A high-throughput screen in mESCs to identify the cross-talk between signaling, endocytosis, and pluripotency.

Embryonic stem cell fate is regulated by various cellular processes. Recently, the process of endocytosis has been implicated in playing a role in the maintenance of self-renewal and pluripotency of mouse embryonic stem cells. A previous siRNA-based screen interrogated the function of core components of the endocytic machinery in maintaining the pluripotency of embryonic stem cells, revealing a crucial role for clathrin mediated endocytosis. A number of other proteins involved in key signaling pathways have also been shown to both regulate and be regulated by endocytosis. We collated a list of 1141 genes in connection to the term "endocytosis" from Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO), excluding those previously interrogated, and examined the effect of their knockdown on the pluripotency of mouse embryonic stem cells (mESCs) using levels of green fluorescent protein driven by the Oct4 promoter. We used high-throughput screening followed by an automated MATrix LABoratory (MATLAB)-based analysis pipeline and assessed changes in GFP fluorescence as a readout for ESC pluripotency. Through this screen we identified a number of genes, many hitherto not associated with stem cell pluripotency, which upon knockdown either resulted in a significant increase or decrease of GFP fluorescence. We further present validation for some of these hits. We present a workflow aimed to identify genes involved in signaling pathways which can be regulated by endocytosis, and that affect the pluripotency of ESCs.

Cell-cell adhesions in embryonic stem cells regulate the stability and transcriptional activity of ß-catenin.

E-cadherin (CDH1) is involved in maintaining cell-cell adhesions in embryonic stem cells (ESCs). However, its function in the context of cell fate decisions is largely unknown. Using mouse ESCs (mESCs), we demonstrate that E-cadherin and ß-catenin interact at the membrane and continue to do so upon internalization within the cell. Cdh1-/- mESCs failed to form tight colonies, with altered differentiation, marker expression and retention of pluripotency factors during differentiation. Interestingly, Cdh1-/- mESCs showed dramatically reduced ß-catenin levels. Transcriptional profiling of Cdh1-/- mESCs displayed a significant alteration in the expression of a subset of ß-catenin targets in a cell state- and GSK3ß-dependent manner. Our findings hint at hitherto unknown roles played by E-cadherin in regulating the activity of ß-catenin in ESCs.

Correction to: A cost-effective and efficient approach for generating and assembling reagents for conducting real-time PCR.

In Volume 46 of the Journal of Biosciences, in the article titled 'A cost-effective and efficient approach for generating and assembling reagents for conducting real-time PCR' by Ridim D Mote, V Shinde Laxmikant, Surya Bansi Singh, Mahak Tiwari, Hemant Singh, Juhi Srivastava, Vidisha Tripathi,Vasudevan Seshadri, Amitabha Majumdar and Deepa Subramanyam, published on 27 November 2021 (https://doi.org/10.1007/s12038-021- 00231-w), the second author's name was incorrectly set as V Shinde Laxmikant. The correct name should read as Shinde Laxmikant V.

A cost-effective and efficient approach for generating and assembling reagents for conducting real-time PCR.

Real-time PCR is a widely used technique for quantification of gene expression. However, commercially available kits for real-time PCR are very expensive. The ongoing coronavirus pandemic has severely hampered the economy in a number of developing countries, resulting in a reduction in available research funding. The fallout of this will result in limiting educational institutes and small enterprises from using cutting edge biological techniques such as real-time PCR. Here, we report a cost-effective approach for preparing and assembling cDNA synthesis and real-time PCR mastermixes with similar efficiencies as commercially available kits. Our results thus demonstrate an alternative to commercially available kits.

Pluripotency of embryonic stem cells lacking clathrin-mediated endocytosis cannot be rescued by restoring cellular stiffness.

Mouse embryonic stem cells (mESCs) display unique mechanical properties, including low cellular stiffness in contrast to differentiated cells, which are stiffer. We have previously shown that mESCs lacking the clathrin heavy chain (Cltc), an essential component for clathrin-mediated endocytosis (CME), display a loss of pluripotency and an enhanced expression of differentiation markers. However, it is not known whether physical properties such as cellular stiffness also change upon loss of Cltc, similar to what is seen in differentiated cells, and if so, how these altered properties specifically impact pluripotency. Using atomic force microscopy (AFM), we demonstrate that mESCs lacking Cltc display higher Young's modulus, indicative of greater cellular stiffness, compared with WT mESCs. The increase in stiffness was accompanied by the presence of actin stress fibers and accumulation of the inactive, phosphorylated, actin-binding protein cofilin. Treatment of Cltc knockdown mESCs with actin polymerization inhibitors resulted in a decrease in the Young's modulus to values similar to those obtained with WT mESCs. However, a rescue in the expression profile of pluripotency factors was not obtained. Additionally, whereas WT mouse embryonic fibroblasts could be reprogrammed to a state of pluripotency, this was inhibited in the absence of Cltc. This indicates that the presence of active CME is essential for the pluripotency of embryonic stem cells. Additionally, whereas physical properties may serve as a simple readout of the cellular state, they may not always faithfully recapitulate the underlying molecular fate.

Clathrin-Mediated Endocytosis Regulates a Balance between Opposing Signals to Maintain the Pluripotent State of Embryonic Stem Cells.

Endocytosis is implicated in the maintenance of embryonic stem cell (ESC) pluripotency, although its exact role and the identity of molecular players remain poorly understood. Here, we show that the clathrin heavy chain (CLTC), involved in clathrin-mediated endocytosis (CME), is vital for maintaining mouse ESC (mESC) pluripotency. Knockdown of Cltc resulted in a loss of pluripotency accompanied by reduced E-cadherin (E-CAD) levels and increased levels of transforming growth factor ß (TGF-ß) and extracellular signal-regulated kinase (ERK) signaling. We demonstrate that both E-CAD and TGF-ß receptor type 1 (TGF-ßR1) are internalized through CME in mESCs. While E-CAD is recycled, TGF-ßR1 is targeted for lysosomal degradation thus maintaining inverse levels of these molecules. Finally, we show that E-CAD interacts with ERK, and that the decreased pluripotency upon CME loss can be rescued by inhibiting TGF-ßR, MEK, and GSK3ß, or overexpressing E-CAD. Our results demonstrate that CME is critical for balancing signaling outputs to regulate ESC pluripotency, and possibly cell fate choices in early development.