Introduction
Combining in silico prediction with in vitro validation is the gold standard for clarifying the pathogenicity of "Variants of Uncertain Significance" (VUS) at non-canonical splice sites. In a study on Autosomal Recessive Congenital Ichthyosis (ARCI), an RDDC bioinformatics tool, RDDCSC, provided a critical and specific prediction that was later perfectly confirmed by a minigene assay, delivering decisive evidence for prenatal diagnosis.
The Clinical Challenge: A VUS Splicing Variant's Pathogenicity
The challenge began with a 24-week gestation fetus showing ultrasound features (like small nares and persistent open mouth) suspicious of ARCI. Whole Exome Sequencing (WES) revealed compound heterozygous variants in the ABCA12 gene: a known paternal nonsense mutation (p.W1928*) and a novel maternal intronic variant, `c.7104+6T>A`.
This `c.7104+6T>A` variant, located at a non-canonical splice site (+6T>A) and absent from population databases, was classified by ACMG as a VUS. Proving its pathogenicity was essential for providing accurate genetic counseling and prenatal diagnosis for this family.
RDDCSC's Precise Prediction: From "Possible" to "Specific"
To assess the VUS's function, the research team used several bioinformatics tools, including RDDC Splice AI and SpliceAI. While other tools suggested a potential splicing impact, the RDDC tool provided a highly specific, testable hypothesis: the variant would likely cause a 69 bp deletion from the exon.
This prediction translated a vague "splicing error" probability into a precise molecular event (a 69 bp deletion), providing a clear target for the subsequent wet-lab validation.
Perfect Validation by Minigene Assay
Based on this clear prediction, the team constructed minigene vectors and performed validation in both HEK293 and HeLa cells. The results showed the mutant vector produced three splice products: a normal transcript, a transcript with a full skip of exon 47 (leading to a frameshift and PTC), and a third product showing a 69 bp deletion (c.7036_7104del) within exon 47.
This "69 bp deletion" finding was in perfect agreement with the RDDC Splice AI prediction. Both aberrant splice products (one with a 23-amino-acid deletion, one truncated) confirmed the pathogenicity of the VUS.
Case Implications
This case provides powerful evidence that RDDCSC is a robust tool for researchers facing non-canonical VUS. It moves beyond a simple "pathogenic/benign" score to provide a specific molecular mechanism (the 69 bp deletion). This provides a clear blueprint for functional experiments, dramatically increasing the accuracy and efficiency of variant pathogenicity assessment.
Content Source and Disclaimer
This article is a compilation and interpretation of the scientific study cited below, intended to highlight the application of RDDC bioinformatics tools. All research data and conclusions belong to the original authors and publication.
Original Article:
Wang Y, Li Q, Zhang J, et al. A novel variant c.7104 + 6T > A of ABCA12 linked to autosomal recessive congenital ichthyosis verified by minigene splicing assay. Clinical, Cosmetic and Investigational Dermatology. 2024 Jan 12;17:41-50.
Article Link: https://pubmed.ncbi.nlm.nih.gov/39748812/
