Biology subjects

Glass, I.

Publications and source records attributed to Glass, I..

23 records · Page 2Linked to original sources

bioRxiv2022

Reconstructing human Brown Fat developmental trajectory in vitro

Brown adipocytes represent a specialized type of mammalian adipocytes able to uncouple nutrient catabolism from ATP generation to dissipate energy as heat. They play an important role in mammals, allowing non-shivering thermogenesis to regulate body temperature in response to cold exposure. In humans, the brown fat tissue is composed of small discrete depots found mostly throughout the neck and trunk region. Increasing brown fat activity either with drug treatment or cell therapy is considered a potential approach for the treatment of metabolic syndrome and obesity. The recent development of in vitro differentiation strategies relying on human pluripotent stem cells (hPSCs) offers the possibility to produce unlimited amounts of brown adipocytes. A strategy efficiently applied to several tissues is to recapitulate step by step the development of the tissue of interest by exposing hPSCs to the signaling cues used during normal embryonic development. However, this strategy has proven difficult to implement for brown fat as the development of this tissue is poorly understood. Here, we first used single cell RNA sequencing to characterize the development of interscapular brown fat in mouse. Our analysis identified a previously unrecognized population of brown adipocytes precursors characterized by expression of the transcription factor GATA6. We show that this precursor population can be efficiently generated from paraxial mesoderm precursors differentiated in vitro from hPSCs by modulating the signaling pathways identified in our transcriptomic analysis. These precursors can in turn be efficiently converted into functional brown adipocytes which can respond to adrenergic stimuli by increasing their metabolism resulting in heat production.

developmental biology↗

bioRxiv2020

Targeted long-read sequencing resolves complex structural variants and identifies missing disease-causing variants

BACKGROUNDDespite widespread availability of clinical genetic testing, many individuals with suspected genetic conditions do not have a precise diagnosis. This limits their opportunity to take advantage of state-of-the-art treatments. In such instances, testing sometimes reveals difficult-to-evaluate complex structural differences, candidate variants that do not fully explain the phenotype, single pathogenic variants in recessive disorders, or no variants in specific genes of interest. Thus, there is a need for better tools to identify a precise genetic diagnosis in individuals when conventional testing approaches have been exhausted. METHODSTargeted long-read sequencing (T-LRS) was performed on 33 individuals using Read Until on the Oxford Nanopore platform. This method allowed us to computationally target up to 100 Mbp of sequence per experiment, resulting in an average of 20x coverage of target regions, a 500% increase over background. We analyzed patient DNA for pathogenic substitutions, structural variants, and methylation differences using a single data source. RESULTSThe effectiveness of T-LRS was validated by detecting all genomic aberrations, including single-nucleotide variants, copy number changes, repeat expansions, and methylation differences, previously identified by prior clinical testing. In 6/7 individuals who had complex structural rearrangements, T-LRS enabled more precise resolution of the mutation, which led, in one case, to a change in clinical management. In nine individuals with suspected Mendelian conditions who lacked a precise genetic diagnosis, T-LRS identified pathogenic or likely pathogenic variants in five and variants of uncertain significance in two others. CONCLUSIONST-LRS can accurately predict pathogenic copy number variants and triplet repeat expansions, resolve complex rearrangements, and identify single-nucleotide variants not detected by other technologies, including short-read sequencing. T-LRS represents an efficient and cost-effective strategy to evaluate high-priority candidate genes and regions or to further evaluate complex clinical testing results. The application of T-LRS will likely increase the diagnostic rate of rare disorders.

genomics↗

bioRxiv2020

Differentiation of human intestinal organoids with endogenous vascular endothelial cells

Human pluripotent stem cell (hPSC)-derived intestinal organoids (HIOs) generated using directed differentiation lack some cellular populations found in the native organ, including vasculature. Using single cell RNA sequencing (scRNAseq), we have identified a transient population of endothelial cells (ECs) present early in HIO differentiation that are lost over time in culture. Here, we have developed a method to enhance co-differentiation and maintenance of ECs within HIOs (vHIOs). Given that ECs are known to possess organ specific gene expression, morphology and function, we used bulk RNAseq and scRNAseq to interrogate the developing human intestine, lung, and kidney in order to identify organ-enriched EC-gene signatures in these organ systems. By comparing organ-specific gene signatures along with markers validated by fluorescent in situ hybridization to HIO ECs, we find that HIO ECs grown in vitro share the highest similarity with native intestinal ECs relative to kidney and lung. Together, these data show that HIOs can co-differentiate a native EC population that are properly patterned with an intestine-specific EC transcriptional signature in vitro.

developmental biology↗

bioRxiv2020

In vitro and in vivo development of the human intestine at single cell resolution

The human intestinal stem cell (ISC) niche supports ISC self-renewal and epithelial function, yet little is known about the development of the human ISC niche. We used single-cell mRNA sequencing (scRNA-seq) to interrogate the human intestine across 7-21 weeks of gestation. Using these data coupled with marker validation in situ, molecular identities and spatial locations were assigned to several cell populations that comprise the epithelial niche, and the cellular origins of many niche factors were determined. The major source of WNT and RSPONDIN ligands were ACTA2+ cells of the muscularis mucosa. EGF was predominantly expressed in the villus epithelium and the EGF-family member NEUREGULIN1 (NRG1) was expressed by subepithelial mesenchymal cells. Functional data from enteroid cultures showed that NRG1 improved cellular diversity, enhanced the stem cell gene signature, and increased enteroid forming efficiency, whereas EGF supported a secretory gene expression profile and stimulated rapid proliferation. This work highlights unappreciated complexities of intestinal EGF/ERBB signaling and identifies NRG1 as a stem cell niche factor.

developmental biology↗

bioRxiv2019

Whole-genome and RNA sequencing reveal variation and transcriptomic coordination in the developing human prefrontal cortex

Variation in gene expression underlies neurotypical development, while genomic variants contribute to neuropsychiatric disorders. BrainVar is a unique resource of paired whole-genome sequencing and bulk-tissue RNA-sequencing from the human dorsolateral prefrontal cortex of 176 neurotypical individuals across prenatal and postnatal development, providing the opportunity to assay genomic and transcriptomic variation in tandem. Leveraging this resource, we identified rare premature stop codons with commensurate reduced and allele-specific expression of corresponding genes, and common variants that alter gene expression (expression quantitative trait loci, eQTLs). Categorizing eQTLs by prenatal and postnatal effect, genes affected by temporally-specific eQTLs, compared to constitutive eQTLs, are enriched for haploinsufficiency, protein-protein interactions, and neuropsychiatric disorder risk loci. Expression levels of over 12,000 genes rise or fall in a concerted late-fetal transition, with the transitional genes enriched for cell type specific genes and neuropsychiatric disorder loci, underscoring the importance of cataloguing developmental trajectories in understanding cortical physiology and pathology.\n\nHighlightsO_LIWhole-genome and RNA-sequencing across human prefrontal cortex development in BrainVar\nC_LIO_LIGene-specific developmental trajectories characterize the late-fetal transition\nC_LIO_LIIdentification of constitutive, prenatal-specific, postnatal-specific, and rare eQTLs\nC_LIO_LIIntegrated analysis reveals genetic and developmental influences on CNS traits and disorders\nC_LI

neuroscience↗