Biology subjects

Keller, E.

Publications and source records attributed to Keller, E..

5 recordsLinked to original sources

bioRxiv2026

Aggregation of misfolded proteins in the sperm head impairs preimplantation embryo development

Paternal contributions to embryogenesis extend beyond DNA, yet the molecular cargo carried by sperm and its impact on development remain poorly defined. Aggresomes (AGG), cytoplasmic inclusions formed by misfolded proteins, are present in mammalian gametes, but their functional consequences are unclear. Here, we show that excessive AGG content in bovine sperm head compromises preimplantation embryo development. Using image-based flow cytometry, sperm from 32 sires were classified into low-, moderate-, and high-AGG groups. AGG levels were unrelated to sire age and did not affect in vitro capacitation or acrosome remodeling. However, embryos derived from high-AGG sires exhibited reduced blastocyst formation, delayed cleavage timing, and a higher incidence of developmental arrest at the 4-6 cell stage. Embryos from high-AGG sires also accumulated more AGG during development, showed elevated reactive oxygen species (ROS) levels, and displayed altered mitophagy dynamics. Supplementation with an ER stress inhibitor temporarily improved cleavage but did not enhance overall blastocyst formation, indicating a limited and stage-specific effect. In vivo, embryos from high-AGG sires showed lower transferable quality compared with those from low-AGG sires. These findings establish sperm head AGG content as a novel paternal determinant of embryo quality. By linking sperm-borne misfolded protein aggregates to disrupted developmental pathways in the resulting embryo, our study reveals a previously unrecognized mechanism of paternal influence on fertility and suggests new opportunities for molecular screening for male fertility. Significance StatementSperm contribute more to the embryo than DNA alone, yet the consequences of sperm-borne molecular cargo for early development remain largely unknown. We show that aggregates of misfolded proteins in the sperm head, a marker of disrupted protein quality control, impair preimplantation embryo development in cattle. Sires with elevated sperm aggregate content produce embryos that cleave later, arrest more frequently, and reach the blastocyst stage at lower rates, both in vitro and in vivo. These embryos carry greater aggregate loads, show heightened oxidative stress, and display dysregulated mitochondrial clearance. Our findings establish paternal proteostasis as a determinant of embryo quality and identify a class of sperm defects invisible to conventional semen analysis, opening new avenues for molecular fertility screening.

cell biology↗

bioRxiv2024

A quantitative approach to poxvirus infection reveals general correlates of antigen presentation and immunogenicity for viral CD8+ T cell epitopes

CD8+ T cells are essential effectors in antiviral immunity that kill infected cells displaying viral peptide epitopes on MHC class I. The pathways underpinning antigen presentation on MHC I are well known but we lack a general understanding of the quantitative and kinetic relationships between source proteins and presented epitopes, and how these relate to immunogenicity. We used quantitative mass spectrometry to interrogate infection with vaccinia virus, the MPOX vaccine, measuring amounts of >40 viral epitopes and their source proteins multiple times after infection in four cell types. This revealed that up to 90% of the epitopes were presented as fast as their source proteins were made and that protein amounts failed to correlate with epitope levels. Further, a significant correlation between epitope levels and immunogenicity required presentation to be quantified ex vivo, with each step away from a matched infection route and natural presenting cell eroding the association.

immunology↗

bioRxiv2024

Complement C3d enables protective immunity capable of distinguishing spontaneously transformed from non-transformed cells

Immune-surveillance depends in part on the recognition of peptide variants by T cell antigen receptors. Given that both normal B cells and malignant B cells accumulate mutations we chose a murine model of multiple myeloma to test conditions to induce cell-mediated immunity targeting malignant plasma cell (PC) clones but sparing of normal PCs. Revealing a novel function for intracellular C3d, we discovered that C3d engaged T cell responses against malignant plasma cells in the bone marrow of mice that had developed multiple myeloma spontaneously. Our results show that C3d internalized by cells augments immune surveillance by several mechanisms. In one, C3d induces a master transcription regulator, E2f1, to increase the expression of long non-coding (lnc) RNAs, to generate peptides for MHC-I presentation and increase MHC-I expression. In another, C3d increases expression of RNAs encoding ribosomal proteins linked to processing of defective ribosomal products (DRiPs) that arise from non-canonical translation and known to promote immunosurveillance. Cancer cells are uniquely susceptible to increased expression and presentation of mutant peptides given the extent of protein misfolding and accumulation of somatic mutations. Accordingly, although C3d can be internalized by any cell, C3d preferentially targets malignant clones by evoking specific T cell mediated immunity (CMI) and sparing most non-transformed polyclonal B cells and plasma cells with lower mutation loads. Malignant plasma cell deletion was blocked by cyclosporin or by CD8 depletion confirming that endogenous T cells mediated malignant clone clearance. Besides the potential for therapeutic application our results highlight how intracellular C3d modifies cellular metabolism to augment immune surveillance. One Sentence SummaryWe show that intracellular soluble fragment 3d of complement (C3d) induces regression of spontaneous multiple myeloma in mice reducing tumor burden by 10 fold, after 8 weeks. C3d enables cell-mediated immunity to target multiple myeloma clones sparing non-transformed polyclonal B cells and plasma cells with lower mutation loads. We show that C3d increases the expression of ribosomal subunits associated with the translation of defective ribosomal products (DRiPs). C3d also decreases expression of protein arginine methyl transferase (PRMT) 5 which in turn relieves E2f1 repression increasing the expression of Lnc RNAs and derived peptides that evoke anti-tumor cellular immunity. The approach increases MHC-I expression by tumor cells and generates a CMI response that overcomes tumor immune-evasion strategies. SignificanceTumors are immunogenic in part because of somatic mutations that originate novel peptides that once presented on MHC engage cell-mediated immunity (CMI). However, in spite of the higher mutation load most tumors evade immunity. We discovered that a component of the complement system (C3d) overcomes tumor immune evasion by augmenting expression of ribosomal proteins and lncRNAs linked to the presentation of novel peptides by tumor cells. C3d induced CMI targets cancer cells sparing non transformed cells uncovering a novel function for complement in immune surveillance.

