Foxp2 loss of function increases striatal direct pathway inhibition via increased GABA release

JRvR is supported by an RUMC Junior Round grant from the Donders institute Ph.D. program, awarded to NNK and SCV. SCV is supported by a Marie Curie Career Integration Grant (PCIG12-GA-2012-333978) and by a Max Planck Research Group Award. SEF is supported by the Max Planck Society.Heterozygous mutations of the Forkhead-box protein 2 (FOXP2) gene in humans cause childhood apraxia of speech. Loss of Foxp2 in mice is known to affect striatal development and impair motor skills. However, it is unknown if striatal excitatory/inhibitory balance is affected during development and if the imbalance persists into adulthood. We investigated the effect of reduced Foxp2 expression, via a loss-of-function mutation, on striatal medium spiny neurons (MSNs). Our data show that heterozygous loss of Foxp2 decreases excitatory (AMPA receptor-mediated) and increases inhibitory (GABA receptor-mediated) currents in D1 dopamine receptor positive MSNs of juvenile and adult mice. Furthermore, reduced Foxp2 expression increases GAD67 expression, leading to both increased presynaptic content and release of GABA. Finally, pharmacological blockade of inhibitory activity in vivo partially rescues motor skill learning deficits in heterozygous Foxp2 mice. Our results suggest a novel role for Foxp2 in the regulation of striatal direct pathway activity through managing inhibitory drive.Publisher PDFPeer reviewe

A human in vitro neuronal model for studying homeostatic plasticity at the network level

Mechanisms that underlie homeostatic plasticity have been extensively investigated at single-cell levels in animal models, but are less well understood at the network level. Here, we used microelectrode arrays to characterize neuronal networks following induction of homeostatic plasticity in human induced pluripotent stem cell (hiPSC)-derived glutamatergic neurons co-cultured with rat astrocytes. Chronic suppression of neuronal activity through tetrodotoxin (TTX) elicited a time-dependent network re-arrangement. Increased expression of AMPA receptors and the elongation of axon initial segments were associated with increased network excitability following TTX treatment. Transcriptomic profiling of TTX-treated neurons revealed up-regulated genes related to extracellular matrix organization, while down-regulated genes related to cell communication; also astrocytic gene expression was found altered. Overall, our study shows that hiPSC-derived neuronal networks provide a reliable in vitro platform to measure and characterize homeostatic plasticity at network and single-cell levels; this platform can be extended to investigate altered homeostatic plasticity in brain disorders.The work was supported by funding from the European Community’s Horizon 2020 Programme (H2020/2014–2020) under grant agreement no. 728018 (Eat2beNICE) (to B.F.); ERA-NET NEURON-102 SYNSCHIZ grant (NWO) 013-17-003 4538 (to D.S.); China Scholarship Council 201906100038 (to X.Y.); ISCIII /MINECO (PT17/0009/0019) and FEDER (to A.E.C.); and M.M. was supported by an internal grant from the Donders Centre for Medical Neurosciences of the Radboud University Medical Center

Distinct cardiotoxic effects by venoms of a spitting cobra (Naja pallida) and a rattlesnake (Crotalus atrox) revealed using an ex vivo Langendorff heart model

Here we describe the acute myocardial effects of an elapid (red spitting cobra, Naja pallida) and a viper (western diamondback rattlesnake, Crotalus atrox) venom using an ex vivo heart model. Our results reveal two different pathophysiological trajectories that influence heart function and morphology. While cobra venom causes a drop in contractile force, rattlesnake venom causes enhanced contractility and frequency that coincides with differences in myocellular morphology. This highlights the medical complexity of snake venom-induced cardiotoxicity

Loss-of-function variants in the schizophrenia risk gene SETD1A alter neuronal network activity in human neurons through the cAMP/PKA pathway

Heterozygous loss-of-function (LoF) mutations in SETD1A, which encodes a subunit of histone H3 lysine 4 methyltransferase, cause a neurodevelopmental syndrome and increase the risk for schizophrenia. Using CRISPR-Cas9, we generate excitatory/inhibitory neuronal networks from human induced pluripotent stem cells with a SETD1A heterozygous LoF mutation (SETD1A+/−). Our data show that SETD1A haploinsufficiency results in morphologically increased dendritic complexity and functionally increased bursting activity. This network phenotype is primarily driven by SETD1A haploinsufficiency in glutamatergic neurons. In accordance with the functional changes, transcriptomic profiling reveals perturbations in gene sets associated with glutamatergic synaptic function. At the molecular level, we identify specific changes in the cyclic AMP (cAMP)/Protein Kinase A pathway pointing toward a hyperactive cAMP pathway in SETD1A+/− neurons. Finally, by pharmacologically targeting the cAMP pathway, we are able to rescue the network deficits in SETD1A+/− cultures. Our results demonstrate a link between SETD1A and the cAMP-dependent pathway in human neurons.publishedVersio

