Foxl2 plays conserved central function in ovarian differentiation and maintenance in several fish species. However, its expression pattern and function in fish embryogenesis are still largely unknown. In this study, we first presented a sequential expression pattern of zebrafish foxl2a and foxl2b during embryo development. They were predominantly expressed in the cranial paraxial mesoderm (CPM) and cranial venous vasculature (CVV) during somitogenesis and subsequently expressed in the pharyngeal arches after 48 h post-fertilization (hpf). Then, we compared the brain structures among zebrafish wildtype (WT) and three homozygous foxl2 mutants (foxl2a^−/−, foxl2b^−/− and foxl2a^−/−;foxl2b^−/−) and found the reduction of the fourth ventricle in the three foxl2 mutants, especially in foxl2a^−/−;foxl2b^−/− mutant. Finally, we detected several key transcription factors involved in the gene regulatory network of midbrain-hindbrain boundary (MHB) patterning, such as wnt1, en1b and pax2a. Their expression levels were obviously downregulated in MHB of foxl2a^−/− and foxl2a^−/−;foxl2b^−/− mutants. Thus, we suggest that Foxl2a and Foxl2b are involved in MHB and the fourth ventricle development in zebrafish. The current study provides insights into the molecular mechanism underlying development of brain ventricular system.

Foxl2 在几种鱼类的卵巢分化和维持中起着保守的中心作用。然而，其在鱼类胚胎发生中的表达模式和功能在很大程度上仍是未知的。在这项研究中，我们首先展示了斑马鱼foxl2a和foxl2b在胚胎发育过程中的顺序表达模式。它们主要在体细胞发生期间在颅旁轴中胚层 (CPM) 和颅静脉血管系统 (CVV) 中表达，随后在受精后 48 小时 (hpf) 中表达在咽弓中。然后，我们比较了斑马鱼野生型 (WT) 和三种纯合foxl2突变体（foxl2a ^-/-、foxl2b ^-/-和foxl2a ^-/- ; foxl2b ^{-/- ）并发现三个}foxl2突变体中第四脑室的减少，尤其是在foxl2a ^-/-中；foxl2b ^-/-突变体。最后，我们检测到几个参与中脑-后脑边界 (MHB) 模式基因调控网络的关键转录因子，如wnt1、en1b和pax2a。它们的表达水平在foxl2a ^-/-和foxl2a ^-/-的 MHB 中明显下调；foxl2b ^-/-突变体。因此，我们建议 Foxl2a 和 Foxl2b 参与斑马鱼的 MHB 和第四脑室发育。目前的研究提供了对脑室系统发育的分子机制的见解。