Biology subjects

van Woerden, G.

Publications and source records attributed to van Woerden, G..

4 recordsLinked to original sources

bioRxiv2024

Purkinje cell intrinsic activity shapes cerebellar development and function

The emergence of functional cerebellar circuits is heavily influenced by activity-dependent processes. However, the role of intrinsic activity in Purkinje neurons, independent of external input, in driving cerebellar development remains less understood. Here, we demonstrate that before synaptic networks mature, Purkinje cell intrinsic activity is essential for regulating dendrite growth, establishing connections with cerebellar nuclei, and ensuring proper cerebellar function. Disrupting this activity during the postnatal period impairs motor function, with earlier disruptions causing more severe effects. Importantly, only disruptions during early development lead to pronounced defects in cellular morphology, highlighting key temporal windows for dendritic growth and maturation. Transcriptomic analysis revealed that early intrinsic activity drives the expression of activity-dependent genes, such as Prkcg and Car8, which are essential for dendritic growth. Our findings emphasize the importance of temporally-specific intrinsic activity in Purkinje cells for guiding cerebellar circuit development, providing a potential common mechanism underlying cerebellum-related disorders.

neuroscience↗

bioRxiv2024

Modeling mTORopathy-related epilepsy in cultured murine hippocampal neurons using the multi-electrode array

The mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway is a ubiquitous cellular pathway. mTORopathies, a group of disorders characterized by hyperactivity of the mTORC1 pathway, illustrate the prominent role of the mTOR pathway in disease pathology, often profoundly affecting the central nervous system. One of the most debilitating symptoms of mTORopathies is drug-resistant epilepsy, emphasizing the urgent need for a deeper understanding of disease mechanisms to develop novel anti-epileptic drugs. In this study, we explored the multiwell Multi-electrode array (MEA) system as a tool to identify robust network activity parameters in an approach to model mTORopathy-related epilepsy in vitro. To this extent, we cultured mouse primary hippocampal neurons on the multiwell MEA to identify robust network activity phenotypes in mTORC1-hyperactive neuronal networks. mTOR-hyperactivity was induced either through deletion of Tsc1 or overexpression of a constitutively active RHEB variant identified in patients, RHEBp.P37L. mTORC1 dependency of the phenotypes was assessed using rapamycin, and vigabatrin was applied to treat epilepsy-like phenotypes. We show that hyperactivity of the mTORC1 pathway leads to aberrant network activity. In both the Tsc1-KO and RHEB-p.P37L models, we identified changes in network synchronicity, rhythmicity, and burst characteristics. The presence of these phenotypes is prevented upon early treatment with the mTORC1-inhibitor rapamycin. Application of rapamycin in mature neuronal cultures could only partially rescue the network activity phenotypes. Additionally, treatment with the anti-epileptic drug vigabatrin reduced network activity and restored burst characteristics. Taken together, we showed that mTORC1-hyperactive neuronal cultures on the multiwell MEA system present reliable network activity phenotypes that can be used as an assay to explore the potency of new drug treatments targeting epilepsy in mTORopathy patients and may give more insights into the pathophysiological mechanisms underlying epilepsy in these patients. ABBREVIATIONS AED, anti-epileptic drug, CoVNIBI, coefficient of variance of NIBI, CTR, control transduced cultures, DIV, days in vitro, DMEM, Dulbeccos modified Eagle medium, DMSO, dimethyl sulfoxide, GABA, gamma-aminobutyric acidergic, GAPDH, Glyceraldehyde-3-Phosphate Dehydrogenase, iPSC, induced pluripotent stem cell, KO, knock-out, LV, lentivirus, MEA, multi-electrode array, MFR, mean firing rate, mTORC1, mechanistic target of rapamycin complex 1, NB, network burst, NBC, network burst composition, NBD, network burst duration, NBM, neurobasal medium, NBR, network burst rate, NIBI, network interburst interval, NT, non-transduced, RHEB, Ras-homolog enriched in brain, %RS, percentage of random spikes, TBS, tris buffered saline, TSC, Tuberous sclerosis complex, WT, wildtype

neuroscience↗

bioRxiv2022

Adult Camk2a gene reinstatement restores the learning and plasticity deficits of Camk2a knockout mice

With the recent findings that mutations in the gene encoding the -subunit of calcium/calmodulin-dependent protein kinase II (CAMK2A) causes neurodevelopmental disorder (NDD), it is of great therapeutic relevance to know if there a critical developmental time window in which CAMK2A needs to be expressed for normal brain development, or whether expression of the protein at later stages is still beneficial to restore normal functioning. To answer this question, we generated an inducible Camk2a mouse model, which allows us to express CAMK2A at any desired time. Here, we show that adult expression of CAMK2A rescues the behavioural and electrophysiological phenotypes seen in the Camk2a knock-out mice, including spatial and conditional learning and synaptic plasticity. These results suggest that CAMK2A does not play a critical irreversible role in neurodevelopment, which is of importance for future therapies to treat CAMK2A-dependent disorders.

neuroscience↗

bioRxiv2022

Bidirectional changes in excitability upon loss of both CAMK2A and CAMK2B.

The mammalian Ca2+/calmodulin-dependent protein kinase II (CAMK2) family consists of 4 different CAMK2 genes, encoding CAMK2A, CAMK2B, CAMK2D and CAMK2G, which have high structural homology. CAMK2A and CAMK2B are abundantly expressed in the brain; they play a unique role in proper neuronal functioning, since both CAMK2A and CAMK2B knockout mice show several behavioural and cellular phenotypes. However, our recent finding that deletion of both CAMK2A and CAMK2B is lethal indicates that they show redundancy and that the full spectrum of CAMK2 function in neurons remains to be uncovered. For example, it still remains unclear which overlapping functions are present at a single cell level in neuronal transmission and excitability. In order to get more insight into the full spectrum of CAMK2 functions in neurons, we performed whole-cell patch clamp experiments in inducible Camk2a/Camk2b double knockout mice, as well as the CAMK2A and CAMK2B knockout mice. We found that whereas deletion of only CAMK2A or CAMK2B did not change excitability, simultaneous deletion of CAMK2A and CAMK2B resulted in a decrease in excitability 10 days after deletion in CA1 pyramidal neurons, which reversed to increased excitability 21 days after deletion. Additionally, loss of both CAMK2A and CAMK2B resulted in a decreased frequency of both miniature excitatory and inhibitory postsynaptic currents (mEPSC and mIPSC) 21 days after deletion, but not 10 days after deletion, an effect not seen in the single mutants. Our results indicate that CAMK2 is critically important to maintain normal excitability of hippocampal CA1 pyramidal cells, as well as normal inhibitory and excitatory synaptic transmission. Together, these results lead to new insights in how CAMK2 regulates normal neuronal function and highlight the importance of having both CAMK2A and CAMK2B expressed in high levels in the brain.

neuroscience↗