A common X-linked inborn error of carnitine biosynthesis may be a risk factor for nondysmorphic autism

作者:Celestino Soper Patricia B S; Violante Sara; Crawford Emily L; Luo Rui; Lionel Anath C; Delaby Elsa; Cai Guiqing; Sadikovic Bekim; Lee Kwanghyuk; Lo Charlene; Gao Kun; Person Richard E; Moss Timothy J; German Jennifer R; Huang Ni; Shinawi Marwan; Treadwell Deering Diane; Szatmari Peter; Roberts Wendy; Fernandez Bridget; Schroer Richard J; Stevenson Roger E; Buxbaum Joseph D; Betancur Catalina; Scherer Stephen W; Sanders Stephan J; Geschwind Daniel H
来源:Proceedings of the National Academy of Sciences of the United States of America, 2012, 109(21): 7974-7981.
DOI:10.1073/pnas.1120210109

摘要

We recently reported a deletion of exon 2 of the trimethyllysine hydroxylase epsilon (TMLHE) gene in a proband with autism. TMLHE maps to the X chromosome and encodes the first enzyme in carnitine biosynthesis, 6-N-trimethyllysine dioxygenase. Deletion of exon 2 of TMLHE causes enzyme deficiency, resulting in increased substrate concentration (6-N-trimethyllysine) and decreased product levels (3-hydroxy-6-N-trimethyllysine and gamma-butyrobetaine) in plasma and urine. TMLHE deficiency is common in control males (24 in 8,787 or 1 in 366) and was not significantly increased in frequency in probands from simplex autism families (9 in 2,904 or 1 in 323). However, it was 2.82-fold more frequent in probands from male-male multiplex autism families compared with controls (7 in 909 or 1 in 130; P = 0.023). Additionally, six of seven autistic male siblings of probands in male-male multiplex families had the deletion, suggesting that TMLHE deficiency is a risk factor for autism (meta-analysis Z-score = 2.90 and P = 0.0037), although with low penetrance (2-4%). These data suggest that dysregulation of carnitine metabolism may be important in nondysmorphic autism; that abnormalities of carnitine intake, loss, transport, or synthesis may be important in a larger fraction of nondysmorphic autism cases; and that the carnitine pathway may provide a novel target for therapy or prevention of autism.