Roslin Institute Chicken Embryology (RICE) Group, Gene Function and Development, The Roslin Institute, University of Edinburgh, Easter Bush Campus, Midlothian, UK.
Sex Dev. 2023;17(2-3):120-133. doi: 10.1159/000529754. Epub 2023 Feb 16.
Primary sex determination is the developmental process that results in the sexual differentiation of the gonads. Vertebrate sex determination is generally considered to follow the model based on the mammalian system, where a sex-specific master regulatory gene activates one of the two different gene networks that underlie testis and ovary differentiation.
It is now known that, while many of the molecular components of these pathways are conserved across different vertebrates, a wide variety of different trigger factors are utilized to initiate primary sex determination. In birds, the male is the homogametic sex (ZZ), and significant differences exist between the avian system of sex determination and that of mammals. For example, DMRT1, FOXL2, and estrogen are key factors in gonadogenesis in birds, but none are essential for primary sex determination in mammals.
Gonadal sex determination in birds is thought to depend on a dosage-based mechanism involving expression of the Z-linked DMRT1 gene, and it may be that this "mechanism" is simply an extension of the cell autonomous sex identity associated with avian tissues, with no sex-specific trigger required.
初级性别决定是导致性腺性分化的发育过程。脊椎动物性别决定通常被认为遵循基于哺乳动物系统的模型，其中一个性别特异性的主调控基因激活了两个不同的基因网络之一，这两个基因网络是睾丸和卵巢分化的基础。
现在已知，虽然这些途径的许多分子成分在不同的脊椎动物中是保守的，但启动初级性别决定的触发因素多种多样。在鸟类中，雄性是同配性别（ZZ），性别决定系统与哺乳动物存在显著差异。例如，DMRT1、FOXL2 和雌激素是鸟类性腺发生的关键因素，但在哺乳动物中，这些因素对于初级性别决定都不是必需的。
鸟类的性腺性别决定被认为取决于涉及 Z 连锁 DMRT1 基因表达的基于剂量的机制，并且可能是这种“机制”只是与鸟类组织相关的细胞自主性别身份的延伸，不需要性别特异性触发因素。
