CAPN2 and Friedreich ataxia: That FA proteins play an important role in modulating the levels of μ-calpain activity found in normal cells is demonstrated by the finding that restoring levels of FA proteins in FA cells to those found in normal cells by transfection of FA cells with a retroviral vector expressing the appropriate FANC cDNA leads to reduction of μ-calpain activity to normal levels (Figure 6) [69].