title: Pitx1 broadly associates with limb enhancers and is enriched on hindlimb cis-regulatory elements.
abstract: Extensive functional analyses have demonstrated that the pituitary homeodomain transcription factor Pitx1 plays a critical role in specifying hindlimb morphology in vertebrates. However, much less is known regarding the target genes and cis-regulatory elements through which Pitx1 acts. Earlier studies suggested that the hindlimb transcription factors Tbx4, HoxC10, and HoxC11 might be transcriptional targets of Pitx1, but definitive evidence for direct regulatory interactions has been lacking. Using ChIP-Seq on embryonic mouse hindlimbs, we have pinpointed the genome-wide location of Pitx1 binding sites during mouse hindlimb development and identified potential gene targets for Pitx1. We determined that Pitx1 binding is significantly enriched near genes involved in limb morphogenesis, including Tbx4, HoxC10, and HoxC11. Notably, Pitx1 is bound to the previously identified HLEA and HLEB hindlimb enhancers of the Tbx4 gene and to a newly identified Tbx2 hindlimb enhancer. Moreover, Pitx1 binding is significantly enriched on hindlimb relative to forelimb-specific cis-regulatory features that are differentially marked by H3K27ac. However, our analysis revealed that Pitx1 also strongly associates with many functionally verified limb enhancers that exhibit similar levels of activity in the embryonic mesenchyme of forelimbs and hindlimbs. We speculate that Pitx1 influences hindlimb morphology both through the activation of hindlimb-specific enhancers as well as through the hindlimb-specific modulation of enhancers that are active in both sets of limbs.
authors.affiliation: Department of Genetics, University of Georgia, Coverdell Building, Room 250A, 500 DW Brooks Drive, Athens, GA 30602, USA.
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Infante
authors.forename: Sungdae
authors.initials: S
authors.lastname: Park
authors.forename: Alexandra G
authors.initials: AG
authors.lastname: Mihala
authors.forename: David M
authors.initials: DM
authors.lastname: Kingsley
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Menke
mesh_terms: D000818:Animals; D001665:Binding Sites; D047369:Chromatin Immunoprecipitation; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D005121:Extremities / Q000196:embryology*; D018507:Gene Expression Regulation, Developmental; D016678:Genome; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D008954:Models, Biological; D051761:Paired Box Transcription Factors / Q000378:metabolism* / Q000502:physiology; D011401:Promoter Regions, Genetic; D019076:Transgenes
chemical_list: D051761:Paired Box Transcription Factors; C101485:homeobox protein PITX1