Biology subjects

Proekt, I.

Publications and source records attributed to Proekt, I..

5 recordsLinked to original sources

bioRxiv2026

A PATHOGENIC NFKB2 VARIANT CAUSES COMBINED IMMUNODEFICIENCY WITH THYMIC AND PERIPHERAL LYMPHOID DEFECTS IN RATS

The non-canonical NF-kappa B pathway, in which NFKB2 plays a central role, is critical for lymphoid organ development and immune homeostasis. Pathogenic NFKB2 variants have been strongly associated with a broad spectrum of human pathologies, notably immunodysregulation syndromes, characterized by recurrent infections, autoantibody production and endocrine abnormalities. The mechanisms underlying the resulting immune defects remain incompletely understood. In the present study, we characterized the immune phenotype of a novel rat model harboring a Nfkb2 non-sense mutation located in the c-terminal region of the gene (c.2602T>A; p.Tyr867*, Nfkb2p.Tyr867*). This variant has been identified in patients with a familial form of common variable immunodeficiency (CVID) presenting with autoimmunity manifestations. Using this model, we demonstrate that mutated NFKB2 resulted in profound alterations of the thymic microenvironment, including reduced K5+ medullary thymic epithelial cells and decreased AIRE expression, accompanied by altered thymocyte development and impaired thymic regulatory T populations. Peripheral lymphoid organization was also profoundly affected, with absence of lymph nodes, defects in the splenic marginal zone, and alterations of CD4+ and CD8+ T-cell homeostasis, including impaired Treg populations and reduced ICOS expression on CD4+ T cells. The B-cell compartment was markedly altered, with impaired B-cell maturation, characterized by accumulation of IgM+IgD- transitional cells and a marked reduction of IgD+ mature B cells. These abnormalities were associated with impaired humoral immunity and complete absence of circulating immunoglobulins. Collectively, our findings define a systemic combined immunodeficiency phenotype in the Nfkb2-mutated rat, highlighting its utility for studying the role of non-canonical NF-kB signaling in immune system organization and adaptative immunity.

immunology↗

bioRxiv2026

Gain-of-function mutation in SKAP2 leads to type 1 diabetes and broader autoimmunity through hyperactive integrin signaling in myeloid cells

Many genetic variants associated with increased type 1 diabetes (T1D) risk are located within the SKAP2 gene; however, the mechanisms by which these variants confer disease risk remain unclear. SKAP2 encodes an adapter protein that functions within the integrin signaling pathway and is found at the highest levels in myeloid leukocytes. We recently identified a de novo gain-of-function SKAP2 mutation in an individual with T1D, leading to hyperactive integrin signaling in myeloid cells. To dissect the mechanisms by which this mutation may lead to T1D, we generated a knock-in mouse line containing the orthologous p.G153R substitution in mouse SKAP2 on the diabetes-prone nonobese diabetic (NOD) genetic background. Both female and male SKAP2G153R/G153R mice developed accelerated T1D. The SKAP2G153R/G153R mice also exhibited a unique spectrum of autoantibodies, leading to immune-complex nephritis. Accelerated infiltration of pancreatic islets by myeloid cells, B lymphocytes, and activated T cells was observed in SKAP2G153R/G153R mice. Single-cell RNA sequencing demonstrated a type 1 IFN{gamma}-driven inflammatory program within the pancreatic islets of SKAP2G153R/G153R mice. Dendritic cells from SKAP2G153R/G153R mice demonstrated increased antigen-presenting capacity, characterized by enhanced adhesion to T cells during immune synapse formation. Macrophages and neutrophils from SKAP2G153R/G153R mice also showed increased integrin signaling responses, with neutrophils expressing high levels of activated {beta}2 integrins on the cell surface. When backcrossed onto the C57BL/6J genetic background, the SKAP2G153R/G153R mice developed spontaneous autoantibody formation and exhibited accelerated autoimmunity, including nephritis, in the pristane-induced model of autoimmune disease. These findings demonstrate that dysregulation of leukocyte integrin signaling, through alterations in SKAP2, may increase the genetic risk for autoimmunity and T1D.

immunology↗

bioRxiv2026

Fezf2 regulates differentiation of Aire-expressing and post-Aire mimetic epithelial populations maintaining thymic homeostasis

