Biology subjects

Koretsky, A.

Publications and source records attributed to Koretsky, A..

6 recordsLinked to original sources

bioRxiv2026

Manganese Accumulation for Genetically Induced Contrast (MAGIC) MRI in the brain across species

Mapping the mesoscale architecture of neural circuits is essential for understanding brain function, yet high-resolution anatomical tracing remains largely dependent on fluorescent reporters that require terminal histology. Here, we present Manganese Accumulation for Genetically Inducible Contrast (MAGIC) MRI, a gene expression reporter system based on the metal ion transporter Zip14 (Slc39a14) which enables noninvasive, in vivo neural tracing. In rodents, viral delivery of Zip14 enables both anterograde and retrograde tracing of cortico-thalamic and basal ganglia circuits. Mechanistic validation via laser ablation-inductively coupled plasma-time-of-flight-mass spectrometry (LA-ICP-TOF-MS) confirmed that MRI contrast changes are driven by specific Mn2+ accumulation. This permitted high-resolution visualization of neural populations and projections using clinical standard MRI sequences without supplementary contrast agents. However, addition of systemic Mn2+ further increased the signal by a factor of 2-5 fold. To facilitate objective, high-throughput analysis, we developed a fully automated pipeline for voxel-wise anomaly detection that accurately identifies and quantifies MAGIC enhanced regions in individual subjects. Finally, it is demonstrated that MAGIC is translatable to the large mammalian brain, providing the first functional demonstration of an MRI-visible reporter in the rhesus macaque. By enabling the non-invasive monitoring of neural connectivity across species, MAGIC provides a versatile, longitudinal tool for studying structural plasticity and circuit organization in the living brain.

neuroscience↗

bioRxiv2026

Electro-Calcium uncoupling precedes neurodegeneration in Alzheimers disease

Alzheimers disease (AD) is categorized as a neurodegenerative disease, but there is a growing recognition of the vascular components in AD pathophysiology. Reduction in cerebral perfusion is routinely observed in AD patients and preclinical models prior to overt clinical symptoms. However, there is a limited mechanistic understanding of the early neurovascular deficits in AD, and how these may ultimately contribute to pathology. Here, we investigated the mechanisms of early neurovascular dysfunction in AD by using 3-month-old 5xFAD mice, a familial mouse model of AD. Functional hyperemia--the increase in cerebral blood flow (CBF) in response to neuronal activity--is driven by inward rectifier K+ (Kir2.1)-mediated hyperpolarizing (electrical) signals and Ca2+-dependent nitric oxide production within the capillary endothelial cells (cECs). Electrical and Ca2+ signals are tightly coupled through cECs membrane potential, referred to as Electro-Calcium (E-Ca) coupling. We hypothesize that E-Ca uncoupling contributes to impaired functional hyperemia in 5xFAD mice and that these neurovascular deficits precede the neurodegeneration and cognitive decline. At three months of age, 5xFAD mice did not exhibit any impairment in spatial learning and memory, or neuronal density. However, whisker stimulation-induced functional hyperemia was significantly reduced in 5xFAD mice compared to controls. Functional hyperemia exhibited a bimodal response in controls--consisting of fast and slow phases--with the slow phase being significantly reduced in 5xFAD mice. To identify mechanisms underlying these deficits, we measured cortical neuronal and endothelial Ca2+ activity using in-vivo imaging. Neuronal Ca2+ activity was comparable between controls and 5xFAD mice, while cECs Ca2+ activity was significantly reduced in 5xFAD mice. Moreover, Kir2.1 channel blocker, barium (100 M) significantly suppressed cECs Ca2+ activity in controls, but not in 5xFAD mice, consistent with crippled E-Ca coupling. Despite these vascular functional impairments, capillary density was preserved in 5xFAD mice. TRPV4 channels are one of the major Ca2+ entry pathways in cECs and potentiate E-Ca coupling. cECs TRPV4 current density was significantly reduced in 5xFAD mice while Kir2.1 current density was unchanged, indicating that impaired TRPV4 function underlies the E-Ca uncoupling. In summary, early E-Ca uncoupling leads to impaired functional hyperemia in 5xFAD mice and may contribute to later neuronal and cognitive decline.

neuroscience↗

bioRxiv2024

Post-Critical Period Transcriptional and Physiological Adaptations of Thalamocortical Connections after Sensory Loss

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=95 SRC="FIGDIR/small/624130v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@100f64aorg.highwire.dtl.DTLVardef@29907corg.highwire.dtl.DTLVardef@cccd63org.highwire.dtl.DTLVardef@1c02318_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG Unilateral whisker denervation activates plasticity mechanisms and circuit adaptations in adults. Single nucleus RNA sequencing and multiplex fluorescence in situ hybridization revealed differentially expressed genes related to altered glutamate receptor distributions and synaptogenesis in thalamocortical (TC) recipient layer 4 (L4) neurons of the sensory cortex, specifically those receiving input from the intact whiskers after whisker denervation. Electrophysiology detected increased spontaneous excitatory events at L4 neurons, confirming an increase in synaptic connections. Elevated expression levels of Gria2 mRNA and functional GluA2 subunit of AMPA receptors at the TC synapse indicate the presence of stabilized and potentiated TC synapses to L4 excitatory neurons along the intact pathway after unilateral whisker denervation. These adaptations likely underlie the increased cortical activity observed in rodents during intact whisker sensation after unilateral whisker denervation. Our findings provide new insights into the mechanisms by which the adult brain supports recovery after unilateral sensory loss.

