title: Long-range regulation by shared retinoic acid response elements modulates dynamic expression of posterior Hoxb genes in CNS development.
abstract: Retinoic acid (RA) signaling plays an important role in determining the anterior boundary of Hox gene expression in the neural tube during embryogenesis. In particular, RA signaling is implicated in a rostral expansion of the neural expression domain of 5׳ Hoxb genes (Hoxb9-Hoxb5) in mice. However, underlying mechanisms for this gene regulation have remained elusive due to the lack of RA responsive element (RARE) in the 5׳ half of the HoxB cluster. To identify cis-regulatory elements required for the rostral expansion, we developed a recombineering technology to serially label multiple genes with different reporters in a single bacterial artificial chromosome (BAC) vector containing the mouse HoxB cluster. This allowed us to simultaneously monitor the expression of multiple genes. In contrast to plasmid-based reporters, transgenic BAC reporters faithfully recapitulated endogenous gene expression patterns of the Hoxb genes including the rostral expansion. Combined inactivation of two RAREs, DE-RARE and ENE-RARE, in the BAC completely abolished the rostral expansion of the 5׳ Hoxb genes. Knock-out of endogenous DE-RARE lead to significantly reduced expression of multiple Hoxb genes and attenuated Hox gene response to exogenous RA treatment in utero. Regulatory potential of DE-RARE was further demonstrated by its ability to anteriorize 5׳ Hoxa gene expression in the neural tube when inserted into a HoxA BAC reporter. Our data demonstrate that multiple RAREs cooperate to remotely regulate 5׳ Hoxb genes during CNS development, providing a new insight into the mechanisms for gene regulation within the Hox clusters.
authors: Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
authors: Youngwook
authors: Y
authors: Ahn
authors: Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
authors: Hillary E
authors: HE
authors: Mullan
authors: Stowers Institute for Medical Research, Kansas City, MO 64110, USA; Department of Anatomy and Cell Biology, Kansas University Medical Center, Kansas City, KS 66160, USA. Electronic address: rek@stowers.org.
authors: Robb
authors: R
authors: Krumlauf
mesh_terms: D000818:Animals; D001483:Base Sequence; D022202:Chromosomes, Artificial, Bacterial / Q000648:ultrastructure; D004742:Enhancer Elements, Genetic; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009154:Mutation; D009474:Neurons / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D011995:Recombination, Genetic; D020218:Response Elements; D012176:Retinoids / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction; D019076:Transgenes; D014212:Tretinoin / Q000378:metabolism*
chemical_list: D018398:Homeodomain Proteins; D012176:Retinoids; D014212:Tretinoin
keywords: Central nervous system; Enhancer sharing; Enhancers; Gene regulation; Hox genes; Long-range regulation; Retinoids; Transgenic reporters