Study Identifies NRN1 as Therapeutic Target Candidate for Alzheimer Disease

A recent investigation leveraging large-scale Alzheimer disease (AD) consortia datasets reported that Neuritin-1 (NRN1), a synaptic plasticity–associated protein previously linked to cognitive resilience, demonstrates genomic and proteomic signals consistent with therapeutic target candidacy. All told, the findings position NRN1 as a biologically plausible target for therapeutic development in AD, particularly within synaptic resilience pathways, although the work remains preclinical and exploratory.¹

Antibody Validation and Protein Characterization

Published in Alzheimer’s & Dementia, a central aim of the study was to validate commercially available antibodies capable of reliably detecting endogenous NRN1 protein. Among 3 tested polyclonal antibodies, Abcam ab64186 demonstrated specificity in rodent neurons and mouse brain tissue, with signal attenuation following siRNA-mediated knockdown.

Western blot analyses consistently identified an approximately 34-kDa band in rodent systems, suggesting that NRN1 may predominantly exist as a homodimer under experimental conditions. In human dorsolateral prefrontal cortex samples, NRN1 levels were comparable between controls and primary tauopathy cases—including progressive supranuclear palsy and corticobasal degeneration—indicating that tau pathology alone may not account for altered NRN1 abundance. Similarly, no significant differences in NRN1 protein levels were observed in Tau P301S (PS19) mice relative to nontransgenic littermates at 3 or 9 months of age.

Study Results and Target Prioritization

NRN1 was originally identified in proteomic analyses of postmortem human brain tissue as one of the strongest proteins associated with cognitive resilience in participants from the Religious Orders Study and Rush Memory and Aging Project (ROSMAP). In those analyses, higher cortical NRN1 abundance correlated with slower cognitive decline despite comparable neuropathologic burden.¹

The present study applied the TREAT-AD target risk framework, an integrative scoring system that incorporates genetic association data, transcriptomics, and proteomics to rank therapeutic candidates. All told, NRN1 received a composite target risk score of 3.29 out of 5, placing it in the 87.5th percentile among evaluated genes. The genomic component—reflecting differential expression in postmortem AD brain tissue—contributed more strongly to the score than genome-wide association signals, consistent with the absence of genome-wide significant single-nucleotide polymorphisms near NRN1.

Jeremy Herskowitz, PhD, professor and scientist at University of Birmingham, School of Medicine, and his colleagues used single-nucleus RNA sequencing data from SEA-AD and found that NRN1 expression was highest in excitatory neurons and declined with increasing donor pseudo-progression, a composite metric reflecting AD clinicopathologic burden. Notably, decreased NRN1 expression appeared to persist within surviving excitatory neurons, suggesting the reduction may not be solely attributable to neuronal loss.¹

“In order to support NRN1 as a rational therapeutic target to promote resilience and delay dementia onset, it is imperative to assess whether NRN1 can provide neuroprotection against tau,” noted study authors.¹ “Our results herein suggest that tau pathology alone may not alter NRN1 protein abundance in the dorsolateral prefrontal cortex.”

Synaptic Biodomain Mapping and Proteomic Context

NRN1 encodes a neurotrophic factor implicated in synaptic maturation and plasticity. Prior work has demonstrated that NRN1 enhances synaptic protein networks and mitigates amyloid beta–associated molecular signatures in vitro.²

In the current analysis, gene set enrichment analysis of rat primary cortical neurons treated with exogenous NRN1 showed upregulation of proteins mapped to synaptic biodomains, including postsynaptic organization and synaptic vesicle cycling. These findings were compared with human brain proteomic data from the Accelerating Medicines Partnership for Alzheimer’s Disease (AMP-AD) consortium,³ revealing that many synaptic terms increased with NRN1 treatment corresponded to terms downregulated in AD brains.

This reciprocal pattern supports the hypothesis that augmenting NRN1 activity may counteract synaptic proteomic signatures observed in AD. However, these findings derive from in vitro and bioinformatic comparisons rather than in vivo interventional studies.

Clinical Context: Synaptic Preservation as a Therapeutic Strategy

Synaptic dysfunction is an early and robust correlate of cognitive decline in AD, often preceding overt neuronal loss.⁴ While recently approved anti-amyloid monoclonal antibodies, including lecanemab and donanemab, target amyloid pathology, there remains substantial interest in therapies aimed at preserving synaptic integrity and enhancing resilience mechanisms.⁵

Proteomic resilience signatures from ROSMAP and related cohorts suggest that certain individuals tolerate significant amyloid and tau pathology without clinical dementia, potentially due to preserved synaptic networks.¹ NRN1’s consistent association with synaptic modules across multiple datasets supports further investigation within this framework.

Limitations and Next Steps

The work by Herskowitz et al was limited by its reliance on postmortem datasets, in vitro neuron models, and relatively small tauopathy cohorts. No in vivo therapeutic modulation of NRN1 was performed in AD models, and the absence of strong genetic association signals raised questions about causality versus correlation.

They concluded that further mechanistic studies will be required to determine whether NRN1 augmentation alters disease trajectory in animal models and whether pharmacologic modulation is feasible. Translation into therapeutic development will depend on demonstration of functional benefit beyond proteomic shifts.

Nonetheless, the work contributes validated research tools and integrative prioritization data supporting NRN1 as a candidate target within synaptic resilience pathways.

REFERENCES
1. Pugh DA, Cary GA, Greathouse KM, et al. NRN1 as a therapeutic target for Alzheimer's disease. Alzheimer's Dement. 2026; 22:e71149. Doi:10.1002/alz.71149
2. Yu L, et al. Association of cortical protein expression with cognitive resilience in Alzheimer disease. Nat Med. 2020;26(1):109-116. https://doi.org/10.1038/s41591-019-0651-4
3. DeKosky ST, Scheff SW. Synapse loss in frontal cortex biopsies in Alzheimer’s disease. Ann Neurol. 1990;27(5):457-464. https://doi.org/10.1002/ana.410270502
4. van Dyck CH, et al. Lecanemab in early Alzheimer’s disease. N Engl J Med. 2023;388:9-21. https://doi.org/10.1056/NEJMoa2212948
5. Mintun MA, et al. Donanemab in early symptomatic Alzheimer disease. N Engl J Med. 2021;384:1691-1704. https://doi.org/10.1056/NEJMoa2100708