1. Clinical and functional studies of MTOR variants in Smith-Kingsmore syndrome reveal deficits of circadian rhythm and sleep-wake behavior.
- Author
-
Liu AC, Shen Y, Serbinski CR, He H, Roman D, Endale M, Aschbacher-Smith L, King KA, Granadillo JL, López I, Krueger DA, Dye TJ, Smith DF, Hogenesch JB, and Prada CE
- Subjects
- Humans, Male, Female, Child, Adolescent, Child, Preschool, Adult, Sleep drug effects, Sleep genetics, Intellectual Disability genetics, Intellectual Disability drug therapy, Young Adult, Mutation, Megalencephaly genetics, Sirolimus pharmacology, Sirolimus therapeutic use, Infant, TOR Serine-Threonine Kinases genetics, TOR Serine-Threonine Kinases metabolism, Circadian Rhythm genetics, Circadian Rhythm drug effects
- Abstract
Heterozygous de novo or inherited gain-of-function mutations in the MTOR gene cause Smith-Kingsmore syndrome (SKS). SKS is a rare autosomal dominant condition, and individuals with SKS display macrocephaly/megalencephaly, developmental delay, intellectual disability, and seizures. A few dozen individuals are reported in the literature. Here, we report a cohort of 28 individuals with SKS that represent nine MTOR pathogenic variants. We conducted a detailed natural history study and found pathophysiological deficits among individuals with SKS in addition to the common neurodevelopmental symptoms. These symptoms include sleep-wake disturbance, hyperphagia, and hyperactivity, indicative of homeostatic imbalance. To characterize these variants, we developed cell models and characterized their functional consequences. We showed that these SKS variants display a range of mechanistic target of rapamycin (mTOR) activities and respond to the mTOR inhibitor, rapamycin, differently. For example, the R1480_C1483del variant we identified here and the previously known C1483F are more active than wild-type controls and less responsive to rapamycin. Further, we showed that SKS mutations dampened circadian rhythms and low-dose rapamycin improved the rhythm amplitude, suggesting that optimal mTOR activity is required for normal circadian function. As SKS is caused by gain-of-function mutations in MTOR, rapamycin was used to treat several patients. While higher doses of rapamycin caused delayed sleep-wake phase disorder in a subset of patients, optimized lower doses improved sleep. Our study expands the clinical and molecular spectrum of SKS and supports further studies for mechanism-guided treatment options to improve sleep-wake behavior and overall health., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)
- Published
- 2024
- Full Text
- View/download PDF