The UCSF Mouse Inventory Database Application, an Open Source Web App for Sharing Mutant Mice Within a Research Community

The UCSF Mouse Inventory Database Application is an open-source Web App that provides information about the mutant alleles, transgenes, and inbred strains maintained by investigators at the university and facilitates sharing of these resources within the university community. The Application is designed to promote collaboration, decrease the costs associated with obtaining genetically-modified mice, and increase access to mouse lines that are difficult to obtain. An inventory of the genetically-modified mice on campus and the investigators who maintain them is compiled from records of purchases from external sources, transfers from researchers within and outside the university, and from data provided by users. These data are verified and augmented with relevant information harvested from public databases, and stored in a succinct, searchable database secured on the university network. Here we describe this resource and provide information about how to implement and maintain such a mouse inventory database application at other institutions.

What comes after a career in science? Asian Art!

Throughout my professional life I was an academic researcher who had a successful career in developmental biology. When I started the process of closing my lab and retiring from the University, I came to the conclusion that I wanted to do something completely different. I trained for and became a docent at the Asian Art Museum of San Francisco. I apply the skills I acquired as a scientist on a regular basis in my work at the museum, often in unexpected ways. In this article, I discuss my journey from the lab to the museum and what I learned along the way.

Menin determines K-RAS proliferative outputs in endocrine cells

Endocrine cell proliferation fluctuates dramatically in response to signals that communicate hormone demand. The genetic alterations that override these controls in endocrine tumors often are not associated with oncogenes common to other tumor types, suggesting that unique pathways govern endocrine proliferation. Within the pancreas, for example, activating mutations of the prototypical oncogene KRAS drive proliferation in all pancreatic ductal adenocarcimomas but are never found in pancreatic endocrine tumors. Therefore, we asked how cellular context impacts K-RAS signaling. We found that K-RAS paradoxically suppressed, rather than promoted, growth in pancreatic endocrine cells. Inhibition of proliferation by K-RAS depended on antiproliferative RAS effector RASSF1A and blockade of the RAS-activated proproliferative RAF/MAPK pathway by tumor suppressor menin. Consistent with this model, a glucagon-like peptide 1 (GLP1) agonist, which stimulates ERK1/2 phosphorylation, did not affect endocrine cell proliferation by itself, but synergistically enhanced proliferation when combined with a menin inhibitor. In contrast, inhibition of MAPK signaling created a synthetic lethal interaction in the setting of menin loss. These insights suggest potential strategies both for regenerating pancreatic β cells for people with diabetes and for targeting menin-sensitive endocrine tumors.

High cell density alters the ratio of type III to I collagen synthesis by fibroblasts

HUMAN fibroblasts in culture synthesise both type I and type III collagen(1), with type I accounting for 70-90% of the total(2). In culture, the rates at which these proteins are synthesised is constant and apparently rather rigidly controlled(3). However, the proportions of these collagens differs in cells cultured with increased amounts of serum (increased type III/I)(4) as well as in cells obtained from patients with certain diseases. Cells from patients with the Ehlers-Danlos type IV syndrome make little or no type III collagen(5,6), whereas cells from patients with osteogenesis imperfecta have an increased type III/I (refs 7, 8). We have found that cells from some patients with systemic sclerosis (scleroderma), have a reduced type III/I ratio. However, as previously reported, these cells grew to a lower density than control cells(9). We report here that normal fibroblasts from human and guinea pig skin produce proportionally more type III collagen at high cell density, probably because of a reduction in the synthesis of type I collagen.

Feasibility of implementing pulse oximetry screening for congenital heart disease in a community hospital

OBJECTIVE

Pulse oximetry has been recognized as a promising screening tool for critical congenital heart disease (CCHD). The aim of this research was to study the feasibility of implementation in a community hospital setting.

STUDY DESIGN

Meetings were conducted to determine an implementation plan. Pulse oximetry was performed on the right hand and foot after 24 h of age. Newborns with a saturation ≤ 95% or a ≥ 3% difference were considered to have a positive screen. Screening barriers, screening time and ability to effectively screen all eligible newborns were noted.

RESULT

From January 2009 through May 2010, of 6841 eligible newborns, 6745 newborns (98.6%) were screened. Of the nine infants with positive pulse oximetry screens, one had CCHD, four had CHD and four others were determined to have false positive screens. Average screening time was 3.5 min (0 to 35 min).

CONCLUSION

Pulse oximetry can be implemented successfully in community hospitals without an excessive number of false positives or additional nursing staff.

