We report the identification of a novel mutation at a highly conserved residue within the N-terminal region of spermine synthase (SMS) in a second family with Snyder–Robinson X-linked mental retardation syndrome (OMIM 309583). This missense mutation, p.G56S, greatly reduces SMS activity and leads to severe epilepsy and cognitive impairment. Our findings contribute to a better delineation and expansion of the clinical spectrum of Snyder–Robinson syndrome, support the important role of the N-terminus in the function of the SMS protein, and provide further evidence for the importance of SMS activity in the development of intellectual processing and other aspects of human development.
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Funding: This work was supported by grants from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), NICHD grant (HD26202) to CES, NIH grant (GM-26290) to AEP and, in part, by a grant from the South Carolina Department of Disabilities and Special Needs (SCDDSN).
Competing interests: None declared.
Patient consent: Obtained.
Ethics approval: The study was approved by the research ethics committee of the Institute of Biosciences, University of São Paulo, Brazil.
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