M. Behrens et al., COMPARATIVE-ANALYSIS OF PAX-6 SEQUENCE AND EXPRESSION IN THE EYE DEVELOPMENT OF THE BLIND CAVE FISH ASTYANAX-FASCIATUS AND ITS EPIGEAN CONSPECIFIC, Molecular biology and evolution, 14(3), 1997, pp. 299-308
The Pax-6 gene encodes a transcription factor essential for eye develo
pment in a wide range of animal phyla. In order to elucidate a possibl
e role of Pax-6 in the eye regression of a blind cave form of the fres
hwater fish Astyanax fasciatus (Characidae, Teleostei) we investigated
the expression of Pax-6 in eyes and brains of different larval stages
by in situ hybridization. Pattern, strength, and time course of Pax-6
expression were not altered in the tissues of the cave form when comp
ared to the epigean form. Pax-6 was even expressed in the highly degen
erated eyes of late larval stages of the cave form. Comparative sequen
ce analysis of Pax-6 cDNA clones of both forms of Astyanax fasciatus s
howed the complete integrity of cave fish Pax-6 mRNA. These results su
ggest that Pax-6 is not involved in the evolutionary process of eye de
generation in this model system of cave-living fishes. Comparison of t
he Astyanax Pax-6 cDNA with the other available fish Pax-6 sequence fr
om zebrafish revealed putative fish-specific regions of homology. A st
retch of 19 N-terminal amino acids is nearly identical on the nucleoti
de and amino acid levels in both fish species but not present in all o
ther known Pax-6 sequences.