Morphological analysis of 13 LMNA variants identified in a cohort of 324 unrelated patients with idiopathic or familial dilated cardiomyopathy.

Abstract

BACKGROUND:

Mutations in the LMNA gene, encoding lamins A/C, represent a significant cause of dilated cardiomyopathy. We recently identified 18 protein-altering LMNA variants in a cohort of 324 unrelated patients with dilated cardiomyopathy. However, at least one family member with dilated cardiomyopathy in each of 6 pedigrees lacked the LMNA mutation (nonsegregation), whereas small sizes of 5 additional families precluded definitive determinations of segregation, raising questions regarding contributions by those variants to disease.

METHODS AND RESULTS:

We have consequently expressed, in COS7 cells, GFP-prelamin A (GFPLaA) fusion constructs incorporating the 6 variants in pedigrees with nonsegregation (R101P, A318T, R388H, R399C, S437Hfsx1, and R654X), the 4 variants in pedigrees with unknown segregation (R89L, R166P [in 2 families], I210S, R471H), and 3 additional missense variants (R190Q, E203K, and L215P) that segregated with disease. Confocal immunofluorescence microscopy was used to characterize GFP-lamin A localization and nuclear morphology. Abnormal phenotypes were observed for 10 of 13 (77%) variants (R89L, R101P, R166P, R190Q, E203K, I210S, L215P, R388H, S437Hfsx1, and R654X), including 4 of 6 showing nonsegregation and 3 of 4 with uncertain segregation. All 7 variants affecting coil 1B and the lamin A-only mutation, R654X, exhibited membrane-bound GFP-lamin A aggregates and nuclear shape abnormalities. Unexpectedly, R388H largely restricted GFP-lamin A to the cytoplasm. Equally unexpected were unique streaked aggregates with S437Hfsx1 and giant aggregates with both S437Hfsx1 and R654X.

CONCLUSIONS:

This work expands the recognized spectrum of lamin A localization abnormalities in dilated cardiomyopathy. It also provides evidence supporting pathogenicity of 10 of 13 tested LMNA variants, including some with uncertain or nonsegregation.

• Authors: Jason Cowan, Duanxiang Li, Jorge Gonzalez-Quintana, Ana Morales, Ray E Hershberger
• Journal: Circulation. Cardiovascular genetics (Circ Cardiovasc Genet) Vol. 3 Issue 1 Pg. 6-14 (Feb 2010) ISSN: 1942-3268 [Electronic] United States
• PMID: 20160190 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Lamin Type A
• Nuclear Proteins
• Protein Precursors
• Recombinant Fusion Proteins
• prelamin A
• Green Fluorescent Proteins

Topics

• Amino Acid Substitution
• Animals
• COS Cells
• Cardiomyopathy, Dilated (genetics, pathology)
• Cell Nucleus (ultrastructure)
• Chlorocebus aethiops
• Cohort Studies
• Female
• Green Fluorescent Proteins (genetics, metabolism)
• Humans
• Lamin Type A (genetics, metabolism)
• Male
• Mutagenesis, Site-Directed
• Nuclear Proteins (genetics)
• Pedigree
• Phenotype
• Protein Precursors (genetics)
• Recombinant Fusion Proteins (genetics, metabolism)