Clinical Report: Alternative Isoforms May Refine Variant Interpretation

Overview

This study reveals that many disease-associated variants are missed when relying solely on reference transcripts. The researchers demonstrated functional effects of a lung-specific DPP9 isoform linked to severe COVID-19 and pulmonary fibrosis.

Background

Understanding the impact of genetic variants on protein function is crucial for disease diagnosis and treatment. Traditional analyses often overlook tissue-specific isoforms, which can harbor significant genetic variation. This study aims to refine variant interpretation by integrating long-read RNA sequencing data with existing genetic databases.

Data Highlights

The study identified approximately 40,000 Genome-Wide Association Studies variants mapping to annotated alternative exons compared to 24,000 mapping to reference exons. About 80% of alternative transcripts containing disease-associated variants were not represented in current reference genome annotations.

Key Findings

• Alternative isoform-specific exons had a greater burden of genetic variation than reference exons.
• Approximately 80% of alternative transcripts with disease-associated variants were not included in current reference genome annotations.
• Computational analyses prioritized multiple missense variants predicted to alter protein structure or stability in alternative isoforms.
• The common DPP9 variant associated with severe COVID-19 was found within an unannotated alternative first exon.
• Biochemical experiments demonstrated altered enzymatic properties due to the leucine-to-proline substitution in the DPP9 isoform.

Clinical Implications

Incorporating alternative transcript isoforms into genetic variant analysis may enhance the identification of protein-coding consequences.

Conclusion

The findings indicate that evaluating genetic variants within tissue-specific alternative transcript isoforms may uncover protein-coding consequences that are often missed by traditional analyses.

Related Resources & Content

1. Weykopf G., MRC Human Genetics Unit, Institute of Genetics and Cancer, 2023 -- Alternative Isoforms May Refine Variant Interpretation
2. Frontiers in Immunology — De novo NFKBIA variants within the N-terminal hotspot: consistent immunophenotype and divergent clinical presentations
3. Basic Research in Cardiology — The Underrecognized and Essential Functions of CaMKII in Cardiac Physiology
4. Blood Cancer Journal — Association of Non-Homologous End Joining Pathway with Alternative Splicing in Multiple Myeloma
5. Bone Marrow Transplantation — Is Assessing Gene Polymorphisms Useful for Personalizing Treatment in HSCT Patients?
6. ClinGen Variant Classification Guidance - ClinGen | Clinical Genome Resource
7. Disease-associated genetic variants can cause missense effects in tissue-specific protein isoforms | Nature Communications
8. Common and rare variant analyses reveal genetic factors underlying idiopathic pulmonary fibrosis and its shared aetiology with severe COVID-19 - ScienceDirect