Endogenous cellular prion protein regulates contractility of the mouse ileum

BACKGROUND

Cellular prion protein (PrP(C) ) is expressed in the enteric nervous system (ENS), however, its physiological role has not been identified. Studies suggest that PrP(C) can function as a metal-binding protein, as absence of the protein has been linked to altered copper metabolism and atypical synaptic activity. Because copper is known to modulate smooth muscle relaxation, we tested the hypothesis that PrP(C) deficiency would alter intestinal contractility.

METHODS

We examined electrically evoked ileal contractility in Prnp(-/-) or wild type littermate mice and the effects of copper or copper chelation. PrP(C) expression was studied in whole mount ileal preparations of mice and guinea pigs by immunohistochemistry.

KEY RESULTS

Relative to wild type mice, ileal tissues of Prnp(-/-) mice exhibited reduced electrical field stimulation (EFS)-evoked contractility. Furthermore, EFS-induced relaxation, as a percentage of that induced by a nitric oxide donor, was enhanced. Addition of a copper donor to the organ bath increased, whereas the addition of a copper chelator inhibited, nitric oxide donor-induced ileal relaxation in Prnp(-/-) mice. PrP(C) was expressed on nerve fibers or terminals, and some cell bodies in the myenteric and submucosal plexuses of wild type mice. PrP(C) colocalized with a neuron-specific ectonucleotidase, nucleoside triphosphate diphosphohydrolase 3 (NTPDase3), but to only a limited extent with GFAP, a marker of enteric glia. Guinea pigs expressed PrP(C) in nerve fibers or terminals and enteric glia in the myenteric and submucosal plexuses.

CONCLUSIONS & INFERENCES

Our findings suggest that PrP(C) , which is abundant in the ENS, has a role in the regulation of ileal contractility.

Assessing the validity of the accelerometry technique for estimating the energy expenditure of diving double-crested cormorants Phalacrocorax auritus

Over the past few years, acceleration-data loggers have been used to provide calibrated proxies of energy expenditure: the accelerometry technique. Relationships between rate of oxygen consumption and a derivation of acceleration data termed "overall dynamic body acceleration" (ODBA) have now been generated for a range of species, including birds, mammals, and amphibians. In this study, we examine the utility of the accelerometry technique for estimating the energy expended by double-crested cormorants Phalacrocorax auritus to undertake a dive cycle (i.e., a dive and the subsequent pause at the surface before another dive). The results show that ODBA does not calibrate with energy expenditure in diving cormorants, where energy expenditure is calculated from measures of oxygen uptake during surface periods between dives. The possible explanations include reasons why energy expenditure may not relate to ODBA but also reasons why oxygen uptake between dives may not accurately represent energy expenditure during a dive cycle.

Control of mitotic spindle angle by the RAS-regulated ERK1/2 pathway determines lung tube shape

During early lung development, airway tubes change shape. Tube length increases more than circumference as a large proportion of lung epithelial cells divide parallel to the airway longitudinal axis. We show that this bias is lost in mutants with increased extracellular signal-regulated kinase 1 (ERK1) and ERK2 activity, revealing a link between the ERK1/2 signaling pathway and the control of mitotic spindle orientation. Using a mathematical model, we demonstrate that change in airway shape can occur as a function of spindle angle distribution determined by ERK1/2 signaling, independent of effects on cell proliferation or cell size and shape. We identify sprouty genes, which encode negative regulators of fibroblast growth factor 10 (FGF10)-mediated RAS-regulated ERK1/2 signaling, as essential for controlling airway shape change during development through an effect on mitotic spindle orientation.

SHH propagates distal limb bud development by enhancing CYP26B1-mediated retinoic acid clearance via AER-FGF signalling

The essential roles of SHH in anteroposterior (AP) and AER-FGF signalling in proximodistal (PD) limb bud development are well understood. In addition, these morphoregulatory signals are key components of the self-regulatory SHH/GREM1/AER-FGF feedback signalling system that regulates distal progression of limb bud development. This study uncovers an additional signalling module required for coordinated progression of limb bud axis development. Transcriptome analysis using Shh-deficient mouse limb buds revealed that the expression of proximal genes was distally extended from early stages onwards, which pointed to a more prominent involvement of SHH in PD limb axis development. In particular, retinoic acid (RA) target genes were upregulated proximally, while the expression of the RA-inactivating Cyp26b1 enzyme was downregulated distally, pointing to increased RA activity in Shh-deficient mouse limb buds. Further genetic and molecular analysis established that Cyp26b1 expression is regulated by AER-FGF signalling. During initiation of limb bud outgrowth, the activation of Cyp26b1 expression creates a distal 'RA-free' domain, as indicated by complementary downregulation of a transcriptional sensor of RA activity. Subsequently, Cyp26b1 expression increases as a consequence of SHH-dependent upregulation of AER-FGF signalling. To better understand the underlying signalling interactions, computational simulations of the spatiotemporal expression patterns and interactions were generated. These simulations predicted the existence of an antagonistic AER-FGF/CYP26B1/RA signalling module, which was verified experimentally. In summary, SHH promotes distal progression of limb development by enhancing CYP26B1-mediated RA clearance as part of a signalling network linking the SHH/GREM1/AER-FGF feedback loop to the newly identified AER-FGF/CYP26B1/RA module.

