Evolutionary analyses of hedgehog and Hoxd-10 genes in fish species closely related to the zebrafish
Abstract
The study of development has relied primarily on the isolation of mutations in genes with specific functions in development and on the comparison of their expression patterns in normal and mutant phenotypes. Comparative evolutionary analyses can complement these approaches. Phylogenetic analyses of Sonic hedgehog (Shh) and Hoxd-10 genes from 18 cyprinid fish species closely related to the zebrafish provide novel insights into the functional constraints acting on Shh. Our results confirm and extend those gained from expression and crystalline structure analyses of this gene. Unexpectedly, exon 1 of Shh is found to be almost invariant even in third codon positions among these morphologically divergent species suggesting that this exon encodes for a functionally important domain of the hedgehog protein. This is surprising because the main functional domain of Shh had been thought to be that encoded by exon 2. Comparisons of Shh and Hoxd-10 gene sequences and of resulting gene trees document higher evolutionary constraints on the former than on the latter. This might be indicative of more general evolutionary patterns in networks of developmental regulatory genes interacting in a hierarchical fashion. The presence of four members of the hedgehog gene family in cyprinid fishes was documented and their homologies to known hedgehog genes in other vertebrates were established.
Footnotes
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↵ * To whom reprint requests should be addressed. e-mail: ameyer{at}life.bio.sunysb.edu.
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Ernst Mayr, Museum of Comparative Zoology, Cambridge, MA
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Abbreviations: MP, maximum parsimony; NJ, neighbor joining; ML, maximum likelihood.
Data deposition: The sequences reported in this paper have been deposited in the GenBank data base (accession nos. U51339–U51423U51339 U51340 U51341 U51342 U51343 U51344 U51345 U51346 U51347 U51348 U51349 U51350 U51351 U51352 U51353 U51354 U51355 U51356 U51357 U51358 U51359 U51360 U51361 U51362 U51363 U51364 U51365 U51366 U51367 U51368 U51369 U51370 U51371 U51372 U51373 U51374 U51375 U51376 U51377 U51378 U51379 U51380 U51381 U51382 U51383 U51384 U51385 U51386 U51387 U51388 U51389 U51390 U51391 U51392 U51393 U51394 U51395 U51396 U51397 U51398 U51399 U51400 U51401 U51402 U51403 U51404 U51405 U51406 U51407 U51408 U51409 U51410 U51411 U51412 U51413 U51414 U51415 U51416 U51417 U51418 U51419 U51420 U51421 U51422 U51423 and U68236–U68241U68236 U68237 U68238 U68239 U68240 U68241).
- Copyright © 1996, The National Academy of Sciences of the USA