Fezf2 has been proposed to serve principally as a transcriptional regulator of broad self-antigen expression in medullary thymic epithelial cells (mTECs). Here, we demonstrate an additional function for Fezf2 as a developmental regulator of TEC lineage commitment. Fezf2 deficiency in the thymus led to a relative expansion of lung mimetic and Ccl21+ immature mTECs at the expense of MHCII-hi Aire-expressing and all other mimetic populations. Consistent with this, the disruption of mTEC development had functional consequences, including alterations in tuft-associated iNKT polarization and microfold-associated B-cell class switching. In addition, high-resolution transcriptomics revealed that Fezf2 and Aire regulate distinct transcriptional programs, with Fezf2 driving both activation and repression of a more limited set of tissue-restricted genes compared to the broad gene activation program observed for Aire. Pure transcriptional repression at Fezf2 target loci was sufficient to partially rescue mTEC development in global Fezf2-/- (tKO) mice, potentially through suppression of Lifr expression and modulation of downstream Stat3 signaling tone. These results expand our understanding of Fezf2 in mTEC biology, highlighting transcriptional repression as a required functional facet for adult steady-state lineage patterning across the mTEC compartment.

immunology↗

bioRxiv2024

Transcriptional control of central T cell tolerance by NR4A family nuclear receptors

Although deletion of self-reactive thymocytes and their diversion into regulatory T cell (Treg) lineage are critical for immune tolerance and homeostasis, the molecular pathways that link antigen recognition to these fates are incompletely understood. The Nr4a nuclear hormone receptors are transcriptionally upregulated in response to TCR signaling in the thymus and are implicated in both deletion and diversion, but the mechanisms by which they operate are not clear. Redundancy among the family members and their requirement for Treg generation and maintenance have obscured their role in negative selection. Here we take advantage of competitive bone marrow chimeras and the OT-II/RIPmOVA model to demonstrate that Nr4a1 and Nr4a3 are essential for upregulation of Bcl2l11/BIM and negative selection by tissue-restricted model self-antigen (TRA). Moreover, we reveal that the Nr4a family is absolutely required for full induction of a broad transcriptional program triggered in self-reactive thymocytes by TRA recognition, and conserved across model systems and the natural repertoire. Importantly, both model self antigen-specific TCR Tg and polyclonal thymocytes lacking Nr4a1/3 that escape negative selection acquire an anergy-like program that persists in the periphery and is also evident among wild-type recent thymic emigrants (RTEs). We propose that the Nr4a family transduces TCR signals during thymic development to enforce the fates of highly self-reactive clones, mediating not only deletion and Treg diversion, but also contributing to a cell-intrinsic, persistent anergy-like program that may operate at the margins of canonical thymic tolerance mechanisms to restrain self-reactive T cells after thymic egress.

immunology↗

bioRxiv2023

Validation of a murine proteome-wide phage display library for the identification of autoantibody specificities

Autoimmunity is characterized by loss of tolerance to tissue-specific as well as systemic antigens, resulting in complex autoantibody landscapes. Here, we introduce and extensively validate the performance characteristics of a murine proteome-wide library for phage display immunoprecipitation and sequencing (PhIP-seq), to profile mouse autoantibodies. This system and library were validated using seven genetic mouse models across a spectrum of autoreactivity. Mice deficient in antibody production (Rag2-/- and MT) were used to model non-specific peptide enrichments, while cross-reactivity was evaluated using anti-ovalbumin B cell receptor (BCR)-restricted OB1 mice as a proof of principle. The PhIP-seq approach was then utilized to interrogate three distinct autoimmune disease models. First, serum from Lyn-/- IgD+/- mice with lupus-like disease was used to identify nuclear and apoptotic bleb reactivities, lending support to the hypothesis that apoptosis is a shared origin of these antigens. Second, serum from non-obese diabetic (NOD) mice, a polygenic model of pancreas-specific autoimmunity, enriched peptides derived from both insulin and predicted pancreatic proteins. Lastly, Aire-/- mouse sera were used to identify numerous auto-antigens, many of which were also observed in previous studies of humans with autoimmune polyendocrinopathy syndrome type 1 (APS1) carrying recessive mutations in AIRE. Among these were peptides derived from Perilipin-1, a validated autoimmune biomarker of generalized acquired lipodystrophy in humans. Autoreactivity to Perilipin-1 correlated with lymphocyte infiltration in adipose tissue and underscores the approach in revealing previously unknown specificities. These experiments support the use of murine proteome-wide PhIP-seq for antigenic profiling and autoantibody discovery, which may be employed to study a range of immune perturbations in mouse models of autoimmunity.

immunology↗