Amin Ghabrial, PhD

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Overview

Academic Appointments

  • Assistant Professor of Pathology & Cell Biology at CUMC

Dr. Ghabrial earned his Ph.D. at Princeton University in the Department of Molecular Biology in the laboratory of Dr. Trudi Schüpbach. His graduate work focused on the checkpoint-dependent coupling of double stranded DNA break repair during meiosis to the establishment of axial polarity in the fruitfly during oogenesis. Dr. Ghabrial did his postdoctoral work with Dr. Mark Krasnow in the Department of Biochemistry at Stanford University. His postdoctoral work focused on the design and completion of a saturation-scale screen for tube morphogenesis genes required during the development of the tracheal (respiratory) system. 

Dr. Ghabrial started his own group at the University of Pennsylvania in 2008. His group published studies on the role of the Rab35GAP, Whacked/TBC1D10, in the polarization of seamless tube growth, the role of endocytosis in shaping seamless tubes, and on the role of Drosophila CCM3 and its binding partner Wheezy/GckIII in regulating seamless tube shape. The human ortholog of CCM3 (Cerebral Cavernous Malformations 3) is one of three genes known to be affected in cases of familial cerebral cavernous malformations. Cerebral angiomas are found in as many as 1 in every 200 individuals, and is currently treated by brain surgery. The work of the Ghabrial lab has been supported by grants from the March of Dimes, the American Cancer Society and the NIH.

Dr. Ghabrial moved to Columbia in July of 2017 and is currently focusing on the regulation of tube morphogenesis using novel optogenetic tools, as well as the further elaboration of the CCM3/GckIII pathway.

Email: asg2236@cumc.columbia.edu

Gender

  • Male

Credentials & Experience

Education & Training

  • AB, Biology/English Literature, Washington University - St. Louis
  • PhD, 2000 Molecular Biology, Princeton University

Honors & Awards

1985-1989  National Merit Scholar

1985-1989  Semcor Scholarship

1989           A.B, Washington University cum laude

2000-2003  NIH NRSA postdoctoral fellowship

2009           McCabe Fellow

2009-2011  Basil O’Connor Scholar of the March of Dimes

2013-2017  Research Scholar of the American Cancer Society

Research

Most organs are composed of interconnected networks of tubes of differing sizes, shapes and cellular architectures; my laboratory aims to understand the genetic, cell biological and molecular mechanisms by which these tubes are generated, shaped, and maintained. We use the Drosophila tracheal system as a model, and have initiated a systematic analysis rooted in a classical forward genetic approach, with follow-up studies utilizing cutting edge cell biological and molecular genetic approaches.

Tip cell selection.  During primary branching of the tracheal system, much like during sprouting angiogenesis, tip cells initiate the outgrowth of new tubes.  Thus, the initial step in the budding of new branches is the selection of a few tip cells from an epithelium in which most if not all cells are competent to behave as tip cells. In the fly tracheal system, Breathless-FGFR and Notch are key receptors that promote or inhibit tip cell selection, respectively (1). We seek to uncover other factors that regulate tip cell selection, and also to identify the genes required to carry out tip cell behaviors. We have identified mutations that result in the selection of excess tip cells in homozygous mutant embryos, and other mutations for which homozygous cells within mosaic animals are disproportionately present at branch tips. We are also carrying out pilot screens to identify genes required for cells to behave as tip cells. In addition, we are developing an optogenetic system to allow activation of the FGFR pathway with precise spatial and temporal resolution, permitting perturbation of tip cell competition in vivo in real time. The preliminary data from these studies will form the basis of a new R01 proposal.

Morphogenesis of seamless tubes. A major interest in the lab is the cell biology of “seamless” tubes. These tubes form intracellularly and lumenize by a process of cell hollowing during which an apical/lumenal membrane is extended internally. Seamless tubes are found throughout the animal kingdom, with the best-characterized examples including the terminal cell tubes of the Drosophila tracheal system and the seamless endothelial cell tubes of the vertebrate vascular system. We have identified mutations in ~ 20 complementation groups in Drosophila that have defects in seamless tube formation or morphology, and have been cloning and characterizing them to pioneer an understanding of how cells generate and shape seamless tubes2. We have published 4 major studies describing the regulation of the apical membrane domain and apical proteins in growing seamless tubes (3-6). One study revealed a novel mechanism for guiding growth of seamless tubes along the proximal-distal axis, and established a requirement for minus-end directed trafficking along microtubules for tube growth (3). 

