MOLECULAR MECHANISMS AND THERAPEUTIC APROACHES FOR RESTORATION OF mRNA TRANSCRIPTION, MATURATION AND TRANSLATION IN INHERITED COAGULATION FACTOR DEFICIENCIES

Although substitutive therapy in coagulation factor deficiencies has recently evolved towards proteins with extended half-life and reduced risk for complications, the quality of life of patients would be significantly ameliorated by innovative approaches, based on alternative strategies and able to provide prolonged/permanent expression of therapeutic levels of the defective factor. Among these, rescuing the altered pre-RNA processing/maturation and mRNA translation has received particular attention because it would in principle permit to restore expression of the mutated gene still maintaining its physiological regulation in the competent tissues, especially hepatocytes which efficiently deliver several coagulation proteins. More recently, gene editing approaches permit specific DNA sequence recognition, cleavage and thus repair/correction of mutated genes in the appropriate cells. Here we focus on molecular mechanisms supporting innovative approaches for restoring transcription, maturation and translation of mRNAs in inherited coagulation factor deficiencies: By engineering transcription activator-like effectors fused with an activation domain (TALE-TFs), able to specifically rescue the coagulation factor VII promoter activity impaired by severe disease-causing mutations. In turn, this triggers synthesis of factor VII mRNA and secretion of functional factor VII protein. By engineering the key component of the spliceosome, the small nuclear RNA U1 (U1 snRNA), able to prevent exon skipping in mutated factor VII and factor IX pre-mRNA exon-intron junctions. In turn, this triggers synthesis of correct mRNA and secretion of functional factors. By aminoglycoside drugs inducing ribosome readthrough on premature translation termination codons affecting factor VII. This permits synthesis of full length protein with procoagulant function instead of truncated non-functional molecules. Depending on the approach and mutations affecting patients' mRNA, we report in cellular and animal models expression levels ranging from negligible to the rescue of potentially therapeutic amounts of coagulation factor activity. Our data support further studies aimed at evaluating clinical translatability of specific molecules in selected groups of patients.