Gene augmentation therapy (GAT) is used to:
Gene augmentation alias addition therapy provides supplemental functional copy gene compensating recessive loss-of-function mutation where endogenous loci produce truncated or misfolded protein rapidly degraded proteasome or nonsense-mediated decay. Delivered cDNA lacks introns and native regulatory elements codon-optimized enhancing translation and CpG depleted reducing TLR9 activation expressed under heterologous constitutive promoter chicken beta-actin with CMV enhancer or tissue-specific transthyretin promoter driving strong transcription independent defective locus that remains present but inactive. After nuclear entry via nuclear pore, construct episomally or integrally transcribed RNA polymerase II mRNA capping polyadenylation SV40 late signal export NXF1 pathway translation rough ER producing protein folding via BiP disulfide isomerases trafficking Golgi acquiring glycans secreted plasma restoring metabolic pathway such as phenylalanine hydroxylase or clotting factor activity above 5 percent threshold converting severe to mild phenotype. Strategy avoids chromosome editing avoiding double-strand break off-target risks while achieving therapeutic threshold suitable dose control. This mechanistic insight guides vector optimization, dosing strategies, and clinical safety monitoring essential for translational development and regulatory evaluation.
Ref: NIH Gene Augmentation Therapy Strategy; Watson Molecular Biology Gene Augmentation Chap 15; NCBI Bookshelf Gene Addition https://www.ncbi.nlm.nih.gov/books/NBK21981/.