Mechanisms of Pbx-directed Genetic &Transcriptional Control of Limb Development

Summary

Principal Investigator: Licia Selleri
Abstract: DESCRIPTION (provided by applicant): In vertebrates, Hox genes play major roles in the formation of most vital organs. It has been proposed that the exquisite DNA-binding specificities that allow different Hox proteins to regulate specific target genes, thus instructing the identity of distinct body structures, depend on interactions with other homeoproteins, which act as Hox cofactors. For the last fifteen years, based on molecular and biochemical analyses, the prevailing view has been that TALE homeodomain proteins, which comprise the products encoded by the Pbx gene family, act as ancillary cofactors for Hox. Pbx1 is a homolog of Drosophila extradenticle (exd), which has critical roles in patterning of the fly body. While exd is the sole Pbx-encoding gene in the fly, the mouse has four such genes (Pbx1-4). Despite their paramount roles in organogenesis and patterning of the body and limb axes, the molecular mechanisms of Hox regulation remain elusive. Our objectives are to use the mouse limb as the most tractable and established system to delineate whether regulation of Hox "collinear" expression, a basic and mysterious biological phenomenon, is governed by Pbx. We have established that different Pbx genes, similarly to Hox genes, share overlapping roles in limb patterning and outgrowth. Accordingly, Pbx1/Pbx2 double homozygous (Pbx1-/-;Pbx2-/-) embryos lack limbs altogether, while Pbx1-/-;Pbx2 mutants exhibit limb truncations similar to those of HoxA/D mutants. Additionally, we have found that Pbx1/Pbx2 control the onset and spatial distribution of 5'HoxA/D expression in limb mesenchyme. These findings establish that Pbx proteins hierarchically govern 5'HoxA/D gene expression in the limb. In view of these new findings, our hypothesis proposes a novel mechanism for Hox gene regulation, whereby 5'Hox expression is directly controlled at the transcriptional level by Pbx in the bud mesenchyme for limb morphogenesis and digit formation. We will test our hypothesis using embryologic, genetic and molecular approaches in the mouse. First, by molecular methods, we will determine whether Pbx1/2 regulate 5'HoxD transcription by direct control of the HoxD GCR, a genomic region that governs HoxD collinear expression in the autopod. We will then test whether Pbx binding to the HoxD GCR has functional bearings on transcription by both transient transfections in cell culture and transient transgenesis experiments in the mouse. Moreover, by tissue-specific and inducible genetic ablation, using our new Pbx1 conditional allele (on a Pbx2-deficient background), and available Cre lines (one of which inducible in the mesenchyme), we will dissect Pbx1/Pbx2 spatial and temporal requirements in the limb field and bud mesenchyme. By this approach, we will determine when Hox expression is first affected by Pbx loss in the limb bud. Completion of these studies will define novel regulatory networks that govern transcription of Hox genes and will directly contribute to the understanding of human congenital limb malformations. Broadly, given the involvement of human HOX genes in leukemias and solid tumors, our studies will inform general comprehension of HOX regulation also in human neoplasia.
Funding Period: 2003-04-01 - 2016-12-31
more information: NIH RePORT

