The collaborative research group of Shigeru Kuratani, Senior Researcher, Kuratani Morphological Evolution Laboratory, Institute of Physical and Chemical Research, and Fumiaki Sugawara, Professor of Biology, Liberal Arts Department, Hyogo Medical University (Visiting Researcher, Kuratani Morphological Evolution Laboratory, RIKEN), is a joint research group of the brain development process of nuta eel and yam eel. It was revealed that most of each region of the brain, which is said to have evolved in stages, was already established more than 5 million years ago.
Vertebrates that currently inhabit the earth are roughly divided into "jaw mouths" including humans and "cyclostomi" that do not have jaws, and evolved more than 5 million years ago. It is said that it branched to.Until now, lamprey, a type of cyclostomi, could not be identified with the medial basal ganglia ridge, which is part of the basal ganglia, and the hindbrain lip, which is the site of cerebellum development.Therefore, these two areas are said to have newly developed in the gnathostomata.However, because it may have degenerated in lamprey, the research group emphasized comparison with the brain of hagfish, another strain of cyclostomi.Hagfish lived in the deep sea and the development process was mysterious, but the research group succeeded in artificially cultivating hagfish (2) and collecting fertilized eggs (1).Analysis of the embryonic genes obtained from them revealed the expression of genes corresponding to two regions, revealing the presence of medial basal ganglia ridges and hindbrain lips.Furthermore, in lamprey, the existence of two regions was identified by reanalysis of embryos, overturning the contents of previous research.
Contrary to the traditional understanding that this has gradually complicated the vertebrate brain, most of the basic patterns of the brain have been inhabited by the common ancestors of gnathostomata and cyclostomita for more than 5 million years. It turned out that it had been established before.Future issues include interesting themes such as elucidating the evolutionary transition of the neocortex and approaching the development of human "intelligence."