Defects of splicing in antithrombin deficiency

Area of Science:

• Genetics and Molecular Biology
• Hematology
• Medical Disorders

Background:

• Aberrant splicing is increasingly recognized as a factor in various diseases.
• Previously, only 7% of SERPINC1 mutations causing antithrombin deficiency were identified as splicing-related.

Purpose of the Study:

• To investigate the role and spectrum of splicing defects in antithrombin deficiency.
• To identify novel SERPINC1 mutations affecting splicing and their functional consequences.

Main Methods:

• Analysis of SERPINC1 by Sanger sequencing and MLPA in 141 patients.
• Functional and Western blot assays for plasma antithrombin.
• Proteomic analysis and in silico splicing predictions using Human Splicing Finder.

Main Results:

• Identified 89 SERPINC1 defects, with 13 potentially affecting splicing.
• Discovered 9 new splicing site mutations and 3 gene defects impacting splicing.
• Characterized a novel exon duplication causing mild deficiency and a deep intronic mutation creating a cryptic splice site.

Conclusions:

• Aberrant splicing accounts for a substantial proportion (up to 13%) of antithrombin deficiency cases.
• SERPINC1 mutations affecting splicing, including deep intronic variants, can lead to Type I, Type II, or moderate antithrombin deficiency.