@article {2110, title = {Cortical neurons derived from human pluripotent stem cells lacking FMRP display altered spontaneous firing patterns.}, journal = {Mol Autism}, volume = {11}, year = {2020}, month = {2020 Jun 19}, pages = {52}, abstract = {

BACKGROUND: Fragile X syndrome (FXS), a neurodevelopmental disorder, is a leading monogenetic cause of intellectual disability and autism spectrum disorder. Notwithstanding the extensive studies using rodent and other pre-clinical models of FXS, which have provided detailed mechanistic insights into the pathophysiology of this disorder, it is only relatively recently that human stem cell-derived neurons have been employed as a model system to further our understanding of the pathophysiological events that may underlie FXS. Our study assesses the physiological properties of human pluripotent stem cell-derived cortical neurons lacking fragile X mental retardation protein (FMRP).

METHODS: Electrophysiological whole-cell voltage- and current-clamp recordings were performed on two control and three FXS patient lines of human cortical neurons derived from induced pluripotent stem cells. In addition, we also describe the properties of an isogenic pair of lines in one of which FMR1 gene expression has been silenced.

RESULTS: Neurons lacking FMRP displayed bursts of spontaneous action potential firing that were more frequent but shorter in duration compared to those recorded from neurons expressing FMRP. Inhibition of large conductance Ca-activated K currents and the persistent Na current in control neurons phenocopies action potential bursting observed in neurons lacking FMRP, while in neurons lacking FMRP pharmacological potentiation of voltage-dependent Na channels phenocopies action potential bursting observed in control neurons. Notwithstanding the changes in spontaneous action potential firing, we did not observe any differences in the intrinsic properties of neurons in any of the lines examined. Moreover, we did not detect any differences in the properties of miniature excitatory postsynaptic currents in any of the lines.

CONCLUSIONS: Pharmacological manipulations can alter the action potential burst profiles in both control and FMRP-null human cortical neurons, making them appear like their genetic counterpart. Our studies indicate that FMRP targets that have been found in rodent models of FXS are also potential targets in a human-based model system, and we suggest potential mechanisms by which activity is altered.

}, issn = {2040-2392}, doi = {10.1186/s13229-020-00351-4}, author = {Das Sharma, Shreya and Pal, Rakhi and Reddy, Bharath Kumar and Selvaraj, Bhuvaneish T and Raj, Nisha and Samaga, Krishna Kumar and Srinivasan, Durga J and Ornelas, Loren and Sareen, Dhruv and Livesey, Matthew R and Bassell, Gary J and Svendsen, Clive N and Kind, Peter C and Chandran, Siddharthan and Chattarji, Sumantra and Wyllie, David J A} } @article {2078, title = {Improved detection of RNA foci in amyotrophic lateral sclerosis post-mortem tissue using BaseScope{\texttrademark} shows a lack of association with cognitive dysfunction.}, journal = {Brain Commun}, volume = {2}, year = {2020}, month = {2020 Jan 31}, pages = {fcaa009}, abstract = {

The hexanucleotide repeat expansion is the commonest known genetic mutation in amyotrophic lateral sclerosis. A neuropathological hallmark is the intracellular accumulation of RNA foci. The role that RNA foci play in the pathogenesis of amyotrophic lateral sclerosis is widely debated. Historically, RNA foci have been identified using hybridization. Here, we have implemented BaseScope{\texttrademark}, a high-resolution modified hybridization technique. We demonstrate that previous studies have underestimated the abundance of RNA foci in neurons and glia. This improved detection allowed us to investigate the abundance, regional distribution and cell type specificity of antisense RNA foci in post-mortem brain and spinal cord tissue of six deeply clinically phenotyped patients and six age- and sex-matched controls. We find a correlation between RNA foci and the accumulation of transactive response DNA-binding protein of 43 kDa in spinal motor neurons ( = 0.93; = 0.008), but not in glia or cortical motor neurons. We also demonstrate that there is no correlation between the presence of RNA foci and the accumulation of transactive response DNA binding protein of 43 kDa in extra-motor brain regions. Furthermore, there is no association between the presence of RNA foci and cognitive indices. These results highlight the utility of BaseScope{\texttrademark} in the clinicopathological assessment of the role of antisense RNA foci in .

}, issn = {2632-1297}, doi = {10.1093/braincomms/fcaa009}, author = {Mehta, Arpan R and Selvaraj, Bhuvaneish T and Barton, Samantha K and McDade, Karina and Abrahams, Sharon and Chandran, Siddharthan and Smith, Colin and Gregory, Jenna M} } @article {1598, title = {FMRP Interacts with C/D Box snoRNA in the Nucleus and Regulates Ribosomal RNA Methylation.}, journal = {iScience}, volume = {9}, year = {2018}, month = {2018 Nov 30}, pages = {399-411}, abstract = {

FMRP is an RNA-binding protein that is known to localize in the cytoplasm and in the nucleus. Here, we have identified an interaction of FMRP with a specific set of C/D box snoRNAs in the nucleus. C/D box snoRNAs guide 2{\textquoteright}O methylations of ribosomal RNA (rRNA) on defined sites, and this modification regulates rRNA folding and assembly of ribosomes. 2{\textquoteright}O methylation of rRNA is partial on several sites in human embryonic stem cells, which results in ribosomes with differential methylation patterns. FMRP-snoRNA interaction affects rRNA methylation on several of these sites, and in the absence of FMRP, differential methylation pattern of rRNA is significantly altered. We found that FMRP recognizes ribosomes carrying specific methylation patterns on rRNA and the recognition of methylation pattern by FMRP may potentially determine the translation status of its target mRNAs. Thus, FMRP integrates its function in the nucleus and in the cytoplasm.

}, issn = {2589-0042}, doi = {10.1016/j.isci.2018.11.007}, author = {D{\textquoteright}Souza, Michelle Ninochka and Gowda, Naveen Kumar Chandappa and Tiwari, Vishal and Babu, Rosana Ottakandathil and Anand, Praveen and Dastidar, Sudhriti Ghosh and Singh, Randhir and James, Owen G and Selvaraj, Bhuvaneish and Pal, Rakhi and Ramesh, Arati and Chattarji, Sumantra and Chandran, Siddharthan and Gulyani, Akash and Palakodeti, Dasaradhi and Muddashetty, Ravi S} }