A Zn-finger protein, Xfin, is expressed during cone differentiation in the retina of the frog Xenopus laevis

Xfin is a member of a Zn-finger multigene family that shares homology with the Drosophila segmentation gene, Krüppel. This paper reports on our identification and cellular localization, through the utilization of specific antibodies, of the expression product of Xfin in the Xenopus laevis retina, and its pattern of expression during the retinal developmental stages. By immunostaining sections of the retina, we show that the major staining is localized in the cytoplasm of the cones. The protein appears at an early differentiation stage of the cones, when they can not be univocally identified by morphological criteria, and is maintained up to the adult retina. The same antigenicity pattern is detectable in the retina of the anuran genus Bufo. The immunostaining data are confirmed by Western blot analysis on Xenopus eye protein extracts. Because of its cytoplasmic localization, and because of the ability of Zn-finger proteins to bind nucleic acids, we think that Xfin may be involved in the terminal differentiation of the cones through RNA-protein interactions