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Neurology. 2015 Dec 15;85(24):2126-35. doi: 10.1212/WNL.0000000000002200. Epub 2015 Nov 18.

A new titinopathy: Childhood-juvenile onset Emery-Dreifuss-like phenotype without cardiomyopathy.

Author information

  • 1From INSERM (R.D.C., C.R., K.C., I.R.), U951; Généthon (R.D.C., C.R., K.C., I.R.), R&D Department, INTEGRARE Research Unit, Evry; Neuromuscular Morphology Unit, Myology Institute (N.B.R., M.B.), and INSERM UMRS_974, CNRS FRE 3617, Center of Research in Myology (R.B.Y., F.L., N.B.R., E.M., M.B., I.N., G.B.), Sorbonne Universités, UPMC Univ Paris 06, and AP-HP, University Hospital, Reference Center for Neuromuscular Diseases, Myology Institute (R.B.Y., N.B.R., E.M., B.E.), Groupe Hospitalier La Pitié-Salpêtrière, Paris; Génopole Campus 2 (S.B., A.C.), PartnerChip, Evry; the Department of Medical Genetics (F.L., A.V., B.U.), Folkhälsan Institute of Genetics, University of Helsinki, Finland; AP-HP (J.N.), Groupe Hospitalier Cochin-Broca-Hôtel Dieu, Laboratoire de Biochimie et Génétique Moléculaire, Paris; CEA-IG-Centre National de Genotypage (L.B.A., C.C., R.O.), Evry; Neuromuscular Research Center (B.U.), Tampere University Hospital and University of Tampere, Finland; and the Department of Neurology (B.U.), Vaasa Central Hospital, Finland. R.D.C. is currently affiliated with Disease Genomics Group, Institut de Medicina Predictiva i Personalitzada del Càncer, Campus de Can Ruti, Camí de les Escoles, Badalona (Barcelona), Spain.
  • 2From INSERM (R.D.C., C.R., K.C., I.R.), U951; Généthon (R.D.C., C.R., K.C., I.R.), R&D Department, INTEGRARE Research Unit, Evry; Neuromuscular Morphology Unit, Myology Institute (N.B.R., M.B.), and INSERM UMRS_974, CNRS FRE 3617, Center of Research in Myology (R.B.Y., F.L., N.B.R., E.M., M.B., I.N., G.B.), Sorbonne Universités, UPMC Univ Paris 06, and AP-HP, University Hospital, Reference Center for Neuromuscular Diseases, Myology Institute (R.B.Y., N.B.R., E.M., B.E.), Groupe Hospitalier La Pitié-Salpêtrière, Paris; Génopole Campus 2 (S.B., A.C.), PartnerChip, Evry; the Department of Medical Genetics (F.L., A.V., B.U.), Folkhälsan Institute of Genetics, University of Helsinki, Finland; AP-HP (J.N.), Groupe Hospitalier Cochin-Broca-Hôtel Dieu, Laboratoire de Biochimie et Génétique Moléculaire, Paris; CEA-IG-Centre National de Genotypage (L.B.A., C.C., R.O.), Evry; Neuromuscular Research Center (B.U.), Tampere University Hospital and University of Tampere, Finland; and the Department of Neurology (B.U.), Vaasa Central Hospital, Finland. R.D.C. is currently affiliated with Disease Genomics Group, Institut de Medicina Predictiva i Personalitzada del Càncer, Campus de Can Ruti, Camí de les Escoles, Badalona (Barcelona), Spain. richard@genethon.fr.

Abstract

OBJECTIVE:

To identify the genetic defects present in 3 families with muscular dystrophy, contractures, and calpain 3 deficiency.

METHODS:

We performed targeted exome sequencing on one patient presenting a deficiency in calpain 3 on Western blot but for which mutations in the gene had been excluded. The identification of a homozygous truncating mutation in the M-line part of titin prompted us to sequence this region in 2 additional patients presenting similar clinical and biochemical characteristics.

RESULTS:

The 3 patients shared similar features: coexistence of limb-girdle weakness and early-onset diffuse joint contractures without cardiomyopathy. The biopsies showed rimmed vacuoles, a dystrophic pattern, and secondary reduction in calpain 3. We identified a novel homozygous mutation in the exon Mex3 of the TTN gene in the first patient. At protein level, this mutation introduces a stop codon at the level of Mex3. Interestingly, we identified truncating mutations in both alleles in the same region of the TTN gene in patients from 2 additional families. Molecular protein analyses confirm loss of the C-ter part of titin.

CONCLUSIONS:

Our study broadens the phenotype of titinopathies with the report of a new clinical entity with prominent contractures and no cardiac abnormality and where the recessive mutations lead to truncation of the M-line titin and secondary calpain 3 deficiency.

© 2015 American Academy of Neurology.

PMID:
26581302
[PubMed - indexed for MEDLINE]
PMCID:
PMC4691685
[Available on 2016-06-15]
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