Biology subjects

Kratschmer, P.

Publications and source records attributed to Kratschmer, P..

5 recordsLinked to original sources

bioRxiv2023

BK channel gain-of-function disrupts limb control by suppressing neurotransmission during a critical developmental window

Gain-of-function mutations in BK potassium channels (BK GOF) cause debilitating involuntary limb movements. BK channels modulate action potential shape and neurotransmission in mature neurons, yet some BK GOF mutations also cause neurodevelopmental morbidities. Thus, whether BK GOF impairs limb control by altering the excitation/inhibition of mature motor circuits, or by disrupting their development, remains unclear. To address this issue, we developed a genetic method enabling spatiotemporal control of BK channel expression in neurons of the fruit fly, Drosophila. In concert with high-resolution measurements of limb kinematics, we demonstrate that GOF BK channels act during a narrow neurodevelopmental period to perturb limb control in adult flies. During this period, BK GOF alters synaptic localisation of the key active zone protein Bruchpilot and suppresses excitatory neurotransmission. In a wild-type background, we find that reducing neural activity during neurodevelopment yields similar motor defects to those observed in BK GOF flies. Conversely, enhancing neural excitability during development rescues alterations in limb kinematics in BK GOF flies. Collectively, our results suggest that BK GOF perturbs limb control largely by disrupting activity-dependent aspects of neuronal development.

neuroscience↗

bioRxiv2020

A knock-in Drosophila model supports a conserved link between potassium channelopathy and involuntary movement

BackgroundGenetic and in vitro studies have linked a heterozygous gain-of-function mutation (D434G) in the hSlo1 BK (Big potassium) channel to paroxysmal dyskinesia. However, support for this linkage from in vivo models has been lacking. ObjectivesWe aimed to re-create the equivalent mutation to hSlo1 D434G in the fruit fly, Drosophila, and examine how this mutation altered movement and action potential waveforms. MethodsWe generated a knock-in Drosophila model of hSlo1 D434G. We used video-tracking and infra-red beam-break systems to test whether locomotion was altered in this model, and patch-clamp electrophysiology to determine how the mutation affected action potential waveforms. ResultsWe identified profound motor dysfunction and sporadic leg twitches, as well as a reduced width and an enhancement of the afterhyperpolarization phase of action potentials, in the model background. ConclusionOur results support a conserved relationship between enhanced BK channel function and disrupted motor control across distantly related species.

neuroscience↗

bioRxiv2020

Altered synaptic plasticity and central pattern generator dysfunction in a Drosophila model of PNKD3 paroxysmal dyskinesia

BackgroundParoxysmal non-kinesigenic dyskinesia type-3 (PNKD3) has been linked to gain-of-function (GOF) mutations in the hSlo1 BK potassium channel, in particular a dominant mutation (D434G) that enhances Ca2+-sensitivity. However, while BK channels play well-known roles in regulating neurotransmitter release, it is unclear whether the D434G mutation alters neurotransmission and synaptic plasticity in vivo. Furthermore, the subtypes of movement-regulating circuits impacted by this mutation are unknown. ObjectivesWe aimed to use a larval Drosophila model of PNKD3 (sloE366G/+) to examine how BK channel GOF in dyskinesia alters synaptic properties and motor circuit function. MethodsWe used video-tracking to test for movement defects in sloE366G/+ larvae, and sharp-electrode recordings to assess the fidelity of Ca2+-dependent neurotransmitter release and short-term plasticity at the neuromuscular junction. We then combined sharp-electrode recording with ex vivo Ca2+-imaging to investigate the functionality of the central pattern generator (CPG) driving foraging behavior in sloE366G/+ larvae. ResultsWe show that the PNKD3 mutation leads to Ca2+-dependent alterations in synaptic release and paired-pulse facilitation. Furthermore, we identify robust alterations in locomotor behaviors in sloE366G/+ larvae which were mirrored by dysfunction of the upstream, movement-generating CPG in the larval ventral nerve cord. ConclusionOur results demonstrate that a BK channel GOF mutation can alter neurotransmitter release and short-term synaptic plasticity, and result in CPG dysfunction, in Drosophila larvae. These data add to a growing body of work linking paroxysmal dyskinesias to aberrant neuronal excitability and synaptic plasticity in pre-motor circuits.

neuroscience↗

bioRxiv2018

A sleep-regulatory circuit integrating circadian, homeostatic and environmental information in Drosophila

In the wild, when to go to sleep is a critical decision. Sleep onset is controlled by two processes: the circadian clock, and a homeostat measuring sleep drive [1, 2]. Environmental stimuli must also clearly intersect with the circadian clock and/or homeostat so that sleep is initiated only when appropriate. Yet how circadian, homeostatic and environmental cues are integrated at the circuit level is unclear. Recently, we found that DN1p clock neurons in Drosophila act to prolong morning wakefulness at elevated ambient temperatures [3]. Here we show that a subset of DN1p neurons exhibit temperature-sensitive increases in excitability, and define an output pathway linking DN1p neurons to downstream sleep-regulatory circuits. We show that DN1p neurons project axons to a subdomain of the Anterior Optic Tubercle (AOTU), and here make inhibitory synaptic connections with sleep-promoting tubercular-bulbar (TuBu) neurons. Using unbiased trans-synaptic labeling, we show that these TuBu neurons form synaptic connections with R-neurons innervating the ellipsoid body, subsets of which control homeostatic sleep drive [4]. DN1p excitability is clock-dependent, peaking in the late night and early morning [5]. Thus, integration of circadian and thermo-sensory information by DN1p neurons and subsequent inhibition of sleep-promoting TuBu neurons provides a mechanism by which an environmental stimulus can regulate sleep onset during a specific compartment of the day-night cycle. Furthermore, our results suggest that the AOTU functionally links circadian and sleep homeostat circuits in Drosophila.

neuroscience↗

bioRxiv2017

Neurocalcin acts in a clock- and light-modulated dopaminergic pathway to promote night sleep in Drosophila

Primary dystonia is a hyperkinetic movement disorder linked to altered dopaminergic signaling and synaptic plasticity in regions of the brain involved in motor control. Mutations in HPCA, encoding the neuronal calcium sensor Hippocalcin, are associated with primary dystonia, suggesting a function for Hippocalcin in regulating the initiation and/or maintenance of activity. However, such a role for Hippocalcin or Hippocalcin homologs has yet to be demonstrated in vivo. Here we investigate the cellular and organismal functions of the Drosophila Hippocalcin homolog Neurocalcin (NCA), and define a role for NCA in promoting sleep by suppressing nighttime hyperactivity. We show that NCA acts in a common pathway with the D1-type Dop1R1 dopamine receptor and facilitates sleep by inhibiting neurotransmitter release from a multi-component activity-promoting circuit. Our results suggest conserved roles for Hippocalcin homologs in modulating motor control through dopaminergic pathways, suppressing aberrant movements in humans and inappropriate nighttime locomotion in Drosophila.

neuroscience↗