immunology↗

bioRxiv2024

Zooplankton bacterial communities are influenced by infection status, environmental conditions and diet quantity across natural epidemics

Zooplankton-associated microbiomes play an important role for host health and contribute to ecosystem processes such as nutrient cycling. Yet, few studies have assessed how environmental gradients and biotic interactions, including parasitism and diet, may shape the microbiome composition of wild zooplankton. Here, we analysed the microbiomes of water fleas from the Daphnia longispina species complex using 16S rRNA gene sequencing and a long-term field dataset spanning six sampling events over 13 years. Sampling coincided with outbreaks of the virulent eukaryotic gut parasite Caullerya mesnili. Additionally, we explored how microbiome structure varied in relation to water parameters, phytoplankton density (i.e. Daphnia diet), and zooplankton density and community structure. Daphnia microbiomes displayed strong temporal variation, and comparatively small differences based on host infection status. Microbiome beta diversity correlated with phytoplankton density but not with its community composition, including green algae, protists and cyanobacteria. Environmental conditions, including temperature, dissolved oxygen and cyanobacterial abundance - previously found to drive Caullerya epidemics - were also associated with distinct microbiome structures. Importantly, microbiome beta diversity co-varied with infection prevalence, suggesting a link between microbiome shifts, epidemic size, and environmental conditions driving large epidemics. Dominant bacterial taxa correlated with Daphnia density, whereas the phylogenetic composition of rare taxa was associated with total zooplankton density. These findings demonstrate the dynamic nature of Daphnia microbiomes and suggest potential mechanisms by which they may mediate disease dynamics, particularly through associations with diet quantity, temperature, and host population density.

ecology↗

bioRxiv2019

Characterization of SETD1A haploinsufficiency in humans and Drosophila defines a novel neurodevelopmental syndrome.

Defects in histone methyltransferases (HMTs) are major contributing factors in neurodevelopmental disorders (NDDs). Heterozygous variants of SETD1A involved in histone H3 lysine 4 (H3K4) methylation were previously identified in individuals with schizophrenia. Here, we define the clinical features of the Mendelian syndrome associated with haploinsufficiency of SETD1A by investigating 15 predominantly pediatric individuals who all have de novo SETD1A variants. These individuals present with a core set of symptoms comprising global developmental delay and/or intellectual disability, subtle facial dysmorphisms, behavioral and psychiatric problems. We examined cellular phenotypes in three patient derived lymphoblastoid cell lines with three variants: p.Gly535Alafs*12, c.4582-2_4582delAG, and p.Tyr1499Asp. These patient cell lines displayed DNA damage repair defects that were comparable to previously observed RNAi-mediated depletion of SETD1A. This suggested that these variants, including the p.Tyr1499Asp in the catalytic SET domain, behave as Loss-of-Function (LoF) alleles. Previous studies demonstrated a role for SETD1A in cell cycle control and differentiation. However, individuals with SETD1A variants do not show major structural brain defects or severe microcephaly, suggesting that defective proliferation and differentiation of neural progenitors is unlikely the single underlying cause of the disorder. We show here that the Drosophila Melanogaster SETD1A orthologue is required in postmitotic neurons of the fly brain for normal memory, suggesting a role in post development neuronal function. Together, this study defines a neurodevelopmental disorder caused by dominant de novo LoF variants in SETD1A and further supports a role for H3K4 methyltransferases in the regulation of neuronal processes underlying normal cognitive functioning.

genetics↗