Muscle and brain tissue are among the tissues with the highest GAPDH mRNA expression, while healthy breast tissue has the lowest expression.21 The reported T2 of Pi in muscle at rest at 7 T is around 100 ms (comparable to the T2 value of Pi in breast cancer tissue), which is substantially shorter than the T2 values for PCr and the PDEs in muscle.22 Recently, we measured the transverse relaxation times of the PMEs, PDEs and Pi in the healthy human brain at 7 T. The gene discussed is GAPDH; the disease is breast cancer.