Starlet sea anemone1/8/2023 ![]() Within the ANTP class, there is evidence for a monophyletic subclass comprising Hox-related genes. The ANTP and PRD classes are substantially larger than the other classes, and these two classes are thought to be sister clades. The homeodomain is commonly 60 amino acids in length, though recognizable homeodomains may be as long as 97 or as short as 54 amino acids (reviewed in ).īased on phylogenetic analyses and chromosomal mapping studies, animal homeodomains can be divided among ten distinct classes: ANTP, CUT, HNF, LIM, POU, PRD, PROS, SINE, TALE, and ZF. The homeobox, which encodes a helix-turn-helix DNA-binding motif known as the homeodomain, originated prior to the evolutionary split between plants, fungi, and metazoans. Homeobox genes constitute an ancient superclass of regulatory genes with diverse developmental functions. Homeodomain loss is also apparent in the bilaterian taxa: eight homeodomain families shared by Drosophila and Nematostella appear absent from human (CG13424, EMXLX, HOMEOBRAIN, MSXLX, NK7, REPO, ROUGH, and UNC4), and six homeodomain families shared by human and Nematostella appear absent from fruit fly (ALX, DMBX, DUX, HNF, POU1, and VAX). Fifty-six homeodomain families found in human and/or fruit fly are also found in Nematostella, though seventeen families shared by human and fly appear absent in Nematostella. The homeodomain superclass underwent extensive radiations prior to the evolutionary split between Cnidaria and Bilateria. A putative Nematostella CUT class gene is also identified. For four of the Nematostella homeodomains, there is disagreement between neighbor-joining and Bayesian trees regarding their class membership. The Nematostella homeodomains appear to be distributed among established homeodomain classes in the following fashion: 72 ANTP class one HNF class four LIM class five POU class 33 PRD class five SINE class and six TALE class. Phylogenetic analyses were performed on 130 homeodomains from the sequenced genome of the sea anemone Nematostella vectensis along with 228 homeodomains from human and 97 homeodomains from Drosophila. Here we report the first near-complete set of homeodomains from a basal (diploblastic) animal. ![]() The origin of particular homeobox genes may, therefore, be associated with the evolution of particular animal traits. While this gene superclass predates the evolutionary split between animals, plants, and fungi, many homeobox genes appear unique to animals. ![]() Homeodomain transcription factors are key components in the developmental toolkits of animals.
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