Despite numerous studies focused on identifying compounds capable of stimulating FXN expression, current knowledge regarding cis-regulatory elements involved in FXN gene expression is lacking. Using a combination of episomal and genome-integrated constructs, the authors defined a minimal endogenous promoter sequence required to efficiently drive FXN expression in human cells. They generated 19 constructs varying in length of the DNA sequences upstream and downstream of the ATG start codon. Using transient transfection, they evaluated the capability of these constructs to drive FXN expression. These analyses allowed the identification of a region of the gene indispensable for FXN expression. Subsequently, selected constructs containing the FXN expression control regions of varying lengths were site-specifically integrated into the genome of HEK293T and human induced pluripotent stem cells (iPSCs). FXN expression was detected in iPSCs and persisted after differentiation to neuronal and cardiac cells, indicating lineage independent function of defined regulatory DNA sequences. Finally, based on these results, this group generated AAV encoding miniFXN genes and demonstrated in vivo FXN expression in mice. Results of these studies identified FXN sequences necessary to express FXN in human and mouse cells and provided rationale for potential use of endogenous FXN sequence in gene therapy strategies for FRDA.
Read the entire article HERE