neuroscience↗

bioRxiv2024

Postmortem MRI of Tissue Frozen at Autopsy

IntroductionPostmortem MRI provides insight into location of pathology within tissue blocks, enabling efficient targeting of histopathological studies. While postmortem imaging of fixed tissue is gaining popularity, imaging tissue frozen at the time of extraction is significantly more challenging. MethodsTissue integrity was examined using RNA integrity number (RIN), in mouse brains placed between -20 {degrees}C and 20 {degrees}C for up to 24 hours, to determine the highest temperature that could potentially be used for imaging without tissue degeneration. Human tissue frozen at the time of autopsy was sealed in a tissue chamber filled with 2-methylbutane to prevent contamination of the MRI components. The tissue was cooled to a range of temperatures in a 9.4T MRI using a recirculating aqueous ethylene glycol solution. MRI was performed using a magnetization-prepared rapid gradient echo (MPRAGE) sequence with inversion time of 1400 ms to null the signal from 2-methylbutane bath, isotropic resolution between 0.3-0.4 mm, and scan time of about 4 hours was used to study the anatomical details of the tissue block. Results and DiscussionA temperature of -7 {degrees}C was chosen for imaging as it was below the highest temperature that did not show significant RIN deterioration for over 12 hours, at the same time gave robust imaging signal and contrast between brain tissue types. Imaging performed on various human tissue blocks revealed good gray-white matter contrast and revealing subpial, subcortical, and deep white matter lesions typical of multiple sclerosis enabling further spatially targeted studies. ConclusionHere, we describe a new method to image cold tissue, while maintaining tissue integrity and biosafety during scanning. In addition to improving efficiency of downstream processes, imaging tissue at sub-zero temperatures may also improve our understanding of compartment specificity of MRI signal.

bioengineering↗

bioRxiv2021

Early detection of cerebrovascular pathology and protective antiviral immunity by MRI

Central nervous system (CNS) infections are a major cause of human morbidity and mortality worldwide. Even patients that survive CNS infections can have lasting neurological dysfunction resulting from immune and pathogen induced pathology. Developing approaches to noninvasively track pathology and immunity in the infected CNS is crucial for patient management and development of new therapeutics. Here, we develop novel MRI-based approaches to monitor virus-specific CD8+ T cells and their relationship to cerebrovascular pathology in the living brain. We studied a relevant murine model in which a neurotropic virus (vesicular stomatitis virus) was introduced intranasally and then entered the brain via olfactory sensory neurons - a route exploited by many pathogens in humans. Using T2*-weighted high-resolution MRI, we identified small cerebral microbleeds as the earliest form of pathology associated with viral entry into the brain. Mechanistically, these microbleeds occurred in the absence of peripheral immune cells and were associated with infection of vascular endothelial cells. We monitored the adaptive response to this infection by developing methods to iron label and track individual virus specific CD8+ T cells by MRI. Transferred antiviral T cells were detected in the brain within a day of infection and were able to reduce cerebral microbleeds. These data demonstrate the utility of MRI in detecting the earliest pathological events in the virally infected CNS as well as the therapeutic potential of antiviral T cells in mitigating this pathology.

neuroscience↗

bioRxiv2019

High-resolution MEMRI characterizes laminar specific ascending and descending spinal cord pathways in rats

Manganese Enhanced MRI (MEMRI) utilizing different manganese chloride (MnCl2) delivery methods, has yielded valuable architectural, functional and connection information about the brain. MEMRI also has the potential in characterizing neural pathways in the spinal cord. The spinal cord grey matter is anatomically composed of nine distinct cellular laminae, where each of the laminae receives input from a specific type of neuronal population and process or serves as a relay region in a specific sensory or motor pathway. This type of laminar arrangement in the spinal cord is currently only visualized by histological methods. It is of significant interest to determine whether laminar specific enhancement by Mn2+ can be achieved in the spinal cord, as has been reported in the brain and olfactory pathway. Here we focus on using MEMRI to determine the specific laminae of the thoracic region of the spinal cord. We focus on MnCl2 changes in the ascending and descending tracts of the spinal cord. Major factors in applying this technique in the spinal cord are the ability to acquire high-resolution spinal cord images and to determine a noninvasive route of administration which will result in uptake by the central nervous system.\n\nWe have applied the MEMRI approach by intraperitoneal (i.p). delivery of MnCl2 and imaged lumbar and thoracic spinal cord levels in rats to determine whether T1 weighted MRI can detect spinal cord laminae 48 hours following MnCl2 administration. T1 weighted images of the lower lumbar level were obtained from MnCl2 injected and control rats. Here we demonstrate laminar specific signal enhancement in the spinal cord of rats administered with MnCl2 vs. controls in MRI of the cord with ultra-high, 69 m in-plane resolution. We also report reduced T1 values over time in MnCl2 groups across laminae I-IX. The regions with the largest T1 enhancements were observed to correspond to laminae that contain either high cell density or large motor neurons, making MEMRI an excellent tool for studying spinal cord architecture, physiology and function in different animal models.

neuroscience↗