ThPOK was identified by Kappes and colleagues [58] by uncovering the molecular cause of the phenotype of HD (helper-deficient) mice, which lack mature CD4+ T cells, and independently by Bosselut and colleagues [59] as a factor induced in DP thymocytes upon MHC class II-mediated positive selection that promotes CD4 lineage development. This evidence concerns the gene ZBTB7B and Huntington disease.