Development of hypomelanotic macules is associated with constitutive activated mTORC1 in tuberous sclerosis complex

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  • Lisbeth Birk Møller, Applied Human Molecular Genetics, Clinical Genetics Clinic, Kennedy Center, Copenhagen University Hospital, Glostrup, Denmark; Department of Science and Environment, Roskilde University, Roskilde, Denmark. Electronic address:
  • ,
  • Bitten Schönewolf-Greulich, University of Copenhagen
  • ,
  • Thomas Rosengren, University of Copenhagen
  • ,
  • Lasse Jonsgaard Larsen, University of Copenhagen
  • ,
  • John R Ostergaard
  • Mette Sommerlund
  • Caroline Ostenfeldt, University of Copenhagen
  • ,
  • Brian Stausbøl-Grøn
  • Karen Markussen Linnet
  • ,
  • Pernille Axél Gregersen
  • Uffe Birk Jensen

TSC1 and TSC2 are genes mutated in the syndrome TSC (tuberous sclerosis complex). We describe a 3-generation family with 17 affected members, all presenting classic TSC features except renal manifestations. The disease segregates with a silent substitution in TSC2, c.4149C>T, p.(Ser1838Ser), which leads to the formation of an active donor splice site, resulting in three shorter alternatively spliced transcripts with premature stop codons. However a small amount of normal spliced transcript is apparently produced from the mutated allele, which might explain the milder phenotype. The gene products of TSC1/2 form a complex which at energy limiting states, down-regulates the activity of the regulator of protein synthesis, the mammalian target of rapamycin complex1 (mTORC1). As expected, in contrast to cultured control fibroblasts, starvation of cultured patient fibroblasts obtained from a hypomelanotic macule did not lead to repression of mTORC1, whereas partial repression was observed in patient fibroblasts obtained from non-lesional skin. The findings indicate that the development of hypomelanotic macules is associated with constitutive activated mTORC1, whereas mild deregulation of mTORC1 allows the maintenance of normal skin. Furthermore, the finding establishes the pathogenic effect of the "silent" c.4149C>T substitution and emphasizes the need for awareness when interpreting silent substitutions in general.

Original languageEnglish
JournalMolecular Genetics and Metabolism
Pages (from-to)384-391
Number of pages8
Publication statusPublished - Apr 2017

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  • Journal Article

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