CLONING OF THE ALPHA-A-CRYSTALLIN GENES OF A BLIND CAVE FORM AND THE EPIGEAN FORM OF ASTYANAX-FASCIATUS - A COMPARATIVE-ANALYSIS OF STRUCTURE, EXPRESSION AND EVOLUTIONARY CONSERVATION

In the present study we have analyzed the integrity and expression of the alpha A-crystallin gene, that codes for a major structural compone nt of the lens, in a blind cave form of the teleostean fish, Astyanax fasciatus. This is the first alpha A-crystallin gene cloned from a tel eostean fish. Sequence comparison of this cave-form gene with its epig ean conspecific and with homologs of distantly related taxa has illust rated conservation of regulatory and coding regions. Although no cryst allin proteins are produced in the lens of the cave form, and the mRNA of this gene could not be detected by in situ hybridization of differ ent developmental stages, the promoter region of cave-fish alpha A-cry stallin is functionally intact. The deduced amino-acid sequence of the alpha A-crystallin gene of the cave form differs from that of its epi gean conspecific at only one position (139). This is within an importa nt, small heat-shock protein-related region, HCR2. A comparison of the 5'-flanking regions of the A. fasciatus alpha A-crystallin gene with the chicken homolog revealed the high conservation of lens-specific re gulatory sequences and further demonstrates the evolutionary conservat ion of this gene. (C) 1998 Elsevier Science B.V. All rights reserved.