Hedgehog signaling regulates the generation of ameloblast progenitors in the continuously growing mouse incisor

In many organ systems such as the skin, gastrointestinal tract and hematopoietic system, homeostasis is dependent on the continuous generation of differentiated progeny from stem cells. The rodent incisor, unlike human teeth, grows throughout the life of the animal and provides a prime example of an organ that rapidly deteriorates if newly differentiated cells cease to form from adult stem cells. Hedgehog (Hh) signaling has been proposed to regulate self-renewal, survival, proliferation and/or differentiation of stem cells in several systems, but to date there is little evidence supporting a role for Hh signaling in adult stem cells. We used in vivo genetic lineage tracing to identify Hh-responsive stem cells in the mouse incisor and we show that sonic hedgehog (SHH), which is produced by the differentiating progeny of the stem cells, signals to several regions of the incisor. Using a hedgehog pathway inhibitor (HPI), we demonstrate that Hh signaling is not required for stem cell survival but is essential for the generation of ameloblasts, one of the major differentiated cell types in the tooth, from the stem cells. These results therefore reveal the existence of a positive-feedback loop in which differentiating progeny produce the signal that in turn allows them to be generated from stem cells.

Cardiac conduction is required to preserve cardiac chamber morphology

Electrical cardiac forces have been previously hypothesized to play a significant role in cardiac morphogenesis and remodeling. In response to electrical forces, cultured cardiomyocytes rearrange their cytoskeletal structure and modify their gene expression profile. To translate such in vitro data to the intact heart, we used a collection of zebrafish cardiac mutants and transgenics to investigate whether cardiac conduction could influence in vivo cardiac morphogenesis independent of contractile forces. We show that the cardiac mutant dco(s226) develops heart failure and interrupted cardiac morphogenesis following uncoordinated ventricular contraction. Using in vivo optical mapping/calcium imaging, we determined that the dco cardiac phenotype was primarily due to aberrant ventricular conduction. Because cardiac contraction and intracardiac hemodynamic forces can also influence cardiac development, we further analyzed the dco phenotype in noncontractile hearts and observed that disorganized ventricular conduction could affect cardiomyocyte morphology and subsequent heart morphogenesis in the absence of contraction or flow. By positional cloning, we found that dco encodes Gja3/Cx46, a gap junction protein not previously implicated in heart formation or function. Detailed analysis of the mouse Cx46 mutant revealed the presence of cardiac conduction defects frequently associated with human heart failure. Overall, these in vivo studies indicate that cardiac electrical forces are required to preserve cardiac chamber morphology and may act as a key epigenetic factor in cardiac remodeling.

CHEMICAL AND MORPHOLOGICAL STUDIES ON THE IN VITRO CALCIFICATION OF AORTA

After a lag period, rat aortas incubated in rat serum in vitro accumulated substantial quantities of calcium and phosphate. Examination of the tissue by x-ray diffraction, microradiography, electron diffraction, and electron microscopy indicated that the calcium-phosphate phase which formed was hydroxyapatite and that the crystals were localized almost exclusively in elastin. Selective elimination of various components of the aorta with proteolytic enzymes indicated that the presence of elastin was required for mineralization. Collagen fibers did not appear to be required for the initiation of calcification, nor did they seem to undergo appreciable calcification in the time periods studied. Analysis of the initial lag period suggested that at least two changes occurred in serum prior to the mineralization of this tissue. Inhibitors of the reaction were destroyed, and the level of dialyzable calcium was elevated owing to its release from serum protein.

