Biology subjects

Breur, M.

Publications and source records attributed to Breur, M..

3 recordsLinked to original sources

bioRxiv2024

Effect of seizures on the severity of myelin vacuolization in a mouse model of megalencephalic leukoencephalopathy with subcortical cysts

ObjectiveMegalencephalic leukoencephalopathy with subcortical cysts (MLC) is a white matter disease characterized by myelin vacuolization and swollen perivascular astrocyte processes. Neuronal activity has been implicated as primary cause of myelin vacuolization and astrocyte swelling. Since acute and excessive increases in neuronal activity occur in MLC during seizures, we investigated whether seizure activity leads to the acute development of myelin vacuoles and swollen astrocyte processes. MethodsGlialcam-null mice (an established MLC mouse model) and wild-type mice received repeated i.p. low dose (5 mg / kg) kainic acid (KA) injections until severe seizures developed. Following a 60-minute period of severe seizure activity, mice were terminated and brains were fixed and processed. Brain tissue was analyzed for myelin vacuolization and astrocyte process thickness using H&E and GFAP stains, respectively. ResultsRepeated low-dose injections of KA resulted in prolonged severe seizure activity in mice of both genotypes. Total amount of seizure activity was comparable between Glialcam-null and wild-type mice. KA-induced severe seizure activity did not significantly increase myelin vacuolization in either Glialcam-null or wild-type mice. The width of perivascular astrocyte processes was also not affected by severe seizure activity. InterpretationWe show that (i) repeatedly injecting a low dose of KA provides the opportunity to regulate seizure development and generate severe seizures in both wild-type and seizure-sensitive Glialcam-null mice, and that (ii) the two major pathological features of MLC, myelin vacuolization and swollen astrocyte endfeet, are not acutely aggravated in response to KA-induced severe seizure activity.

neuroscience↗

bioRxiv2023

Gemcitabine therapeutically disrupts essential SIRT1-mediated p53 repression in Atypical Teratoid/Rhabdoid Tumors

BackgroundAtypical Teratoid/Rhabdoid Tumors (ATRT) are highly malignant embryonal tumors of the central nervous system with a dismal prognosis. Despite recent advances in understanding the molecular characteristics and subclasses of these tumors, effective therapeutic options remain scarce. MethodsIn this study, we developed and validated a novel patient-derived ATRT culture and xenograft model, which we used alongside a panel of other primary ATRT models for large-scale drug discovery assays. The identified hits were mechanistically and therapeutically investigated using an array of molecular assays and two orthotopic xenograft murine models. ResultsWe found that ATRT are selectively sensitive to the nucleoside analogue gemcitabine, with additional efficacy in Sonic Hedgehog (SHH)-subtype ATRT. Gene expression profiles and protein analyses indicated that gemcitabine treatment causes degradation of Sirtuin 1 (SIRT1), resulting in cell death through activation of NF-kB and p53. Furthermore, we discovered that gemcitabine-induced loss of SIRT1 results in a nucleus-to-cytoplasm translocation of the SHH signaling activator GLI2, explaining the additional gemcitabine sensitivity in SHH-subtype ATRT. Treatment of SHH-subgroup ATRT xenograft-bearing mice with gemcitabine resulted in a >30% increase in median survival (p<0.005, log-rank test) and yielded long-term survivors in two independent patient-derived xenograft models. ConclusionsThese findings demonstrate that ATRT are highly sensitive to gemcitabine treatment, and we propose that gemcitabine may form part of a future multimodal treatment strategy for ATRT. Key points- ATRT are specifically sensitive to gemcitabine treatment - SIRT1 may serve as a novel therapeutic target in ATRT - Gemcitabine should be considered for clinical use in ATRT patients Importance of the studyAtypical Teratoid/Rhabdoid Tumors (ATRT) are highly malignant pediatric brain tumors with a 5-year survival of merely 30%, for which effective treatment options are limited. In this study, we propose a potential novel treatment strategy for ATRT patients. We show that ATRT are highly sensitive to the chemotherapeutic gemcitabine, that takes advantage of ATRT-specific SIRT1 overexpression and disrupts p53 suppression and hedgehog signaling. Importantly, we show that gemcitabine significantly prolongs survival of ATRT patient-derived xenograft models, prolonging survival by over 30%. This effect was achieved using gemcitabine concentrations that are achievable in human brain and well-tolerated in pediatric patients. As such, gemcitabine could be readily incorporated into clinical treatment protocols and expand the still very limited therapeutic options for ATRT-patients.

cancer biology↗

bioRxiv2022

Cortical interneuron development is affected in leukodystrophy 4H

4H leukodystrophy is a rare genetic disorder classically characterized by hypomyelination, hypodontia and hypogonadotropic hypogonadism. With the discovery that 4H is caused by mutations that affect RNA polymerase III, mainly involved in the transcription of small non-coding RNAs, also patients with atypical presentations with mainly a neuronal phenotype were identified. Pathomechanisms of 4H brain abnormalities are still unknown and research is hampered by a lack of preclinical models. We aimed to identify cells and pathways that are affected by 4H mutations using induced pluripotent stem cell models. RNA sequencing analysis on induced pluripotent stem cell-derived cerebellar cells revealed several differentially expressed genes between 4H patients and control samples, including reduced ARX expression. As ARX is involved in early brain and interneuron development, we studied and confirmed interneuron changes in primary tissue of 4H patients. Subsequently, we studied interneuron changes in more depth and analyzed induced pluripotent stem cell-derived cortical neuron cultures for changes in neuronal morphology, synaptic balance, network activity and myelination. We showed a decreased percentage of GABAergic synapses in 4H, which correlated to increased neuronal network activity. Treatment of cultures with GABA antagonists led to a significant increase in neuronal network activity in control cells but not in 4H cells, also pointing to lack of inhibitory activity in 4H. Myelination and oligodendrocyte maturation in cultures with 4H neurons was normal, and treatment with sonic hedgehog agonist SAG did not improve 4H related neuronal phenotypes. qPCR analysis revealed increased expression of parvalbumin interneuron marker ERBB4, suggesting that the development rather than generation of interneurons may be affected in 4H. Together, these results indicate that interneurons are involved, possibly parvalbumin interneurons, in disease mechanisms of 4H leukodystrophy.

neuroscience↗