A second study identified an essential role of endocytosis in regulating the levels of apical proteins (Crumbs, Phospho-Moesin), which in turn regulate stiffness of the apical actin cytoskeleton, thereby constraining tube shape and growth (4). We have also broken new ground on the question of how seamed and seamless tubes connect within terminal cells, and published the characterization of the first set of mutations in which seamed and seamless tubes fail to connect, fail to maintain that connection, or become grossly dilated at the site of connection. One of these studies uncovered a key role of the TOR pathway, via regulation of vATPase function (6), in terminal cell/stalk cell connection.  We found that when a terminal cell’s ability to expand the apical membrane domain is compromised, a neighboring wild type stalk cell is induced to undergo hypertrophy and ectopic branching. Wounding of the terminal cell was also able to elicit the compensatory branching program in the neighboring stalk cell. In both cases, this implies communication from the mutant or wounded cell to the neighboring healthy wild type neighbor. Another study revealed that the Cerebral Cavernous Malformation 3 (CCM3) pathway regulates tube morphology in the fly trachea (5) just as it does in the human vascular system.

How cells activate the seamless tube formation program remains an open question, and how seamless tubes are then elaborated and maintained remain incompletely understood. To elucidate these processes we plan to characterize additional complementation groups from the screen, as well as to examine the genesis and growth of seamless tubes by live imaging in wild type and mutant backgrounds.  An ongoing project dissecting the function of ichor2 is leading us to define the role of apical extracellular matrix in seamless tube morphogenesis (Rosa and Ghabrial; in preparation). To follow formation and growth of seamless tubes in real time, we have generated tagged reporters including the Rab35GAP TBC1D1/Whacked (that we show is localized apically) and an apically localized transmembrane protein (Tweedle-D). Our optogenetic FGFR system will allow us to induce formation of new seamless tubes, by blue light treatment of a small area of a growing terminal cell, and to follow local changes in vesicle trafficking and the cytoskeletal architecture. These studies are supported by a recently renewed R01 award.

Cerebral Cavernous Malformations 3 and Germinal Center Kinase III. Our studies of the CCM3 pathway in Drosophila provide novel insights into the cell biology of CCM3-deficiency and have important implications for human disease. Identification of CCM3-suppressors may lead to novel therapeutic approaches for a disease that affects as many as 1 in every 200 individuals in the general population, and that is currently treated, when possible, by brain surgery. We identified the CCM3/GCKIII pathway as playing a critical role in the regulation of tube morphology in tracheal terminal cells at the site of seamed/seamless tube connection, as well as in seamless tubes. Current work in the lab focuses on the regulation of Rab11 and the FIP, Nuclear Fallout (Song and Ghabrial, unpublished) by GCKIII, and the roles of Mo25, Tao1 and the Hippo pathway (with Kieran Harvey at the Peter MacCallum Cancer Centre) acting upstream of GCKIII. In follow-up studies we aim to: 1) identify substrates of GCKIII kinase activity, 2) identify other genes – both upstream and downstream of CCM3, 3) determine how CCM3 potentiates GCKIII kinase activity, and 4) test models derived from our fly studies in the vertebrate (zebrafish) vascular system. These studies are supported by an award from the American Cancer Society, and form the basis of an R01 proposal that is currently in preparation.  In unpublished work, we generated constitutively active GCKIII transgenic strains, and will use them to identify enhancers and suppressors of GCKIII, which are likely to encode other genes acting in the CCM3/GCKIII pathway, a subset of which may be GCKIII substrates.  We will also characterize a phospho-specific GCKIII antibody that will allow us to better determine the subcellular site of GCKIII activity and to determine the identity of other factors required for GCKIII activation.

REFERENCES:

1) Ghabrial, A.S. & Krasnow, M.A. Social interactions among epithelial cells during tracheal branching morphogenesis. Nature 441, 746-749 (2006).

2) Ghabrial, A.S., Levi, B.P. & Krasnow, M.A. A systematic screen for tube morphogenesis and branching genes in the Drosophila tracheal system. PLoS Genetics 7, e1002087 (2011).

3) Schottenfeld-Roames, J. & Ghabrial, A.S. Whacked and Rab35 polarize dynein-motor-complex-dependent seamless tube growth. Nature Cell Biology 14, 386-393 (2012).

4) Schottenfeld-Roames, J., Rosa, J. & Ghabrial, A.S. Seamless tube shape is constrained by endocytosis-dependent regulation of active Moesin. Current Biology 24(15), 1756-64 (2014).

