Biology subjects

Falk, T.

Publications and source records attributed to Falk, T..

13 recordsLinked to original sources

bioRxiv2026

Neuroprotective activity of sub-anesthetic ketamine in a preclinical model of Parkinson's disease is not blocked by antagonizing brain-derived neurotrophic factor signaling

Treatment with low-dose ketamine is neuroprotective in rodent models of acute damage, while high doses of ketamine can be neurotoxic. Our group has previously shown that sub-anesthetic ketamine treatment leads to long-term reduction of L-DOPA-induced dyskinesia (LID) via brain-derived neurotrophic factor (BDNF)-signaling in a rat 6-hydroxydopamine (6-OHDA) model of Parkinson's disease (PD). In this report, we investigated if sub-anesthetic ketamine is also neuroprotective in a progressive 6-OHDA model of PD via neurotrophic action through the tropomyosin receptor kinase B (TrkB) receptor. We demonstrated that ketamine-treatment (20 mg/kg, i.p.) prior to striatal administration of the neurotoxin 6-OHDA is neuroprotective, providing near complete protection against development of parkinsonian motor deficits. This robust behavioral efficacy occurred in the presence of only modest preservation of tyrosine hydroxylase (TH) striatal levels (~50-60% loss). Interestingly, based on data from an additional cohort treated with ketamine and ANA-12 (TrkB antagonist) we found that the neuroprotective effects of ketamine are not mediated by TrkB receptors. Semi-quantitative western analysis showed that the relative tyrosine hydroxylase content in the striatum was not significantly increased in ketamine-treated rats compared to vehicle. Unbiased stereology of dopamine neurons in the substantia nigra pars compacta (SNc) revealed no significant differences between any of the groups. The role of BDNF was evaluated with in situ hybridization for RNA of BDNF and TrkB. While BDNF expression was not changed, co-administration of ketamine and ANA-12 led to a significant decrease in TrkB receptor expression compared to ketamine-only on the lesioned but not the intact hemisphere in the SNc. In conclusion, we show that ketamine at the low dose currently pursued for therapeutic benefit for LID led to robust behavioral motor improvement in this rodent PD degeneration model, yet these protective effects were not driven by neurotrophic BDNF-signaling, indicating complex mechanisms are underlying neuroprotective activities of low-dose ketamine.

neuroscience↗

bioRxiv2026

L-DOPA Rescues Reach Height but Not Trajectory Area in a Bimanual String-Pulling Behavior in Parkinsonian Rats

While gross motor changes in Parkinson's disease, bradykinesia, hypokinesia, difficulty initiating movement, have been well studied in rodent models of the disease, limb movements, and especially bimanual coordination deficits, are more difficult to study in these animal models. Here we describe a novel bimanual string-pulling task that can be used to generate a rich repertoire of behaviors that require limb and bimanual coordination in rats with unilateral 6-hydroxydopamine (6-OHDA) lesion. We show that 6-OHDA lesion significantly reduces string speed, pulling bout duration, paw speed especially during reaching, and reduces the area of paw trajectories during pulling. However, it does not affect the variability around that movement trajectory. We also show that levodopa (L-DOPA) treatment restores many of these measures but not all. L-DOPA restores paw speed and string-pulling speed and fully restores paw reach height and pulling bout duration, but has no effect on trajectory area. Together, our results demonstrate that dopamine depletion differentially effects features of this bimanual coordination task, that L-DOPA mostly, but not fully, restores string pulling performance, and opens up a new avenue for measuring the effect of Parkinson's disease treatments on motor movement, allowing for better assessment of how effectively treatments restore motor activity.

neuroscience↗

bioRxiv2025

Epitranscriptomic landscape of vascular smooth muscle cell phenotypic transitions highlights uridine RNA modifications associated with post-transcriptional regulation

