This is the case for some G protein regulators (RASD family, member 2/Ras homolog enriched in striatum (Rasd2/Rhes), RAS guanyl-releasing protein 2/calcium and DAG-regulated guanine nucleotide exchange factor I (Rasgrp2/CalDEG-GEF1), and regulator of G protein signaling 2 (Rgs2)) which actively contribute to the mHtt-induced toxicity and are downregulated at the transcript level in HD (reviewed in Seredenina and Luthi-Carter [41]). This evidence concerns the gene RGS2 and Huntington disease.