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A Dominant C150Y Mutation in FHL1 Induces Structural Alterations in LIM2 Domain Causing Protein Aggregation In Human
Rashmi Santhoshkumar1, Veeramani Preethish-Kumar2, Kiran K Mangalaparthi3
1Department of Neuropathology, National Institute of Mental Health and Neuro Sciences, Bengaluru, 560 029, Karnataka, India.
Abstract:
FHL1-related myopathies are rare X-linked dominant myopathies. Though clinically classified into several subgroups, spinal and scapuloperoneal muscle involvement are common to all. In this study, we identified c.449G > A, p.C150Y mutation by clinical exome sequencing in two patients from same family (son and mother) of Indian origin who presented with multiple contractures. Muscle biopsy showed numerous intracytoplasmic aggregates intensely stained on HE and MGT. The strong reactions to M-NBT revealed aggregates to be reducing bodies and positively labeled to anti-FHL1 antibody. Ultrastructurally, Z-band streaming and granular and granulofilamentous material were seen. Further, the translational evidence of mutant peptide was confirmed using mass spectrometric analysis. To establish p.C150Y as the cause for protein aggregation, in vivo studies were carried out using transgenic Drosophila model which highlighted Z-band abnormalities and protein aggregates in indirect flight muscles with compromised physiological function. Thus, recapitulating the X-linked human disease phenotype. Additionally, the molecular dynamics simulation analysis unraveled the drastic change in α-helix of LIM2, the region immediately next to site of C150Y mutation that could be the plausible cause for protein aggregation. To the best of our knowledge, this is the first study of p.C150Y mutation in FHL1 identified in Indian patients with in vivo and in silico analysis to establish the cause for protein aggregation in muscle.
Insights
This study identifies a novel FHL1 mutation (p.C150Y) in Indian patients with X-linked myopathy, revealing protein aggregates and Z-band abnormalities. In vivo and in silico analyses confirm this mutation causes the observed muscle pathology.
Area of Science:
- Genetics
- Molecular Biology
- Neurology
Background:
- FHL1-related myopathies are rare X-linked dominant disorders.
- Common features include spinal and scapuloperoneal muscle involvement.
- Clinical classification into subgroups exists, but underlying molecular mechanisms require further elucidation.
Observation:
- A novel c.449G>A, p.C150Y mutation in the FHL1 gene was identified in two Indian patients (mother-son) with multiple contractures.
- Muscle biopsies revealed intracytoplasmic aggregates, identified as reducing bodies positive for FHL1.
- Ultrastructural analysis showed Z-band streaming and granular material in muscle fibers.
Findings:
- Mass spectrometry confirmed the translational evidence of the mutant FHL1 peptide.
- A transgenic Drosophila model recapitulated X-linked myopathy phenotypes, including Z-band abnormalities and protein aggregates in flight muscles.
- Molecular dynamics simulations indicated that the p.C150Y mutation disrupts the α-helix structure near the mutation site, leading to protein aggregation.
Implications:
- This study provides the first in vivo and in silico evidence linking the FHL1 p.C150Y mutation to protein aggregation and myopathy in Indian patients.
- The findings enhance understanding of FHL1-related myopathies' molecular pathogenesis.
- This research may inform future diagnostic and therapeutic strategies for rare genetic muscle disorders.
