These can be missense mutations, such as INS-C96Y [122] or HNF1B-R165H [134], associated with neonatal diabetes and MODY, respectively, as well as, nonsense mutations resulting in truncated proteins—RFX6 [262] or GCK [263] variants—or repeat insertions such as GAA trinucleotide repeat insertion in exon 1 of FXN, associated with Friedreich’s ataxia [139]. Here, FXN is linked to Friedreich ataxia.