G.P.34

• Published in: Neuromuscular disorders : NMD 2014-10, Vol.24 (9), p.804-805
• Main Authors: Chauveau, C, Bönnemann, C.G, Julien, C, Kho, A.L, Marks, H, Talim, B, Maury, P, Uro-Coste, E, Alexandrovich, A, Vihola, A, Foley, A.R, Santi, M, Udd, B, Topaloglu, H, Moore, S.A, Gotthardt, M, Samuels, M.E, Gautel, M, Ferreiro, A
• Format: Article
• Language: English
• Subjects: Neurology
• ISSN: 0960-8966
• DOI: 10.1016/j.nmd.2014.06.048

Congenital core myopathies (CM) remain genetically unexplained in many cases. Heart disease is not considered part of the typical CM spectrum. Childhood-onset dilated cardiomyopathy (DCM) was reported in two families with minicores and homozygous TTN mutations. TTN encodes the giant sarcomere protein titin. Relatively few titin mutations (mostly heterozygous and associated to adult-onset cardiac or skeletal muscle disease) have been reported, TTN size and complexity precluding full screening before NGS. Thus, the prevalence and spectrum of titinopathies is probably underestimated. Here we report the analysis of 23 families with CM and primary heart disease using TTN M-line targeted sequencing followed in selected patients by whole-exome sequencing and functional studies. We found 7 novel homozygous or compound heterozygous TTN mutations (5 in the M-line, 5 truncating) in 5 patients. All heterozygous parents were healthy. We identified 4 novel phenotypes previously unreported or non-associated with TTN , including several congenital cardiopathies. The first antenatal-onset titinopathy presented with multi-minicore disease (MmD), arthrogryposis, left ventricular non-compaction and ventricular septal defect, and was associated with the first-reported absence of a functional titin kinase domain in humans. Other novel phenotypes associate MmD with auricular and/or ventricular septal defects, Rigid Spine, Emery-Dreifuss phenotype and/or adult-onset DCM. The histological pattern consistently showed minicores, central nuclei and structural lesions. Conversely, the spectrum of severity and heart disease was large. Thus, we demonstrate that TTN M-line truncating mutations are typically recessive and represent a significant cause of MmD with heart disease. Our results represent the first series of recessive titinopathies, expand TTN mutational and phenotypic spectrum, and identify TTN as a candidate gene in arthrogryposis, EDMD and pediatric heart defects.