Downregulation of the ubiquitin ligase UBR5 during iPSC differentiation, or UBR5 knock-down, impaired the proteasomal degradation of mHtt, increasing mHtt aggregation and toxicity, and suggesting that a decline of UBR5 during ageing may aggravate HD pathology (Koyuncu et al., 2018). This evidence concerns the gene UBR5 and Huntington disease.