Top Publications

  1. ncbi Spatio-temporal expression of Pbx3 during mouse organogenesis
    Giuseppina Di Giacomo
    Department of Cell and Developmental Biology, Cornell University Weill Medical School, New York, NY 10021, USA
    Gene Expr Patterns 6:747-57. 2006
  2. pmc The hSSB1 orthologue Obfc2b is essential for skeletogenesis but dispensable for the DNA damage response in vivo
    Niklas Feldhahn
    Laboratory of Molecular Immunology, Rockefeller University, New York, NY 10065, USA
    EMBO J 31:4045-56. 2012
  3. pmc Congenital asplenia in mice and humans with mutations in a Pbx/Nkx2-5/p15 module
    Matthew Koss
    Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, NY 10065, USA
    Dev Cell 22:913-26. 2012
  4. pmc A conserved Pbx-Wnt-p63-Irf6 regulatory module controls face morphogenesis by promoting epithelial apoptosis
    Elisabetta Ferretti
    Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, NY 10065, USA
    Dev Cell 21:627-41. 2011
  5. pmc Hox and Pbx factors control retinoic acid synthesis during hindbrain segmentation
    Antonio Vitobello
    Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
    Dev Cell 20:469-82. 2011
  6. pmc Control of pelvic girdle development by genes of the Pbx family and Emx2
    Terence D Capellini
    Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, USA
    Dev Dyn 240:1173-89. 2011
  7. pmc Pbx homeodomain proteins: TALEnted regulators of limb patterning and outgrowth
    Terence D Capellini
    Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, USA
    Dev Dyn 240:1063-86. 2011
  8. pmc Cytomegalovirus viruria and DNAemia in healthy seropositive women
    Nitin Arora
    Department of Pediatrics, University of Alabama at Birmingham, Alabama 35233, USA
    J Infect Dis 202:1800-3. 2010
  9. pmc Scapula development is governed by genetic interactions of Pbx1 with its family members and with Emx2 via their cooperative control of Alx1
    Terence D Capellini
    Department of Cell and Developmental Biology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA
    Development 137:2559-69. 2010
  10. pmc Cytomegalovirus reinfections in healthy seroimmune women
    Shannon A Ross
    Departments of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA
    J Infect Dis 201:386-9. 2010

