Mechanisms underlying the direct programming of mouse embryonic fibroblasts to thymic epithelial cells by FOXN1.

Thymic epithelial cells (TECs) are crucial to the ability of the thymus to generate T cells for the adaptive immune system in vertebrates. However, no in vitro system for studying TEC function exists. Overexpressing the transcription factor FOXN1 initiates transdifferentiation of fibroblasts into TEC-like cells (iTECs) that support T-cell differentiation in culture or after transplant.

Foxn1 overexpression promotes thymic epithelial progenitor cell proliferation and mTEC maintenance, but does not prevent thymic involution.

The transcription factor FOXN1 is essential for fetal thymic epithelial cell (TEC) differentiation and proliferation. Postnatally, Foxn1 levels vary widely between TEC subsets, from low/undetectable in putative TEC progenitors to highest in differentiated TEC subsets. Correct Foxn1 expression is required to maintain the postnatal microenvironment; premature downregulation of Foxn1 causes a rapid involution-like phenotype, and transgenic overexpression can cause thymic hyperplasia and/or delayed involution.

Embryology of the Parathyroid Glands.

The parathyroid glands are essential for regulating calcium homeostasis in the body. The genetic programs that control parathyroid fate specification, morphogenesis, differentiation, and survival are only beginning to be delineated, but are all centered around a key transcription factor, GCM2. Mutations in the Gcm2 gene as well as in several other genes involved in parathyroid organogenesis have been found to cause parathyroid disorders in humans.

The untapped potential of the GENSAT mice-A valuable resource for developmental biology.

Gene Expression Nervous System Atlas (GENSAT) transgenic mice express EGFP, tdTomato, or Cre recombinase in a wide range of cell types. The mice and the bacterial artificial chromosome transgenes are available from repositories (MMRRC or CHORI), thereby making these resources readily available to the research community. This resource of 1,386 transgenic lines was developed and validated for neuroscience research.

Using the Textpresso Site-Specific Recombinases Web server to identify Cre expressing mouse strains and floxed alleles.

Effective tools for searching the biomedical literature are essential for identifying reagents or mouse strains as well as for effective experimental design and informed interpretation of experimental results. We have built the Textpresso Site Specific Recombinases (Textpresso SSR) Web server to enable researchers who use mice to perform in-depth searches of a rapidly growing and complex part of the mouse literature. Our Textpresso Web server provides an interface for searching the full text of most of the peer-reviewed publications that report the characterization or use of mouse strains that express Cre or Flp recombinase.

SDF and GABA interact to regulate axophilic migration of GnRH neurons.

Stromal derived growth factor (SDF-1) and gamma-aminobutyric acid (GABA) are two extracellular cues that regulate the rate of neuronal migration during development and may act synergistically. The molecular mechanisms of this interaction are still unclear. Gonadotropin releasing hormone-1 (GnRH) neurons are essential for vertebrate reproduction.

A focused in situ hybridization screen identifies candidate transcriptional regulators of thymic epithelial cell development and function.

Background: Thymic epithelial cells (TECs) are necessary for normal T cell development. Currently, one transcription factor, Foxn1 is known to be necessary for the progression of fetal TEC differentiation. However, some aspects of fetal TEC differentiation occur in Foxn1 mutants, suggesting the existence of additional transcriptional regulators of TEC differentiation.

Whole mount in situ hybridization of E8.5 to E11.5 mouse embryos.

Whole mount in situ hybridization is a very informative approach for defining gene expression patterns in embryos. The in situ hybridization procedures are lengthy and technically demanding with multiple important steps that collectively contribute to the quality of the final result. This protocol describes in detail several key quality control steps for optimizing probe labeling and performance.

Structure and function of the thymic microenvironment.

