Search bioRxiv⌕ Search

Biology subjects

Margolis, R. L.

Publications and source records attributed to Margolis, R. L..

3 recordsLinked to original sources

BlueNuclei: automated identification and classification of live and dead transfected neurons using interpretable features

In vitro modeling of neuronal disorders using transfected primary neurons is one of the fundamental approaches for studying disease mechanisms and therapeutic screening. Assessing neuronal viability is an everyday yet critical task in such experiments and requires accurate identification and classification of live and dead transfected neurons from dual-channel fluorescence images; however, this step is typically performed manually, resulting in inconsistent, labor-intensive, and poorly scalable analysis due to limitations of existing image analysis tools. Here, we present BlueNuclei, a user-friendly software with two modules: Hyades, which identifies nuclei of transfected neurons using dual-channel fluorescence image processing techniques, and Pleiades, an SVM-based classifier that distinguishes live from dead neurons using human-vision-inspired, biologically interpretable subnuclear features. Benchmarking on real images showed that BlueNuclei achieves near-human accuracy with substantially faster processing and minimal computational resources compared to deep learning alternatives when applied to the classification step. BlueNuclei provides a simple local user interface for data input and interactive visualizations that display classification results, including feature metrics and a confidence score for each nucleus. BlueNuclei offers the first scalable, fully automated, solution to viability assessment of transfected neurons, facilitating in vitro mechanistic studies of genetic neuronal disorders and therapeutic screening.

neuroscience↗

Bidirectional transcription at the PPP2R2B gene locus in spinocerebellar ataxia type 12

OBJECTIVESpinocerebellar ataxia type 12 (SCA12) is a neurodegenerative disease caused by expansion of a CAG repeat in the PPP2R2B gene. Here we tested the hypothesis that the PPP2R2B antisense (PPP2R2B-AS1) transcript containing a CUG repeat is expressed and contributes to SCA12 pathogenesis. METHODSExpression of PPP2R2B-AS1 transcript was detected in SCA12 human induced pluripotent stem cells (iPSCs), iPSC-derived NGN2 neurons, and SCA12 knock-in mouse brains using strand-specific RT-PCR (SS-RT-PCR). The tendency of expanded PPP2R2B-AS1 (expPPP2R2B-AS1) RNA to form foci, a marker of toxic processes involving mutant RNAs, was examined in SCA12 cell models by fluorescence in situ hybridization. The toxic effect of expPPP2R2B-AS1 transcripts on SK-N-MC neuroblastoma cells was evaluated by caspase 3/7 activity. Western blot was used to examine the expression of repeat associated non-ATG-initiated (RAN) translation of expPPP2R2B-AS1 transcript in SK-N-MC cells. RESULTSThe repeat region in PPP2R2B gene locus is bidirectionally transcribed in SCA12 iPSCs, iPSC-derived NGN2 neurons, and SCA12 mouse brains. Transfected expPPP2R2B-AS1 transcripts are toxic to SK-N-MC cells, and the toxicity may be mediated, at least in part, by the RNA secondary structure. The expPPP2R2B-AS1 transcripts form CUG RNA foci in SK-N-MC cells. expPPP2R2B-AS1 transcript is translated in the Alanine ORF via repeat-associated non-ATG (RAN) translation, which is diminished by single nucleotide interruptions within the CUG repeat, and MBNL1 overexpression. INTERPRETATIONThese findings suggest that PPP2R2B-AS1 contributes to SCA12 pathogenesis, and may therefore provide a novel therapeutic target for the disease.

neuroscience↗

RNA toxicity and perturbation of rRNA processing in spinocerebellar ataxia type 2

BACKGROUNDSpinocerebellar ataxia type 2 (SCA2) is a neurodegenerative disease caused by expansion of a CAG repeat in Ataxin-2 (ATXN2) gene. The mutant ATXN2 protein with a polyglutamine tract is known to be toxic and contributes to the SCA2 pathogenesis. OBJECTIVEHere we tested the hypothesis that the mutant ATXN2 transcript with an expanded CAG repeat (expATXN2) is also toxic and contributes to SCA2 pathogenesis. METHODSThe toxic effect of expATXN2 transcripts on SK-N-MC neuroblastoma cells and primary mouse cortical neurons was evaluated by caspase 3/7 activity and nuclear condensation assay, respectively. RNA immunoprecipitation assay was performed to identify RNA binding proteins (RBPs) that bind to expATXN2 RNA. Quantitative PCR was used to examine if rRNA processing is disrupted in SCA2 and Huntington disease (HD) human brain tissue. RESULTSexpATXN2 RNA induces neuronal cell death, and aberrantly interacts with RBPs involved in RNA metabolism. One of the RBPs, transducin {beta}-like protein 3 (TBL3), involved in rRNA processing, binds to both expATXN2 and expanded huntingtin (expHTT) RNA in vitro. rRNA processing is disrupted in both SCA2 and HD human brain tissue. CONCLUSIONThese findings provide the first evidence of a contributory role of expATXN2 transcripts in SCA2 pathogenesis, and further support the role expHTT transcripts in HD pathogenesis. The disruption of rRNA processing, mediated by aberrant interaction of RBPs with expATXN2 and expHTT transcripts, suggest a point of convergence in the pathogeneses of repeat expansion diseases with potential therapeutic implications.

neuroscience↗