Retinoic Acid Signaling:A New Piece in the Spoken Language Puzzle

Speech requires precise motor control and rapid sequencing of highly complex vocal musculature. Despite its complexity, most people produce spoken language effortlessly. This is due to activity in distributed neuronal circuitry including cortico-striato-thalamic loops that control speech-motor output. Understanding the neuro-genetic mechanisms involved in the correct development and function of these pathways will shed light on how humans can effortlessly and innately use spoken language and help to elucidate what goes wrong in speech-language disorders. FOXP2 was the first single gene identified to cause speech and language disorder. Individuals with FOXP2 mutations display a severe speech deficit that includes receptive and expressive language impairments. The neuro-molecular mechanisms controlled by FOXP2 will give insight into our capacity for speech-motor control, but are only beginning to be unraveled. Recently FOXP2 was found to regulate genes involved in retinoic acid (RA) signaling and to modify the cellular response to RA, a key regulator of brain development. Here we explore evidence that FOXP2 and RA function in overlapping pathways. We summate evidence at molecular, cellular, and behavioral levels that suggest an interplay between FOXP2 and RA that may be important for fine motor control and speech-motor output. We propose RA signaling is an exciting new angle from which to investigate how neuro-genetic mechanisms can contribute to the (spoken) language ready brain. </p

Foxp2 loss of function increases striatal direct pathway inhibition via increased GABA release

Heterozygous mutations of the Forkhead-box protein 2 (FOXP2) gene in humans cause childhood apraxia of speech. Loss of Foxp2 in mice is known to affect striatal development and impair motor skills. However, it is unknown if striatal excitatory/inhibitory balance is affected during development and if the imbalance persists into adulthood. We investigated the effect of reduced Foxp2 expression, via a loss-of-function mutation, on striatal medium spiny neurons (MSNs). Our data show that heterozygous loss of Foxp2 decreases excitatory (AMPA receptor-mediated) and increases inhibitory (GABA receptor-mediated) currents in D1 dopamine receptor positive MSNs of juvenile and adult mice. Furthermore, reduced Foxp2 expression increases GAD67 expression, leading to both increased presynaptic content and release of GABA. Finally, pharmacological blockade of inhibitory activity in vivo partially rescues motor skill learning deficits in heterozygous Foxp2 mice. Our results suggest a novel role for Foxp2 in the regulation of striatal direct pathway activity through managing inhibitory drive.</p

Distinct cardiotoxic effects by venoms of a spitting cobra (Naja pallida) and a rattlesnake (Crotalus atrox) revealed using an ex vivo Langendorff heart model

Here we describe the acute myocardial effects of an elapid (red spitting cobra, Naja pallida) and a viper (western diamondback rattlesnake, Crotalus atrox) venom using an ex vivo heart model. Our results reveal two different pathophysiological trajectories that influence heart function and morphology. While cobra venom causes a drop in contractile force, rattlesnake venom causes enhanced contractility and frequency that coincides with differences in myocellular morphology. This highlights the medical complexity of snake venom-induced cardiotoxicity.</p

Loss-of-function variants in the schizophrenia risk gene SETD1A alter neuronal network activity in human neurons through the cAMP/PKA pathway

Heterozygous loss-of-function (LoF) mutations in SETD1A, which encodes a subunit of histone H3 lysine 4 methyltransferase, cause a neurodevelopmental syndrome and increase the risk for schizophrenia. Using CRISPR-Cas9, we generate excitatory/inhibitory neuronal networks from human induced pluripotent stem cells with a SETD1A heterozygous LoF mutation (SETD1A+/−). Our data show that SETD1A haploinsufficiency results in morphologically increased dendritic complexity and functionally increased bursting activity. This network phenotype is primarily driven by SETD1A haploinsufficiency in glutamatergic neurons. In accordance with the functional changes, transcriptomic profiling reveals perturbations in gene sets associated with glutamatergic synaptic function. At the molecular level, we identify specific changes in the cyclic AMP (cAMP)/Protein Kinase A pathway pointing toward a hyperactive cAMP pathway in SETD1A+/− neurons. Finally, by pharmacologically targeting the cAMP pathway, we are able to rescue the network deficits in SETD1A+/− cultures. Our results demonstrate a link between SETD1A and the cAMP-dependent pathway in human neurons