However, there are conflicting reports on the expression of calcium signalling genes in HD iPSC-derived neuronal cultures, with Mattis et al. reporting no difference in the expression of the N-methyl-D-aspartate (NMDA) receptor subunit GRIN2B [41], and the HD iPSC Consortium reporting reduced expression of GRIN2B as well as other calcium signalling genes [43]. The gene discussed is GRIN2B; the disease is Huntington disease.