Biology subjects

Villegas, A.

Publications and source records attributed to Villegas, A..

6 recordsLinked to original sources

bioRxiv2026

Mechanisms of resilience to autosomal dominant Alzheimer's disease via oligogenic modulation of rare variants in the entorhinal cortex

Two PSEN1 E280A carriers have presented extreme protection against autosomal dominant Alzheimers disease (ADAD), with over two decades of delay for dementia onset. One of them, a male heterozygous for the RELN-COLBOS protective variant showed increased neuronal density in the entorhinal cortex 1. We conducted a deep phenotyping and genotyping study of the entorhinal cortex in protected and unprotected PSEN1 E280A cases, sporadic AD, and non-demented controls. We used single nuclei and spatial transcriptomics, whole genome sequencing, and candidate genotype-associated expression changes (GAEC) analysis. Our results showed unique neuronal and oligodendrocytic populations in the male RELN-COLBOS patient. Unique RELN positive inhibitory interneurons were enriched in cortical Layer I, while unique abundant ADAMTSL1 positive excitatory neurons were distributed in Layers II/III and Layer Va. These neurons and mature myelinated oligodendrocytes benefitted from increased expression of LRP6 receptor, functioning as a non-canonical receptor for the mutated Reelin protein encoded by RELN-COLBOS. Finally, GAEC and pathway enrichment analyses suggested that other mutations enhanced RELN-COLBOS effects in oligodendrocytes in the male RELN-COLBOS patient, explaining the phenotypic differences with his sister, a RELN-COLBOS carrier with no evident protection from ADAD. Our findings suggest that extreme deviations of the PSEN1 E280A phenotype are more likely attributed to oligogenic effects, including simultaneous mutations occurring in genes including ITGA2, involved in single molecular pathways, such as the Integrins / Focal Adhesion pathway, as potential disease modifiers for Alzheimers disease (AD).

neuroscience↗

bioRxiv2026

Astrocyte-driven small vessel disease is an early, amyloid-independent feature of PSEN1 E280A familial Alzheimer's disease

Cerebral Small vessel disease (cSVD) is a prevalent feature of Alzheimers disease (AD) pathology. Whether this pathology is a late consequence of amyloid and tau accumulation or an early, direct effect of PSEN1 dysfunction has remained unresolved. We found that it is more severe in familial AD (FAD) caused by E280A mutation in presenilin 1 (PSEN1). These cases present with a distinctive proteomic signature, associated with pathological features, more dysregulated in the occipital cortex (OC) compared to the frontal cortex (FC), and characterized by multiple dysregulated proteins involved in extracellular matrix (ECM) and RNA-associated processes. This proteomic fingerprint was associated with abnormal collagen build up, ECM disorganization, and signatures of aberrant angiogenesis. Six months old transgenic knock-in mice homozygous for Psen1 E280A mutation (PSEN1Ki) also showed a similar phenotype with microvascular tortuosity and proteomic changes. Critically, these mice develop neither A{beta} plaques nor tau tangles, indicating that the shared microvascular and RNA-associated changes are direct consequences of PSEN1 dysfunction rather than downstream effects of amyloid pathology. Remarkably, dysregulated RNA-associated protein networks overlapped between FAD and PSEN1Ki mice. Cerebral microvessels microstructure in PSEN1Ki mice at two months and six months showed abnormal astrocytic end-feet with lamellar deposits implicating blood-brain barrier damage. Finally, single nuclei transcriptomic analysis of AD patients and controls showed similar abnormal astrocytes in both sporadic and familial variants, but FAD astrocytes expressed dysregulated genes identified in the proteomic analyses, such as GLUL, APOE, and CLU. Our findings suggest that cSVD is an early pathological event in PSEN1 FAD and that is driven by abnormal RNA-associated processes and astrocytic dysfunction.

neuroscience↗

bioRxiv2024

The ventral CA2 region of the hippocampus and its differential contributions to social memory and social aggression

