Mechanistic description
FRAP-based measurement of TDP-43 liquid-liquid phase separation state provides a continuous biomarker of nuclear-cytoplasmic compartmentalization. Endogenous TDP-43-eGFP knock-in in iPSC neurons enables longitudinal monitoring; orthogonal validation via mAb414 nuclear pore integrity anchors imaging to ultrastructure. Primary constraint is imaging endpoint gap—two-photon FRAP is not deployable in standard trials; PET ligand development is the critical path to clinical utility.
Evidence for (8)
TDP-43 pathology present in >95% of ALS cases
Nuclear import defects cause cytoplasmic TDP-43 accumulation
Phase separation of TDP-43 directly observed by super-resolution microscopy
TDP-43 seeding induces cytoplasmic aggregation heterogeneity and nuclear loss of function of TDP-43.
Stress-induced TDP-43 nuclear condensation causes splicing loss of function and STMN2 depletion.
TDP-43 dysfunction leads to bioenergetic failure and lipid metabolic rewiring in human cells.
TDP-43 pathology disrupts nuclear pore complexes and nucleocytoplasmic transport in ALS/FTD.
TDP-43 nuclear condensation and neurodegenerative proteinopathies.
Evidence against (2)
FRAP measures protein mobility influenced by viscosity and crowding, not exclusively liquid-to-solid transition; cannot distinguish phase separation defects from nuclear import defects without orthogonal anchor
TDP-43 aggregates may form via mechanisms distinct from liquid-to-solid phase transition, making FRAP kinetics an indirect read-out