Microsatellite disorders are a specific class of human diseases that are due to the expansion of repeated sequences above pathological thresholds. These disorders have varying symptoms and pathogenic mechanisms, caused by the expanded repeat. No cure exists for any of these dramatic conditions. This thesis is investigating new gene editing approaches to remove pathological expansions in the human genome. In a first part, a yeast-based screen was constructed to identify potent CRISPR-associated nucleases that can cut these microsatellites. The second part focuses on myotonic dystrophy type 1 (DM1), which is due to and expanded CTG repeat tract located at the 3’UTR of the DMKP gene. A nuclease, TALENCTG was designed to induce a double strand break into the CTG repeats. It was previously shown to be active in yeast cells, inducing contractions of CTG repeats from a DM1 patient integrated into the yeast genome. The TALEN was tested in DM1 patient cells. The nuclease was found to trigger some contraction events in patient cells. In vivo experiments were carried out in a mouse model of myotonic dystrophy type 1 containing a human genomic fragment from a patient and 1000 CTG. Intramuscular injections of recombinant AAV encoding the TALENCTG revealed that the nuclease is toxic and/or immunogenic in muscle cells in the tested experimental conditions. Finally, the reporter assay integrated in yeast to screen nucleases was transposed in HEK293FS cell line. The integrated cassette contains a CTG expansion from a myotonic dystrophy type 1 patient flanked by two halves of GFP genes. This system would enable to find nucleases active in human cells.