title: Amino acid repeats cause extraordinary coding sequence variation in the social amoeba Dictyostelium discoideum.
abstract: Protein sequences are normally the most conserved elements of genomes owing to purifying selection to maintain their functions. We document an extraordinary amount of within-species protein sequence variation in the model eukaryote Dictyostelium discoideum stemming from triplet DNA repeats coding for long strings of single amino acids. D. discoideum has a very large number of such strings, many of which are polyglutamine repeats, the same sequence that causes various human neurological disorders in humans, like Huntington's disease. We show here that D. discoideum coding repeat loci are highly variable among individuals, making D. discoideum a candidate for the most variable proteome. The coding repeat loci are not significantly less variable than similar non-coding triplet repeats. This pattern is consistent with these amino-acid repeats being largely non-functional sequences evolving primarily by mutation and drift.
authors.affiliation: Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas, United States of America.
authors.forename: Clea
authors.initials: C
authors.lastname: Scala
authors.forename: Xiangjun
authors.initials: X
authors.lastname: Tian
authors.forename: Natasha J
authors.initials: NJ
authors.lastname: Mehdiabadi
authors.forename: Margaret H
authors.initials: MH
authors.lastname: Smith
authors.forename: Gerda
authors.initials: G
authors.lastname: Saxer
authors.forename: Katie
authors.initials: K
authors.lastname: Stephens
authors.forename: Prince
authors.initials: P
authors.lastname: Buzombo
authors.forename: Joan E
authors.initials: JE
authors.lastname: Strassmann
authors.forename: David C
authors.initials: DC
authors.lastname: Queller
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D004023:Dictyostelium / Q000235:genetics*; D040961:Genetic Drift; D056426:Genetic Loci; D014644:Genetic Variation; D018503:Genome, Protozoan; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames; D010455:Peptides / Q000235:genetics*; D010802:Phylogeny; D018911:Trinucleotide Repeats
chemical_list: D010455:Peptides; C097188:polyglutamine