RECOVERIN AND HIPPOCALCIN DISTRIBUTION IN THE LAMPREY (LAMPRETA-FLUVIATILIS) RETINA

Recoverin is a calcium-sensing protein which is involved in the transd uction of light in vertebrate photoreceptors. It is also detected in o ther retina cell types in which its function is not yet elucidated, an d is an autoantigen in a cancer-associated degenerative disease of the retina. Recently, hippocalcin, an homologous protein of recoverin, be longing to the same family of fatty acylated EF-hand calcium binding p roteins was described in mammals. The immunohistochemical studies pres ented in this paper demonstrate, that, in the retina of the lamprey, a n Agnathan considered the living ancestor of actual jawed vertebrates, recoverin was present in all photoreceptors and, to a lesser extent i n subpopulations of amacrine and ganglion cells whereas hippocalcin wa s detected in numerous amacrine and ganglion cells and in the inner se gments of long photoreceptors. The existence of these calcium-binding proteins shows that they have a high degree of conservation during evo lution. Their presence in the same cells that in jawed vertebrates (ph otoreceptors and ganglion cells for recoverin; amacrine and ganglion c ells for hippocalcin) suggests that some retinal functions are well co nserved but because they were also found in different cell types than in other species (amacrine for recoverin; photoreceptors for hippocalc in), they may have functions more specific to the lamprey retina. (C) 1998 Elsevier Science Ireland Ltd.