A multistage sequencing strategy pinpoints novel candidate alleles for Emery-Dreifuss muscular dystrophy and supports gene misregulation as its pathomechanism.

BACKGROUND

As genome-wide approaches prove difficult with genetically heterogeneous orphan diseases, we developed a new approach to identify candidate genes. We applied this to Emery-Dreifuss muscular dystrophy (EDMD), characterised by early onset contractures, slowly progressive muscular wasting, and life-threatening heart conduction disturbances with wide intra- and inter-familial clinical variability. Roughly half of EDMD patients are linked to six genes encoding nuclear envelope proteins, but the disease mechanism remains unclear because the affected proteins function in both cell mechanics and genome regulation.

METHODS

A primer library was generated to test for mutations in 301 genes from four categories: (I) all known EDMD-linked genes; (II) genes mutated in related muscular dystrophies; (III) candidates generated by exome sequencing in five families; (IV) functional candidates - other muscle nuclear envelope proteins functioning in mechanical/genome processes affected in EDMD. This was used to sequence 56 unlinked patients with EDMD-like phenotype.

FINDINGS

Twenty-one patients could be clearly assigned: 18 with mutations in genes of similar muscular dystrophies; 3 with previously missed mutations in EDMD-linked genes. The other categories yielded novel candidate genes, most encoding nuclear envelope proteins with functions in gene regulation.

INTERPRETATION

Our multi-pronged approach identified new disease alleles and many new candidate EDMD genes. Their known functions strongly argue the EDMD pathomechanism is from altered gene regulation and mechanotransduction due to connectivity of candidates from the nuclear envelope to the plasma membrane. This approach highlights the value of testing for related diseases using primer libraries and may be applied for other genetically heterogeneous orphan diseases.

FUNDING

The Wellcome Trust, Muscular Dystrophy UK, Medical Research Council, European Community's Seventh Framework Programme "Integrated European -omics research project for diagnosis and therapy in rare neuromuscular and neurodegenerative diseases (NEUROMICS)".

Informations de copyright

Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.

Déclaration de conflit d'intérêts

Declaration of Competing Interest Dr. Meinke reports personal fees from Greenovation Biopharmaceuticals, outside the submitted work; Dr. Harris reports grants from Muscular Dystrophy-UK, during the conduct of the study; Dr. Koelbel reports personal fees from Santhera, personal fees from Sarepta, personal fees from Biogen, personal fees from Avexis, outside the submitted work; Dr Schara reports personal fees for consulting from Alexion, Santhera, PTC, Ipsen, Biogen, Sarepta, Dynacure, Novartis, Avexis and Sanofi; Dr. Muntoni reports personal fees from Pfizer, personal fees from Roche, personal fees from Biogen, personal fees from Avexis, personal fees from Sarepta, grants from Sarepta, outside the submitted work; Dr. Schoser reports Advisory boards: Amicus Therapeutics, Audentes Therapeutics, Nexien Biopharm, Lupin therapeutics, Sanofi Genzyme. Contracted research: Amicus therapeutics, Greenovation Biopharm, Sanofi Genzyme. Honoraria: Kedrion. Travel expenses: Sanofi Genzyme. Dr. Kerr, Dr. Czapiewski, Dr. de las Heras, Mr. Dixon, Dr. Straub, Dr. Wehnert and Dr. Schirmer have nothing to disclose.