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1. Cardiac inducing RNAs (CIRs) from human fetal heart promote the differentiation of non-muscle cells to form into cardiomyocytes in vitro.

   https://doi.org/10.31031/AICS.2021.03.000553  

   Lemanski, L.F. (April 2021, Advancements in case studies)

   null (Ed.)

   We have discovered a cardiac-inducing RNA (CIR) in the axolotl, Ambystoma mexicanum, (a salamander) and two cardiac inducing RNAs (CIR-6 and CIR-30) in human heart that have the ability to induce the differentiation of non-muscle cells, including induced pluripotent stem cells from human skin, mouse embryonic stem cells, and mouse fibroblasts into cardiomyocytes in vitro. Although the primary sequences of salamander and human RNAs are not homologous, their secondary structures are very similar and we believe account for their shared unique abilities to promote differentiation of non-muscle cells into definitive cardiomyocytes. We are beginning to explore the potential for repair/regeneration of cardiac muscle in vivo using mouse and rat models with induced acute myocardial infarctions (AMI) to determine if pluripotent stem cells or fibroblasts transfected with the human CIRs or CIRs alone injected into the damaged areas of the hearts can effect repair of the damaged cardiac muscle tissue, and return the infarcted hearts and the AMI animal models to pre-heart-attack function again. If cardiac cells damaged in heart attacks can be replaced with living, functioning cardiomyocytes, patients with heart disease would be able to have normal heart function restored and could return to normal pre-heart-attack activity levels. Understanding how CIR transforms non-muscle cells into vigorously contracting, functional cardiac muscle and effectively replacing damaged heart cells with newly-formed cardiac muscle tissue would represent a major breakthrough in modern biology and medicine with the potential to have a significant impact on the survival rate and quality of life of millions of individuals worldwide who suffer heart attacks each year. 

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2. Differentiation of mouse embryonic fibroblasts (MEFs) into cardiomyocytes using human-derived cardiac inducing RNA (CIR).

   Lemanski, L.F. (April 2021, Stem cell and regenerative medicine)

   null (Ed.)

   The present study explores an RNA we have discovered in human heart that induces differentiation of mouse embryonic stem cells and human induced pluripotent stem cells into cardiomyocytes in vitro. We have designated this RNA as Cardiac Inducing RNA or CIR. We now find that CIR also induces mouse embryonic fibroblasts (MEF) to form cardiomyocytes in vitro. For these studies, human-derived CIR is transfected into MEF using lipofectamine. The CIR-transfected mouse fibroblasts exhibit spindle-shaped cells, characteristic of myocardial cells in culture, and express cardiac-specific troponin-T and cardiac tropomyosin. As such, the CIR-induced conversion of the fibroblasts into cardiomyocytes in vitro appears to take place without initial dedifferentiation into pluripotent stem cells. Instead, after CIR transfection using a lipofectamine transfection system, over the next 8 days there appears to be a direct transdifferentiation of ˃80% of the cultured fibroblasts into definitive cardiomyocytes. Fewer than ˂7% of the untreated controls using non-active RNA or lipofectamine by itself show cardiomyocyte characteristics. Thus, discovery of CIR may hold significant potential for future use in repair/regeneration of damaged myocardial tissue in humans after myocardial infarction or other disease processes such that affected patients may be able to return to pre-heart-disease activity levels. 

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3. Transcriptomic changes due to early, chronic intermittent alcohol exposure during forebrain development implicate WNT signaling, cell‐type specification, and cortical regionalization as primary determinants of fetal alcohol syndrome

   https://doi.org/10.1111/acer.14590  

   Fischer, Máté; Chander, Praveen; Kang, Huining; Mellios, Nikolaos; Weick, Jason P. (April 2021, Alcoholism: Clinical and Experimental Research)

   Abstract BackgroundFetal alcohol syndrome (FAS) due to gestational alcohol exposure represents one of the most common causes of nonheritable lifelong disability worldwide. In vitro and in vivo models have successfully recapitulated multiple facets of the disorder, including morphological and behavioral deficits, but far less is understood regarding the molecular and genetic mechanisms underlying FAS. MethodsIn this study, we utilized an in vitro human pluripotent stem cell‐based (hPSC) model of corticogenesis to probe the effects of early, chronic intermittent alcohol exposure on the transcriptome of first trimester‐equivalent cortical neurons. ResultsWe used RNA sequencing of developing hPSC‐derived neurons treated for 50 days with 50 mM ethanol and identified a relatively small number of biological pathways significantly altered by alcohol exposure. These included cell‐type specification, axon guidance, synaptic function, and regional patterning, with a notable upregulation of WNT signaling‐associated transcripts observed in alcohol‐exposed cultures relative to alcohol‐naïve controls. Importantly, this effect paralleled a shift in gene expression of transcripts associated with regional patterning, such that caudal forebrain‐related transcripts were upregulated at the expense of more anterior ones. Results from H9 embryonic stem cells were largely replicated in an induced pluripotent stem cell line (IMR90‐4), indicating that these patterning alterations are not cell line‐specific. ConclusionsWe found that a major effect of chronic intermittent alcohol on the developing cerebral cortex is an overall imbalance in regionalization, with enrichment of gene expression related to the production of posterodorsal progenitors and a diminution of anteroventral progenitors. This finding parallels behavioral and morphological phenotypes observed in animal models of high‐dose prenatal alcohol exposure, as well as patients with FAS. 

