Biology subjects

Sarrafha, L.

Publications and source records attributed to Sarrafha, L..

3 recordsLinked to original sources

bioRxiv2022

Disruption of lysosomal proteolysis in astrocytes facilitates midbrain proteostasis failure in an early-onset PD model.

Accumulation of advanced glycation end products (AGEs) on biopolymers accompany cellular aging and drives poorly understood disease processes. Here, we studied how AGEs contribute to development of early on-set Parkinsons Disease (PD) caused by loss-of-function of DJ1, a protein deglycase. In induced pluripotent stem cell (iPSC)-derived midbrain organoid models deficient for DJ1 activity, we find that lysosomal proteolysis is impaired, causing AGEs to accumulate, -synuclein (-syn) phosphorylation to increase, and proteins to aggregate. These processes are at least partly driven by astrocytes, as DJ1 loss reduces their capacity to provide metabolic support and triggers acquisition of a pro-inflammatory phenotype. Consistently, in co-cultures, we find that DJ1-expressing astrocytes are able to reverse the proteolysis deficits of DJ1 knockout midbrain neurons. In conclusion, astrocytes capacity to clear toxic damaged proteins is critical to preserve neuronal function and their dysfunction contributes to the neurodegeneration observed in PD.

neuroscience↗

bioRxiv2021

A reference induced pluripotent stem cell line for large-scale collaborative studies

Human induced pluripotent stem cell (iPSC) lines are a powerful tool for studying development and disease, but the considerable phenotypic variation between lines makes it challenging to replicate key findings and integrate data across research groups. To address this issue, we sub-cloned candidate iPSC lines and deeply characterised their genetic properties using whole genome sequencing, their genomic stability upon CRISPR/Cas9-based gene editing, and their phenotypic properties including differentiation to commonly-used cell types. These studies identified KOLF2.1J as an all-around well-performing iPSC line. We then shared KOLF2.1J with groups around the world who tested its performance in head-to-head comparisons with their own preferred iPSC lines across a diverse range of differentiation protocols and functional assays. On the strength of these findings, we have made KOLF2.1J and hundreds of its gene-edited derivative clones readily accessible to promote the standardization required for large-scale collaborative science in the stem cell field. SummaryThe authors of this collaborative study deeply characterized human induced pluripotent stem cell (iPSC) lines to rationally select a clonally-derived cell line that performs well across multiple modalities. KOLF2.1J was identified as a candidate reference cell line based on single-cell analysis of its gene expression in the pluripotent state, whole genome sequencing, genomic stability after highly efficient CRISPR-mediated gene editing, integrity of the p53 pathway, and the efficiency with which it differentiated into multiple target cell populations. Since it is deeply characterized and can be readily acquired, KOLF2.1J is an attractive reference cell line for groups working with iPSCs. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/472643v6_ufig1.gif" ALT="Figure 1"> View larger version (84K): org.highwire.dtl.DTLVardef@cef106org.highwire.dtl.DTLVardef@31d5d8org.highwire.dtl.DTLVardef@1ce6d8corg.highwire.dtl.DTLVardef@17a19d2_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2021

Identification and characterization of hPSC-derived FOXA2+ progenitor cells with ventricular cardiac differentiation potential

While much progress has been made in understanding early cardiac development, the precise mechanisms that specify the different cardiomyocyte subtypes remain poorly understood. Recent data from our lab have shown that transient Foxa2 expression identifies a progenitor population with exclusive ventricular differentiation potential in the mouse heart. Here we have translated this concept to the human pluripotent stem cell (hPSC) system. Using a FOXA2-GFP reporter cell line we characterized expression of FOXA2 during hPSC cardiac differentiation and found that a subset of cardiac mesoderm precursors transiently expresses FOXA2. Gene expression analysis of FOXA2+ and FOXA2- cardiac mesoderm revealed that both populations similarly express early cardiac specification markers such as PDGFRA, TBX5, and ISL1, while other key candidates including TBX20 and GATA4 are significantly upregulated in the FOXA2+ population. Isolation and subsequent differentiation of FOXA2+ and FOXA2- populations demonstrates their comparable differentiation potential to both cardiomyocytes and epicardial cells. However, cardiomyocytes derived from FOXA2+ precursors showed enhanced differentiation efficiency toward ventricular cardiomyocytes compared to cardiomyocytes derived from FOXA2- precursors. To identify new mechanisms that regulate ventricular specification, we performed small molecule screening and found that inhibition of the EGFR pathway strongly increased the cardiac mesoderm population in general, and the FOXA2+ precursors in particular. Finally, we have identified a combination of cell surface markers to specifically isolate FOXA2+ cardiac precursors. In summary, our results suggest that FOXA2+ cardiac mesoderm harbors ventricular-specific differentiation potential and isolation of these cells permits the generation of cultures enriched for ventricular cardiomyocytes. Generating such enriched cardiac populations will be relevant for regenerative medicine approaches, as well as for disease modeling from induced pluripotent stem cells.

developmental biology↗