title: The C. elegans Hox gene ceh-13 regulates cell migration and fusion in a non-colinear way. Implications for the early evolution of Hox clusters.
abstract: BACKGROUND
  Hox genes play a central role in axial patterning during animal development. They are clustered in the genome and specify cell fate in sequential domains along the anteroposterior (A-P) body axis in a conserved order that is co-linear with their relative genomic position. In the soil worm Caenorhabditis elegans, this striking rule of co-linearity is broken by the anterior Hox gene ceh-13, which is located between the two middle Hox paralogs, lin-39 and mab-5, within the loosely organized nematode Hox cluster. Despite its evolutionary and developmental significance, the functional consequence of this unusual genomic organization remains unresolved.
  
  
  RESULTS
  In this study we have investigated the role of ceh-13 in different developmental processes, and found that its expression and function are not restricted to the anterior body part. We show that ceh-13 affects cell migration and fusion as well as tissue patterning in the middle and posterior body regions too. These data reveal novel roles for ceh-13 in developmental processes known to be under the control of middle Hox paralogs. Consistently, enhanced activity of lin-39 and mab-5 can suppress developmental arrest and morphologic malformation in ceh-13 deficient animals.
  
  
  CONCLUSIONS
  Our findings presented here show that, unlike other Hox genes in C. elegans which display region-specific accumulation and function along the A-P axis, the expression and functional domain of the anterior Hox paralog ceh-13 extends beyond the anterior region of the worm. Furthermore, ceh-13 and the middle Hox paralogs share several developmental functions. Together, these results suggest the emergence of the middle-group Hox genes from a ceh-13-like primordial Hox ancestor.
authors.affiliation: Department of Genetics, Eötvös Loránd University, Budapest, H-1117, Hungary.
authors.forename: Borbála
authors.initials: B
authors.lastname: Tihanyi
authors.forename: Tibor
authors.initials: T
authors.lastname: Vellai
authors.forename: Agnes
authors.initials: A
authors.lastname: Regos
authors.forename: Eszter
authors.initials: E
authors.lastname: Ari
authors.forename: Fritz
authors.initials: F
authors.lastname: Müller
authors.forename: Krisztina
authors.initials: K
authors.lastname: Takács-Vellai
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000196:embryology*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D002465:Cell Movement; D004625:Embryo, Nonmammalian / Q000378:metabolism; D019143:Evolution, Molecular; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000378:metabolism*
chemical_list: C118851:CEH-13 protein, C elegans; D029742:Caenorhabditis elegans Proteins; D018398:Homeodomain Proteins