Armbruster Daniel, Mueller Thomas, Driever Wolfgang
Institute for Biology I, Faculty of Biology, University of Freiburg, Freiburg, Germany.
MeInBio Research Training Group, University of Freiburg, Freiburg, Germany.
J Comp Neurol. 2025 Aug;533(8):e70079. doi: 10.1002/cne.70079.
The amygdala is a heterogeneous, multinuclear telencephalic structure critical for motivated and emotion-related behaviors in vertebrates. In ray-finned fish (Actinopterygii) like the teleost zebrafish, a telencephalic outward-growing process called eversion makes defining amygdaloid territories particularly challenging. Teleosts are also peculiar in that they develop numerous dopaminergic (DA) neurons in the subpallium, while in tetrapods, such populations are less prominent or appear only transiently. To shed light on the organization of the amygdala in teleosts, we pursued an evolutionary developmental approach focusing on the topological origin of subpallial DA neurons. Specifically, we analyzed the distribution of tyrosine hydroxylase (Th) in conjunction with expression patterns of pax6a+b, isl1a, nkx2.1, lhx8a, otpa+b, and calb2a as markers of different telencephalic subdivisions in brains of 5- and 30-day-old zebrafish (Danio rerio, Teleostei). Our data show that the previously identified dorsalmost division of the ventral telencephalon (Vdd) needs to be subdivided into an anteroventral pax6a/b-positive portion (Vdd1) and a posterodorsal pax6a/b-negative portion (Vdd2). This pax6a-negative Vdd2 portion develops into the extended medial amygdala (EMeA), including the DA population adjacent to the pallial-subpallial border. Our results also show that the EMeA DA neurons form a heterogeneous group of amygdaloid neurons because they differentially express calb2a and sst7. Our work sheds light on the early evolution and development of the amygdala and provides a foundation for functional analysis of the newly defined DA subtypes of the extended amygdala in zebrafish.
杏仁核是一种异质性、多核的端脑结构，对脊椎动物的动机和情绪相关行为至关重要。在硬骨鱼（辐鳍鱼纲）如硬骨鱼斑马鱼中，一种称为外翻的端脑向外生长过程使得定义杏仁核区域极具挑战性。硬骨鱼也很特别，因为它们在大脑皮层下发育出大量多巴胺能（DA）神经元，而在四足动物中，这类神经元群体不那么突出或仅短暂出现。为了阐明硬骨鱼杏仁核的组织结构，我们采用了一种进化发育方法，重点关注大脑皮层下DA神经元的拓扑起源。具体而言，我们结合酪氨酸羟化酶（Th）的分布以及pax6a + b、isl1a、nkx
2.1、lhx8a、otpa + b和calb2a的表达模式进行分析，这些基因可作为5日龄和30日龄斑马鱼（Danio rerio，硬骨鱼纲）大脑中不同端脑亚区的标记物。我们的数据表明，先前确定的腹侧端脑最背侧部分（Vdd）需要细分为前腹侧pax6a / b阳性部分（Vdd1）和后背侧pax6a / b阴性部分（Vdd2）。这个pax6a阴性的Vdd2部分发育成扩展的内侧杏仁核（EMeA），包括与脑皮层 - 大脑皮层下边界相邻的DA神经元群体。我们的结果还表明，EMeA DA神经元形成了一组异质性的杏仁核神经元，因为它们差异表达calb2a和sst7。我们的工作揭示了杏仁核的早期进化和发育，并为斑马鱼扩展杏仁核新定义的DA亚型的功能分析奠定了基础。
