Disease-causing missense mutations in actin binding domain 1 of dystrophin induce thermodynamic instability and...

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Duchenne muscular dystrophy (DMD) is often caused by dystrophin loss.
• Missense mutations in dystrophin's actin-binding domain 1 (ABD1) are linked to DMD, Becker muscular dystrophy, and X-linked cardiomyopathy.
• Understanding the molecular mechanisms of ABD1 mutations is crucial for disease insight.

Purpose of the Study:

• To investigate whether missense mutations in dystrophin's ABD1 impair actin-binding activity.
• To characterize the biochemical properties of six engineered ABD1 missense mutations.
• To determine the primary cause of disease associated with ABD1 missense mutations.

Main Methods:

• Engineered six specific missense mutations (K18N, L54R, D165V, A168D, L172H, Y231N) into full-length dystrophin cDNA.
• Characterized biochemical properties of wild-type (WT) and mutant dystrophin proteins.
• Assessed actin-binding affinity and thermal denaturation/aggregation propensity.

Main Results:

• Two severe mutations (K18N, L54R) showed a minor decrease in actin-binding affinity.
• All six mutant dystrophin proteins exhibited increased susceptibility to thermal denaturation and aggregation compared to WT.
• WT dystrophin unfolded cooperatively, while mutants showed less stable unfolding.

Conclusions:

• Dystrophin ABD1 missense mutations likely cause disease primarily through protein instability and aggregation.
• Impaired actin-binding may contribute to disease severity in some cases, potentially in combination with aggregation.
• These findings offer new perspectives on the molecular pathology of dystrophinopathies.