Lab Affiliations

All Publications

  • GRHL2 and AP2a coordinate early surface ectoderm lineage commitment during development. iScience Collier, A. E., Piekos, S. N., Liu, A., Pattison, J. M., Felix, F., Bailetti, A. A., Sedov, E., Gaddam, S., Zhen, H., Oro, A. E. 2023; 26 (3): 106125


    Ectodermal dysplasias including skin abnormalities and cleft lip/palate result from improper surface ectoderm (SE) patterning. However, the connection between SE gene regulatory networks and disease remains poorly understood. Here, we dissect human SE differentiation with multiomics and establish GRHL2 as a key mediator of early SE commitment, which acts by skewing cell fate away from the neural lineage. GRHL2 and master SE regulator AP2a balance early cell fate output, with GRHL2 facilitating AP2a binding to SE loci. In turn, AP2a restricts GRHL2 DNA binding away from de novo chromatin contacts. Integration of these regulatory sites with ectodermal dysplasia-associated genomic variants annotated within the Biomedical Data Commons identifies 55 loci previously implicated in craniofacial disorders. These include ABCA4/ARHGAP29 and NOG regulatory regions where disease-linked variants directly affect GRHL2/AP2a binding and gene transcription. These studies elucidate the logic underlying SE commitment and deepen our understanding of human oligogenic disease pathogenesis.

    View details for DOI 10.1016/j.isci.2023.106125

    View details for PubMedID 36843855

  • Notch Dosage: Jagged1 Haploinsufficiency Is Associated With Reduced Neuronal Division and Disruption of Periglomerular Interneurons in Mice FRONTIERS IN CELL AND DEVELOPMENTAL BIOLOGY Blackwood, C. A., Bailetti, A., Nandi, S., Gridley, T., Hebert, J. M. 2020; 8: 113


    Neural stem cells in the lateral ganglionic eminence (LGE) generate progenitors that migrate through the rostral migratory stream (RMS) to repopulate olfactory bulb (OB) interneurons, but the regulation of this process is poorly defined. The evolutionarily conserved Notch pathway is essential for neural development and maintenance of neural stem cells. Jagged1, a Notch ligand, is required for stem cell maintenance. In humans, heterozygous mutations in JAGGED1 cause Alagille syndrome, a genetic disorder characterized by complications such as cognitive impairment and reduced number of bile ducts in the liver, suggesting the presence of a JAGGED1 haploinsufficient phenotype. Here, we examine the role of Jagged1 using a conditional loss-of-function allele in the nervous system. We show that heterozygous Jagged1 mice possess a haploinsufficient phenotype that is associated with a reduction in size of the LGE, a reduced proliferative state, and fewer progenitor cells in the LGE and RMS. Moreover, loss of Jagged1 leads to deficits in periglomerular interneurons in the OB. Our results support a dose-dependent role for Jagged1 in maintaining progenitor division within the LGE and RMS.

    View details for DOI 10.3389/fcell.2020.00113

    View details for Web of Science ID 000525112100001

    View details for PubMedID 32161758

    View details for PubMedCentralID PMC7054221

  • First person - Alessandro A. Bailetti DISEASE MODELS & MECHANISMS Bailetti, A. A. 2019; 12 (5)

    View details for DOI 10.1242/dmm.040535

    View details for Web of Science ID 000470069500015

  • Enhancer of Polycomb and the Tip60 complex repress hematological tumor initiation by negatively regulating JAK/STAT pathway activity DISEASE MODELS & MECHANISMS Bailetti, A. A., Negron-Pineiro, L. J., Dhruva, V., Harsh, S., Lu, S., Bosula, A., Bach, E. A. 2019; 12 (5)


