Biology subjects

Olfat, S.

Publications and source records attributed to Olfat, S..

4 recordsLinked to original sources

bioRxiv2024

Motor learning is regulated by GDNF levels in postnatal cerebellar Purkinje cells

Purkinje cells, the sole output neurons of the cerebellar cortex, are crucial for cerebellum-dependent motor learning. Previously we demonstrated that a ubiquitous 2-3-fold increase of endogenous glial cell line-derived neurotrophic factor (GDNF) improves motor learning. However, GDNF impacts many organ systems and cell types throughout the body leaving the underlying mechanism elusive. Here, we utilize an innovative conditional GDNF Hypermorphic mouse model to show that a 2-fold increase in endogenous GDNF specifically in postnatal Purkinje cells (PCs) is sufficient to enhance motor learning in adult animals. We demonstrate that improved motor learning is associated with increased glutamatergic input to PCs and elevated spontaneous firing rate of these cells, opposite to cerebellar ataxia where reduction in motor function and learning associates with decreased spontaneous activity of PCs. Notably, the GDNF expression levels variation range studied in our mouse models cerebellum falls within the normal range of variation observed in healthy human cerebellums. Our findings uncover a molecular pathway and a specific cell type that regulate motor learning, potentially explaining some individual differences in human motor skill acquisition.

neuroscience↗

bioRxiv2021

Nicotinamide riboside alleviates Parkinson's disease symptoms but downregulates dopamine metabolism upon lactacystin-induced proteostasis failure

Activation of mitochondrial metabolism and proteostasis with the NAD+ precursor nicotinamide riboside (NR) has emerged as a potential therapeutic approach for neurodegenerative disorders including Parkinsons disease (PD). However, despite recently started clinical trials, studies on NR in animal models of PD are scarce. In this study, we investigated the effect of NR in multiple models of PD. In transgenic C. elegans overexpressing -synuclein, a protein of which aggregation is believed to promote PD, NR rescued PD-like phenotypes including mitochondrial dysfunction and motility defects, decreased oxidative stress, and age-related dopamine (DA) neuron loss. We found that NR eased symptoms of disease by activating the mitochondrial unfolded protein response (UPRmt) via the transcription factor atfs-1. Similarly, in a proteasome inhibitor, lactacystin, -induced mouse model of PD, NR rescued mitochondrial dysfunction and behavioural deficits caused by lactacystin lesion. However, long-term NR supplementation, in conjunction with proteasome inhibition, resulted in decreased DA levels in both the lesioned and unlesioned sides of the substantia nigra with concomitant downregulation of key genes in DA metabolism. Our results suggest specific endpoints that should be monitored in ongoing NR clinical trials.

neuroscience↗

bioRxiv2020

Tumor-free elongation of mammalian nephrogenesis by excess fetal GDNF

Due to poor regenerative capacity of adult kidneys, nephron endowment defined by the nephrogenic program during the fetal period dictates renal and related cardiovascular health throughout life. We show that the neurotropic factor GDNF, which is in clinical trials for Parkinsons disease, is capable of prolonging the nephrogenic program beyond its normal cessation without increasing the risk of kidney tumors. Our data demonstrates that excess GDNF expands the nephrogenic program by maintaining nephron progenitors and nephrogenesis in postnatal mouse kidneys. GDNF, through its transcriptional targets excreted from the adjacent epithelium, has a major effect on nephron progenitor self-renewal and maintenance; abnormally high GDNF inhibits nephron progenitor proliferation, but lowering its level normalizes the nephrogenic program to that permissive for nephron progenitor self-renewal and differentiation. Based on our results, we propose that the lifespan of nephron progenitors is determined by mechanisms related to perception of GDNF and other signaling levels.

developmental biology↗

bioRxiv2019

Gene Knock Up via 3’UTR editing to study gene function in vivo

Currently available genetic tools do not allow researchers to upregulate ( Knock Up) the levels of a given protein while retaining its cell-type-specific regulation. As a result, we have limited ability to develop overexpression-related disease models, to study the contribution of single genes in diseases caused by copy number variations and to identify disease pathways for drug targets. Here we develop two approaches for endogenous gene upregulation: conditional Knock Up (cKU) utilizing the Cre/lox system, and CRISPR-Cas9 mediated gene Knock Up (KU) in wild-type mouse embryos and human cells. Using glial cell line derived neurotrophic factor (GDNF) as a proof of concept, we show that both approaches resulted in upregulation of endogenous GDNF levels without disturbing Gdnfs expression pattern. Furthermore, CNS-specific GDNF cKU resulted in dopaminergic abnormalities and schizophrenia-like phenotypes. Our results suggest that gene Knock Up can reveal unknown gene functions and provide novel entry points for studying neurological disease.

neuroscience↗