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Alk1 Signaling in Vascular Development

Laux, Derek William (2013) Alk1 Signaling in Vascular Development. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Heterozygous loss of the endothelial-specific transforming growth factor-beta (TGF-β) Type 1 receptor, activin receptor-like kinase 1 (ALK1), results in the autosomal dominant disorder, hereditary hemorrhagic telangiectasia type 2 (HHT2), which is characterized by mucocutaneous telangiectasias as well as arteriovenous malformations (AVMs) in the brain, lungs, liver, gastrointestinal tract, and spinal cord. As a result, patients suffer from a range of clinical symptoms including epistaxis, hemorrhage, and stroke. Using zebrafish, our laboratory has demonstrated that AVMs form via a two-step mechanism involving an initial increase in endothelial cell number caused by lack of alk1, and then an adaptive response to increased blood flow in downstream vessels. This adaptive response involves increased arterial caliber and maintenance of normally transient connections between arteries and veins, thereby forming high-flow AVMs. Furthermore, we have demonstrated that alk1 expression is dependent on blood flow, and that lack of flow mimics loss of alk1, suggesting that Alk1 might act downstream of blood flow to stabilize arterial caliber. To date, the in vivo ligand and intracellular mediators required for flow-dependent, Alk1-mediated endothelial quiescence and AVM prevention remain unknown. In this work, I demonstrate that bone morphogenetic protein 10 (Bmp10) is the physiologically relevant Alk1 ligand during zebrafish embryonic development. Bmp10 paralogs are expressed exclusively in the heart, and loss of blood flow affects arterial pSmad1/5/9, cxcr4a, and edn1 expression similarly to loss of alk1, even when alk1 expression is restored via a flow-independent transgene. Together, these data suggest that flow is required not only for alk1 expression but also to deliver cardiac-derived Bmp10 ligand to arterial endothelial cell Alk1 to promote endothelial cell quiescence. Downstream of Bmp10/Alk1, Alk1 kinase activity is required to prevent AVMs. However characterization of a pSmad1/5-responsive transgenic reporter, Tg(BRE:EGFP), suggests that although phosphorylation of Smad1/5/9 in arterial endothelium is clearly dependent on Alk1, pSmad1/5/9 may not activate transcription via a canonical mechanism within these cells. In sum, the work presented in this thesis constructs a novel blood flow-responsive signaling pathway, suggests novel mechanisms by which Alk1 may control gene expression, and finally, describes a new tool for studying Alk1 and BMP signaling in vivo.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Laux, Derek Williamdwl8@pitt.eduDWL8
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairRoman, Beth Lromanb@pitt.eduROMANB
Committee MemberCampbell, Gerard Lcamp@pitt.eduCAMP
Committee MemberHildebrand, Jeffrey Djeffh@pitt.eduJEFFH
Committee MemberChapman, Deborah Ldlc7@pitt.eduDLC7
Date: 30 September 2013
Date Type: Publication
Defense Date: 20 May 2013
Approval Date: 30 September 2013
Submission Date: 5 August 2013
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 164
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Biological Sciences
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Bmp10, Alk1, Hereditary Hemorrhagic Telangiectasia, Arteriovenous Malformation, Zebrafish, Flow Response
Date Deposited: 30 Sep 2013 12:05
Last Modified: 15 Nov 2016 14:14


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