Paris-Saclay Institute of Neuroscience (Neuro-PSI), CNRS UMR9197, Univ Paris Sud, Université Paris-Saclay, CNRS Bâtiment 5, Avenue de la Terrasse, 91190, Gif-sur-Yvette, France.
Present address: Plateau de phénotypage TEFOR, LPGP-INRA UR1037, 35042, Rennes, France.
BMC Biol. 2019 Mar 8;17(1):22. doi: 10.1186/s12915-019-0631-y.
Although the overall brain organization is shared in vertebrates, there are significant differences within subregions among different groups, notably between Sarcopterygii (lobe-finned fish) and Actinopterygii (ray-finned fish). Recent comparative studies focusing on the ventricular morphology have revealed a large diversity of the hypothalamus. Here, we study the development of the inferior lobe (IL), a prominent structure forming a bump on the ventral surface of the teleost brain. Based on its position, IL has been thought to be part of the hypothalamus (therefore forebrain).
Taking advantage of genetic lineage-tracing techniques in zebrafish, we reveal that cells originating from her5-expressing progenitors in the midbrain-hindbrain boundary (MHB) participate in the formation of a large part of the IL. 3D visualization demonstrated how IL develops in relation to the ventricular system. We found that IL is constituted by two developmental components: the periventricular zone of hypothalamic origin and the external zone of mesencephalic origin. The mesencephalic external zone grows progressively until adulthood by adding new cells throughout development.
Our results disprove a homology between the IL and the mammalian lateral hypothalamus. We suggest that the IL is likely to be involved in multimodal sensory integration rather than feeding motivation. The teleost brain is not a simpler version of the mammalian brain, and our study highlights the evolutionary plasticity of the brain which gives rise to novel structures.
尽管脊椎动物的整体大脑组织是共享的，但不同群体之间的亚区存在显著差异，尤其是在肉鳍鱼（Sarcopterygii）和条鳍鱼（Actinopterygii）之间。最近的比较研究集中在脑室形态上，揭示了下丘脑的多样性。在这里，我们研究了下叶（IL）的发育，这是一个在硬骨鱼脑腹面形成肿块的突出结构。根据其位置，IL 被认为是下丘脑（因此是前脑）的一部分。
利用斑马鱼中的遗传谱系追踪技术，我们揭示了从中脑-后脑边界（MHB）中表达 her5 的祖细胞起源的细胞参与了 IL 的大部分形成。3D 可视化显示了 IL 如何与脑室系统发育相关。我们发现 IL 由两个发育成分组成：下丘脑起源的室周区和中脑起源的外部区。中脑外部区通过在整个发育过程中添加新细胞逐渐生长到成年。
我们的结果否定了 IL 与哺乳动物外侧下丘脑之间的同源性。我们认为 IL 可能参与多模态感觉整合，而不是摄食动机。硬骨鱼的大脑不是哺乳动物大脑的简化版本，我们的研究强调了大脑的进化可塑性，这导致了新结构的出现。