BackgroundVascular smooth muscle cells (VSMCs) phenotypic plasticity can modulate atherosclerosis progression. Although several gene regulatory steps towards pro-inflammatory phenotypes have been well-studied, epitranscriptomic changes during this transition and their regulatory roles remain unexplored. Methods and ResultsPrimary human VSMCs stimulated with TGF-{beta}1 to induce atheroprotective, contractile, and matrix-producing state and with IL1-{beta} plus PDGF-BB to induce a highly energetic, pro-inflammatory state, confirmed by Illumina bulk RNA sequencing and proteomics. Untargeted screening of mRNA base modifications using Oxford Nanopore Technologies direct RNA sequencing and xPore analysis revealed enhanced uridine modification within a GUUUU motif in pro-inflammatory VSMCs. Modified uridines were enriched in 3-UTR and accessible RNA structures, with implications on Poly(A) tail dynamics and miRNA binding. ConclusionsAtheroprotective and pro-atherogenic treatments induce distinct epitranscriptomic landscapes composed of different modification types, often co-localized in the transcript. Modified uridines in mRNAs are abundant in a high-energy, pro-inflammatory VSMC state and associated with post-transcriptional regulation. n summary, epitranscriptomics adds a novel regulatory layer to VSMC phenotypic transitions critical for atherosclerosis development and progression. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=74 SRC="FIGDIR/small/694735v2_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@933071org.highwire.dtl.DTLVardef@151564borg.highwire.dtl.DTLVardef@f862e9org.highwire.dtl.DTLVardef@125c509_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphic AbstractC_FLOATNO C_FIG

molecular biology↗

bioRxiv2025

Early intervention with a PACAP lactoside following repetitive mild traumatic brain injury prevents persistent LHb hyperactivity and motivational deficits in male mice

Mild traumatic brain injury (mTBI) often leads to long-lasting mood disorders and motivational deficits, significantly decreasing quality of life. The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) has known neuroprotective effects and is often deficient in neurological conditions, but its role in preventing mTBI's long-term effects on mood circuits remains unclear. Our previous studies of repetitive closed-head mTBI in murine models found that the lateral habenula (LHb) is a key area for post-injury impairments. These impairments are characterized by mTBI-induced LHb hyperactivity and mood-related behavioral deficits. Here we investigated if a novel PACAP type I receptor (PAC1R) agonist, TES2320, could prevent or treat these long-term mTBI effects. The drug is based on a truncated glycoside analogue of PACAP that is stable and brain penetrant. Using RNAscope, we first found that mTBI caused a persistent and widespread reduction in PACAP mRNA within the LHb, suggesting a possible mTBI-related PACAP signaling deficiency in LHb circuits. We then used two intervention strategies in young adult male mice: an early intervention administered immediately after injury and a late intervention given as a single injection one-month post-injury. One month after injury, we measured LHb activity and self-care grooming motivation. Both early and late PAC1 agonist interventions almost completely normalized the mTBI-induced increases in LHb spontaneous tonic activity and hyperexcitability. However, only the early intervention improved the delayed initiation of grooming seen in mTBI mice. Unfortunately, a single late PAC1R agonist injection not only failed to reverse the grooming delay, but also significantly reduced total grooming behavior 24 hours after treatment. This finding points to a potential behavioral side effect of late PAC1R agonist administration on grooming. Overall, our findings confirm that an early PAC1R agonist intervention effectively prevents mTBI-induced LHb hyperactivity and associated motivational deficits, likely by restoring the persistent PACAP signaling deficiency in the LHb and its related circuits. This preclinical study provides strong evidence that novel PAC1R agonists could be a valuable preventive therapy for mTBI-related depression and anti-reward circuit dysfunction.

neuroscience↗

bioRxiv2025

Vgll4 Proteins limit Organ Size in Zebrafish through Yap1-Dependent and -Independent Mechanisms

Precise control of organ size is crucial during development and homeostasis. Dysregulation of the underlying mechanisms can result in organ malformation and tumorigenesis. Although the Hippo signaling pathway plays a key role in regulating organ growth, the precise regulation of its effectors, YAP1 and WWTR1, remains unclear. To gain insights into tissue growth control during organ formation, we used the zebrafish posterior lateral line primordium (pLLP), a migratory group of epithelial cells that forms sensory organs, as a model. We demonstrate that Yap1 growth-promoting activity in the pLL system is modulated not only in the cytoplasm but also in the nucleus by Vgll4 proteins. We propose a model in which Yap1, together with Tead proteins, ensures that the pLLP contains a sufficient number of cells before migration begins. Vgll4b and Vgll4l, in contrast, function partially redundantly, to limit pLLP cell number, with Vgll4b showing a stronger tumor-suppressor activity. Our data indicate that Vgll4b/4l counteract Yap1 activity by competing with Yap1 for binding to Tead proteins, but also via a Yap1-independent mechanism. Altogether, this study reveals that a precise balance between Yap1 and Vgll4 proteins ensures proper regulation of cell number in the pLLP.

developmental biology↗

bioRxiv2024

Differential effects of statins on the anti-dyskinetic activity of sub-anesthetic ketamine

