海马表现出男性怀孕的独特特征,它在育龄袋中孵化了许多胚胎,在增强后代的生存能力中起着至关重要的作用。盆腹海马(海马腹部海马)具有海马中最大的体型,是中国水产养殖中的重要物种。在这项研究中,我们揭示了细胞学和形态学特征,以及监管机制,贯穿腹部H.的整个育宫袋发育。育宫袋起源于腹部真皮,向腹侧中线延伸。随着真皮层的增厚,内部上皮折叠,基质松动,血管化发生,最终形成育卵袋。此外,通过对不同发育阶段的育儿袋进行转录组学分析,8个关键基因(tgfb3、fgf2、wnt7a、pgf,mycn,tln2,jund,ccn4)与育宫袋发育密切相关的MAPK,Rap1,TGF-β,和Wnt信号通路。通过原位杂交(ISH)检查,这些基因在新形成阶段在假胎盘和真皮层中高度表达。血管生成,胶原纤维的致密化,海马育儿袋形成中的成纤维细胞和内皮细胞的增殖可能受这些基因和途径的调控。此外,雄性激素受体基因(AR)的表达在育宫袋的形成过程中显著上调,ISH证实了AR基因在育宫袋的真皮和假胎盘中的表达,强调其在发展过程中的作用。雄激素和氟他胺(雄激素受体拮抗剂)治疗分别显着加速了育儿袋的形成并完全抑制了其发生,伴随着与上述信号通路有关的差异表达基因的上调表达。这些发现表明育宫袋的形成由雄激素决定,雄激素受体通过调节fgf2,tgfb3,pgf,wnt7a有趣的是,雄激素甚至诱导雌性育儿袋的形成。我们首先阐明了海马育儿袋的形成,证明雄激素及其受体直接诱导增厚,折叠,和血管化的腹部真皮层通过多个信号通路形成胎盘样结构。这些发现为进一步探索雄性妊娠的进化和脊椎动物胎生的适应性收敛提供了基础见解。
Seahorses exhibit the unique characteristic of male pregnancy, which incubates numerous embryos in a brood pouch that plays an essential role in enhancing offspring survivability. The pot-belly seahorse (Hippocampus abdominalis) possesses the largest body size among seahorses and is a significant species in Chinese aquaculture. In this study, we revealed the cytological and morphological characteristics, as well as regulatory mechanisms, throughout the entire brood pouch development in H. abdominalis. The brood pouch originated from the abdominal dermis, extending towards the ventral midline. As the dermal layers thicken, the inner epithelium folds, the stroma loosens, and vascularization occurs, culminating in the formation of the brood pouch. Furthermore, through transcriptomic analysis of brood pouches at various developmental stages, 8 key genes (tgfb3, fgf2, wnt7a, pgf, mycn, tln2, jund, ccn4) closely related to the development of brood pouch were identified in the MAPK, Rap1, TGF-β, and Wnt signaling pathways. These genes were highly expressed in the pseudoplacenta and dermal layers at the newly formed stage as examined by in situ hybridization (ISH). The angiogenesis, densification of collagen fibers, and proliferation of fibroblasts and endothelial cells in seahorse brood pouch formation may be regulated by these genes and pathways. Additionally, the expression of the
androgen receptor gene (ar) was significantly upregulated during the formation of the brood pouch, and ISH confirmed the expression of the ar gene in the dermis and pseudoplacenta of the brood pouch, highlighting its role in the developmental process.
Androgen and flutamide (
androgen receptor antagonist) treatments significantly accelerated the formation of the brood pouch and completely inhibited its occurrence respectively, concomitant to the upregulated expression of differentially expressed genes involved above signaling pathways. These findings demonstrated that formation of the brood pouch is determined by
androgen and the
androgen receptor activates the above signaling pathways in the brood pouch through the regulation of fgf2, tgfb3, pgf, and wnt7a. Interestingly,
androgen even induced the formation of the brood pouch in females. We firstly elucidated the formation of the seahorse brood pouch, demonstrating that androgens and their receptors directly induce the thickening, folding, and vascularization of the abdominal dermal layer into a placenta-like structure through multiple signaling pathways. These findings provide foundational insights to further exploring the evolution of male pregnancy and adaptive convergence in viviparity across vertebrates.