Frank B. Gertler

Bio: Frank B. Gertler is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Ena/Vasp homology proteins & Actin cytoskeleton. The author has an hindex of 92, co-authored 209 publications receiving 27146 citations. Previous affiliations of Frank B. Gertler include University of Wisconsin-Madison & Albert Einstein College of Medicine.

A lentivirus-based system to functionally silence genes in primary mammalian cells, stem cells and transgenic mice by RNA interference

Abstract: RNA interference (RNAi) has recently emerged as a specific and efficient method to silence gene expression in mammalian cells either by transfection of short interfering RNAs (siRNAs; ref. 1) or, more recently, by transcription of short hairpin RNAs (shRNAs) from expression vectors and retroviruses. But the resistance of important cell types to transduction by these approaches, both in vitro and in vivo, has limited the use of RNAi. Here we describe a lentiviral system for delivery of shRNAs into cycling and non-cycling mammalian cells, stem cells, zygotes and their differentiated progeny. We show that lentivirus-delivered shRNAs are capable of specific, highly stable and functional silencing of gene expression in a variety of cell types and also in transgenic mice. Our lentiviral vectors should permit rapid and efficient analysis of gene function in primary human and animal cells and tissues and generation of animals that show reduced expression of specific genes. They may also provide new approaches for gene therapy.

Multisite phosphorylation of a CDK inhibitor sets a threshold for the onset of DNA replication

Abstract: SCF ubiquitin ligases target phosphorylated substrates for ubiquitin-dependent proteolysis by means of adapter subunits called F-box proteins. The F-box protein Cdc4 captures phosphorylated forms of the cyclin-dependent kinase inhibitor Sic1 for ubiquitination in late G1 phase, an event necessary for the onset of DNA replication. The WD40 repeat domain of Cdc4 binds with high affinity to a consensus phosphopeptide motif (the Cdc4 phospho-degron, CPD), yet Sic1 itself has many sub-optimal CPD motifs that act in concert to mediate Cdc4 binding. The weak CPD sites in Sic1 establish a phosphorylation threshold that delays degradation in vivo, and thereby establishes a minimal G1 phase period needed to ensure proper DNA replication. Multisite phosphorylation may be a more general mechanism to set thresholds in regulated protein–protein interactions.

Three-dimensional microfluidic model for tumor cell intravasation and endothelial barrier function

Abstract: Entry of tumor cells into the blood stream is a critical step in cancer metastasis. Although significant progress has been made in visualizing tumor cell motility in vivo, the underlying mechanism of cancer cell intravasation remains largely unknown. We developed a microfluidic-based assay to recreate the tumor-vascular interface in three-dimensions, allowing for high resolution, real-time imaging, and precise quantification of endothelial barrier function. Studies are aimed at testing the hypothesis that carcinoma cell intravasation is regulated by biochemical factors from the interacting cells and cellular interactions with macrophages. We developed a method to measure spatially resolved endothelial permeability and show that signaling with macrophages via secretion of tumor necrosis factor alpha results in endothelial barrier impairment. Under these conditions intravasation rates were increased as validated with live imaging. To further investigate tumor-endothelial (TC-EC) signaling, we used highly invasive fibrosarcoma cells and quantified tumor cell migration dynamics and TC-EC interactions under control and perturbed (with tumor necrosis factor alpha) barrier conditions. We found that endothelial barrier impairment was associated with a higher number and faster dynamics of TC-EC interactions, in agreement with our carcinoma intravasation results. Taken together our results provide evidence that the endothelium poses a barrier to tumor cell intravasation that can be regulated by factors present in the tumor microenvironment.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Molecular mechanisms of epithelial–mesenchymal transition

Abstract: The transdifferentiation of epithelial cells into motile mesenchymal cells, a process known as epithelial-mesenchymal transition (EMT), is integral in development, wound healing and stem cell behaviour, and contributes pathologically to fibrosis and cancer progression. This switch in cell differentiation and behaviour is mediated by key transcription factors, including SNAIL, zinc-finger E-box-binding (ZEB) and basic helix-loop-helix transcription factors, the functions of which are finely regulated at the transcriptional, translational and post-translational levels. The reprogramming of gene expression during EMT, as well as non-transcriptional changes, are initiated and controlled by signalling pathways that respond to extracellular cues. Among these, transforming growth factor-β (TGFβ) family signalling has a predominant role; however, the convergence of signalling pathways is essential for EMT.

Targeting HIF-1 for cancer therapy

Abstract: Hypoxia-inducible factor 1 (HIF-1) activates the transcription of genes that are involved in crucial aspects of cancer biology, including angiogenesis, cell survival, glucose metabolism and invasion. Intratumoral hypoxia and genetic alterations can lead to HIF-1alpha overexpression, which has been associated with increased patient mortality in several cancer types. In preclinical studies, inhibition of HIF-1 activity has marked effects on tumour growth. Efforts are underway to identify inhibitors of HIF-1 and to test their efficacy as anticancer therapeutics.

Microenvironmental regulation of tumor progression and metastasis.

Abstract: Cancers develop in complex tissue environments, which they depend on for sustained growth, invasion and metastasis. Unlike tumor cells, stromal cell types within the tumor microenvironment (TME) are genetically stable and thus represent an attractive therapeutic target with reduced risk of resistance and tumor recurrence. However, specifically disrupting the pro-tumorigenic TME is a challenging undertaking, as the TME has diverse capacities to induce both beneficial and adverse consequences for tumorigenesis. Furthermore, many studies have shown that the microenvironment is capable of normalizing tumor cells, suggesting that re-education of stromal cells, rather than targeted ablation per se, may be an effective strategy for treating cancer. Here we discuss the paradoxical roles of the TME during specific stages of cancer progression and metastasis, as well as recent therapeutic attempts to re-educate stromal cells within the TME to have anti-tumorigenic effects.