Laminopathies disrupt epigenomic developmental programs and cell fate.

Area of Science:

• Cell Biology
• Epigenetics
• Molecular Biology

Background:

• Lamin A, a nuclear envelope protein encoded by the LMNA gene, is crucial for maintaining nuclear structure and regulating gene expression.
• Missense mutations in LMNA cause Emery-Dreifuss muscular dystrophy (EDMD), a severe muscle-wasting disorder.
• Epigenetic dysregulation, particularly altered heterochromatin formation, is increasingly recognized in various genetic disorders.

Purpose of the Study:

• To investigate the impact of LMNA mutations on epigenomic transitions at the nuclear envelope during myogenesis.
• To determine how specific lamin A mutations affect heterochromatin formation and gene expression.
• To elucidate the role of epigenetic programming defects in the pathogenesis of EDMD.

Main Methods:

• DamID-seq (DNA adenine methyltransferase identification by sequencing) to map heterochromatin domains.
• Chromatin immunoprecipitation-DNA sequencing (ChIP-seq) to validate findings.
• DNA methylation studies in patient-derived fibroblasts.
• Analysis of muscle biopsies from EDMD patients.

Main Results:

• Lamin A mutations disrupted the formation of lamin A-associated heterochromatin domains in an allele-specific manner.
• Perturbations in epigenomic transitions were observed, including altered euchromatin-heterochromatin states during myogenesis.
• EDMD patients showed loss of heterochromatin at the Sox2 pluripotency locus, leading to persistent Sox2 mRNA expression.
• Overexpression of Sox2 inhibited myogenic differentiation in human cells.

Conclusions:

• Nuclear envelopathies, such as EDMD, are disorders of developmental epigenetic programming.
• Altered formation of lamina-associated domains due to LMNA mutations contributes to disease pathogenesis.
• Targeting epigenetic dysregulation may offer therapeutic strategies for EDMD.