Ablation of SUN2-containing LINC complexes drives cardiac hypertrophy without interstitial fibrosis

Area of Science:

• Cardiovascular Biology
• Cellular and Molecular Medicine
• Nuclear Envelope Dynamics

Background:

• Cardiomyopathies are linked to LINC complexes and A-type lamins, but disease mechanisms remain unclear.
• The cardiomyocyte cytoskeleton connects to nuclear envelope proteins, influencing cellular function.
• Understanding LINC complex roles is crucial for deciphering cardiomyopathy etiology.

Purpose of the Study:

• To investigate the role of SUN2 in cardiac hypertrophy and associated signaling pathways.
• To determine if SUN2 deficiency uncouples cardiac hypertrophy from profibrotic signaling.
• To elucidate the interplay between SUN2, A-type lamins, and TGFβ signaling in the heart.

Main Methods:

• Generation and analysis of SUN2-null mice.
• Assessment of cardiac morphology, hypertrophy markers, and signaling pathways (AKT/MAPK, TGFβ).
• Evaluation of nuclear envelope protein levels, specifically MAN1.

Main Results:

• SUN2-null mice exhibit cardiac hypertrophy with enhanced AKT/MAPK signaling, similar to lamin A/C-null mice.
• Unlike lamin A/C-null mice, SUN2-null mice do not develop cardiac fibrosis or pathological hypertrophy markers.
• Absence of SUN2 leads to elevated MAN1 at the nuclear envelope, inhibiting TGFβ signaling.

Conclusions:

• SUN2 is essential for productive TGFβ signaling, required for cardiac fibrosis.
• A-type lamins and SUN2 play antagonistic roles in profibrotic signaling through MAN1 regulation.
• This uncoupling of hypertrophy from fibrosis in SUN2-null mice offers a new perspective on cardiomyopathy pathogenesis.