Biology subjects

Schultz, C.

Publications and source records attributed to Schultz, C..

26 records · Page 2Linked to original sources

bioRxiv2022

MRI Guided Fresh Tissue Procurement in Radical Prostatectomy Specimens: An Evolutionary Paradigm

PurposeThe aim of this work is to assess the feasibility of novel targeted methods for fresh tissue procurement that facilitate accurate identification of lesion location and tissue sample extraction in an excised prostate gland, while minimizing the tissue deformation or damage. Methods and ResultsProposed fresh tissue procurement methods are based on utilizing a custom 3D printed patient-specific prostate mold. In the semi-freehand method, the access cut is guided by a set of markers on the bottom of the mold that define the boundary of a lesion in two orthogonal directions. The procurement site is identified by palpation. In the guided cut with-locator card method the procurement sites are identified by a cutout in the locator cards inserted into the access cuts. The two approaches were utilized to procure >50 samples. In the biopsy needle method guiding channels were designed into the prostate mold to procure fresh tissue. This method was used 4 times. Finally, a mixed-reality biopsy needle method was developed for phantom testing. ConclusionsPreliminary results of fresh tissue procurement utilizing novel methods showed improve precision of obtaining cancerous fresh tissue for molecular and genomic cancer research compared to current methods which rely on surgical estimation of lesion location.

bioengineering↗

bioRxiv2022

A global lipid map reveals host dependency factors conserved across SARS-CoV-2 variants

A comprehensive understanding of host dependency factors for SARS-CoV-2 remains elusive. We mapped alterations in host lipids following SARS-CoV-2 infection using nontargeted lipidomics. We found that SARS-CoV-2 rewires host lipid metabolism, altering 409 lipid species up to 64-fold relative to controls. We correlated these changes with viral protein activity by transfecting human cells with each viral protein and performing lipidomics. We found that lipid droplet plasticity is a key feature of infection and that viral propagation can be blocked by small-molecule glycerolipid biosynthesis inhibitors. We found that this inhibition was effective against the main variants of concern (alpha, beta, gamma, and delta), indicating that glycerolipid biosynthesis is a conserved host dependency factor that supports this evolving virus.

microbiology↗

bioRxiv2021

Rapid decline in Western monarch butterflies leads to phenological and geographic Allee effects

Allee effects - the breakdown of biological processes at low population densities - are ecologically important because they can potentially drag already struggling populations to extinction. However, identifying and documenting Allee effects is challenging, especially for natural populations, because it is difficult to know when populations have dropped to critically low densities, and to observe them both above and below this threshold. Here, we compared demographic processes in the western monarch butterfly, Danaus plexippus, before and after the population had fallen below the size at which Allee effects were hypothesized to take hold. Comparisons drew on data we collected after a dramatic population crash in 2018, previously published data from other researchers, and community science data. We found no evidence for Allee effects in winter survival, the fraction of females mated in early spring, or eggs laid per day. We did identify a 43% decline in the distance of seasonal range expansion, which could reflect Allee effects in terms of summer population growth rates or density-dependent movement behavior. In addition, overwinter survival of western monarch butterflies has substantially declined since first estimated in 1975 and may be contributing to the long-term population decline. The lack of evidence for Allee effects and the recent rebound in population size provide a more hopeful view for monarch conservation in the future but do not supersede the documented density-independent population decline across the last several decades.

ecology↗

bioRxiv2021

Incorporation of unnatural amino acid for the tagging of cannabinoid receptors 1 and 2 reveals receptor roles in regulating cAMP levels

The role of CB1/CB2 co-expression in cell signaling remains elusive. We established a simplified mammalian cell model system in which expression of CB1 or CB2 can be easily monitored under a confocal microscope. For this, we applied amber codon suppression in live cells to incorporate a single trans-cyclooctene (TCO) bearing amino acid in one of the extracellular loops of CB1 or CB2, followed by fluorescent labeling via click chemistry. We employed genetically encoded biosensors to measure the roles of CB1 and/or CB2 in regulating intracellular calcium ([Ca2+]i) and cAMP ([cAMP]i) levels. We show that the agonist-mediated activation of tagged-CB1 or -CB2 can transiently elevate [Ca2+]i levels. However, when the two receptors were co-expressed in the same cell, CB2 no longer signaled through calcium although CB1-mediated transient elevation of [Ca2+]i levels was unaffected. Because of the existence of crosstalk between calcium and cAMP signaling, we measured the effects of CB1 and/or CB2 in regulating adenylate cyclase activity. We found that the expression of CB1 increased forskolin-induced [cAMP]i levels compared to non-transfected cells. Conversely, CB2 expression decreased stimulated [cAMP]i levels under the same conditions. Finally, co-expressed CB1 and CB2 receptors showed additive yet opposing effects on stimulated [cAMP]i levels. These observations suggest that co-expressed CB1/CB2 act locally as a pair in regulating cell excitability by modulating stimulated [cAMP]i levels.

