DHFR and Huntington disease: In a TWAS, increased expression of both MSH3 and DHFR in prefrontal cortex (CMC, 2017) was associated with faster progression in TRACK-HD (Moss et al., 2017) at similar levels of significance (P = 2.52 × 10−6 and P = 4.08 × 10−6, respectively; Supplementary Table 10), making it difficult to distinguish which is more functionally relevant.