Sub-anesthetic ketamine has been demonstrated to reduce abnormal involuntary movements (AIMs) in preclinical models of L-DOPA-induced dyskinesia (LID) and retrospective Parkinsons disease case reports. In this study, we examined the effects on L-DOPA-induced dyskinesia of two statins alone and in combination with ketamine in unilateral 6-hydroxydopamine-lesioned male rats, the standard preclinical LID model. Sub-anesthetic ketamine attenuated the development of AIMs, while lovastatin only showed anti-dyskinetic activity at the beginning of the priming but did not prevent the development of LID. The polar pravastatin blocked the long-term anti-dyskinetic effects of ketamine, while the non-polar lovastatin did not. This study shows different classes of statins affect LID differentially, points to an important drug interaction and further supports ongoing clinical testing of sub-anesthetic ketamine to treat LID in individuals with Parkinsons disease.

neuroscience↗

bioRxiv2023

Antagonism of kappa opioid receptors worsens the development of L-DOPA-induced dyskinesia in a preclinical model of moderate dopamine depletion

Levels of the opioid peptide dynorphin, an endogenous ligand selective for kappa-opioid receptors (KORs), its mRNA and pro-peptide precursors are differentially dysregulated in Parkinsons disease (PD) and following the development of L-DOPA-induced dyskinesia (LID). It remains unclear whether these alterations contribute to the pathophysiological mechanisms underlying PD motor impairment and the subsequent development of LID, or whether they are part of compensatory mechanisms. We sought to investigate nor-BNI, a KOR antagonist, 1) in the dopamine (DA)-depleted PD state, 2) during the development phase of LID, and 3) via measuring of tonic levels of striatal DA. While nor-BNI (3 mg/kg; s.c.) did not lead to functional restoration in the DA-depleted state, it affected the dose-dependent development of abnormal voluntary movements (AIMs) in response to escalating doses of L-DOPA in a rat PD model with a moderate striatal 6-hydroxdopamine (6-OHDA) lesion. We tested five escalating doses of L-DOPA (6, 12, 24, 48, 72 mg/kg; i.p.), and nor-BNI significantly increased the development of AIMs at the 12 and 24 mg/kg L-DOPA doses. However, after reaching the 72 mg/kg L-DOPA, AIMs were not significantly different between control and nor-BNI groups. In summary, while blocking KORs significantly increased the rate of development of LID induced by chronic, escalating doses of L-DOPA in a moderate-lesioned rat PD model, it did not contribute further once the overall severity of LID was established. While we observed an increase of tonic DA levels in the moderately lesioned dorsolateral striatum, there was no tonic DA change following administration of nor-BNI. HighlightsO_LIMild L-DOPA-induced dyskinesia develops in moderately lesioned parkinsonian rats C_LIO_LIIn the moderately-lesioned dorsolateral striatum tonic dopamine is increased C_LIO_LIAntagonizing dynorphin does not affect parkinsonian motor symptoms in rodents C_LIO_LIAntagonizing dynorphin increases rate of development of L-DOPA-induced dyskinesia C_LIO_LITonic dopamine in dorsolateral striatum is unchanged after antagonizing dynorphin C_LI

neuroscience↗

bioRxiv2023

Automated system for training and assessing string-pulling behaviors in rodents

String-pulling tasks have been used for centuries to study coordinated bimanual motor behavior and problem solving. String pulling is rapidly learned, ethologically grounded, and has been applied to many species and disease conditions. Typically, training of string-pulling behaviors is achieved through manual shaping and baiting. Furthermore, behavioral assessment of reaching, grasping, and pulling is often performed through labor intensive manual video scoring. No system, to our knowledge, currently exists for the automated shaping and assessment of string-pulling behaviors. Here we describe the PANDA system (Pulling And Neural Data Analysis), an inexpensive hardware and software system that utilizes a continuous string loop connected to a rotary encoder, feeder, microcontroller, high-speed camera, and analysis software for assessment and training of string-pulling behaviors and synchronization with neural recording data. We demonstrate this system in unimplanted rats and rats implanted with electrodes in motor cortex and hippocampus and show how the PANDA system can be used to assess relationships between paw movements and single-unit and local-field activity. We also found that automating the shaping procedure significantly improved overall performance, with rats regularly pulling >100 meters during a 15-minute session. In conclusion, the PANDA system will be of general use to researchers investigating motor control, motivation, and motor disorders such as Parkinsons disease, Huntingtons disease, and stroke. It will also support the investigation of neural mechanisms involved in sensorimotor integration. HighlightsO_LIHigh-speed tracking of continuous grasping and pulling behaviors. C_LIO_LIAutomated and adaptive reinforcement of string-pulling behavior. C_LIO_LIIntegration with neural recording and video tracking systems. C_LIO_LIOpen-source software and hardware. C_LI Supplemental FilesThe supplemental pdf contains additional designs and behavioral data and has been uploaded. Source code and 3D and laser cut design files can be found at: https://github.com/CowenLab/String_Pulling_System/ Videos are in the GitHub repository at: https://github.com/CowenLab/String_Pulling_System/tree/main/Videos

