Laboratory of Fish Biology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan; Institute for Advanced Research, Nagoya University, Nagoya, Japan
Manon Thomas
Paris-Saclay Institute of Neuroscience (Neuro-PSI), Université Paris-Saclay, CNRS, Gif-sur-Yvette, France
Aurélie Heuzé
Paris-Saclay Institute of Neuroscience (Neuro-PSI), Université Paris-Saclay, CNRS, Gif-sur-Yvette, France
Laboratory of Molecular and Developmental Biology, National Institute of Genetics, Mishima, Japan; Department of Genetics, SOKENDAI (The Graduate University for Advanced Studies), Mishima, Japan
Naoyuki Yamamoto
Laboratory of Fish Biology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
Ascending visual projections similar to the mammalian thalamocortical pathway are found in a wide range of vertebrate species, but their homology is debated. To get better insights into their evolutionary origin, we examined the developmental origin of a thalamic-like sensory structure of teleosts, the preglomerular complex (PG), focusing on the visual projection neurons. Similarly to the tectofugal thalamic nuclei in amniotes, the lateral nucleus of PG receives tectal information and projects to the pallium. However, our cell lineage study in zebrafish reveals that the majority of PG cells are derived from the midbrain, unlike the amniote thalamus. We also demonstrate that the PG projection neurons develop gradually until late juvenile stages. Our data suggest that teleost PG, as a whole, is not homologous to the amniote thalamus. Thus, the thalamocortical-like projections evolved from a non-forebrain cell population, which indicates a surprising degree of variation in the vertebrate sensory systems.