5) Song, Y., Eng, M. & Ghabrial, A.S. Focal Defects in Single-Celled Tubes Mutant for Cerebral Cavernous Malformation 3, GCKIII, or NSF2. Developmental Cell 25, 507-519 (2013).

6) Francis, D. & Ghabrial, A.S. Compensatory branching morphogenesis of stalk cells in the Drosophila trachea. Development 142, 2048-2057 (2015).

Research Interests

  • Regulation of tube morphogenesis using novel optogenetic tools, as well as the further elaboration of the CCM3/GckIII pathway.

Grants

R01 GM089782                                  Ghabrial (PI)                                                   8/2019 – 07/2023

Competition and morphogenesis in tip cell-mediated branching of tubular networks. Goals of the project: to pioneer an understanding of the genetic and molecular framework required to make, shape and maintain seamless tubes.

Role: PI

COMPETITION AND MORPHOGENESIS IN TIP CELL-MEDIATED BRANCHING OF TUBULAR NETWORKS (Federal Gov)

Jul 1 2017 - Jun 30 2019

Selected Publications

Burguete A.S., Francis, D., Rosa, J., and Ghabrial, A.S. (2019) The regulation of cell size and branch complexity in the terminal cells of the Drosophila tracheal system. Developmental Biology 451: 79-85.

Poon, C.L.C., Liu, W., Song, Y., Gomez, M., Kulaberoglu, Y., Zhang, X., Xu, W.,Verasksa, A., Hergovich, A., Ghabrial, AS*. and Harvey, K.F.* (2018) A Hippo-like signaling pathway controls tracheal development in Drosophila melanogaster. Developmental Cell 47: 564-75. *Co-Senior PIs.

Rosa, J. and Ghabrial, A.S. (2018) An Ichor-dependent apical extracellular matrix regulates seamless tube shape and integrity. PLoS Genetics 14(1):e1007146.

Francis, D. and Ghabrial, A.S. (2015) Compensatory branching morphogenesis of stalk cells in the Drosophila trachea. Development 142: 2048-2057.

Schottenfeld-Roames, J., Rosa, J. and Ghabrial, A.S. (2014) Seamless tube shape is constrained by endocytosis-dependent regulation of active Moesin. Current Biology 24(15): 1756-64.

Song Y, Eng M, and Ghabrial, A.S. (2013) Focal Defects in Single-Celled Tubes Mutant for Cerebral Cavernous Malformation 3, GCKIII, or NSF2. Developmental Cell 25(5):507-19.

Schottenfeld-Roames J and Ghabrial, A.S. (2012) Whacked and Rab35 polarize dynein-motor-complex-dependent seamless tube growth. Nature Cell Biology 14(4): 386-93.

Ghabrial, A.S., Levi, B.P., and Krasnow, M.A. (2011) A systematic screen for tube morphogenesis and branching genes in the Drosophila tracheal system. PLoS Genetics 7(7): e1002087.

Ghabrial, A.S., and Krasnow, M.A. (2006) Social interactions among epithelial cells during tracheal branching morphogenesis. Nature 441: 746-9.

Leading Edge summary: R.P. Kruger (2006) In Migration, Its Lead, Follow, or Get out of the Way. Cell 125: 1211.

Levi, B.P., Ghabrial, A.S., and Krasnow, M.A. (2006) Drosophila talin and integrin genes are required for maintenance of tracheal terminal branches and luminal organization. Development 133: 2383-93.

Abdu, U*., Gonzalez-Reyes, A*., Ghabrial, A.S., and Schüpbach, T. (2003) The Drosophila spn-D gene encodes a RAD51C-like protein that is required exclusively during meiosis. Genetics 165: 197-204.

Ghabrial, A.S. and Schüpbach, T. (1999) Activation of a meiotic checkpoint regulates translation of Gurken during Drosophila oogenesis. Nat Cell Biol. 1:354-7

     News and Views article: Gonzalez-Reyes, A. (1999) DNA repair and pattern formation come together. Nature Cell Biology 1, E150 - E152.

Ghabrial, A.S., Ray, R.P., and Schüpbach, T. (1998) okra and spindle-B encode components of the RAD52 DNA repair pathway and affect meiosis and patterning in Drosophila oogenesis. Genes & Development 12: 2711-23.

Queenan, A.M., Ghabrial, A.S., and Schüpbach, T. (1997) Ectopic activation of torpedo/Egfr, a Drosophila receptor tyrosine kinase, dorsalizes both the eggshell and the embryo. Development 124: 3871-80.