However, in the R6/2 transgenic HD mouse model, no increase in the number of proliferating nuclear antigen (PCNA)-labeled cells was observed in the SVZ, and none of the detected BrdU-labeled cells co-expressed DCX or NeuN, indicating that, in this transgenic model, the striatum does not provide the necessary environment for the development of progenitor cells into mature neurons (Kohl et al., 2010). This evidence concerns the gene PCNA and Huntington disease.