cell biology↗

bioRxiv2020

Sensory input drives rapid homeostatic scaling of the axon initial segment in mouse barrel cortex

The axon initial segment (AIS) is an important axonal microdomain for action potential initiation and implicated in the regulation of neuronal excitability during activity-dependent cortical plasticity. While structural AIS plasticity has been suggested to fine-tune neuronal activity when network states change, whether it acts as a homeostatic regulatory mechanism in behaviorally relevant contexts remains poorly understood. Using an in vivo model of the mouse whisker-to-barrel pathway in combination with immunofluorescence, confocal analysis and patch-clamp electrophysiological recordings, we observed bidirectional AIS plasticity. Furthermore, we find that structural and functional AIS remodeling occurs in distinct temporal domains: long-term sensory deprivation elicits an AIS length increase, accompanied with an increase in neuronal excitability, while sensory enrichment results in a rapid AIS shortening, accompanied by a decrease in action potential generation. Our findings highlight a central role of the AIS in the homeostatic regulation of neuronal input-output relations.

neuroscience↗

bioRxiv2019

Dynamic trafficking and turnover of Jam-C is essential for endothelial cell migration

Junctional complexes between endothelial cells form a dynamic barrier that hinder passive diffusion of blood constituents into interstitial tissues. Re-modelling of junctions is an essential process during leukocyte trafficking, vascular permeability and angiogenesis. However, for many junctional proteins the mechanisms of junctional remodelling have yet to be determined. Here we used receptor mutagenesis, HRP and APEX-2 proximity labelling, alongside light and electron microscopy, to map the intracellular trafficking routes of junctional adhesion molecule-C (Jam-C). We found that Jam-C co-traffics with receptors associated with changes in permeability, such as VE-Cadherin, NRP-1 and 2, but not with junctional proteins associated with the transmigration of leukocytes. Dynamic Jam-C trafficking and degradation is necessary for junctional remodelling during cell migration and angiogenesis. By identifying new trafficking machinery we show that a key point of regulation is the ubiquitylation of Jam-C by the E3 ligase CBL, this controls the rate of recycling versus lysosomal degradation.

cell biology↗

bioRxiv2018

A combinatorial extracellular code tunes the intracellular signaling network activity to distinct cellular responses

Cells constantly survey a complex set of inputs that is processed by the intracellular signaling network, but little is known of how cells integrate input information from more than one cue. We employed a FRET biosensor-based imaging platform to study the effect of combinatorial growth factor levels on the signaling network in human cells. We found that pairwise stimuli caused distinct concentration- and ratio-dependent signaling states through signaling signatures such as antagonism, additivity and synergy. The unique signaling states correlated with differential gene expression and non-additive transcription patterns. We further elucidated how a signal-rich environment can fine-tune the signaling network and adjust physiological outcomes, by kinase and phosphatase activity profiling. We describe how complex extracellular conditions affect phospho-turnover and the basal phosphorylation status. Thus, we provide mechanistic insights into cellular processing of multiple cues and explain part of the complexity of cellular adaptation to changes in the extracellular environment.

cell biology↗

bioRxiv2018

Onset of differentiation is posttranscriptionally controlled in adult neural stem cells

The contribution of posttranscriptional regulation of gene expression to neural stem cell differentiation during tissue homeostasis remains elusive. Here we show highly dynamic changes in protein synthesis along differentiation of stem cells to neurons in vivo. Examination of individual transcripts using RiboTag mouse models reveals that neural stem cells efficiently translate abundant transcripts, whereas translation becomes increasingly controlled with the onset of differentiation. Stem cell generation of early neuroblasts involves translational repression of a subset of mRNAs including the stem cell-identity factors Sox2 and Pax6 as well as translation machinery components. In silico motif analysis identifies a pyrimidine-rich motif (PRM) in this repressed subset. A drop in mTORC1 activity at the onset of differentiation selectively blocks translation of PRM-containing transcripts. Our data uncovers how a drop in mTORC1 allows robust simultaneous posttranscriptional repression of key stem cell identity-factors and translation-components and thereby stemness exit and migration.

neuroscience↗