SLC29A1 and frontotemporal dementia: In support of this observation, the expression level of the SLC29A1 and SLC29A2 genes was extremely low (Fig. 6B) and FTD incorporation into nuclear DNA was not observed unless cells were cultured in the presence of a high concentration (10 μM) of FTD in human fibroblasts, the cellular components of the surrounding matrix (Fig. 6A).