bioengineering↗

bioRxiv2023

piRNA processing by a trimeric Schlafen-domain nuclease

Transposable elements are genomic parasites that expand within and spread between genomes1. Piwi proteins control transposon activity, notably in the germline2,3. These proteins recognize their targets through small RNA co-factors named piRNAs, making piRNA biogenesis a key specificity-determining step in this crucial genome immunity system. While the processing of piRNA precursors is an essential step in this process, many molecular details of this process remain unknown. We identify a novel endoribonuclease, PUCH, that initiates piRNA processing in the nematode Caenorhabditis elegans. Genetic and biochemical studies show that PUCH, a trimer of Schlafen-like-domain proteins (SLFL proteins), executes 5-end piRNA precursor cleavage. PUCH-mediated processing strictly requires an m7G-Cap and a uracil at position three. We also demonstrate how PUCH interacts with PETISCO, a complex that binds piRNA precursors4, and that this interaction enhances piRNA production in vivo. The identification of PUCH completes the repertoire of C. elegans piRNA biogenesis factors and uncovers a novel type of RNA endonuclease formed by three SLFL proteins. Mammalian Schlafen (Slfn) genes have been associated with immunity responses5, exposing a thus far unknown molecular link between immune responses in mammals and deeply conserved RNA-based mechanisms that control transposable elements.

molecular biology↗

bioRxiv2022

Heterogeneous patterns of ventral tegmental area neuronal activity coordinate nucleus accumbens dopamine release

Dopamine release in the ventral striatum is fundamental to adaptive appetitive behavior. Frustratingly, technological, and methodological hurdles have limited the investigation of the mechanisms that drive phasic dopamine release. Although dopamine neuron activation in the ventral tegmental area (VTA) surely results in dopamine release, how populations of these neurons coordinate their activities in time to modulate the temporal pattern of release remains unclear. Additionally, burgeoning evidence suggests that control over striatal dopamine release is not solely regulated by the burst firing of VTA neurons or even cell-body activation of these neurons. Here, we recorded VTA neurons while simultaneously monitoring pharmacologically induced phasic dopamine release events in the ventral striatum (nucleus accumbens core) of anesthetized rats. On average, dopaminergic and non-dopaminergic neurons increased activity at the time of the onset of release and decreased at the time of peak release; however, the tuning of individual VTA neurons to dopamine release was notably heterogenous, with subsets of neurons responding prior to release, at release onset, or during release. Other neurons were notably silent during release but active otherwise. Interestingly, both putative dopaminergic and non-dopaminergic neurons expressed this temporally heterogeneous response pattern. Furthermore, the firing activity of dopaminergic, but not non-dopaminergic neurons, correlated with the magnitude of dopamine release. These data suggest that populations of VTA neurons become active at distinct times of a dopamine release event to sculpt the temporal pattern of release.

neuroscience↗

bioRxiv2020

Can quantifying morphology and TMEM119 expression distinguish between microglia and infiltrating macrophages after ischemic stroke and reperfusion in male and female mice?

BackgroundIschemic stroke is an acquired brain injury with gender dependent outcomes. A persistent obstacle in understanding the sex-specific neuroinflammatory contributions to ischemic brain injury is distinguishing between resident microglia versus infiltrating macrophages--both phagocytes--and determining cell population specific contributions to injury evolution and recovery processes. Our purpose was to identify microglial and macrophage populations regulated by ischemic stroke using morphology analysis and the presence of microglia transmembrane protein 119 (TMEM119). Second, we examined sex and menopause differences in microglia/macrophage cell populations after an ischemic stroke. MethodsMale and female, premenopausal and postmenopausal, mice underwent either 60-min of middle cerebral artery occlusion and 24-h of reperfusion or sham surgery. The accelerated ovarian failure model was used to model post-menopause. Brain tissue was collected to quantify infarct area and for immunohistochemistry and western blot methods. Ionized calcium-binding adapter molecule, TMEM119, and confocal microscopy were used to analyze microglia morphology and TMEM119 area in ipsilateral brain regions. Western blot was used to quantify protein quantity. ResultsPost-stroke injury is increased in male and female post-menopause mice versus pre-menopause female mice (p<0.05) with differences primarily occurring in caudal sections. After stroke, microglia underwent a region, but not sex group, dependent transformation into less ramified cells (p<0.0001). However, the number of phagocytic microglia were increased in distal ipsilateral regions of postmenopausal mice versus the other sex groups (p<0.05). The number of TMEM119 positive cells was decreased in proximity to the infarct (p<0.0001) but without a sex group effect. Two key findings prevented distinguishing microglia from systemic macrophages. First, morphological data were not congruent with TMEM119 immunofluorescence data. Cells with severely decreased TMEM119 immunofluorescence were ramified, a distinguishing microglia characteristic. Second, whereas TMEM119 immunofluorescence area decreased in proximity to the infarcted area, TMEM119 protein quantity was unchanged in ipsilateral hemisphere regions using western blot methods. ConclusionsOur findings suggest that TMEM119 is not a stable microglia marker in male and female mice in the context of ischemic stroke. Until TMEM119 function in the brain is elucidated, its use to distinguish between cell populations following brain injury with cell infiltration is cautioned.

