RAB6 and dynein drive post-Golgi apical transport to prevent neuronal progenitor delamination.

Radial glial (RG) cells are the neural stem cells of the developing neocortex. Apical RG (aRG) cells can delaminate to generate basal RG (bRG) cells, a cell type associated with human brain expansion. Here, we report that aRG delamination is regulated by the post-Golgi secretory pathway.

Inversion of a topological domain leads to restricted changes in its gene expression and affects interdomain communication.

The interplay between the topological organization of the genome and the regulation of gene expression remains unclear. Depletion of molecular factors (e.g.

Endosomal trafficking defects alter neural progenitor proliferation and cause microcephaly.

Primary microcephaly and megalencephaly are severe brain malformations defined by reduced and increased brain size, respectively. Whether these two pathologies arise from related alterations at the molecular level is unclear. Microcephaly has been largely associated with centrosomal defects, leading to cell death.

Endothelial cell invasion is controlled by dactylopodia.

Sprouting angiogenesis is fundamental for development and contributes to cancer, diabetic retinopathy, and cardiovascular diseases. Sprouting angiogenesis depends on the invasive properties of endothelial tip cells. However, there is very limited knowledge on how tip cells invade into tissues.

Targeted Transgenic Mice Using CRISPR /Cas9 Technology.

CRISPR /Cas9 is a powerful technology that has transformed gene editing of mammalian genomes, being faster and more cost-effective than standard gene targeting techniques. In this chapter, we provide a step-by-step protocol to obtain Knock-Out (KO ) or Knock-In (KI ) mouse models using CRISPR /Cas9 technology. Detailed instructions for the design of single guide RNAs (sgRNA ) for KO approaches and single-strand oligonucleotide (ssODN ) matrix for generation of KI animals are included.

A Conserved Noncoding Locus Regulates Random Monoallelic Xist Expression across a Topological Boundary.

cis-Regulatory communication is crucial in mammalian development and is thought to be restricted by the spatial partitioning of the genome in topologically associating domains (TADs). Here, we discovered that the Xist locus is regulated by sequences in the neighboring TAD. In particular, the promoter of the noncoding RNA Linx (LinxP) acts as a long-range silencer and influences the choice of X chromosome to be inactivated.

Active cell migration is critical for steady-state epithelial turnover in the gut.

Steady-state turnover is a hallmark of epithelial tissues throughout adult life. Intestinal epithelial turnover is marked by continuous cell migration, which is assumed to be driven by mitotic pressure from the crypts. However, the balance of forces in renewal remains ill-defined.

Author Correction: Cancer-associated fibroblasts induce metalloprotease-independent cancer cell invasion of the basement membrane.

In the original version of this Article, financial support and contributions in manuscript preparation were not fully acknowledged. The PDF and HTML versions of the Article have now been corrected to include the following:'M.P.

Cancer-associated fibroblasts induce metalloprotease-independent cancer cell invasion of the basement membrane.

At the stage of carcinoma in situ, the basement membrane (BM) segregates tumor cells from the stroma. This barrier must be breached to allow dissemination of the tumor cells to adjacent tissues. Cancer cells can perforate the BM using proteolysis; however, whether stromal cells play a role in this process remains unknown.

Transient transcription in the early embryo sets an epigenetic state that programs postnatal growth.

The potential for early embryonic events to program epigenetic states that influence adult physiology remains an important question in health and development. Using the imprinted Zdbf2 locus as a paradigm for the early programming of phenotypes, we demonstrate here that chromatin changes that occur in the pluripotent embryo can be dispensable for embryogenesis but instead signal essential regulatory information in the adult. The Liz (long isoform of Zdbf2) transcript is transiently expressed in early embryos and embryonic stem cells (ESCs).

Protocols for Analyzing the Role of Paneth Cells in Regenerating the Murine Intestine using Conditional Cre-lox Mouse Models.

The epithelial surface of the mammalian intestine is a dynamic tissue that renews every 3 - 7 days. Understanding this renewal process identified a population of rapidly cycling intestinal stem cells (ISCs) characterized by their expression of the Lgr5 gene. These are supported by a quiescent stem cell population, marked by Bmi-1 expression, capable of replacing them in the event of injury.

Insertion of a Stent in Obstructive Colon Cancer Can Induce a Metastatic Process in an Experimental Murine Model.

Background: Colonic self-expanding metallic stents (SEMS) are used in obstructive colorectal cancer patients as a bridge to surgery. However, its oncologic safety remains uncertain. Therefore, we attempted to clarify this further with an experimental study and constructed a mouse model of colonic cancer.

Concomitant Notch activation and p53 deletion trigger epithelial-to-mesenchymal transition and metastasis in mouse gut.

Epithelial-to-mesenchymal transition-like (EMT-like) is a critical process allowing initiation of metastases during tumour progression. Here, to investigate its role in intestinal cancer, we combine computational network-based and experimental approaches to create a mouse model with high metastatic potential. Construction and analysis of this network map depicting molecular mechanisms of EMT regulation based on the literature suggests that Notch activation and p53 deletion have a synergistic effect in activating EMT-like processes.

