A conditioning lesion of the peripheral sensory axon triggers robust central axon regeneration in mammals. We visualize the ASJ neuron of C. elegans with a cell-specific green fluorescent protein reporter driven by a thioredoxin trx-1 promoter and trigger conditioned regeneration by laser surgery or genetic disruption of sensory pathways. Utilizing calibrated fluorescent beads, we demonstrate that these neurons brighten when conditioned, suggesting that trx-1 expression indicates regenerative capacity. We show that trx-1 functionally enhances conditioned regeneration but inhibits non-conditioned regeneration. Finally, six strains isolated in a forward genetic screen for reduced fluorescence also show reduced axon outgrowth. We demonstrate a link between trx-1 expression and the conditioned state that we leverage to rapidly assess regenerative capacity.

A conditioning lesion of the peripheral sensory axon triggers robust central axon regeneration in mammals. We trigger conditioned regeneration in the Caenorhabditis elegans ASJ neuron by laser surgery or genetic disruption of sensory pathways. Conditioning upregulates thioredoxin-1 (trx-1) expression, as indicated by trx-1 promoter-driven expression of green fluorescent protein and fluorescence in situ hybridization (FISH), suggesting trx-1 levels and associated fluorescence indicate regenerative capacity. The redox activity of trx-1 functionally enhances conditioned regeneration, but both redoxdependent and -independent activity inhibit non-conditioned regeneration. Six strains isolated in a forward genetic screen for reduced fluorescence, which suggests diminished regenerative potential, also show reduced axon outgrowth. We demonstrate an association between trx-1 expression and the conditioned state that we leverage to rapidly assess regenerative capacity.

Background Mutations in PSEN1, PSEN2, and APP can lead to Alzheimer’s disease (AD) with an early age at onset (AAO) and hallmark progressive cognitive decline. These mutations are highly penetrant. Although mutations in PSEN1 are more common and usually have an earlier AAO, certain mutations in PSEN1 cause a later AAO, similar to PSEN2 and APP mutations. We sought to determine whether common disease endotypes exist across these mutations with a relatively late AAO. Methods We generated hiPSC-derived neurons from patients harboring autosomal-dominant, familial Alzheimer’s disease (FAD) mutations in PSEN1, PSEN2, and APP with a documented age at onset (AAO) around 55 years: PSEN1A79V, PSEN2N141I, and APPV717I. We carried out RNA-seq and ATAC-seq to mechanistically characterize the gene expression and chromatin accessibility changes, respectively. Differential expression analysis, enrichment analysis, TF activity identification, and co-expression module detection were performed for RNA-seq. Differential peak analysis and annotation, TF motif footprinting and differential motif accessibility, and peak functional enrichment were performed for ATAC-seq. This approach allowed us to identify the correlation between gene expression and chromatin accessibility associated with key disease endotypes. Results Using a multiomics approach, we identify and characterize common endotypes in mutations across all three FAD genes: dedifferentiation of a mature neuron to a less differentiated quasi-neuron state, dysregulation of synaptic signaling, repression of mitochondrial function and metabolism, and inflammation. The integrativeanalysis allowed us to ascertain the master transcriptional regulators associated with these endotypes, including REST, ASCL1, and ZIC family members (activation), as well as NRF1 (repression). Conclusions Our findings characterize the common regulatory changes within endotypes across these FAD mutations. However, the severity of dysregulation often differs between PSEN1, PSEN2, and APP mutations both in magnitude and direction. The overarching common link between mutations in FAD genes is the reversion to a less-differentiated neuron state. The transcriptional regulatory mechanisms described within disease endotypes offer potential targets for therapeutic interventions.