physiology↗

bioRxiv2020

Spectral Signatures of L-DOPA-Induced Dyskinesia Depend on L-DOPA Dose and are Suppressed by Ketamine

L-DOPA-induced dyskinesias (LID) are debilitating motor symptoms of dopamine-replacement therapy for Parkinsons disease (PD) that emerge after years of L-DOPA treatment. While there is an abundance of research into the cellular and synaptic origins of LID, less is known about how LID impacts systems-level circuits and neural synchrony, how synchrony is affected by the dose and duration of L-DOPA exposure, or how potential novel treatments for LID, such as sub-anesthetic ketamine, alter this activity. Sub-anesthetic ketamine treatments have recently been shown to reduce LID, and ketamine is known to affect neural synchrony. To investigate these questions, we measured movement and local-field potential (LFP) activity from the motor cortex (M1) and the striatum of preclinical rodent models of PD and LID. In the first experiment, we investigated the effect of the LID priming procedures and L-DOPA dose on neural signatures of LID. Two common priming procedures were compared: a high-dose procedure that exposed unilateral 6-hydroxydopamine-lesioned rats to 12 mg/kg L-DOPA for 7 days, and a low-dose procedure that exposed rats to 7 mg/kg L-DOPA for 21 days. Consistent with reports from other groups, 12 mg/kg L-DOPA triggered LID and 80-Hz oscillations; however, these 80-Hz oscillations were not observed after 7 mg/kg administration despite clear evidence of LID, indicating that 80-Hz oscillations are not an exclusive signature of LID. We also found that weeks-long low-dose priming resulted in the emergence of non-oscillatory broadband gamma activity (> 30 Hz) in the striatum and theta-to-high-gamma cross-frequency coupling (CFC) in M1. In a second set of experiments, we investigated how ketamine exposure affects spectral signatures of low-dose L-DOPA priming. During each neural recording session, ketamine was delivered through 5 injections (20 mg/kg, i.p.) administered every 2 hours. We found that ketamine exposure suppressed striatal broadband gamma associated with LID but enhanced M1 broadband activity. We also found that M1 theta-to-high-gamma CFC associated with the LID on-state was suppressed by ketamine. These results suggest that ketamines therapeutic effects are region specific. Our findings also have clinical implications, as we are the first to report novel oscillatory signatures of the common low-dose LID priming procedure that more closely models dopamine replacement therapy in individuals with PD. We also identify neural correlates of the anti-dyskinetic activity of sub-anesthetic ketamine treatment.

pathology↗

bioRxiv2018

Light dynamically regulates growth rate and cellular organisation of the Arabidopsis root meristem.

1Large-scale methods and robust algorithms are needed for a quantitative analysis of cells status/geometry in situ. It allows the understanding the cellular mechanisms that direct organ growth in response to internal and environmental cues. Using advanced whole-stack imaging in combination with pattern analysis, we have developed a new approach to investigate root zonation under different dark/light conditions. This method is based on the determination of 3 different parameters: cell length, cell volume and cell proliferation on the cell-layer level. This method allowed to build a precise quantitative 3D cell atlas of the Arabidopsis root tip. Using this approach we showed that the meristematic (proliferation) zone length differs between cell layers. Considering only the rapid increase of cortex cell length to determine the meristematic zone overestimates of the proliferation zone for epidermis/cortex and underestimates it for pericycle. The use of cell volume instead of cell length to define the meristematic zone correlates better with cell proliferation zone.

plant biology↗