P18

Identification of regulatory factors of FKRP gene expression in skeletal muscle

V Desmeure(1,2) M Geoffroy(1,2) E Gicquel(1,2) I Richard(1,2)

1:GENETHON; 2:Université Paris-Saclay, Univ Evry, Inserm, Genethon, Integrare research unit UMR_S951

The Fukutin-related protein (FKRP) is a ribitol 5’phosphatase which contributes to the α-dystroglycan (αDG) glycosylation and allows the connexion of extracellular matrix to the cytoskeleton. In striated muscle, this linkage is crucial for stability of the fibers and protection against the mechanical stress induced by muscle contraction. Mutations in the FKRP gene cause αDG hypoglycosylation leading to disruption of the aforementioned functions. Depending on the nature of the mutation, FKRP deficiency results in a whole range of pathologies including Limb Girdle Muscular Dystrophy R9 (LGMDR9). To date, there is no cure for these diseases except palliative care. We previously described the in vivo potential of rAAV mediated FKRP gene therapy in FKRP deficient mice, which led us to develop a gene therapy approach. A clinical trial is currently ongoing in LGMDR9 patients, showing promising preliminary results. Since the endogenous mutated FKRP can be expressed in patients and to define whether there is any possible feedback due to the transgene expression, we performed RNAseq and miRseq experiments following gene transfer. We combined the information of dysregulated genes with an in silico analysis of potential regulatory signals at the FKRP gene locus. This analysis allowed us to identify 20 transcription factors, 3 micro-RNAs and 19 RNA-binding proteins as potential FKRP regulators. We performed in vitro experiments by transfecting some of these factors and observed that 2 micro-RNAs modulate positively or negatively FKRP gene expression. Improving our understanding of FKRP regulation will help to understand the consequences of rAAV mediated FKRP gene therapy.