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4. Abundance and localization of human UBE3A protein isoforms

   https://doi.org/10.1093/hmg/ddaa191  

   Sirois, Carissa L; Bloom, Judy E; Fink, James J; Gorka, Dea; Keller, Steffen; Germain, Noelle D; Levine, Eric S; Chamberlain, Stormy J (August 2020, Human Molecular Genetics)

   null (Ed.)

   Abstract Loss of UBE3A expression, a gene regulated by genomic imprinting, causes Angelman syndrome (AS), a rare neurodevelopmental disorder. The UBE3A gene encodes an E3 ubiquitin ligase with three known protein isoforms in humans. Studies in mouse suggest that the human isoforms may have differences in localization and neuronal function. A recent case study reported mild AS phenotypes in individuals lacking one specific isoform. Here we have used CRISPR/Cas9 to generate isogenic human embryonic stem cells (hESCs) that lack the individual protein isoforms. We demonstrate that isoform 1 accounts for the majority of UBE3A protein in hESCs and neurons. We also show that UBE3A predominantly localizes to the cytoplasm in both wild type and isoform-null cells. Finally, we show that neurons lacking isoform 1 display a less severe electrophysiological AS phenotype. 

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5. Connectomic comparison of mouse and human cortex

   https://doi.org/10.1126/science.abo0924  

   Loomba, Sahil; Straehle, Jakob; Gangadharan, Vijayan; Heike, Natalie; Khalifa, Abdelrahman; Motta, Alessandro; Ju, Niansheng; Sievers, Meike; Gempt, Jens; Meyer, Hanno S.; et al (July 2022, Science)

   INTRODUCTION The analysis of the human brain is a central goal of neuroscience, but for methodological reasons, research has focused on model organisms, the mouse in particular. Because substantial homology was found at the level of ion channels, transcriptional programs, and basic neuronal types, a strong similarity of neuronal circuits across species has also been assumed. However, a rigorous test of the configuration of local neuronal circuitry in mouse versus human—in particular, in the gray matter of the cerebral cortex—is missing. The about 1000-fold increase in number of neurons is the most obvious evolutionary change of neuronal network properties from mouse to human. Whether the structure of the local cortical circuitry has changed as well is, however, unclear. Recent data from transcriptomic analyses has indicated an increase in the proportion of inhibitory interneurons from mouse to human. But what the effect of such a change is on the circuit configurations found in the human cerebral cortex is not known. This is, however, of particular interest also to the study of neuropsychiatric disorders because in these, the alteration of inhibitory-to-excitatory synaptic balance has been identified as one possible mechanistic underpinning. RATIONALE We used recent methodological improvements in connectomics to acquire data from one macaque and two human individuals, using biopsies of the temporal, parietal, and frontal cortex. Human tissue was obtained from neurosurgical interventions related to tumor removal, in which access path tissue was harvested that was not primarily affected by the underlying disease. A key concern in the analysis of human patient tissue has been the relation to epilepsy surgery, when the underlying disease has required often year-long treatment with pharmaceuticals, plausibly altering synaptic connectivity. Therefore, the analysis of nonepileptic surgery tissue seemed of particular importance. We also included data from one macaque individual, who was not known to have any brain-related pathology. RESULTS We acquired three-dimensional electron microscopy data from temporal and frontal cortex of human and temporal and parietal cortex of macaque. From these, we obtained connectomic reconstructions and compared these with five connectomes from mouse cortex. On the basis of these data, we were able to determine the effect of the about 2.5-fold expansion of the interneuron pool in macaque and human cortex compared with that of mouse. Contrary to expectation, the inhibitory-to-excitatory synaptic balance on pyramidal neurons in macaque and human cortex was not substantially altered. Rather, the interneuron pool was selectively expanded for bipolar-type interneurons, which prefer the innervation of other interneurons, and which further increased their preference for interneuron innervation from mouse to human. These changes were each multifold, yielding in effect an about 10-fold expanded interneuron-to-interneuron network in the human cortex that is only sparsely present in mouse. The total amount of synaptic input to pyramidal neurons, however, did not change according to the threefold thickening of the cortex; rather, a modest increase from about 12,000 synaptic inputs in mouse to about 15,000 in human was found. CONCLUSION The principal cells of the cerebral cortex, pyramidal neurons, maintain almost constant inhibitory-to-excitatory input balance and total synaptic input across 100 million years of evolutionary divergence, which is particularly noteworthy with the concomitant 1000-fold expansion of the neuronal network size and the 2.5-fold increase of inhibitory interneurons from mouse to human. Rather, the key network change from mouse to human is an expansion of almost an order of magnitude of an interneuron-to-interneuron network that is virtually absent in mouse but constitutes a substantial part of the human cortical network. Whether this new network is primarily created through the expansion of existing neuronal types, or is related to the creation of new interneuron subtypes, requires further study. The discovery of this network component in human cortex encourages detailed analysis of its function in health and disease. Connectomic screening across mammalian species: Comparison of five mouse, two macaque, and two human connectomic datasets from the cerebral cortex. ( A ) Automated reconstructions of all neurons with their cell bodies in the volume shown, using random colors. The analyzed connectomes comprised a total of ~1.6 million synapses. Arrows indicate evolutionary divergence: the last common ancestor between human and mouse, approximately 100 million years ago, and the last common ancestor between human and macaque, about 20 million years ago. ( B ) Illustration of the about 10-fold expansion of the interneuron-to-interneuron network from mouse to human. 

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