Cold-adapted Antarctic fish: the discovery of neuroglobin in the dominant suborder Notothenioidei.

Novel globins, such as neuroglobin (Ngb) and cytoglobin, have recently been discovered in many vertebrates. Ngb is mainly expressed in neurons and plays a neuroprotective role during hypoxic stress. Neuronal hypoxia and cerebral ischemia induce Ngb expression; knocking down Ngb expression increases hypoxic neuronal injury in vitro and ischemic cerebral injury in vivo. Although Ngb was originally identified in mammals, it is also present in fish, including the zebrafish Danio rerio. We have discovered the Ngb gene to be present in red-blooded notothenioid fish species, and in at least 13 of the 16 species of the white-blooded icefish family Channichthyidae. The deduced amino-acid sequences are well conserved. The retention of the Ngb gene by channichthyids, despite the loss of hemoglobin and myoglobin, appears very intriguing.