Table 2.
In vitro evidence of mHTT seeding capacities.
| Protein form | Cell model | Observations | References |
|---|---|---|---|
| Co-transfection with poly25Q EGFP and poly104Q c-Myc | Cos-1 | Co-aggregation of normal length and extended polyQ tracts into cell cytoplasm | Kazantsev et al., 1999 |
| Co-transfection with poly25Q nucleolin EGFP and poly104Q c-Myc | Cos-1 | Heterogeneous aggregates of 104Q c-Myc and 25Q-nucleolin- EGFP within cell nuclei Appearance of homogenous cytoplasmic aggregates with the expression of 104Q c-Myc only |
|
| Transfection with 104Q nucleolin EGFP and 104Q c-Myc | Cos-1 | Extended polyglutamine colocalization in both the cytoplasm and nucleus with the coexpression of 104Q nucleolin EGFP and 104Q c-Myc Interactions between polyglutamines causes relocation 104Q c-Myc into the nucleus |
|
| Co-transfection of HA-HDQ20 and/or HA-HDQ32 with GFP-HDQ72 | Cos-1 | Elongated HTT polyQ fragments can recruit wild-type HTT | Busch et al., 2003 |
| Transfection with CFP-Q25HTTExon1 and exposure to K2Q44K2 fibrils | HEK | Co-localization of CFP-Q25HTTExon1 with K2Q44K2 induces amyloid nucleation in a sequence-specific manner | Ren et al., 2009 |
| Transfection with ChFP-HTTExon1Q25 and exposure to positive, neutral or negatively charged FITC-labeled Q44 fibrils | HEK | Induction of nucleation within the cytoplasm of ChFP- HTTExon1Q25 transfected cells by all three types of fibrils (i.e., positive, neutral, and negative net charges) | Trevino et al., 2012 |
| Transfection with ChFP-HTTExon1Q25 and exposure to non-fibrillar K2Q44K2 aggregates | HEK | Reduced internalization of non-fibrillar K2Q44K2 and nucleation of cytoplasmic ChFP-HTTExon1Q25 in comparison to fibrillar forms | |
| Transfection with ChFP-HTTExon1Q25 and exposure to HTTExon1Q44 or Q44 fibrils | HeLa | Internalization of HTTExon1Q44 and Q44 fibrils into HeLa cells and nucleation within the cytoplasm ChFP-HTTExon1Q25 transfected cells HTTExon1Q44 fibril internalization is less efficient than for the Q44 fibrils | |
| Transfection with HTT(Q25)CFP/YFP and exposure to HTT Q50 fibrils | C17.2 | Heparan sulfate proteoglycans-independent internalization of Q50 fibrils and nucleation with exogenous HTT(Q25)CFP/YFP | Holmes et al., 2013 |
| Transfection with ChFP-HTTExon1Q25 and exposure to HTTExon1Q44 fibrils | Undifferentiated and differentiated N2A | Seeding capacity of transfected HTTExon1Q44 fibrils with ChFP-HTTExon1Q25 in undifferentiated and differentiated N2A cells | Ruiz-Arlandis et al., 2016 |
| PolyQ (KKQ30KK or KKQ40KK) oligomers | HTT14A2.6 | Seeding of polyQ oligomers in HTT14A2.6 cells | Tan et al., 2015 |
| Exposure to media and lysates from induced HTT14A2.6 cells | Naïve | Media and lysates from induced HTT14A2.6 cells can seed aggregation in naïve cells | |
| CSF from deceased HD patients | HTT14A2.6 | CSF obtained from HD patients postmortem increase aggregate number in HTT14A2.6 cells | |
| CSF from BACHD rats | HTT14A2.6 | CSF from living BACHD rats can seed aggregation | |
| Expression of PrDQ19, PrDQ54 and PrDQ92 | GT17 | Soluble Sup35 protein converts into insoluble aggregates following expression of PrDpolyQ pathogenic (≥54 glutamines) proteins | Goehler et al., 2010 |
| Transfection with Rnq1Q19, Rnq1Q54 and Rnq1Q91 | GT17 | Pathogenic PolyQ tracts convert soluble Rnq1 into insoluble aggregates | |
| Transfection with HTT25Q-/103Q-GFP | 74-D694 | HTT103Q induce insoluble aggregates of Def1, Pub1, Rpn10, Bmh2, Sgt2, and Sup35 proteins | Nizhnikov et al., 2014 |
| Transfection with HTT25Q-/103Q-GFP | BY4742 and 74-D694 | HTTQ103 promotes it own aggregation and that of Sup35 and Def1 in different yeast strains Deletion of Def1, which normally enhances mHTT aggregation and toxicity, decreases selectively the amount of polymerized HTTQ103 and its cytotoxic effect in BY4742 cells | Serpionov et al., 2017 |
BACHD, bacterial artificial chromosome (BAC) transgenic rat model of HD; Bmh2, protein BMH2; BY4742, yeast strain; C17.2 cells, murine C17.2 neural precursor cells; c-Myc, c-Myc tag peptide; CFP, cyan fluorescent protein; ChFP, mCherry fluorescent protein; Cos-1, fibroblast-like cell lines derived from monkey kidney; Cryo-ET, cryo-electron tomography; Cryo-FLM, cryogenic-fluorescent light microscopy; CSF, cerebrospinal fluid; Def1, RNA polymerase II degradation factor 1; EGFP, enhanced green fluorescent protein; FITC, fluorescein isothiocyanate; GFP, green fluorescent protein; GT17, yeast strain; HA-tag, human influenza hemaglutinin tag; HD, Huntington's disease; HEK, human embryonic kidney cells; HeLa, human uterine cervical carcinoma cells; HTT14A2.6:PC12 cells, (cell line from pheomochromocytoma) that inducibly express a fragment of mHTT (truncated exon 1) epitope tagged with enhanced green fluorescent protein (mHTTex1-GFP) in the presence of ponasterone A; N2A, murine neuroblastoma cell line; PolyQ, polyglutamine; PrD, prion domain; Pub1, nuclear and cytoplasmic polyadenylated RNA-binding protein; Rnq1, yeast prion protein; Rpn10, proteasome regulatory particle base subunit RPN10; Sgt2, small glutamine-rich tetratricopeptide repeat-containing protein 2; Sup35, yeast eukaryotic release factor 3; YFP, yellow fluorescent protein.