DNA replication timing is maintained genome-wide in primary human myoblasts independent of D4Z4 contraction in FSH muscular dystrophy.

Benjamin D Pope,Melanie Ehrlich,Dana Battaglia,David M Gilbert,Ichiro Hiratani,Koji Tsumagari,Tyrone Ryba

doi:10.1371/journal.pone.0027413

Benjamin D Pope, Melanie Ehrlich + Show 5 more

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https://doi.org/10.1371/journal.pone.0027413

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Journal: PloS one	Publication Date: Nov 11, 2011
Citations: 71	License type: CC BY 4.0

Affiliation: Florida State University, Tulane Medical Center

Abstract

Facioscapulohumeral muscular dystrophy (FSHD) is linked to contraction of an array of tandem 3.3-kb repeats (D4Z4) at 4q35.2 from 11-100 copies to 1-10 copies. The extent to which D4Z4 contraction at 4q35.2 affects overall 4q35.2 chromatin organization remains unclear. Because DNA replication timing is highly predictive of long-range chromatin interactions, we generated genome-wide replication-timing profiles for FSHD and control myogenic precursor cells. We compared non-immortalized myoblasts from four FSHD patients and three control individuals to each other and to a variety of other human cell types. This study also represents the first genome-wide comparison of replication timing profiles in non-immortalized human cell cultures. Myoblasts from both control and FSHD individuals all shared a myoblast-specific replication profile. In contrast, male and female individuals were readily distinguished by monoallelic differences in replication timing at DXZ4 and other regions across the X chromosome affected by X inactivation. We conclude that replication timing is a robust cell-type specific feature that is unaffected by FSHD-related D4Z4 contraction.

Highlights

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant genetic disorder characterized by progressive muscle weakness and wasting that typically initiates in the face, shoulder-girdle and upper arm
We showed that .85% of the cells in aliquots from all batches of FSHD and control myoblasts used in this study were myoblasts by immunostaining with desmin, a muscle-specific marker not expressed in fibroblasts
Because full-length Double Homeobox Protein 4 (DUX4) transcripts from the pathogenic, contracted D4Z4 repeat array at 4q35 are associated with FSHD, we assayed, by previously described methods [4], six control and six FSHD myoblast samples, including three samples used in the present study [2]

Summary

Introduction

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant genetic disorder characterized by progressive muscle weakness and wasting that typically initiates in the face, shoulder-girdle and upper arm. 11-100 copies of the 3.3 kb repeat unit are non-pathogenic while 1-10 copies correlate with onset of FSHD in 95% of patients [3]. Another D4Z4 macrosatellite array highly homologous to that of 4q35.2 is present at 10q26.3, yet D4Z4 contractions at 10q26 are almost never pathogenic [4]. The open reading frame encoding DUX4 protein within each D4Z4 repeat unit lacks a consensus signal for polyadenylation [7]. A single nucleotide polymorphism distal to the last D4Z4 repeat is found in all FSHD patients and stabilizes DUX4 transcripts by providing a polyadenylation signal and thereby creating a toxic gain-offunction mutation [4,8]. Forced DUX4 expression inhibits myogenesis and decreases Myogenic Differentiation

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