In agreement with the in situ detected TG6-based enzymatic activity is the fact that enzymatically active TG6 can increase the aggregate load in double transfected SH-SY5Y cells, in comparison to cells expressing the mutated huntingtin exon 1 fragment alone, thus further pointing towards a key role of TG6 for the pathophysiology of HD. The gene discussed is HTT; the disease is Huntington disease.