Although it is well-known that the hippocampus mediates declarative memory (the repository of information of people, places, things and events) and influences behavior, the differential contributions of the dorsal and ventral hippocampus to specific forms of memory and behavior remain largely unknown. Studies to date show that the dorsal hippocampal CA1 region is important for cognitive and spatial tasks whereas the ventral CA1 region is associated with affective or emotional processing. Whether other regions and forms of hippocampal-dependent memory and behavior show a similar distinction remains unclear. Here we examine how social memory and related social behaviors are encoded across the dorso-ventral axis of the hippocampus. Although recent studies show that the dorsal hippocampal CA2 region is required for social memory and acts to promote social aggression, the behavioral role of ventral CA2 remains unknown. Indeed, whether a defined CA2 region extends throughout ventral hippocampus is controversial. Here, we report that a molecularly, anatomically and electrophysiologically defined CA2 region extends to the extreme ventral pole of hippocampus, with both similarities and important differences in its projection patterns and synaptic impact compared to dorsal CA2. Of particular importance, we find that ventral CA2 is not required for social memory but is critical for promoting social aggression. These results support the view that the ventral region of hippocampus is more generally tuned for emotionally-related behaviors compared to the cognitively-tuned dorsal hippocampus.

neuroscience↗

bioRxiv2024

Modulation of aggression by social novelty recognition memory in the hippocampal CA2 region

The dorsal CA2 subregion (dCA2) of the hippocampus exerts a critical role in social novelty recognition (SNR) memory and in the promotion of social aggression. Whether the social aggression and SNR memory functions of dCA2 are related or represent independent processes is unknown. Here we investigated the hypotheses that an animal is more likely to attack a novel compared to familiar animal and that dCA2 promotes social aggression through its ability to discriminate between novel and familiar conspecifics. To test these ideas, we conducted a multi-day resident intruder (R-I) test of aggression towards novel and familiar conspecifics. We found that mice were more likely to attack a novel compared to familiarized intruder and that silencing of dCA2 caused a more profound inhibition of aggression towards a novel than familiarized intruder. To explore whether and how dCA2 pyramidal neurons encode aggression, we recorded their activity using microendoscopic calcium imaging throughout the days of the R-I test. We found that a fraction of dCA2 neurons were selectively activated or inhibited during exploration, dominance, and attack behaviors and that these signals were enhanced during interaction with a novel compared to familiarized conspecific. Based on dCA2 population activity, a set of binary linear classifiers accurately decoded whether an animal was engaged in each of these forms of social behavior. Of particular interest, the accuracy of decoding aggression was greater with novel compared to familiarized intruders, with significant cross-day decoding using the same familiar animal on each day but not for a familiar-novel pair. Together, these findings demonstrate that dCA2 integrates information about social novelty with signals of behavioral state to promote aggression towards novel conspecifics.

neuroscience↗

bioRxiv2023

A Serum- and Feeder-Free System to Generate CD4 and Regulatory T Cells from Human iPSCs

iPSCs can serve as a renewable source of a consistent edited cell product, overcoming limitations of primary cells. While feeder-free generation of clinical grade iPSC-derived CD8 T cells has been achieved, differentiation of iPSC-derived CD4sp and regulatory T cells requires mouse stromal cells in an artificial thymic organoid. Here we report a serum- and feeder-free differentiation process suitable for large-scale production. Using an optimized concentration of PMA/Ionomycin, we generated iPSC-CD4sp T cells at high efficiency and converted them to Tregs using TGF{beta} and ATRA. Using genetic engineering, we demonstrated high, non-viral, targeted integration of an HLA-A2 CAR in iPSCs. iPSC-Tregs +/- HLA-A2-targeted CAR phenotypically, transcriptionally and functionally resemble primary Tregs and suppress T cell proliferation in vitro. Our work is the first to demonstrate an iPSC-based platform amenable to manufacturing CD4 T cells to complement iPSC-CD8 oncology products and functional iPSC-Tregs to deliver Treg cell therapies at scale.

cell biology↗

bioRxiv2020

A druggable oxidative folding pathway in the endoplasmic reticulum of human malaria parasites

Malaria remains a major global health problem, and there exists a constant need to identify druggable weaknesses in P. falciparum biology. The endoplasmic reticulum (ER) has many essential roles in the asexual lifecycle and may offer new drug targets, but it remains critically understudied. We generated conditional mutants of the putative redox-active, ER chaperone PfJ2, and show that it is essential for parasite survival. Using a redox-active cysteine crosslinker, we identify its substrates to be other mediators of oxidative folding, PfPDI8 and PfPDI11, suggesting a redox-regulatory role for PfJ2. Knockdown of these protein disulfide isomerases in PfJ2 conditional mutants show that PfPDI11 is not essential, while PfPDI8 is essential for asexual growth and may work in a complex with PfJ2 and other ER chaperones. Finally, we show that these redox interactions in the parasite ER are sensitive to small molecule inhibition. Together these data build a model for how oxidative folding occurs in the P. falciparum ER and demonstrate its suitability for antimalarial drug development.

microbiology↗