Research Grants

  1. Pax6 as a key regulator of lens development
    Ales Cvekl; Fiscal Year: 2013

Detail Information

Publications18

  1. ncbi Spatio-temporal expression of Pbx3 during mouse organogenesis
    Giuseppina Di Giacomo
    Department of Cell and Developmental Biology, Cornell University Weill Medical School, New York, NY 10021, USA
    Gene Expr Patterns 6:747-57. 2006
    ..Finally, Pbx3 is expressed only in the forelimb buds during early limb development, while the hindlimb bud is devoid of Pbx3. This finding leads us to add Pbx3 to the sparse list of early forelimb-specific molecular markers...
  2. pmc The hSSB1 orthologue Obfc2b is essential for skeletogenesis but dispensable for the DNA damage response in vivo
    Niklas Feldhahn
    Laboratory of Molecular Immunology, Rockefeller University, New York, NY 10065, USA
    EMBO J 31:4045-56. 2012
    ..While being dispensable in most other cell lineages, its absence leads to a compensatory increase in Obfc2a protein, a homologue required for the maintenance of genomic integrity...
  3. pmc Congenital asplenia in mice and humans with mutations in a Pbx/Nkx2-5/p15 module
    Matthew Koss
    Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, NY 10065, USA
    Dev Cell 22:913-26. 2012
    ..This study establishes that a Pbx/Nkx2-5/p15 regulatory module is essential for spleen development...
  4. pmc A conserved Pbx-Wnt-p63-Irf6 regulatory module controls face morphogenesis by promoting epithelial apoptosis
    Elisabetta Ferretti
    Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, NY 10065, USA
    Dev Cell 21:627-41. 2011
    ..Dysregulation of this network leads to localized suppression of midfacial apoptosis and CL/P. Ectopic Wnt ectodermal expression in Pbx mutants rescues the clefting, opening avenues for tissue repair...
  5. pmc Hox and Pbx factors control retinoic acid synthesis during hindbrain segmentation
    Antonio Vitobello
    Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
    Dev Cell 20:469-82. 2011
    ..These findings reveal a feed-forward mechanism linking Hox-Pbx-dependent RA synthesis during early axial patterning with the establishment of spatially restricted Hox-Pbx activity in the developing hindbrain...
  6. pmc Control of pelvic girdle development by genes of the Pbx family and Emx2
    Terence D Capellini
    Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, USA
    Dev Dyn 240:1173-89. 2011
    ..Lastly, we identify potential Pbx1-Emx2-regulated enhancers for Tbx15, Prrx1, and Pax1, using bioinformatics analyses...
  7. pmc Pbx homeodomain proteins: TALEnted regulators of limb patterning and outgrowth
    Terence D Capellini
    Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, USA
    Dev Dyn 240:1063-86. 2011
    ..Interestingly, at least in limb buds, Pbx appear to act not only as Hox cofactors, but also in the upstream control of 5' HoxA/D gene expression...
  8. pmc Cytomegalovirus viruria and DNAemia in healthy seropositive women
    Nitin Arora
    Department of Pediatrics, University of Alabama at Birmingham, Alabama 35233, USA
    J Infect Dis 202:1800-3. 2010
    ..In young seropositive women, CMV DNAemia and viruria are common, which suggests that naturally acquired immunity to CMV does not alter shedding patterns...
  9. pmc Scapula development is governed by genetic interactions of Pbx1 with its family members and with Emx2 via their cooperative control of Alx1
    Terence D Capellini
    Department of Cell and Developmental Biology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA
    Development 137:2559-69. 2010
    ..Our results establish an essential role for Pbx1 in genetic interactions with its family members and with Emx2 and delineate novel regulatory networks in shoulder girdle development...
  10. pmc Cytomegalovirus reinfections in healthy seroimmune women
    Shannon A Ross
    Departments of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA
    J Infect Dis 201:386-9. 2010
    ..None of the exposure factors were associated with CMV reinfection. Women with antibodies against at least 1 of the 4 antigens at baseline had a 63% decreased risk of reinfection, suggesting a protective role for strain-specific immunity...
  11. pmc Conservation of notochord gene expression across chordates: insights from the Leprecan gene family
    Terence D Capellini
    Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York 10065, USA
    Genesis 46:683-96. 2008
    ..These results have interesting implications for the evolution and development of chordates...
  12. ncbi Pbx1/Pbx2 govern axial skeletal development by controlling Polycomb and Hox in mesoderm and Pax1/Pax9 in sclerotome
    Terence D Capellini
    Department of Cell and Developmental Biology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA
    Dev Biol 321:500-14. 2008
    ....
  13. pmc B-cell development fails in the absence of the Pbx1 proto-oncogene
    Mrinmoy Sanyal
    Department of Pathology, Stanford University, School of Medicine, Stanford, CA 94305, USA
    Blood 109:4191-9. 2007
    ..Thus, Pbx1 critically functions at a stage between hematopoietic stem cell development and B-cell commitment and, therefore, is one of the earliest-acting transcription factors that regulate de novo B-lineage lymphopoiesis...
  14. ncbi Development and function of the mammalian spleen
    Andrea Brendolan
    Department of Cell and Developmental Biology, Cornell University, Weill Medical School, New York, NY, USA
    Bioessays 29:166-77. 2007
    ..The lack of these populations in asplenic mice and humans may go some way to explaining this susceptibility...
  15. pmc Hypomorphic mutation of the TALE gene Prep1 (pKnox1) causes a major reduction of Pbx and Meis proteins and a pleiotropic embryonic phenotype
    Elisabetta Ferretti
    Laboratory of Molecular Genetics, DIBIT, Via Olgettina 58, 20132 Milano, Italy
    Mol Cell Biol 26:5650-62. 2006
    ..Our data indicate that Prep1 is an essential gene that acts upstream of and within a Pbx-Meis network that regulates multiple aspects of embryonic development...
  16. ncbi Pbx1/Pbx2 requirement for distal limb patterning is mediated by the hierarchical control of Hox gene spatial distribution and Shh expression
    Terence D Capellini
    Department of Cell and Developmental Biology, Cornell University Weill Medical School, New York, NY 10021, USA
    Development 133:2263-73. 2006
    ....
  17. ncbi Hox cofactors in vertebrate development
    Cecilia B Moens
    Division of Basic Science and HHMI, Fred Hutchinson Cancer Research Center, Seattle, WA 98115, USA
    Dev Biol 291:193-206. 2006
    ....
  18. pmc ADAM17 controls endochondral ossification by regulating terminal differentiation of chondrocytes
    Katherine C Hall
    Arthritis and Tissue Degeneration Program, The Hospital for Special Surgery, New York, New York, USA
    Mol Cell Biol 33:3077-90. 2013
    ....

Research Grants30

  1. Pax6 as a key regulator of lens development
    Ales Cvekl; Fiscal Year: 2013
    ..abstract_text> ..