Sleeping Beauty Transposon System is a Reliable Gene Delivery Tool for Hereditary Tyrosinaemia Type 1 Disease Gene Therapy: Size of the Foreign Gene Decides the Timing of Stable Integration into the Host Chromosomes

Abstract

This study investigated compensation for loss of the fumaryl-acetoacetate hydrolase gene (Fah) by gene therapy using the Sleeping Beauty transposon system (SBTS), in a hereditary tyrosinaemia type 1 (HT-1) mouse model (Fah-/-). Twenty Fah-/- study mice, five wild-type positive controls and five Fah-/- negative controls were included. All Fah-/- mice received 2-(2-nitro-4-trifluoro-methylbenzoyl)-1,3-cyclo hexaedione (NTBC). Fah-/- study mice were randomly injected with one of two SBTS constructs: Fah-SBTS (containing mouse Fah gene), or forkhead box M1b (FOXM1B)-Fah-SBTS (containing mouse Fah and human FOXM1B genes). Firefly luciferase-SBTS was injected as a trace marker. NTBC treatment stopped after construct injection; Fah-/- negative controls were kept healthy with continued NTBC. Mice were weighed daily; the luciferase signal was monitored by in vivo bioluminescence, and Fah and FOXM1B gene expression were evaluated. The Fah gene integrated into the mouse chromosomes within 1 week of Fah-SBTS injection (mice survived without NTBC thereafter) and within 1 month of FOXM1B-Fah-SBTS injection (mice lost weight dramatically and needed additional NTBC). The shorter Fah gene had an advantage over the longer FOXM1B-Fah gene for stable integration into the host mouse chromosomes.