Deep intronic variations may cause mild hemophilia A.

Area of Science:

• Genetics
• Molecular Biology
• Hematology

Background:

• Approximately 10% of mild hemophilia A cases lack identifiable gene mutations after full sequencing.
• Mild hemophilia A can present with reduced response to desmopressin, suggesting underlying genetic complexities.

Purpose of the Study:

• To investigate factor VIII gene (F8) mRNA for mutations in families with mild hemophilia A.
• To identify mutations in patients with no apparent genomic mutation and diminished desmopressin response.

Main Methods:

• Analysis of F8 mRNA transcripts in affected individuals.
• DNA sequencing of identified abnormal mRNA.
• In silico prediction of splice site alterations and protein changes.
• In vitro expression studies to confirm mutation effects.

Main Results:

• Abnormal F8 mRNA transcripts were found in four of five families.
• Three novel deep intronic variations (c.2113+1152delA, c.5587-93C>T, c.5999-277G>A) were identified at the DNA level.
• Two mutations were confirmed to cause detrimental effects via in vitro studies, impacting splicing and protein structure.

Conclusions:

• Deep intronic variations are a rare but significant cause of mild hemophilia A when standard F8 mutations are absent.
• These variations may correlate with reduced biologic response to desmopressin.
• F8 mRNA analysis is an effective method for detecting deep intronic variations missed by conventional DNA sequencing.