    Myeloproliferative neoplasms (MPNs) are clonal hematopoietic disorders that cause excessive production of myeloid cells. Most MPN patients have a point mutation in JAK2 (JAK2V617F ), which encodes a dominant-active kinase that constitutively triggers JAK/STAT signaling. In Drosophila, this pathway is simplified, with a single JAK, Hopscotch (Hop), and a single STAT transcription factor, Stat92E. The hopTumorous-lethal [hop Tum ] allele encodes a dominant-active kinase that induces sustained Stat92E activation. Like MPN patients, hopTum mutants have significantly more myeloid cells, which form invasive tumors. Through an unbiased genetic screen, we found that heterozygosity for Enhancer of Polycomb [E(Pc)], a component of the Tip60 lysine acetyltransferase complex (also known as KAT5 in humans), significantly increased tumor burden in hopTum animals. Hematopoietic depletion of E(Pc) or other Tip60 components in an otherwise wild-type background also induced blood cell tumors. The E(Pc) tumor phenotype was dependent on JAK/STAT activity, as concomitant depletion of hop or Stat92E inhibited tumor formation. Stat92E target genes were significantly upregulated in E(Pc)-mutant myeloid cells, indicating that loss of E(Pc) activates JAK/STAT signaling. Neither the hop nor Stat92E gene was upregulated upon hematopoietic E(Pc) depletion, suggesting that the regulation of the JAK/STAT pathway by E(Pc) is dependent on substrates other than histones. Indeed, E(Pc) depletion significantly increased expression of Hop protein in myeloid cells. This study indicates that E(Pc) works as a tumor suppressor by attenuating Hop protein expression and ultimately JAK/STAT signaling. Since loss-of-function mutations in the human homologs of E(Pc) and Tip60 are frequently observed in cancer, our work could lead to new treatments for MPN patients.This article has an associated First Person interview with the first author of the paper.

    View details for DOI 10.1242/dmm.038679

    View details for Web of Science ID 000470069500008

    View details for PubMedID 31072879

    View details for PubMedCentralID PMC6550037

  • A Genetic Screen Reveals an Unexpected Role for Yorkie Signaling in JAK/STAT-Dependent Hematopoietic Malignancies in Drosophila melanogaster G3-GENES GENOMES GENETICS Anderson, A. M., Bailetti, A. A., Rodkin, E., De, A., Bach, E. A. 2017; 7 (8): 2427–38


    A gain-of-function mutation in the tyrosine kinase JAK2 (JAK2V617F ) causes human myeloproliferative neoplasms (MPNs). These patients present with high numbers of myeloid lineage cells and have numerous complications. Since current MPN therapies are not curative, there is a need to find new regulators and targets of Janus kinase/Signal transducer and activator of transcription (JAK/STAT) signaling that may represent additional clinical interventions . Drosophila melanogaster offers a low complexity model to study MPNs as JAK/STAT signaling is simplified with only one JAK [Hopscotch (Hop)] and one STAT (Stat92E). hopTumorous-lethal( Tum-l ) is a gain-of-function mutation that causes dramatic expansion of myeloid cells, which then form lethal melanotic tumors. Through an F1 deficiency (Df) screen, we identified 11 suppressors and 35 enhancers of melanotic tumors in hopTum-l animals. Dfs that uncover the Hippo (Hpo) pathway genes expanded (ex) and warts (wts) strongly enhanced the hopTum-l tumor burden, as did mutations in ex, wts, and other Hpo pathway genes. Target genes of the Hpo pathway effector Yorkie (Yki) were significantly upregulated in hopTum-l blood cells, indicating that Yki signaling was increased. Ectopic hematopoietic activation of Yki in otherwise wild-type animals increased hemocyte proliferation but did not induce melanotic tumors. However, hematopoietic depletion of Yki significantly reduced the hopTum-l tumor burden, demonstrating that Yki is required for melanotic tumors in this background. These results support a model in which elevated Yki signaling increases the number of hemocytes, which become melanotic tumors as a result of elevated JAK/STAT signaling.

    View details for DOI 10.1534/g3.117.044172

    View details for Web of Science ID 000407314000003

    View details for PubMedID 28620086

    View details for PubMedCentralID PMC5555452