Human DNA sequence differs among individuals and the most common variations are known as single nucleotide polymorphisms, or SNPs. Studies have shown that non-synonymous coding SNPs (nsSNPs - SNPs occurring in protein coding regions which lead to amino acid substitutions) can be responsible for many human diseases. X-linked mental retardation (XLMR) is a particular example of a group of heterogeneous conditions with an estimated frequency of 5-12% in the mentally retarded populations. Specifically, in this proposal we focus on XLMR caused by a defect in spearmine synthase (SMS). Polyamines are ubiquitous molecules that interact with variety of other molecules in the cell and are essential for normal cell growth and differentiation. Especially spearmine have been shown to modulate ion channel activities is particular cells. In this proposal we will investigate three nsSNP within SMS known to cause XLMP to reveal the molecular mechanism of effect of mutations on structure, function and interactions of SMS. Three nsSNPs (G56S, V132G and I150T) in the spearmine sythase gene that encodes a protein of 366 amino acids were shown to be responsible for XLMR by our collaborator Dr. Schwartz and co-workers. However, no explanation of the effects on molecular level is available. Therefore, further investigation of these variants by combined efforts of computational modeling at molecular level with experimental investigations in Dr. Schwartz lab will provide valuable information of the molecular basis of how these snSNP affect the spearnime synthase stability, function and interactions. The outcome of the proposed research has the potential to provide valuable insights towards understanding the cause of the disease. The project will enable PI's lab to enter the field of the clinical research by collaborating with the Greenwood Genetic Center (Dr. Charles Schwartz). The results of the computational modeling will be used to generate testable hypothesizes and other still unknown missense mutations will be suggested. These hypotheses and mutants will be biochemically tested in Dr. Schwartz lab and screened against available clinical data.

Public Health Relevance

to Human Health Many human diseases are caused by non-synonymous coding SNPs (nsSNP). Thus, the ability to rationalize disease causing nsSNPs and to provide methods for altering their effects is of enormous importance for the human health. This proposal is aimed to model molecular details of nsSNPs in spearmine synthase gene causing X- linked mental retardation. Thus, this proposed research is relevant to that part of NIH's mission that pertains to developing fundamental knowledge that will potentially reduce the burdens of human disability.

Agency
National Institute of Health (NIH)
Institute
National Library of Medicine (NLM)
Type
Small Research Grants (R03)
Project #
1R03LM009748-01A2
Application #
7660053
Study Section
Biomedical Library and Informatics Review Committee (BLR)
Program Officer
Ye, Jane
Project Start
2009-07-01
Project End
2011-06-30
Budget Start
2009-07-01
Budget End
2010-06-30
Support Year
1
Fiscal Year
2009
Total Cost
$70,744
Indirect Cost
Name
Clemson University
Department
Physics
Type
Schools of Engineering
DUNS #
042629816
City
Clemson
State
SC
Country
United States
Zip Code
29634
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Zhang, Zhe; Witham, Shawn; Petukh, Marharita et al. (2013) A rational free energy-based approach to understanding and targeting disease-causing missense mutations. J Am Med Inform Assoc 20:643-51
Zhang, Zhe; Norris, Joy; Kalscheuer, Vera et al. (2013) A Y328C missense mutation in spermine synthase causes a mild form of Snyder-Robinson syndrome. Hum Mol Genet 22:3789-97
Zhang, Zhe; Zheng, Yueli; Petukh, Margo et al. (2013) Enhancing human spermine synthase activity by engineered mutations. PLoS Comput Biol 9:e1002924
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Takano, Kyoko; Liu, Dan; Tarpey, Patrick et al. (2012) An X-linked channelopathy with cardiomegaly due to a CLIC2 mutation enhancing ryanodine receptor channel activity. Hum Mol Genet 21:4497-507
Alexov, Emil; Mehler, Ernest L; Baker, Nathan et al. (2011) Progress in the prediction of pKa values in proteins. Proteins 79:3260-75
Zhang, Zhe; Norris, Joy; Schwartz, Charles et al. (2011) In silico and in vitro investigations of the mutability of disease-causing missense mutation sites in spermine synthase. PLoS One 6:e20373
Witham, Shawn; Takano, Kyoko; Schwartz, Charles et al. (2011) A missense mutation in CLIC2 associated with intellectual disability is predicted by in silico modeling to affect protein stability and dynamics. Proteins 79:2444-54
Talley, Kemper; Alexov, Emil (2010) On the pH-optimum of activity and stability of proteins. Proteins 78:2699-706

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