Grant Abstracts: Dr. Melkani's Lab Home Page


Title: Genetic analysis and regulation of laminopathy induced cardiac defects

Funding Source: NIH/NIA 2015-2017

Abstract:
Laminopathies are a group of genetic disorders caused by dominant mutations in the human LMNA gene encoding A-type lamins, intermediate filaments that line the inner nuclear membrane. Patients with laminopathies exhibit phenotypes of aging, including cardiac and skeletal muscle dysfunction, dysplasia, diabetes, and premature aging. Lamins are nearly ubiquitously expressed, however many laminopathies are associated with cardiomyopathy, which is frequently fatal; yet, the underlying molecular mechanisms are not well understood. Given that many of the laminopathy patients die from cardiomyopathy, it is vital to understand the functions of lamins in the heart. The majority of mutations in LMNA that cause heart disease result in single amino acid substitutions within the rod and Ig-fold domains, which interact with different partner proteins. How mutant lamins cause disease is unknown and there is a lack of efficient genetic models to functionally dissect the physiological and pathological role(s) of lamins in heart function.

To determine the function of mutant lamins within the rod and Ig-fold domains, we have established a novel Drosophila melanogaster model. Using tissue-specific expression tools, mutant lamins are expressed specifically in the heart. Expression of wild-type lamin causes no obvious phenotypes. In contrast, expression of mutant lamins results in cardiac dysfunction accompanied by cytoplasmic aggregation and impairment of cellular redox homeostasis. Based on our preliminary findings, we hypothesize that expression of mutant lamins results in cytoplasmic aggregates, which leads to an impairment of cellular redox homeostasis and defective clearance pathways thus affecting cardiac defects. Furthermore, to mimic human disease condition and to identify nonautonomous or cardiac restricted dyfunctions linked with lamin mutations, we will use a complementary CRISPR/Cas9 expression approach. Specific Aim 1 will define the progressive dysfunction, at the physiological, functional, biochemical and ultrastructural levels, caused by the mutant lmains. Specific Aim 2 will identify genetic and pharmacological suppressors of the cardiac phenotypes caused by mutant lamins to generate insight into the primary cause of cardiac-based laminopathies and to identify potential avenues for therapies. Our suppression approach will involve protein interactions between Lamin and other nuclear envelope and aggregation clearance pathways in cardiac tissue will help us to identify heart-specific features of laminopathy-associated mechanisms that may provide new and potentially therapeutic targets.

Identifying genetic factors and pathways that modulate or mediate cardiac laminopathies is expected to uncover molecular pathways that define how cardiac laminopathies develop. The outcome of our studies will then allow the design of strategies to identify therapeutic targets. Furthermore, this study will likely provide insight into how laminopathy is linked with cardiac failure. Future directions in research will include validation of the findings in mouse models of laminopathies and human biospy tissue.

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Title: Genetic analysis and regulation of amyloids flux in the Drosophila heart

Funding Source: NIH/NCRR (No cost extension 08/2014) 1R21 RR032100-01A1 (Melkani, G.C., P.I.) 09/01/2011 - 08/31/2013

Abstract:
The specific aims of the project are to: 1) Expression and detection of HD- and AD-causing amyloids in the Drosophila heart to explore their impact on cardiac physiology. 2) Ameliorate cardiac amyloidosis by over-expression of chaperones and superoxide dismutase (SOD) or by using pharmacological agents.

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Title: Tau-induced cardiomyopathy in a Drosophila heart model

Funding Source: AHA, WSA-Beginning Grant in Aid 13BGIA17260057 (Melkani, G.C., P.I.) 07/01/13 - 08/31/15

Abstract:
The aims of the project are to: 1) Establish a Drosophila cardiac model to investigate structural and functional defects in heart caused by hyperphosphorylation of Tau; and, 2) identification of genetic and pharmacological suppressors of Tau-mediated cardiomyopathy.

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Title: Mechanism of Myosin Chaperone UNC-45: Structural, Functional & Genetic Approaches

Funding Source: NIH/NIAMS 1 R01 AR055958 (Bernstein, S.I., PI) 04/01/13 - 03/31/18

Abstract:
The aims of the project are to: 1) Investigate the dimerization of UNC-45 at a structural level and determine the importance of dimerization in UNC-45 function, 2) perform a structure-function analysis of a conserved surface cleft of UNC-45 that we identified by crystallography and phylogenetic sequence comparisons and 3) use combined genetic and biochemical approaches to identify additional partners and targets of UNC-45.

Role on project: Collaborator

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