Expression Profiling of Differentiating Emerin-Null Myogenic Progenitor Identifies Molecular Pathways Implicated in Their Impaired Differentiation

Abstract

Mutations in the gene encoding emerin cause Emery-Dreifuss muscular dystrophy (EDMD), a disorder causing progressive skeletal muscle wasting, irregular heart rhythms and contractures of major tendons. RNA sequencing was performed on differentiating wildtype and emerin-null myogenic progenitors to identify molecular pathways implicated in EDMD, 340 genes were uniquely differentially expressed during the transition from day 0 to day 1 in wildtype cells. 1605 genes were uniquely expressed in emerin-null cells; 1706 genes were shared among both wildtype and emerin-null cells. One thousand and forty-seven transcripts showed differential expression during the transition from day 1 to day 2. Four hundred and thirty-one transcripts showed altered expression in both wildtype and emerin-null cells. Two hundred and ninety-five transcripts were differentially expressed only in emerin-null cells and 321 transcripts were differentially expressed only in wildtype cells. DAVID, STRING and Ingenuity Pathway Analysis identified pathways implicated in impaired emerin-null differentiation, including cell signaling, cell cycle checkpoints, integrin signaling, YAP/TAZ signaling, stem cell differentiation, and multiple muscle development and myogenic differentiation pathways. Functional enrichment analysis showed biological functions associated with the growth of muscle tissue and myogenesis of skeletal muscle were inhibited. The large number of differentially expressed transcripts upon differentiation induction suggests emerin functions during transcriptional reprograming of progenitors to committed myoblasts.

EDMD-Causing Emerin Mutant Myogenic Progenitors Exhibit Impaired Differentiation Using Similar Mechanisms

“…This is similar to the effects we previously saw upon treatment with pharmacological activators of HDAC3 activity [30], histone acetylase inhibitors [38], and inhibitors of ERK activity [30]. Collectively, the results presented here, combined with our earlier studies [30,[34][35][36]38], strongly support emerin regulating transcriptional reprograming events early in differentiation to impact myoblast commitment and myotube formation through its functional interaction with HDAC3.…”

“…Transcripts were considered to be significantly differentially expressed if the q-value <0.05. It was expected that the expression of a large number of differentially expressed transcripts would be seen during differentiation of each EDMD-causing mutant based on previous studies [34].…”

“…A more powerful analysis, which we have used previously [34], was to compare transcripts differentially expressed between wildtype progenitors and either EMD −/y or each EDMD-causing emerin mutant progenitors at important differentiation transitions. Differentially expressed genes between each day and the preceding day were determined for either differentiating +EMD, EMD −/y , or each EDMD-causing emerin mutant progenitor line.…”

Histone acetyltransferase inhibition rescues differentiation of emerin-deficient myogenic progenitors

“…This reprogramming activates the myogenic differentiation program and represses the proliferative program, thereby leading to myoblast commitment followed by fusion to form myotubes 37 . Transcriptional reprogramming is compromised in emerin-deficient progenitors 38 . The failure of emerin-deficient progenitors to coordinate the temporal reorganization of their genome during differentiation is predicted to cause this defective transcriptional reprogramming.…”

The Pathogenesis and Therapies of Striated Muscle Laminopathies

“…Nuclear translocation of MKL1 was inefficient in Lmna Δ 8−11/Δ8−11 , Emd −/y , and Lmna N195K/N195K MEF as well as in patient skin fibroblasts with LMNA mutation leading to isolated cardiomyopathy ( LMNA p.K219T) following serum stimulation, while it was not altered in another patient's skin fibroblasts with LMNA mutations leading to congenital muscular dystrophy ( LMNA p.K32del) (Ho et al, 2013a , b ). Finally, mRNA of the YAP/TAZ pathway were increased in Emd −/y myoblasts, while at the protein level the nuclear localization of YAP/TAZ was increased in patient myoblasts with LMNA mutations cultured at baseline compared with WT, but not following mechanical stimulation or increase matrix stiffness (Bertrand et al, 2014 ; Iyer et al, 2017 ).…”