Biomedical subjects

Mridul Johari

Publications and source records attributed to Mridul Johari.

2 recordsLinked to original sources

PubMed2025

The burden of TTN variants in the genomic era: Analysis of 18,462 individuals from the Solve-RD consortium and general recommendations.

PURPOSE: Titin, the largest protein in the human body, has been associated with several disease phenotypes caused by variants in the TTN gene. With around 20% of the population carrying a rare TTN variant and over 60 million genomes expected to have been sequenced worldwide by 2025, interpreting these findings presents major challenges. This study analyzed TTN variants in the Solve-RD cohort, the European network for unsolved rare disease cases. METHODS: We collected data from 11,072 individuals with suspected rare diseases and 7390 healthy relatives from the Solve-RD consortium, checking and manually reviewing TTN variants. We then used a filtering approach focused on clinical relevance, and we provided updated recommendations based on recent literature. RESULTS: Among the cohort, 240 individuals (1.3%) carried at least one heterozygous TTN truncating variant (TTNtv), with a 3.8% prevalence in the neuromuscular subgroup, primarily composed of unsolved cases. Four individuals received a titinopathy diagnosis. Additionally, 99 participants (0.5%) had a TTNtv in a high cardiac percent spliced in exon (>80%), and 4 had an overt cardiomyopathy. CONCLUSION: This study highlights the need for standardized approach to TTN variants, and investigation of missing heritability in individuals with skeletal myopathy with het TTNtv. Establishing consensus on percent spliced in-based thresholds will be essential for assessing cardiac risk and guiding the management of asymptomatic individuals.

Humans↗

PubMed2025

Heterozygous loss-of-function variants in SPTAN1 cause an early childhood onset distal myopathy.

PURPOSE: Heterozygous pathogenic variants in SPTAN1 cause a diverse spectrum of neurogenetic disorders ranging from peripheral and central nervous system involvement to complex syndromic presentations. We set out to investigate the role of SPTAN1 in genetically unsolved hereditary myopathies. METHODS: Through international collaboration we identified 14 families with distal weakness and heterozygous SPTAN1 loss-of-function variants. Clinical data, electrophysiology, muscle computed tomography or magnetic resonance imaging, and muscle biopsy findings were collected and standardized. SPTAN1 protein, messenger RNA expression analysis and copy DNA sequencing was performed on muscle tissue from 2 participants. RESULTS: Five families showed autosomal dominant mode of inheritance, whereas in 9 patients the variant was shown to be de novo, including 2 pairs of monozygotic twins. In 2 families, further segregation analysis was not possible. All affected participants presented with early childhood-onset distal weakness and foot abnormalities. Muscle magnetic resonance imaging or computed tomography in 10 patients showed fatty infiltration of the distal lower limb anterior compartment and/or selective involvement of the extensor hallucis longus muscle. Muscle biopsy revealed myopathic changes in 7 patients. Finally, we provide proof for nonsense-mediated decay in muscle tissue derived from 2 patients. CONCLUSION: We present evidence linking heterozygous SPTAN1 loss-of-function variants to childhood-onset distal myopathy in 14 unrelated families.

Humans↗