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Exploiting Drosophila as a model system for studying anaplastic lymphoma kinase in vivo
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Anaplastic Lymphoma Kinase (ALK) is a Receptor Tyrosine Kinase (RTK) and an oncogene associated with several human diseases, but its normal function in humans and other vertebrates is unclear. Drosophila melanogaster has an ALK homolog, demonstrating that the RTK has been conserved throughout evolution. This makes Drosophila a suitable model organism for studying not only Drosophila ALK function, but also to study mammalian forms of ALK. In Drosophila the ligand Jeb activates ALK, initiating signaling crucial for visceral mesoderm development. The activating ligand for mammalian ALK is unclear, and for this reason Drosophila was employed in a cross-species approach to investigate whether Drosophila Jeb can activate mouse ALK. Jeb is unable to activate mouse ALK, and therefore mouse ALK is unable to substitute for and rescue the Drosophila ALK mutant phenotype. This suggests that there has been significant evolution in the ALK-ligand relationship between the mouse and Drosophila.

In humans ALK has recently been shown to be involved in the development of neuroblastoma, a cancer tumor in children. I have developed a Drosophila model for examining human gain of function ALK mutants found in neuroblastoma patients. The various ALK variants have acquired point mutations in the kinase domain that have been predicted to activate the RTK in a constitutive and ligand independent manner. When expressed in the fly eye, active human ALK mutants result in a rough eye phenotype, while inactive wild type ALK does not, due to the lack of an activating ligand in the fly. In this way  several of the ALK mutations identified in neuroblastoma patients could be confirmed to be activated in a ligand independent manner. Moreover, a novel ALK mutant; ALKF1174S, was discovered in a neuroblastoma patient and was in the Drosophila model shown to be a gain of function mutation, and a previously predicted gain of function mutation; ALKI1250T, was shown to be a kinase dead mutation. This fly model can also be used for testing ALK selective inhibitors, for identifying activating ligands for human ALK and for identifying conserved components of the ALK signaling pathway.

Gut musculature development in Drosophila is dependent on ALK signaling, while somatic muscle development is not. Proteins of the Wasp-Scar signaling network regulate Arp2/3-complex mediated actin polymerization, and I have investigated their function in visceral and somatic muscle fusion. I found that Verprolin and other members of this protein family are essential for somatic but not visceral muscle development. Despite fusion defects in both tissues in Verprolin and other examined mutants, gut development proceeds, suggesting that fusion is not crucial for visceral mesoderm development. Hence the actin polymerization machinery functions in both somatic and visceral muscle fusion, but this process only appears to be essential in somatic muscle development.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2010. , 58 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1376
Keyword [en]
Anaplastic lymphoma kinase, Receptor tyrosine kinase, Jeb, neuroblastoma, actin polymerization, Wasp, Scar, Vrp1, Arp2/3
National Category
Cell and Molecular Biology
Research subject
Molecular Biology
Identifiers
URN: urn:nbn:se:umu:diva-36991ISBN: 978-91-7459-090-6 (print)OAI: oai:DiVA.org:umu-36991DiVA: diva2:356976
Public defence
2010-11-05, Major Groove, Byggnad 6L, Umeå universitet, Umeå, 09:00 (English)
Opponent
Supervisors
Projects
Exploiting Drosophila as a model system for studying Anaplastic Lymphoma Kinase in vivo
Available from: 2010-10-15 Created: 2010-10-14 Last updated: 2010-10-15Bibliographically approved
List of papers
1. The ligand Jelly Belly (Jeb) activates the Drosophila Alk RTK to drive PC12 cell differentiation, but is unable to activate the mouse ALK RTK
Open this publication in new window or tab >>The ligand Jelly Belly (Jeb) activates the Drosophila Alk RTK to drive PC12 cell differentiation, but is unable to activate the mouse ALK RTK
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2007 (English)In: Journal of experimental zoology, part B Molecular and developmental evolution, ISSN 1552-5007, Vol. 308, no 3, 269-282 p.Article in journal (Refereed) Published
Abstract [en]

The Drosophila Alk receptor tyrosine kinase (RTK) drives founder cell specification in the developing visceral mesoderm and is crucial for the formation of the fly gut. Activation of Alk occurs in response to the secreted ligand Jelly Belly. No homologues of Jelly Belly are described in vertebrates, therefore we have approached the question of the evolutionary conservation of the Jeb-Alk interaction by asking whether vertebrate ALK is able to function in Drosophila. Here we show that the mouse ALK RTK is unable to rescue a Drosophila Alk mutant, indicating that mouse ALK is unable to recognise and respond to the Drosophila Jeb molecule. Furthermore, the overexpression of a dominant-negative Drosophila Alk transgene is able to block the visceral muscle fusion event, which an identically designed dominant-negative construct for the mouse ALK is not. Using PC12 cells as a model for neurite outgrowth, we show here for the first time that activation of dAlk by Jeb results in neurite extension. However, the mouse Alk receptor is unable to respond in any way to the Drosophila Jeb protein in the PC12 system. In conclusion, we find that the mammalian ALK receptor is unable to respond to the Jeb ligand in vivo or in vitro. These results suggest that either (i) mouse ALK and mouse Jeb have co-evolved to the extent that mALK can no longer recognise the Drosophila Jeb ligand or (ii) that the mALK RTK has evolved such that it is no longer activated by a Jeb-like molecule in vertebrates.

