Mireia Moreno-Estellés

Lafora disease (LD) is a devastating form of progressive myoclonus epilepsy characterized by the accumulation of insoluble forms of glycogen [polyglucosan bodies (PGBs)] in the brain and peripheral tissues. It has been proposed that the accumulation of PGBs is pathogenic. Several mouse models of LD have been generated to study the relationship between PGBs and the pathophysiology of LD. However, the use of LD mice is difficult and time consuming; thus, more amenable cellular systems would be desirable. We recently described a cellular model based on the culture of primary postnatal astrocytes from LD mice that are able to accumulate small PGBs. In this study, we extended this astrocytic model by maturing the astrocytes for longer times. These more mature astrocyte cultures accumulated larger and granular PGBs, which have similar properties to the ones present in the hippocampus of Nhlrc1−/− (Epm2b−/−) mice. Importantly, this model expresses inflammatory mediators related to LD pathophysiology. This astrocytic model could be used to better understand the formation of the PGBs and also to define how the accumulation of PGBs activates the expression of inflammatory mediators.

Lafora progressive myoclonus epilepsy (LD, OMIM#254780, ORPHA:501) is an ultra-rare and severe autosomal recessive neurological disorder that typically manifests in early adolescence. It is characterized by the accumulation of insoluble forms of aberrant glycogen in the brain and peripheral tissues. Given the urgent need for reliable tools to monitor disease progression, we aimed to identify reliable biomarkers in minimally invasive fluids, which could also provide valuable insights into the natural history of the disease. Plasma-EDTA samples from eleven LD patients and healthy controls were analyzed to identify potential biomarkers of LD using a high-throughput assay. The findings were subsequently validated using specific enzyme-linked immunosorbent assays (ELISAs). Eleven cytokines and growth factors were identified to be significantly reduced in LD patient samples compared to healthy controls. Among these, four mediators [platelet-derived growth factor subunit B (PDGF-BB), epidermal growth factor (EGF), brain derived growth factor (BDNF), and macrophage migration inhibitory factor (MIF)] exhibited the greatest fold change between the groups and were further validated. Given the minimally invasive nature of plasma sampling and the straightforward quantification via ELISA assays, these biomarkers hold strong promise for rapid translation to the clinic, potentially enhancing early diagnosis and longitudinal disease monitoring in LD patients.

Lafora progressive myoclonus epilepsy (LD, OMIM#254780, ORPHA:501) is an ultra-rare and severe autosomal recessive neurological disorder that typically manifests in early adolescence. It is characterized by the accumulation of insoluble forms of aberrant glycogen in the brain and peripheral tissues. Given the urgent need for reliable tools for diagnosis and to monitor disease progression, in this work, we aimed to identify reliable biomarkers in minimally invasive fluids, which could also provide valuable insights into the natural history of the disease. Plasma-EDTA samples from eleven LD patients and healthy controls were analyzed to identify potential biomarkers of LD. Eleven cytokines and growth factors were identified to be significantly reduced in LD patient samples compared to healthy controls. Among these, four mediators [platelet-derived growth factor subunit B (PDGF-BB), epidermal growth factor (EGF), brain derived growth factor (BDNF), and macrophage migration inhibitory factor (MIF)], exhibited the greatest fold change between the groups and were further validated. Receiver operating characteristic (ROC) analysis confirmed the robust diagnostic potential of these four proteins. Notably, the levels of these proteins were reduced even in asymptomatic patients, suggesting potential utility for early diagnosis. Given the minimally invasive nature of plasma sampling and the straightforward quantification via ELISA assays, these biomarkers hold strong promise for rapid translation to the clinic, potentially enhancing early diagnosis in LD patients. Our findings offer a promising step toward the development of accessible, non-invasive diagnostic tools for LD.,. Key points: - Several plasma biomarkers associated with Lafora disease (LD) have been identified. - These biomarkers are reduced in LD patients compared to healthy controls. - Reduced levels of these biomarkers were detectable even in asymptomatic patients. - Their reduced levels may contribute to the neurological alterations observed in LD.

A wide range of approaches can be used to detect micro RNA (miRNA)–target gene pairs (mTPs) from expression data, differing in the ways the gene and miRNA expression profiles are calculated, combined and correlated. However, there is no clear consensus on which is the best approach across all datasets. Here, we have implemented multiple strategies and applied them to three distinct rare disease datasets that comprise smallRNA-Seq and RNA-Seq data obtained from the same samples, obtaining mTPs related to the disease pathology. All datasets were preprocessed using a standardized, freely available computational workflow, DEG_workflow. This workflow includes coRmiT, a method to compare multiple strategies for mTP detection. We used it to investigate the overlap of the detected mTPs with predicted and validated mTPs from 11 different databases. Results show that there is no clear best strategy for mTP detection applicable to all situations. We therefore propose the integration of the results of the different strategies by selecting the one with the highest odds ratio for each miRNA, as the optimal way to integrate the results. We applied this selection-integration method to the datasets and showed it to be robust to changes in the predicted and validated mTP databases. Our findings have important implications for miRNA analysis. coRmiT is implemented as part of the ExpHunterSuite Bioconductor package available from https://bioconductor.org/packages/ExpHunterSuite.

