title: Hippo pathway genes developed varied exon numbers and coevolved functional domains in metazoans for species specific growth control.
abstract: BACKGROUND
  The Hippo pathway controls growth by mediating cell proliferation and apoptosis. Dysregulation of Hippo signaling causes abnormal proliferation in both healthy and cancerous cells. The Hippo pathway receives inputs from multiple developmental pathways and interacts with many tissue-specific transcription factors, but how genes in the pathway have evolved remains inadequately revealed.
  
  
  RESULTS
  To explore the origin and evolution of Hippo pathway, we have extensively examined 16 Hippo pathway genes, including upstream regulators and downstream targets, in 24 organisms covering major metazoan phyla. From simple to complex organisms, these genes are varied in the length and number of exons but encode conserved domains with similar higher-order organization. The core of the pathway is more conserved than its upstream regulators and downstream targets. Several components, despite existing in the most basal metazoan sponges, cannot be convincingly identified in other species. Potential recombination breakpoints were identified in some genes. Coevolutionary analysis reveals that most functional domains in Hippo genes have coevolved with interacting functional domains in other genes.
  
  
  CONCLUSIONS
  The two essential upstream regulators cadherins fat and dachsous may have originated in the unicellular organism Monosiga brevicollis and evolved more significantly than the core of the pathway. Genes having varied numbers of exons in different species, recombination events, and the gain and loss of some genes indicate alternative splicing and species-specific evolution. Coevolution signals explain some species-specific loss of functional domains. These results significantly unveil the structure and evolution of the Hippo pathway in distant phyla and provide valuable clues for further examination of Hippo signaling.
authors.affiliation: Bioinformatics Section, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, China.
authors.forename: Henan
authors.initials: H
authors.lastname: Zhu
authors.forename: Ziwei
authors.initials: Z
authors.lastname: Zhou
authors.forename: Daxi
authors.initials: D
authors.lastname: Wang
authors.forename: Wenyin
authors.initials: W
authors.lastname: Liu
authors.forename: Hao
authors.initials: H
authors.lastname: Zhu
mesh_terms: D000818:Animals; D017209:Apoptosis; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation; D019143:Evolution, Molecular; D006801:Humans; D010802:Phylogeny; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D015820:Cadherins; D017346:Protein Serine-Threonine Kinases
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