Dictyostelium discoideum huntingtin null rescue

Huntingtin (HTT) is an important gene for cellular processes such as autophagy, and its loss leads to neurodegenerative disease phenotypes. In Dictyostelium discoideum, HTT-null (htt-) cells exhibit impaired basal autophagy and fail to develop in the presence of ammonium chloride. We conducted a mutagenesis screen on htt- cells to identify potential genetic suppressors of the htt- phenotype. A mutant strain (M1) was isolated that counteracts many of the hallmark defects engendered with htt loss. This mutant, htt-;supX, rescues the growth, cargo degradation defects, developmental timing, and autophagic flux of htt- cells under ammonium chloride stress, representing a partial rescue of the htt- phenotype. Whole-genome sequencing revealed four mutations in the mutant strain affecting genes involved in vesicle trafficking, signal transduction, metal ion regulation, and fatty acid elongation. Transcriptome sequencing identified differentially expressed genes in the mutant strain that include genes whose expression was returned to wild-type levels, including autophagy-related genes that may be implicated in pathways such as Rab GTPase regulation and SNARE-mediated vesicle fusion.