title: Characterization of microRNAs in cephalochordates reveals a correlation between microRNA repertoire homology and morphological similarity in chordate evolution.
abstract: Cephalochordates, urochordates, and vertebrates comprise the three extant groups of chordates. Although higher morphological and developmental similarity exists between cephalochordates and vertebrates, molecular phylogeny studies have instead suggested that the morphologically simplified urochordates are the closest relatives to vertebrates. MicroRNAs (miRNAs) are regarded as the major factors driving the increase of morphological complexity in early vertebrate evolution, and are extensively characterized in vertebrates and in a few species of urochordates. However, the comprehensive set of miRNAs in the basal chordates, namely the cephalochordates, remains undetermined. Through extensive sequencing of a small RNA library and genomic homology searches, we characterized 100 miRNAs from the cephalochordate amphioxus, Branchiostoma japonicum, and B. floridae. Analysis of the evolutionary history of the cephalochordate miRNAs showed that cephalochordates possess 54 miRNA families homologous to those of vertebrates, which is threefold higher than those shared between urochordates and vertebrates. The miRNA contents demonstrated a clear correlation between the extent of miRNA overlapping and morphological similarity among the three chordate groups, providing a strong evidence of miRNAs being the major genetic factors driving morphological complexity in early chordate evolution.
authors.affiliation: Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Dai
authors.forename: Zuozhou
authors.initials: Z
authors.lastname: Chen
authors.forename: Hua
authors.initials: H
authors.lastname: Ye
authors.forename: Longhai
authors.initials: L
authors.lastname: Zhou
authors.forename: Lixue
authors.initials: L
authors.lastname: Cao
authors.forename: Yiquan
authors.initials: Y
authors.lastname: Wang
authors.forename: Sihua
authors.initials: S
authors.lastname: Peng
authors.forename: Liangbiao
authors.initials: L
authors.lastname: Chen
mesh_terms: D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002816:Chordata, Nonvertebrate / Q000033:anatomy & histology* / Q000235:genetics*; D019295:Computational Biology; D017931:DNA Primers / Q000235:genetics; D019143:Evolution, Molecular; D015723:Gene Library; D035683:MicroRNAs / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D013045:Species Specificity
chemical_list: D017931:DNA Primers; D035683:MicroRNAs