National Category
Cell and Molecular Biology
Research subject
Molecular Biology
Identifiers
urn:nbn:se:umu:diva-17925 (URN)10.1002/jez.b.21146 (DOI)17285636 (PubMedID)
Available from: 2008-01-10 Created: 2008-01-10 Last updated: 2010-10-15Bibliographically approved
2. Appearance of the novel activating F1174S ALK mutation in neuroblastoma correlates with aggressive tumour progression and unresponsiveness to therapy
Open this publication in new window or tab >>Appearance of the novel activating F1174S ALK mutation in neuroblastoma correlates with aggressive tumour progression and unresponsiveness to therapy
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2011 (English)In: Cancer Research, ISSN 0008-5472, E-ISSN 1538-7445, Vol. 71, no 1, 98-105 p.Article in journal (Other academic) Published
Abstract [en]

Mutations in the kinase domain of the ALK kinase have emerged recently as important players in the genetics of the childhood tumor neuroblastoma. Here we report the appearance of a novel ALK mutation in neuroblastoma, correlating with aggressive tumor behaviour. Analyses of genomic DNA from biopsy samples initially showed ALK sequence to be wild type. However, during disease progression mutation of amino acid F1174 to a serine within the ALK kinase domain was observed, which correlated with aggressive neuroblastoma progression in the patient. We show that mutation of F1174 to serine generates a potent gain-of-function mutant, as observed in two independent systems. Firstly, PC12 cell lines expressing ALKF1174S display ligand independent activation of ALK and further downstream signaling activation. Secondly, analysis of ALKF1174S in Drosophila models confirms that the mutation mediates a strong rough eye phenotype upon expression in the developing eye. Thus, we report a novel ALKF1174S mutation, which displays ligand independent activity in vivo, correlating with rapid and treatment resistant tumor growth. The study also shows that initial screening in the first tumor biopsy of a patient may not be sufficient and that further molecular analyses in particular in tumor progression and/or tumor relapse is warranted for better understanding of the treatment of neuroblastoma patients.

Place, publisher, year, edition, pages
American Association for Cancer Research, 2011
Keyword
ALK, neuroblastoma, gain of function
National Category
Cell and Molecular Biology
Research subject
Molecular Biology
Identifiers
urn:nbn:se:umu:diva-36978 (URN)10.1158/0008-5472.CAN-10-2366 (DOI)
Projects
Exploiting Drosophila as a model system for studying Anaplastic Lymphoma Kinase in vivo
Available from: 2010-10-14 Created: 2010-10-14 Last updated: 2012-09-04Bibliographically approved
3. The neuroblastoma ALK(I1250T) mutation is a kinase-dead RTK in vitro and in vivo
Open this publication in new window or tab >>The neuroblastoma ALK(I1250T) mutation is a kinase-dead RTK in vitro and in vivo
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2011 (English)In: Translational Oncology, ISSN 1944-7124, E-ISSN 1936-5233, Vol. 4, no 4, 258-265 p.Article in journal (Other academic) Published
Abstract [en]

Activating mutations in the kinase domain of anaplastic lymphoma kinase (ALK) have recently been shown to be an important determinant in the genetics of the childhood tumor neuroblastoma. Here we discuss an in-depth analysis of one of the reported gain-of-function ALK mutations—ALKI1250T—identified in the germ line DNA of one patient. Our analyses were performed in cell culture-based systems and subsequently confirmed in a Drosophila model. The results presented here indicate that the germ line ALKI1250T mutation is most probably not a determinant for tumor initiation or progression and, in contrast, seems to generate a kinase-dead mutation in the ALK receptor tyrosine kinase (RTK). Consistent with this, stimulation with agonist ALK antibodies fails to lead to stimulation of ALKI1250T and we were unable to detect tyrosine phosphorylation under any circumstances. In agreement, ALKI1250T is unable to activate downstream signaling pathways or to mediate neurite outgrowth, in contrast to the activated wild-type ALK receptor or the activating ALKF1174S mutant. Identical results were obtained when the ALKI1250T mutant was expressed in a Drosophila model, confirming the lack of activity of this mutant ALK RTK. We suggest that the ALKI1250T mutation leads to a kinase-dead ALK RTK, in stark contrast to assumed gain-of-function status, with significant implications for patients reported to carry this particular ALK mutation.

