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Alzheimer9s disease (AD) is a multifactorial pathology responsible for most cases of dementia worldwide. Only a small percentage of AD cases are due to autosomal dominant mutations, while the vast majority have a sporadic presentation. Yet, preclinical research studies relied for decades on animal models that overexpress human genes found in AD autosomal dominant patients. Thus, one could argue that these models do not recapitulate sporadic AD. To avoid human gene overexpression artifacts, knock-in (KI) models have been developed, such as the novel hAβ-KI mouse model, which are still in early phases of characterization. We hypothesize that comparisons at the transcriptomic level may elucidate critical similarities and differences between transgenic/KI models and AD patients. Thus, we aimed at comparing the hippocampal transcriptomic profiling of overexpression (5xFAD and APP/PS1) and KI (hAβ-KI) mouse models with early- (EOAD) and late- (LOAD) onset AD patients. We first evaluated differentially expressed genes (DEGs) and Gene Ontology biological processes (GOBP) overlapping cross-species. After, we explored a network-based strategy to identify master regulators (MR) and the similarities of such elements among models and AD subtypes. A multiple sclerosis (MS) dataset was included to test the molecular specificity of the mouse models to AD. Our analysis revealed that all three mouse models presented more DEGs, GOBP terms and enriched signaling pathways in common with LOAD than with EOAD subjects. Furthermore, semantic similarity of enriched GOBP terms showed mouse model-specific biological alterations, and protein-protein interaction analysis of DEGs identified clusters of genes exclusively shared between hAβ-KI mice and LOAD. Furthermore, we identified 17 transcription factor candidates potentially acting as MR of AD in all three models. Finally, though all mouse models showed transcriptomic similarities to LOAD, hAβ-KI mice presented a remarkable specificity to this AD subtype, which might support the use of the novel hAβ-KI mouse model to advance our understanding of sporadic LOAD.

Most age-associated neurodegenerative disorders involve the aggregation of specific proteins within the nervous system, as occurs in Alzheimer’s disease (AD). Recent evidence indicates that Aβ can misfold and aggregate into seeds that structurally corrupt native proteins, mimicking a prion-like process of template protein corruption or seeding. In fact, studies in FAD-based animal models show that Aβ deposition and cerebral amyloid angiopathy may be induced by intracerebral infusion of brain extracts from AD patients or from aged APP-transgenic mice. These studies have shown that the characteristic of both the seeding agent and the host influence the pathologic signature of the Aβ seeds. In this regard, the majority of the Aβ-seeding studies have been done in APP-transgenic animal models that overproduce APP and/or Aβ. However, it remains to be elucidated whether Aβ deposition can be induced by Aβ seeds in an animal model that does not overexpress APP and produces wild type human Aβ and if these aggregates are similar to the human condition. Here, we used an innovative animal model to better understand the amyloidogenic events that occur in the sporadic form of the disease. Our model, termed hAβ-KI, expresses wild-type human Aβ under the control of the endogenous mouse APP gene. Thus, amyloid seeds from AD patients (stage C for amyloid) from the Alzheimer’s Disease Research Center (ADRC) at UCI were administered into 7-8-month-old hAβ-KI and as positive controls 3xTg-AD mice were employed. Our findings demonstrated that amyloid seeds differentially occur in 3xTg-AD and hAb-KI mice and these aggregates are developed earlier in the familial model, 3xTg-AD mice. These results suggest that multiple factors such as the seed, recipient model and time are critical factors that can modulate the amyloid pathology onset and progression. Thus, more profound understanding these factors will provide key insight on how amyloid pathology progress in AD. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

We described a reduction of target of Myb1 (TOM1) protein levels by Western blot in the postmortem hippocampus of subjects with Alzheimer’s disease (AD) versus nondemented subjects (1), validating similar findings by an independent research group in a separate human cohort (2). Based on single-cell transcriptomic data (3), Peng and Zhao (4) conclude that TOM1 levels are, contrariwise to our findings, higher in AD. Although we do not disagree with their hypothesis that TOM1 expression could be up-regulated in AD, at least at early disease stages, precautions should be taken when comparing our findings to theirs. First, we determined the protein levels in the hippocampus whereas the RNAseq was performed in the prefrontal cortex. Discrepancies could therefore be related to … [↵][1]1To whom correspondence may be addressed. Email: d.baglietto{at}uci.edu, rodrigo.medeiros{at}neurula.org, or laferla{at}uci.edu. [1]: #xref-corresp-1-1