Identification of distant Agouti-like sequences and re-evaluation of the evolutionary history of the Agouti-related peptide (AgRP)

PLoS One. 2012;7(7):e40982. doi: 10.1371/journal.pone.0040982. Epub 2012 Jul 16.

Abstract

The Agouti-like peptides including AgRP, ASIP and the teleost-specific A2 (ASIP2 and AgRP2) peptides have potent and diverse functional roles in feeding, pigmentation and background adaptation mechanisms. There are contradictory theories about the evolution of the Agouti-like peptide family as well the nomenclature. Here we performed comprehensive mining and annotation of vertebrate Agouti-like sequences. We identified A2 sequences from salmon, trout, seabass, cod, cichlid, tilapia, gilt-headed sea bream, Antarctic toothfish, rainbow smelt, common carp, channel catfish and interestingly also in lobe-finned fish. Moreover, we surprisingly found eight novel homologues from the kingdom of arthropods and three from fungi, some sharing the characteristic C-x(6)-C-C motif which are present in the Agouti-like sequences, as well as approximate sequence length (130 amino acids), positioning of the motif sequence and sharing of exon-intron structures that are similar to the other Agouti-like peptides providing further support for the common origin of these sequences. Phylogenetic analysis shows that the AgRP sequences cluster basally in the tree, suggesting that these sequences split from a cluster containing both the ASIP and the A2 sequences. We also used a novel approach to determine the statistical evidence for synteny, a sinusoidal Hough transform pattern recognition technique. Our analysis shows that the teleost AgRP2 resides in a chromosomal region that has synteny with Hsa 8, but we found no convincing synteny between the regions that A2, AgRP and ASIP reside in, which would support that the Agouti-like peptides were formed by whole genome tetraplodization events. Here we suggest that the Agouti-like peptide genes were formed through classical subsequent gene duplications where the AgRP is the most distantly related to the three other members of that group, first splitting from a common ancestor to ASIP and A2, and then later the A2 split from ASIP followed by a split resulting in ASIP2 and AgRP2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agouti Signaling Protein / chemistry*
  • Agouti Signaling Protein / metabolism
  • Agouti-Related Protein / chemistry*
  • Agouti-Related Protein / metabolism
  • Algorithms
  • Amino Acid Motifs
  • Amino Acid Sequence
  • Animals
  • Bass
  • Chromosome Mapping
  • Evolution, Molecular
  • Humans
  • Models, Statistical
  • Molecular Sequence Data
  • Multigene Family
  • Pattern Recognition, Automated
  • Peptides / chemistry
  • Phylogeny
  • Sequence Homology, Amino Acid
  • Software

Substances

  • Agouti Signaling Protein
  • Agouti-Related Protein
  • Peptides