Biology subjects

Albrecht, M.

Publications and source records attributed to Albrecht, M..

4 recordsLinked to original sources

bioRxiv2026

Chlamydia trachomatis infection upregulates MicroRNA21 to deplete tumor suppressor PTEN

Infection with obligate intracellular Chlamydia trachomatis (Ct) has been associated with cervical and ovarian carcinoma in humans. The possible cause of the tumor-promoting effect of the infection is thought to be a manipulation of host signaling pathways, which are essential for the growth of the bacteria, and which at the same time can support tumor growth. The PI3K and MAPK signaling cascades are outstanding candidates for this concept, as they are persistently activated during infection and required for the growth of Chlamydia and many tumors. The mechanism by which Chlamydia activates these pre-transforming survival signals in the cells is not well understood. Here we show that Ct infection up-regulates the oncomiR, miR21 by activating the host transcription factor AP-1. This depletes the target gene of miR-21, the tumor suppressor PTEN that ensures the persistent activation of the PI3K pathway. Blocking miR21 adversely affects the growth and development of the pathogen. We show here that miR21 KO mice are less susceptible to infection with Ct compared to control mice. Our data thus provides direct in vivo evidence of the induction and dependency of this obligate human pathogen on tumor-promoting miR-21-induced signaling. ImportanceChlamydia trachomatis is an obligate intracellular pathogen that relies on host metabolism for survival, yet the mechanisms by which it sustains nutrient access remain incompletely understood. Here, we identify a conserved host regulatory axis in which infection induces miR-21 to deplete the tumor suppressor PTEN, thereby enabling persistent activation of PI3K signaling. This pathway promotes a tumor-like metabolic state that supports bacterial growth while protecting infected cells from apoptosis. We further demonstrate that the AP-1-miR-21-PTEN circuit is required for efficient chlamydial replication in vitro and in vivo, and that disruption of miR-21 significantly impairs bacterial propagation in epithelial tissues. These findings reveal how C. trachomatis hijacks a central oncogenic signaling network to remodel host cell physiology and highlight a mechanistic link between infection and cancer-associated pathways. Targeting this host-driven signaling axis may provide new strategies for controlling infection independent of traditional antibiotics.

microbiology↗

bioRxiv2024

Is it me or the train moving? Humans resolve sensory conflicts with a nonlinear feedback mechanism in balance control

Humans use multiple sensory systems to estimate body orientation in space. Sensory contributions change depending on context. A predominant concept for the underlying multisensory integration (MSI) is the linear summation of weighted inputs from individual sensory systems. Changes of sensory contributions are typically attributed to some mechanism explicitly adjusting weighting factors. We provide evidence for a conceptually different mechanism that performs a multisensory correction if the reference of a sensory input moves in space without the need to explicitly change sensory weights. The correction is based on a reconstruction of the sensory reference frame motion (RFM) and automatically corrects erroneous inputs, e.g., when looking at a moving train. The proposed RFM estimator contains a nonlinear dead-zone that blocks corrections at slow velocities. We first demonstrate that this mechanism accounts for the apparent changes in sensory contributions. Secondly, using a balance control model, we show predictions of specific distortions in body sway responses to perturbations caused by this nonlinearity. Experiments measuring sway responses of 24 subjects (13 female, 11 male) to visual scene movements confirmed these predictions. The findings indicate that the central nervous system resolves sensory conflicts by an internal reconstruction of the cause of the conflict. Thus, the mechanism links the concept of causal inference to shifts in sensory contributions, providing a cohesive picture of MSI for the estimation of body orientation in space. Significance StatementHow the central nervous system (CNS) constructs body orientation in space from multiple sensory inputs is a fundamental question in neuroscience. It is a prerequisite to maintain balance, navigate and interact with the world. To estimate body orientation, the CNS dynamically changes the contribution of individual sensory inputs depending on context and reliability of the cues. However, it is not clear how the CNS achieves these dynamic changes. The findings in our study resolve major aspects of this question. Importantly, the proposed solution using nonlinear multisensory feedback contrasts with traditional approaches assuming context-dependent gain-scaling of individual inputs. Thus, our findings demonstrate how complex, intelligent, and unintuitive behavior can emerge from a comparably simple nonlinear feedback mechanism.

neuroscience↗

bioRxiv2019

A global synthesis reveals biodiversity-mediated benefits for crop production

Human land use threatens global biodiversity and compromises multiple ecosystem functions critical to food production. Whether crop yield-related ecosystem services can be maintained by few abundant species or rely on high richness remains unclear. Using a global database from 89 crop systems, we partition the relative importance of abundance and species richness for pollination, biological pest control and final yields in the context of on-going land-use change. Pollinator and enemy richness directly supported ecosystem services independent of abundance. Up to 50% of the negative effects of landscape simplification on ecosystem services was due to richness losses of service-providing organisms, with negative consequences for crop yields. Maintaining the biodiversity of ecosystem service providers is therefore vital to sustain the flow of key agroecosystem benefits to society.

ecology↗

bioRxiv2018

Pollinator size and its consequences: Predictive allometry for pollinating insects

O_LIBody size is an integral functional trait that underlies pollination-related ecological processes, yet it is often impractical to measure directly. Allometric scaling laws have been used to overcome this problem. However, most existing models rely upon small sample sizes, geographically restricted sampling and have limited applicability for non-bee taxa. Predictive allometric models that consider biogeography, phylogenetic relatedness and intraspecific variation are urgently required to ensure greater accuracy.\nC_LIO_LIHere, we measured body size, as dry weight, and intertegular distance (ITD) of 391 bee species (4035 specimens) and 103 hoverfly species (399 specimens) across four biogeographic regions: Australia, Europe, North America and South America. We updated existing models within a Bayesian mixed-model framework to test the power of ITD to predict interspecific variation in pollinator dry weight in interaction with different co-variates: phylogeny or taxonomy, sexual dimorphism and biogeographic region. In addition, we used ordinary least squares (OLS) regression to assess intraspecific dry weight - ITD relationships for 10 bee and five hoverfly species.\nC_LIO_LIIncluding co-variates led to more robust interspecific body size predictions for both bees (Bayesian R2: 0.946; {Delta}R2 0.047) and hoverflies (Bayesian R2: 0.821; {Delta}R2 0.058) relative to models with ITD alone. In contrast, at the intraspecific level, our results demonstrate that ITD is an inconsistent predictor of body size for bees (R2: 0.02 - 0.66) and hoverflies (R2: -0.11 - 0.44).\nC_LIO_LITherefore, predictive allometry is more suitable for interspecific comparative analyses than assessing intraspecific variation. Collectively, these models form the basis of the dynamic R package, pollimetry, which provides a comprehensive resource for allometric research concerning insect pollinators worldwide.\nC_LI

ecology↗