Keyword
ALK, neuroblastoma, gain of function, kinase dead
National Category
Cell and Molecular Biology
Research subject
Molecular Biology
Identifiers
urn:nbn:se:umu:diva-36979 (URN)10.1593/tlo.11139 (DOI)000294253200008 ()21804922 (PubMedID)
Projects
Exploiting Drosophila as a model system for studying Anaplastic Lymphoma Kinase in vivo
Available from: 2010-10-14 Created: 2010-10-14 Last updated: 2017-01-17Bibliographically approved
4. WASP and SCAR have distinct roles in activating the Arp2/3 complex during myoblast fusion
Open this publication in new window or tab >>WASP and SCAR have distinct roles in activating the Arp2/3 complex during myoblast fusion
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2008 (English)In: Journal of Cell Science, ISSN 0021-9533, E-ISSN 1477-9137, Vol. 121, no Pt 8, 1303-1313 p.Article in journal (Refereed) Published
Abstract [en]

Myoblast fusion takes place in two steps in mammals and in Drosophila. First, founder cells (FCs) and fusion-competent myoblasts (FCMs) fuse to form a trinucleated precursor, which then recruits further FCMs. This process depends on the formation of the fusion-restricted myogenic-adhesive structure (FuRMAS), which contains filamentous actin (F-actin) plugs at the sites of cell contact. Fusion relies on the HEM2 (NAP1) homolog Kette, as well as Blow and WASP, a member of the Wiskott-Aldrich-syndrome protein family. Here, we show the identification and characterization of schwächling--a new Arp3-null allele. Ultrastructural analyses demonstrate that Arp3 schwächling mutants can form a fusion pore, but fail to integrate the fusing FCM. Double-mutant experiments revealed that fusion is blocked completely in Arp3 and wasp double mutants, suggesting the involvement of a further F-actin regulator. Indeed, double-mutant analyses with scar/WAVE and with the WASP-interacting partner vrp1 (sltr, wip)/WIP show that the F-actin regulator scar also controls F-actin formation during myoblast fusion. Furthermore, the synergistic phenotype observed in Arp3 wasp and in scar vrp1 double mutants suggests that WASP and SCAR have distinct roles in controlling F-actin formation. From these findings we derived a new model for actin regulation during myoblast fusion.

Keyword
Drosophila, Myogenesis, F-actin, Arp3, FuRMAS, Actin cytoskeleton, kette
National Category
Cell and Molecular Biology
Research subject
Molecular Biology
Identifiers
urn:nbn:se:umu:diva-20623 (URN)10.1242/jcs.022269 (DOI)18388318 (PubMedID)
Available from: 2009-03-24 Created: 2009-03-24 Last updated: 2010-10-15Bibliographically approved
5. Characterization of the role of Vrp1 in cell fusion during the development of visceral muscle of Drosophila melanogaster
Open this publication in new window or tab >>Characterization of the role of Vrp1 in cell fusion during the development of visceral muscle of Drosophila melanogaster
2010 (English)In: BMC Developmental Biology, ISSN 1471-213X, Vol. 10, no 86Article in journal (Refereed) Published
Abstract [en]

Background: In Drosophila muscle cell fusion takes place both during the formation of the somatic mesodermand the visceral mesoderm, giving rise to the skeletal muscles and the gut musculature respectively. The coreprocess of myoblast fusion is believed to be similar for both organs. The actin cytoskeleton regulator Verprolin actsby binding to WASP, which in turn binds to the Arp2/3 complex and thus activates actin polymerization. WhileVerprolin has been shown to be important for somatic muscle cell fusion, the function of this protein in visceralmuscle fusion has not been determined.Results: Verprolin is specifically expressed in the fusion competent myoblasts of the visceral mesoderm, suggestinga role in visceral mesoderm fusion. We here describe a novel Verprolin mutant allele which displays subtle visceralmesoderm fusion defects in the form of mislocalization of the immunoglobulin superfamily molecule Duf/Kirre,which is required on the myoblast cell surface to facilitate attachment between cells that are about to fuse,indicating a function for Verprolin in visceral mesoderm fusion. We further show that Verprolin mutant cells arecapable of both migrating and fusing and that the WASP-binding domain of Verprolin is required for rescue of theVerprolin mutant phenotype.Conclusions: Verprolin is expressed in the visceral mesoderm and plays a role in visceral muscle fusion as shownby mislocalization of Duf/Kirre in the Verprolin mutant, however it is not absolutely required for myoblast fusion ineither the visceral or the somatic mesoderm.

Place, publisher, year, edition, pages
BioMed Central, 2010
Keyword
Vrp1, fusion, visceral mesoderm, Duf
National Category
Biochemistry and Molecular Biology
Research subject
Molecular Biology
Identifiers
urn:nbn:se:umu:diva-36983 (URN)10.1186/1471-213X-10-86 (DOI)
Projects
Exploiting Drosophila as a model system for studying Anaplastic Lymphoma Kinase in vivo
Available from: 2010-10-14 Created: 2010-10-14 Last updated: 2012-02-21Bibliographically approved

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