GE Homanics¹, SJ Sukoff Rizzo², AC Silva², PL Strick², GW Carter³, JE Park²

Mutations in the presenilin 1 (PSEN1) gene are the most common cause of familial, early-onset Alzheimer's disease (AD), yet rodent models fail to fully recapitulate human AD pathology because they do not naturally develop amyloid plaques or tau aggregates. The common marmoset (Callithrix jacchus) offers a compelling alternative. It is a small non-human primate whose brain closely resembles the human brain, and it develops spontaneous age-related amyloid and tau pathology. We used CRISPR/Cas9 gene editing to independently introduce two PSEN1 point mutations (C410Y and A426P) — the same single-nucleotide changes found in human patients — into marmoset embryos. Several genetically engineered founders were produced; however, most died prematurely. One C410Y founder survived to adulthood and sired germline offspring. Phenotypic outcomes observed in these animals will be the subject of companion talks. In addition, experiments are underway to develop marmoset models of sporadic, late-onset AD. These nonhuman primate models are unprecedented for studying the earliest molecular events that initiate AD, evaluating preventive interventions, and bridging the rodent-to-human translational gap.

Departments of ¹Anesthesiology and ²Neurobiology, University of Pittsburgh, Pittsburgh PA, 15261. ³The Jackson Laboratory, Bar Harbor, ME 04609.

Funding Support: NIA U19 AG074866 and UPMC-ITTC grant IPA 2019 No. 16.

Lauren Bailey, PhD¹, Takeshi Murai, PhD¹, Lauren Mongeau¹, Abbey Setlik¹, Tingting Zhang, PhD¹, Seung-Kwon Ha, PhD, DVM¹, Gregory W. Carter², Afonso C Silva, PhD¹ and Stacey J Sukoff Rizzo, PhD¹,

Fundamental questions remain regarding the mechanisms that initiate Alzheimer’s disease (AD), drive its progression, and link pathology to cognitive impairment. As part of our MARMO-AD consortium, we established a comprehensive testing battery sensitive to detecting age-dependent cognitive decline across the lifespan in our colony of aging marmosets, and marmosets genetically engineered with mutations in the PSEN1 gene which confers early onset AD in humans. Beginning in adolescence, marmosets are trained using touchscreens through a battery of tests that captures a spectrum of cognitive domains including spatial working memory (delayed match to position), behavioral flexibility and reversal learning (delayed non-match to position), recognition memory (trial unique delayed match to sample), attention (serial reaction time task), and episodic-like memory (paired associative learning task). Behavioral and cognitive function are aligned with longitudinal PET neuroimaging and blood-based biomarkers to track AD progression. Similar to human PSEN1 mutation carriers, plasma Aβ42:40 is significantly elevated relative to non-carrier controls Despite robust biomarker and pathological changes, PSEN1 marmosets show no significant deficits in task acquisition or performance across cognitive domains up to 4 years of age. These data are not surprising and recapitulate the disease trajectory of increased amyloid in plasma and brain years before cognitive decline. These ongoing longitudinal studies are enabling the identification of the molecular and cellular mechanisms other than amyloid that contribute to and precede cognitive decline associated with Alzheimer’s disease progression.

(1)University of Pittsburgh School of Medicine, Pittsburgh, PA, USA (2) The Jackson Laboratory, Bar Harbor, Maine, USA

This work is supported by U19AG074866 and 5T32AG021885-19.

Thais Rafael Guimarães¹, Jung Eun Park¹, Catrina Spruce², Stephanie Hachem¹, Swati Banerjee¹, Lauren K Hayrynen Schaeffer¹, Gregg E Homanics¹, Stacey J Sukoff Rizzo¹, Gregory W Carter,², Afonso C Silva¹, and Amantha Thathiah¹

Progress in preclinical Alzheimer’s disease (AD) research has been constrained by models that fail to faithfully recapitulate human aging and overt AD neuropathology. The common marmoset (Callithrix jacchus), a New World non-human primate, exhibits aging trajectories, genetic heterogeneity, and complex social behaviors closely resembling those of humans, providing a highly translational platform for age-related neurodegenerative research. Importantly, marmoset studies uniquely enable longitudinal correlation of in vitro cellular models with in vivo assessments across the marmoset lifespan. We performed an integrated ex vivo and in vitro characterization of marmoset AD and tauopathy models. Immunohistochemical analyses of postmortem brains revealed robust amyloid-β (Aβ) and tau pathology, along with the associated cellular pathology. To establish an in vitro cellular system, we adapted a well-established human direct reprogramming protocol to generate age-conserved induced neurons (iNs) from marmoset fibroblasts. Comparative, unbiased RNA-seq analyses of marmoset and human iN conversion trajectories revealed significant species-specific differences, guiding targeted optimization of the reprogramming strategy. The refined protocol achieved high-efficiency neuronal conversion, improved cell survival and maturation, and preserved AD-relevant protein expression, including amyloid precursor protein (APP)/Aβ and tau. Together, this integrated framework establishes the marmoset as a powerful translational model for AD research. This platform enables minimally invasive mechanistic studies, longitudinal analyses, high-throughput drug screening, and therapeutic discovery aimed at accelerating disease-modifying strategies for AD.

¹University of Pittsburgh School of Medicine, Pittsburgh, PA, USA

²The Jackson Laboratory, Bar Harbor, ME, USA

Gregory W. Carter

Laboratory mice and marmosets provide potential models of aging and Alzheimer’s disease with the capacity to track the initiation and progress of pathology across compressed lifespans. We have performed genetic, genomics, and proteomic analyses of plasma and postmortem tissues to map multi-modal aspects of disease development and progression in these model species. We have drawn from human genetic studies to engineer multiple mouse strains carrying candidate genetic factors for late-onset Alzheimer's disease. In the marmoset, we are combining genetic engineering of select loci with outbred genetic variability to analyze biomarkers of aging and dementia. We assembled a new telomere-to-telomere reference genome for the common marmoset (Callithrix jacchus) and performed whole-genome Illumina sequencing on over 230 marmosets. For both model systems, we have used high-coverage proteomics, Alamar NULISA, and transcriptomics to assess the disease-relevant consequences of genetic factors. We have identified a broad range of disease-associated signatures in knock-in mouse and marmoset models, including immune, metabolic, and synaptic alterations. These outcomes frequently correlate with clinically relevant biomarkers and behavioral outcomes. We have also used multi-omic signatures to understand the molecular pharmacodynamics of candidate drugs. Our findings constitute a data and model resource for identifying the appropriate animal model for understanding genetic liability in Alzheimer's and preclinical testing of targeted therapeutics.

The Jackson Laboratory, Bar Harbor, ME, USA