Organs are more than the sum of their component parts--functional competence requires that these parts not only be present in the appropriate proportions, but also be arranged and function together in specific ways. The thymus is an excellent example of the connection between cellular organization and organ function. Unlike more familiar organs, such as lung or kidney, the thymus is not organized into easily identifiable structures such as tubes and ordered cell layers, but instead is a complex meshwork of microenvironments through which T cell progenitors migrate, receiving signals that instruct them to differentiate, proliferate, or die.

An evolving NGF-Hoxd1 signaling pathway mediates development of divergent neural circuits in vertebrates.

Species are endowed with unique sensory capabilities that are encoded by divergent neural circuits. One potential explanation for how divergent circuits have evolved is that conserved extrinsic signals are differentially interpreted by developing neurons of different species to yield unique patterns of axonal connections. Although nerve growth factor (NGF) controls survival, maturation and axonal projections of nociceptors of different vertebrates, whether the NGF signal is differentially transduced in different species to yield unique features of nociceptor circuits is unclear.

Transcriptional regulation of thymus organogenesis and thymic epithelial cell differentiation.

Transcriptional regulatory networks are the central regulatory mechanisms that control organ identity, patterning, and differentiation. In the case of the thymus, several key transcription factors have been identified that are critical for various aspects of thymus organogenesis and thymic epithelial cell (TEC) differentiation. The thymus forms from the third pharyngeal pouch endoderm during embryogenesis.

Mouse and zebrafish Hoxa3 orthologues have nonequivalent in vivo protein function.

Hox genes play evolutionarily conserved roles in specifying axial position during embryogenesis. A prevailing paradigm is that changes in Hox gene expression drive evolution of metazoan body plans. Conservation of Hox function across species, and among paralogous Hox genes within a species, supports a model of functional equivalence.

Cleft palate is caused by CNS dysfunction in Gad1 and Viaat knockout mice.

Background: Previous studies have shown that disruption of GABA signaling in mice via mutations in the Gad1, Gabrb3 or Viaat genes leads to the development of non-neural developmental defects such as cleft palate. Studies of the Gabrb3 and Gad1 mutant mice have suggested that GABA function could be required either in the central nervous system or in the palate itself for normal palatogenesis.

Methodology/principal Findings: To further examine the role of GABA signaling in palatogenesis we used three independent experimental approaches to test whether Gad1 or Viaat function is required in the fetal CNS for normal palate development.

Loss of Rab25 promotes the development of intestinal neoplasia in mice and is associated with human colorectal adenocarcinomas.

Transformation of epithelial cells is associated with loss of cell polarity, which includes alterations in cell morphology as well as changes in the complement of plasma membrane proteins. Rab proteins regulate polarized trafficking to the cell membrane and therefore represent potential regulators of this neoplastic transition. Here we have demonstrated a tumor suppressor function for Rab25 in intestinal neoplasia in both mice and humans.

Textpresso site-specific recombinases: A text-mining server for the recombinase literature including Cre mice and conditional alleles.

Textpresso Site Specific Recombinases (http://ssrc.genetics.uga.

Temporal migration of gonadotrophin-releasing hormone-1 neurones is modified in GAD67 knockout mice.

Gonadotrophin-releasing hormone (GnRH-1) neurones reside in the forebrain and regulate gonadal function via the hypothalamic-pituitary-gonadal axis. Disruption of this axis results in reproductive dysfunction. During embryonic development, GnRH-1 neurones migrate from the nasal pit through the nasal/forebrain junction (NFJ) into the developing brain.

Specific expression of lacZ and cre recombinase in fetal thymic epithelial cells by multiplex gene targeting at the Foxn1 locus.

Background: Thymic epithelial cells (TECs) promote thymocyte maturation and are required for the early stages of thymocyte development and for positive selection. However, investigation of the mechanisms by which TECs perform these functions has been inhibited by the lack of genetic tools. Since the Foxn1 gene is expressed in all presumptive TECs from the early stages of thymus organogenesis and broadly in the adult thymus, it is an ideal locus for driving gene expression in differentiating and mature TECs.

