A group of specially appointed researchers Yohei Ogawa of the University of Tokyo conducted research using zebrafish with four-color type color vision, which is the prototype of vertebrates, and conducted research on color sensors (photoreceptive proteins related to color vision) that sense blue and green. We discovered a key molecule essential for gene regulation.
The retina of an animal is equipped with multiple types of color sensors, which can be combined to perceive "color".The ancestral species of vertebrates have four types of color sensors (purple, blue, green, and red), and the four-color type of color vision is the prototype.So far, purple and red color sensors have been studied, but the role of blue and green color sensors and the mechanism of their gene regulation have not been clarified.
The research group searched for molecules essential for the control of color sensor genes using small fish zebrafish with four-color vision.The gene expression pattern in the retina was analyzed, and the transcriptional regulators Six4 and Six6 were identified as molecules strongly expressed in pyramidal cells.Furthermore, it was found that Six7 and Six6 coordinately regulate the expression of blue and green color sensor genes.In addition, it was found that the development of color vision by the action of these key molecules is essential for the survival of animals because the ability of animals to feed (feed) is significantly reduced when Six7 and Six6 are deleted by genetic engineering.
Mammals once evolved from diurnal to nocturnal and lost blue and green of the four color sensors.The human ancestors doubled the red sensor of the remaining two species to create a green sensor, and acquired a modified three-color type (blue, green, red) color vision that can cover the blue to green wavelength range.In order to utilize sunlight as an environmental signal, acceptance of blue to green in the central wavelength region may have been advantageous.Future research is expected to elucidate the genetic regulatory mechanisms that support various color vision types and their evolutionary processes.
