Chromatin regulation by Brg1 underlies heart muscle development and disease

Area of Science:

• Molecular biology
• Cardiovascular research
• Epigenetics

Background:

• Cardiac hypertrophy and failure involve gene expression changes.
• Adult cardiomyocytes express alpha-myosin heavy chain (MHC), while embryonic ones express beta-MHC.
• Cardiac stress induces a shift from alpha-MHC to beta-MHC in adult hearts.

Purpose of the Study:

• To investigate the role of Brg1 in regulating cardiac growth, differentiation, and gene expression.
• To elucidate the epigenetic mechanism by which Brg1 controls developmental and pathological gene expression in cardiomyocytes.

Main Methods:

• Studied Brg1's function in embryonic and adult mouse cardiomyocytes.
• Investigated Brg1's interaction with histone deacetylase (HDAC) and poly (ADP ribose) polymerase (PARP).
• Analyzed Brg1 expression in patients with hypertrophic cardiomyopathy.

Main Results:

• In embryos, Brg1 promotes myocyte proliferation and maintains fetal cardiac differentiation by regulating MHC expression.
• In adults, Brg1 is reactivated by stress, forming a complex with HDAC and PARP to induce an alpha-MHC to beta-MHC shift.
• Preventing Brg1 re-expression reduced cardiac hypertrophy and reversed the MHC switch.
• Elevated BRG1 levels correlated with disease severity in hypertrophic cardiomyopathy patients.

Conclusions:

• Brg1 plays a critical role in maintaining cardiomyocytes in an embryonic state.
• Brg1, HDAC, and PARP cooperate via an epigenetic mechanism to control cardiac gene expression during development and disease.
• Targeting Brg1 re-expression may offer therapeutic potential for cardiac hypertrophy and failure.