Ceramide regulates atypical PKCzeta/lambda-mediated cell polarity in primitive ectoderm cells. A novel function of sphingolipids in morphogenesis.

In mammals, the primitive ectoderm is an epithelium of polarized cells that differentiates into all embryonic tissues. Our study shows that in primitive ectoderm cells, the sphingolipid ceramide was elevated and co-distributed with the small GTPase Cdc42 and cortical F-actin at the apicolateral cell membrane. Pharmacological or RNA interference-mediated inhibition of ceramide biosynthesis enhanced apoptosis and impaired primitive ectoderm formation in embryoid bodies differentiated from mouse embryonic stem cells.

Notch signaling is inactive but inducible in human embryonic stem cells.

The NOTCH signaling pathway performs a wide range of critical functions in a number of different cell types during development and differentiation. The role of NOTCH signals in human embryonic stem cells (hESCs) has not been tested. We measured the activity of canonical NOTCH signaling in undifferentiated embryonic stem (ES) cells and tested the requirement for NOTCH activity in hESC self-renewal or differentiation by growing hESCs in the presence of gamma-secretase inhibitors.

[Ala12]MCD peptide: a lead peptide to inhibitors of immunoglobulin E binding to mast cell receptors.

An effort was made to discover mast cell degranulating (MCD) peptide analogs that bind with high affinity to mast cell receptors without triggering secretion of histamine or other mediators of the allergic reaction initiated by immunoglobulin E (IgE) after mast cell activation. Such compounds could serve as inhibitors of IgE binding to mast cell receptors. An alanine scan of MCD peptide reported previously showed that the analog [Ala12]MCD was 120-fold less potent in histamine-releasing activity and fivefold more potent in binding affinity to mast cell receptors than the parent MCD peptide.

Designer antibacterial peptides kill fluoroquinolone-resistant clinical isolates.

A significant number of Escherichia coli and Klebsiella pneumoniae bacterial strains in urinary tract infections are resistant to fluoroquinolones. Peptide antibiotics are viable alternatives although these are usually either toxic or insufficiently active. By applying multiple alignment and sequence optimization steps, we designed multifunctional proline-rich antibacterial peptides that maintained their DnaK-binding ability in bacteria and low toxicity in eukaryotes, but entered bacterial cells much more avidly than earlier peptide derivatives.

Direct binding to ceramide activates protein kinase Czeta before the formation of a pro-apoptotic complex with PAR-4 in differentiating stem cells.

We have reported that ceramide mediates binding of atypical protein kinase C (PKC) zeta to its inhibitor protein, PAR-4 (prostate apoptosis response-4), thereby inducing apoptosis in differentiating embryonic stem cells. Using a novel method of lipid vesicle-mediated affinity chromatography, we showed here that endogenous ceramide binds directly to the PKCzeta.PAR-4 complex.

The mouse vesicular inhibitory amino acid transporter gene: expression during embryogenesis, analysis of its core promoter in neural stem cells and a reconsideration of its alternate splicing.

The vesicular inhibitory amino acid transporter, VIAAT (also known as vesicular GABA transporter VGAT) transports GABA or glycine into synaptic vesicles. To initiate an analysis of the expression and regulation of VIAAT during neurogenesis we have cloned and characterized the mouse Viaat gene. We find that the mouse Viaat coding sequence is encoded by two exons spanning 5.

Differentiation of human embryonic stem cells to dopaminergic neurons in serum-free suspension culture.

The use of human embryonic stem cells (hESCs) as a source of dopaminergic neurons for Parkinson's disease cell therapy will require the development of simple and reliable cell differentiation protocols. The use of cell cocultures, added extracellular signaling factors, or transgenic approaches to drive hESC differentiation could lead to additional regulatory as well as cell production delays for these therapies. Because the neuronal cell lineage seems to require limited or no signaling for its formation, we tested the ability of hESCs to differentiate to form dopamine-producing neurons in a simple serum-free suspension culture system.