Six1 is a key regulator of the developmental and evolutionary architecture of sensory neurons in craniates

Hiroshi Yajima, Makoto Suzuki, Haruki Ochi, Keiko Ikeda, Shigeru Sato, Ken-ichi Yamamura, Hajime Ogino, Naoto Ueno, Kiyoshi Kawakami

Various senses and sensory nerve architectures of animals have evolved during adaptation to exploit diverse environments. In craniates, the trunk sensory system has evolved from simple mechanosensory neurons inside the spinal cord (intramedullary), called Rohon-Beard (RB) cells, to multimodal sensory neurons of dorsal root ganglia (DRG) outside the spinal cord (extramedullary). The fish and amphibian trunk sensory systems switch from RB cells to DRG during development, while amniotes rely exclusively on the DRG system. The mechanisms underlying the ontogenic switching and its link to phylogenetic transition remain unknown.