Lafora disease (LD) is a neurological disorder characterized by progressive myoclonus epilepsy. The hallmark of the disease is the presence of insoluble forms of glycogen (polyglucosan bodies, or PGBs) in the brain. The accumulation of PGBs is causative of the pathophysiological features of LD. However, despite the efforts made by different groups, the question of why PGBs accumulate in the brain is still unanswered. We have recently demonstrated that, in vivo, astrocytes accumulate most of the PGBs present in the brain, and this could lead to astrocyte dysfunction. To develop a deeper understanding of the defects present in LD astrocytes that lead to LD pathophysiology, we obtained pure primary cultures of astrocytes from LD mice from the postnatal stage under conditions that accumulate PGBs, the hallmark of LD. These cells serve as novel in vitro models for studying PGBs accumulation and related LD dysfunctions. In this sense, the metabolomics of LD astrocytes indicate that they accumulate metabolic intermediates of the upper part of the glycolytic pathway, probably as a consequence of enhanced glucose uptake. In addition, we also demonstrate the feasibility of using the model in the identification of different compounds that may reduce the accumulation of polyglucosan inclusions.

Lafora disease is a rare, fatal form of progressive myoclonus epilepsy characterized by continuous neurodegeneration with epileptic seizures, characterized by the intracellular accumulation of aberrant polyglucosan granules called Lafora bodies. Several works have provided numerous evidence of molecular and cellular alterations in neural tissue from experimental mouse models deficient in either laforin or malin, two proteins related to the disease. Oxidative stress, alterations in proteostasis, and deregulation of inflammatory signals are some of the molecular alterations underlying this condition in both KO animal models. Lafora bodies appear early in the animal’s life, but many of the aforementioned molecular aberrant processes and the consequent neurological symptoms ensue only as animals age. Here, using small RNA-seq and quantitative PCR on brain extracts from laforin and malin KO male mice of different ages, we show that two different microRNA species, miR-155 and miR-146a, are overexpressed in an age-dependent manner. We also observed altered expression of putative target genes for each of the microRNAs studied in brain extracts. These results open the path for a detailed dissection of the molecular consequences of laforin and malin deficiency in brain tissue, as well as the potential role of miR-155 and miR-146a as specific biomarkers of disease progression in LD.

Neuronal programming by forced expression of transcription factors (TFs) holds promise for clinical applications of regenerative medicine. However, the mechanisms by which TFs coordinate their activities on the genome and control distinct neuronal fates remain obscure. Using direct neuronal programming of embryonic stem cells, we dissected the contribution of a series of TFs to specific neuronal regulatory programs. We deconstructed the Ascl1-Lmx1b-Foxa2-Pet1 TF combination that has been shown to generate serotonergic neurons and found that stepwise addition of TFs to Ascl1 canalizes the neuronal fate into a diffuse monoaminergic fate. The addition of pioneer factor Foxa2 represses Phox2b to induce serotonergic fate, similar to in vivo regulatory networks. Foxa2 and Pet1 appear to act synergistically to upregulate serotonergic fate. Foxa2 and Pet1 co-bind to a small fraction of genomic regions but mostly bind to different regulatory sites. In contrast to the combinatorial binding activities of other programming TFs, Pet1 does not strictly follow the Foxa2 pioneer. These findings highlight the challenges in formulating generalizable rules for describing the behavior of TF combinations that program distinct neuronal subtypes.

Although previous studies suggest that neural stem cells (NSCs) exist in the adult olfactory bulb (OB), their location, identity, and capacity to generate mature neurons in vivo has been little explored. Here, we injected enhanced green fluorescent protein (EGFP)-expressing retroviral particles into the OB core of adult mice to label dividing cells and to track the differentiation/maturation of any neurons they might generate. EGFP-labeled cells initially expressed adult NSC markers on days 1 to 3 postinjection (dpi), including Nestin, GLAST, Sox2, Prominin-1, and GFAP. EGFP+-doublecortin (DCX) cells with a migratory morphology were also detected and their abundance increased over a 7-day period. Furthermore, EGFP-labeled cells progressively became NeuN+ neurons, they acquired neuronal morphologies, and they became immunoreactive for OB neuron subtype markers, the most abundant representing calretinin expressing interneurons. OB-NSCs also generated glial cells, suggesting they could be multipotent in vivo. Significantly, the newly generated neurons established and received synaptic contacts, and they expressed presynaptic proteins and the transcription factor pCREB. By contrast, when the retroviral particles were injected into the subventricular zone (SVZ), nearly all (98%) EGFP+-cells were postmitotic when they reached the OB core, implying that the vast majority of proliferating cells present in the OB are not derived from the SVZ. Furthermore, we detected slowly dividing label-retaining cells in this region that could correspond to the population of resident NSCs. This is the first time NSCs located in the adult OB core have been shown to generate neurons that incorporate into OB circuits in vivo.

Lafora disease (LD) is a rare, fatal form of progressive myoclonus epilepsy. The molecular basis of this devastating disease is still poorly understood, and no treatment is available yet, which leads to the death of the patients around 10 years from the onset of the first symptoms. The hallmark of LD is the accumulation of insoluble glycogen-like inclusions in the brain and peripheral tissues, as a consequence of altered glycogen homeostasis. In addition, other determinants in the pathophysiology of LD have been suggested, such as proteostasis impairment, with reduction in autophagy, and oxidative stress, among others. In order to gain a general view of the genes involved in the pathophysiology of LD, in this work, we have performed RNA-Seq transcriptome analyses of whole-brain tissue from two independent mouse models of the disease, namely Epm2a−/− and Epm2b−/− mice, at different times of age. Our results provide strong evidence for three major facts: first, in both models of LD, we found a common set of upregulated genes, most of them encoding mediators of inflammatory response; second, there was a progression with the age in the appearance of these inflammatory markers, starting at 3 months of age; and third, reactive glia was responsible for the expression of these inflammatory genes. These results clearly indicate that neuroinflammation is one of the most important traits to be considered in order to fully understand the pathophysiology of LD, and define reactive glia as novel therapeutic targets in the disease.