Conditional expression of fascin increases tumor progression in a mouse model of intestinal cancer.

While absent from normal epithelia, an actin bundling protein, fascin, becomes expressed in invasive carcinoma of different origins. It is highly enriched at the tumors' invasive front suggesting that it could play a role in cancer invasion. Multiple studies have shown that fascin, through its role in formation of cellular protrusions such as filopodia and invadopodia, enhances cancer cell migration and invasion in vitro.

Heterochromatin reorganization during early mouse development requires a single-stranded noncoding transcript.

The equalization of pericentric heterochromatin from distinct parental origins following fertilization is essential for genome function and development. The recent implication of noncoding transcripts in this process raises questions regarding the connection between RNA and the nuclear organization of distinct chromatin environments. Our study addresses the interrelationship between replication and transcription of the two parental pericentric heterochromatin (PHC) domains and their reorganization during early embryonic development.

Enterocyte loss of polarity and gut wound healing rely upon the F-actin-severing function of villin.

Efficient wound healing is required to maintain the integrity of the intestinal epithelial barrier because of its constant exposure to a large variety of environmental stresses. This process implies a partial cell depolarization and the acquisition of a motile phenotype that involves rearrangements of the actin cytoskeleton. Here we address how polarized enterocytes harboring actin-rich apical microvilli undergo extensive cell remodeling to drive injury repair.

Evidence for a crucial role of paneth cells in mediating the intestinal response to injury.

The identification of the intestinal stem cell (ISC) markers Lgr5 and Bmi-1 has furthered our understanding of how they accomplish homeostasis in this rapidly self-renewing tissue. Recent work indicates that these markers identify a cycling Lgr5(+) ISC which can be replaced by a quiescent Bmi-1(+) ISC. Currently, there is little data on how these cells interact to control intestinal crypt homeostasis and regeneration.

A new role for the architecture of microvillar actin bundles in apical retention of membrane proteins.

Actin-bundling proteins are identified as key players in the morphogenesis of thin membrane protrusions. Until now, functional redundancy among the actin-bundling proteins villin, espin, and plastin-1 has prevented definitive conclusions regarding their role in intestinal microvilli. We report that triple knockout mice lacking these microvillar actin-bundling proteins suffer from growth delay but surprisingly still develop microvilli.

A strand-specific burst in transcription of pericentric satellites is required for chromocenter formation and early mouse development.

At the time of fertilization, the paternal genome lacks the typical configuration and marks characteristic of pericentric heterochromatin. It is thus essential to understand the dynamics of this region during early development, its importance during that time period and how a somatic configuration is attained. Here, we show that pericentric satellites undergo a transient peak in expression precisely at the time of chromocenter formation.

APC and oncogenic KRAS are synergistic in enhancing Wnt signaling in intestinal tumor formation and progression.

Background & Aims: Synchronous activation of the Wnt signaling pathway, mostly because of loss of function of the APC tumor suppressor, and of the oncogenic KRAS-signaling pathway is very frequent in colorectal cancer and is associated with poor prognosis.

Methods: We have generated a compound transgenic mouse model, KRAS(V12G)/Apc(+/1638N), to recapitulate the human disease and compared it with single transgenic littermates.

Results: Compound mutant mice are characterized by a 10-fold increase in tumor multiplicity and by accelerated tumor progression, resulting in strongly enhanced morbidity and mortality.

Mouse models of K-ras-initiated carcinogenesis.

Activating mutations of the oncogene K-ras are found in one third of all human cancers. Much of our knowledge on K-ras signal transduction and its influence on tumor initiation and progression comes from in vitro studies with cell lines. However, mouse models of human cancer allow a much more faithful recapitulation of the human disease, and the in vivo perspective is crucial for our understanding of neoplasia.

Tissue-specific and inducible Cre-mediated recombination in the gut epithelium.

We generated two complementary systems for Cre-mediated recombination of target genes in the mouse digestive epithelium and tested them with a Cre-reporter mouse strain. Cre was expressed under the control of a 9 kb regulatory region of the murine villin gene (vil-Cre). Genetic recombination was initiated at embryonic day (E) 9 in the visceral endoderm, and by E12.

Targeted expression of oncogenic K-ras in intestinal epithelium causes spontaneous tumorigenesis in mice.

Background & Aims: Ras oncoproteins are mutated in about 50% of human colorectal cancers, but their precise role in tumor initiation or progression is still unclear.

Methods: This study presents transgenic mice that express K-ras(V12G), the most frequent oncogenic mutation in human tumors, under control of the murine villin promoter in epithelial cells of the large and small intestine.

Results: More than 80% of the transgenic animals displayed single or multiple intestinal lesions, ranging from aberrant crypt foci (ACF) to invasive adenocarcinomas.