌网络的发育在青春期早期发生，但促性腺激素释放激素 (GnRH) 神经元的发育延迟或加速会分别导致青春期开始的延迟或提前。在人类和实验室模型中发现的基因中，只有少数基因显示与性成熟提前相关的多态性，但也与大理石花纹、生长性状和臀部形状有关。这可能与以下事实有关，即大多数研究监测的是性成熟，而不是青春期开始。性成熟发生在青春期开始之后，涉及调节性腺成熟和性行为表达的因素。与生长和代谢性状的关联并不奇怪，因为营养是主要的环境因素，将作用于青春期开始的晚期遗传决定因素。然而，最近出现了一个假设，即 GnRH 神经元网络的产后激活诱导了生长和体重增加的加速。因此，营养因素需要首先激活 GnRH 神经元，然后才能作用于青春期开始的晚期遗传决定因素。此外，营养因素还可以影响亲代配子基因组的表观遗传景观，导致胚胎中参与 GnRH 神经元发育的基因的特异性甲基化。季节是季节性小反刍动物青春期开始的另一个重要调节因素，似乎涉及到涉及成年季节性过渡的相同机制。社会环境也是影响家畜青春期开始的一个被低估的因素，大多数研究都集中在嗅觉线索上，但科学界尚未充分解决其遗传基础。此外，有一些证据表明存在跨代效应，即父母所暴露的营养和社会线索可能会影响亲代配子的表观遗传景观，从而导致其后代青春期开始的早期遗传决定因素的表观遗传调控。
