New intronic splicing mutation in the LMNA gene causing progressive cardiac conduction defects and variable myopathy

Area of Science:

• Genetics
• Molecular Biology
• Biochemistry

Background:

• Mutations in the LMNA gene are often unique, complicating genetic variant interpretation, especially for non-coding regions.
• Accurate interpretation of novel genetic variants requires advanced investigative techniques.

Observation:

• Patients with progressive cardiac conduction defects and neuromuscular involvement were studied.
• Genetic analysis involved Sanger sequencing of the LMNA gene, followed by RT-PCR and in silico modeling.

Findings:

• A new intronic variant, c.513+45T>G, was identified in the LMNA gene of a patient and their affected daughter, leading to a 45bp insertion in the cDNA.
• This variant is predicted to result in a longer lamin A/C protein, adding 15 amino acids.

Implications:

• The identified intronic LMNA variant is considered pathogenic and likely contributes to limb-girdle muscular dystrophy type 1B.
• Intronic variants near splice sites may explain genotype-negative laminopathy cases, highlighting the importance of deep intronic variant analysis.