GRM1 and Huntington disease: The expression of SYT13, LRRTM1, GRM1, EPB41L2, DLGAP3, and AGAP2 is reduced in HD OPCs derived from human embryonic stem cells (Osipovitch et al., 2019), which is consistent with the expression patterns we observed in patient-derived striatal tissue, knock-in mouse model striatal tissue, and in neuronal tissue from Drosophila expressing mHTT in glia (Figure 3C).