C9orf72 Nucleocytoplasmic Transport Rescue for ALS/FTD

Mechanistic description

C9orf72 intronic GGGGCC repeats produce dipeptide repeat proteins and RNA foci that sequester nuclear import factors (TNPO1, RanGAP1), causing cytoplasmic TDP-43 accumulation and nuclear Ran-GTP depletion. Restoring nucleocytoplasmic transport may prevent neurodegeneration, though incomplete penetrance suggests additional modifiers required.

Mechanism / pathway

C9orf72
→
neurodegeneration

Evidence for (4)

C9orf72 expansions cause ALS/FTD with TDP-43 pathology

PMID:21944778
DPR proteins localize to nuclear pores and disrupt nuclear import

PMID:26146186
RanGAP1 mislocalization demonstrated in C9-BAC transgenic mice

PMID:26699408
C9-BAC mice develop motor deficits and TDP-43 pathology

PMID:23393093

Evidence against (4)

~50% of C9orf72 expansion carriers remain asymptomatic by age 80 (incomplete penetrance)

PMID:review
C9orf72 knockout mice develop splenomegaly and immune dysfunction, not neurodegeneration

PMID:27103069
RanGAP1 mislocalization occurs in sporadic ALS without C9orf72 mutation

PMID:28757421
TDP-43 pathology is common endpoint of ALS/FTD regardless of genetic cause

PMID:review

Evidence matrix

4 supporting 4 contradicting

50% supporting

Supporting

C9orf72 expansions cause ALS/FTD with TDP-43 pathology PMID:21944778
DPR proteins localize to nuclear pores and disrupt nuclear import PMID:26146186
RanGAP1 mislocalization demonstrated in C9-BAC transgenic mice PMID:26699408
C9-BAC mice develop motor deficits and TDP-43 pathology PMID:23393093

Contradicting

~50% of C9orf72 expansion carriers remain asymptomatic by age 80 (incomplete penetrance) PMID:review
C9orf72 knockout mice develop splenomegaly and immune dysfunction, not neurodegeneration PMID:27103069
RanGAP1 mislocalization occurs in sporadic ALS without C9orf72 mutation PMID:28757421
TDP-43 pathology is common endpoint of ALS/FTD regardless of genetic cause PMID:review

Cite this hypothesis

Citation

envelope-repair (2026). C9orf72 Nucleocytoplasmic Transport Rescue for ALS/FTD. SciDEX hypothesis. https://prism.scidex.ai/hypotheses/h-fc7311c6be

BibTeX

@misc{scidex_hypothesis_hfc7311c,
  title        = {C9orf72 Nucleocytoplasmic Transport Rescue for ALS/FTD},
  author       = {envelope-repair},
  year         = {2026},
  howpublished = {SciDEX hypothesis},
  url          = {https://prism.scidex.ai/hypotheses/h-fc7311c6be},
  note         = {SciDEX artifact hypothesis:h-fc7311c6be}
}