Biology subjects

Culver, J. C.

Publications and source records attributed to Culver, J. C..

3 recordsLinked to original sources

bioRxiv2021

Normal Aging in Mice is Associated with a Global Reduction in Cortical Spectral Power and a Network-Specific Decline in Functional Connectivity

Normal aging is associated with a variety of neurologic changes including declines in cognition, memory, and motor activity. These declines correlate with neuronal changes in synaptic structure and function. Degradation of brain network activity and connectivity represents a likely mediator of age-related functional deterioration resulting from these neuronal changes. Human studies have demonstrated both general decreases in spontaneous cortical activity and disruption of cortical networks with aging. Current techniques used to study cerebral network activity are hampered either by limited spatial resolution (e.g. electroencephalography, EEG) or limited temporal resolution (e.g., functional magnetic resonance imaging, fMRI). Here we utilize mesoscale imaging of neuronal activity in Thy1-GCaMP6f mice to characterize neuronal network changes in aging with high spatial resolution across a wide frequency range. We show that while evoked activity is unchanged with aging, spontaneous neuronal activity decreases across a wide frequency range (0.01-4Hz) involving all regions of the cortex. In contrast to this global reduction in cortical power, we found that aging is associated with functional connectivity (FC) deterioration of select networks including somatomotor, cingulate, and retrosplenial nodes. These changes are corroborated by reductions in homotopic FC and node degree within somatomotor and visual cortices. Finally, we found that whole cortex delta power and delta band node degree correlate with exploratory activity in young but not aged animals. Together these data suggest that aging is associated with global declines in spontaneous cortical activity and focal deterioration of network connectivity, and that these reductions may be associated with age-related behavioral declines.

neuroscience↗

bioRxiv2019

CreLite: An Optogenetically Controlled Cre/loxP System Using Red Light

Precise manipulation of gene expression with temporal and spatial control is essential for functional studies and the determination of cell lineage relationships in complex biological systems. The Cre-loxP system is commonly used for gene manipulation at desired times and places. However, specificity is dependent on the availability of tissue- or cell-specific regulatory elements used in combination with Cre or CreER (tamoxifen-inducible). Here we present CreLite, an optogenetically-controlled Cre system using red light in developing zebrafish embryos. Cre activity is disabled by splitting Cre and fusing the inactive halves with the Arabidopsis thaliana red light-inducible binding partners, PhyB and PIF6. In addition, PhyB-PIF6 binding requires phycocyanobilin (PCB), providing an additional layer of control. Upon exposure to red light (660 nm) illumination, the PhyB-CreC and PIF6-CreN fusion proteins come together in the presence of PCB to restore Cre activity. Red-light exposure of transgenic zebrafish embryos harboring a Cre-dependent multi-color fluorescent protein reporter (ubi:zebrabow) injected with CreLite mRNAs and PCB, resulted in Cre activity as measured by the generation of multi-spectral cell labeling in various tissues, including heart, skeletal muscle and epithelium. We show that CreLite can be used for gene manipulations in whole embryos or small groups of cells at different stages of development. CreLite provides a novel optogenetic tool for precise temporal and spatial control of gene expression in zebrafish embryos that may also be useful in cell culture, ex vivo organ culture, and other animal models for developmental biology studies.

molecular biology↗

bioRxiv2019

The kynurenine pathway is essential for rhodoquinone biosynthesis in Caenorhabditis elegans

A key metabolic adaptation for some species that face hypoxia as part of their life-cycle involves an alternative electron transport chain in which rhodoquinone (RQ) is required for fumarate reduction and ATP production. RQ biosynthesis in bacteria and protists requires ubiquinone (Q) as a precursor. In contrast, Q is not a precursor for RQ biosynthesis in animals such as parasitic helminths, and this pathway has remained elusive. We used Caenorhabditis elegans as a model animal to elucidate several key steps in RQ biosynthesis. Through RNA interference and a series of mutants, we found that arylamine metabolites from the kynurenine pathway are essential precursors for RQ biosynthesis de novo. Deletion of kynu-1, which encodes a kynureninase that converts L-kynurenine (KYN) into anthranilic acid (AA), and 3-hydroxykynurenine (HKYN) into 3-hydroxyanthranilic acid (3HAA), completely abolishes RQ biosynthesis, but does not affect Q levels. Deletion of kmo-1, which encodes a kynurenine 3-monooxygenase that converts KYN to HKYN, drastically reduces RQ, but not Q levels. Knockdown of the Q biosynthetic genes, coq-5 and coq-6, affects both Q and RQ levels demonstrating that common enzymes are used in both biosynthetic pathways. Our study reveals that two pathways for RQ biosynthesis have independently evolved. In contrast to bacteria, where amination is the last step in RQ biosynthesis, worms begin with the arylamine precursor, AA or 3HAA. Since RQ is absent in mammalian hosts of helminths, inhibition of RQ biosynthesis may have broad implications for targeting parasitic infections which cause important neglected tropical diseases.

biochemistry↗