title: Co-option of an anteroposterior head axis patterning system for proximodistal patterning of appendages in early bilaterian evolution.
abstract: The enormous diversity of extant animal forms is a testament to the power of evolution, and much of this diversity has been achieved through the emergence of novel morphological traits. The origin of novel morphological traits is an extremely important issue in biology, and a frequent source of this novelty is co-option of pre-existing genetic systems for new purposes (Carroll et al., 2008). Appendages, such as limbs, fins and antennae, are structures common to many animal body plans which must have arisen at least once, and probably multiple times, in lineages which lacked appendages. We provide evidence that appendage proximodistal patterning genes are expressed in similar registers in the anterior embryonic neurectoderm of Drosophila melanogaster and Saccoglossus kowalevskii (a hemichordate). These results, in concert with existing expression data from a variety of other animals suggest that a pre-existing genetic system for anteroposterior head patterning was co-opted for patterning of the proximodistal axis of appendages of bilaterian animals.
authors.affiliation: Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0349, USA.
authors.forename: Derek
authors.initials: D
authors.lastname: Lemons
authors.forename: Jens H
authors.initials: JH
authors.lastname: Fritzenwanker
authors.forename: John
authors.initials: J
authors.lastname: Gerhart
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Lowe
authors.forename: William
authors.initials: W
authors.lastname: McGinnis
mesh_terms: D000818:Animals; D005075:Biological Evolution; D019521:Body Patterning; D043344:Chordata / Q000196:embryology; D015509:Developmental Biology / Q000379:methods; D004331:Drosophila melanogaster / Q000196:embryology; D005121:Extremities / Q000196:embryology*; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect; D017403:In Situ Hybridization; D008954:Models, Biological; D008969:Molecular Sequence Data; D054258:Neural Plate / Q000378:metabolism; D009841:Oligonucleotides / Q000378:metabolism
chemical_list: D009841:Oligonucleotides