MicroRNA-21 contributes to myocardial disease by stimulating MAP kinase signalling in fibroblasts

MicroRNAs comprise a broad class of small non-coding RNAs that control expression of complementary target messenger RNAs. Dysregulation of microRNAs by several mechanisms has been described in various disease states including cardiac disease. Whereas previous studies of cardiac disease have focused on microRNAs that are primarily expressed in cardiomyocytes, the role of microRNAs expressed in other cell types of the heart is unclear. Here we show that microRNA-21 (miR-21, also known as Mirn21) regulates the ERK-MAP kinase signalling pathway in cardiac fibroblasts, which has impacts on global cardiac structure and function. miR-21 levels are increased selectively in fibroblasts of the failing heart, augmenting ERK-MAP kinase activity through inhibition of sprouty homologue 1 (Spry1). This mechanism regulates fibroblast survival and growth factor secretion, apparently controlling the extent of interstitial fibrosis and cardiac hypertrophy. In vivo silencing of miR-21 by a specific antagomir in a mouse pressure-overload-induced disease model reduces cardiac ERK-MAP kinase activity, inhibits interstitial fibrosis and attenuates cardiac dysfunction. These findings reveal that microRNAs can contribute to myocardial disease by an effect in cardiac fibroblasts. Our results validate miR-21 as a disease target in heart failure and establish the therapeutic efficacy of microRNA therapeutic intervention in a cardiovascular disease setting.

Genetic mosaic analysis reveals FGF receptor 2 function in terminal end buds during mammary gland branching morphogenesis

FGF signaling is associated with breast cancer and is required for mammary placode formation in the mouse. In this study, we employed a genetic mosaic analysis based on Cre-mediated recombination to investigate FGF receptor 2 (Fgfr2) function in the postnatal mammary gland. Mosaic inactivation of Fgfr2 by the MMTV-Cre transgene enabled us to compare the behavior of Fgfr2 null and Fgfr2 heterozygous cells in the same gland. Fgfr2 null cells were at a competitive disadvantage to their Fgfr2 heterozygous neighbors in the highly proliferative terminal end buds (TEBs) at the invasion front, owing to a negative effect of loss of Fgfr2 function on cell proliferation. However, Fgfr2 null cells were tolerated in mature ducts. In these genetic mosaic mammary glands, the epithelial network is apparently built by TEBs that over time are composed of a progressively larger proportion of Fgfr2-positive cells. However, subsequently, most cells lose Fgfr2 function, presumably due to additional rounds of Cre-mediated recombination. Using an independent strategy to create mosaic mammary glands, which employed an adenovirus-Cre that acts only once, we confirmed that Fgfr2 null cells were out-competed by neighboring Fgfr2 heterozygous cells. Together, our data demonstrate that Fgfr2 functions in the proliferating and invading TEBs, but it is not required in the mature ducts of the pubertal mammary gland.

The regulation of basement membrane formation and cell-matrix interactions by defined supramolecular complexes

Several constituents of basement membranes, including type IV collagen, laminin, heparan sulphate proteoglycan and nidogen, form a defined supramolecular complex that is an obligatory intermediate in the formation of this matrix. We have named this defined supramolecular complex the 'basement membrane matrisome'. Matrisome structures composed of other collagens, proteoglycans and glycoproteins may participate in the formation of other extracellular matrices. Cells show specific interactions with components of the extracellular matrix. We discuss studies that indicate that melanoma cells can express receptors for both laminin and fibronectin. However, these receptors are expressed in a reciprocal fashion, depending on the exposure of the cell to these proteins. Binding of either fibronectin or laminin to the cells elicits a distinct phenotype. This represents a mechanism in which cellular activity can be regulated by extracellular matrix factors during development and in repair.

A Cre transgene active in developing endodermal organs, heart, limb, and extra-ocular muscle

Cre-mediated recombination, a method widely used in mice for tissue-specific inactivation of endogenous genes or activation of transgenes, is critically dependent on the availability of mouse lines in which Cre recombinase functions in the tissue of interest or its progenitors. Here we describe a transgenic mouse line, Osr1-cre, in which Cre is active from embryonic day (E)11.5 in a few specific tissues. These include the endoderm of the posterior foregut, midgut, hindgut, and developing urogenital system, the heart left atrium, extra-ocular muscle progenitors, and mesenchyme in particular regions of the limb. Furthermore, starting at E12.5, Cre functions in limb interdigital mesenchyme. Within the urogenital system, recombination appears to be virtually complete in the epithelium of the bladder and urethra just posterior to it by E14.5. In males, some of these urethral cells form the prostate. The spatiotemporal pattern of Cre activity in Osr1-cre makes it a unique resource among the lines available for Cre-mediated recombination experiments.

Specific regions within the embryonic midbrain and cerebellum require different levels of FGF signaling during development

Prospective midbrain and cerebellum formation are coordinated by FGF ligands produced by the isthmic organizer. Previous studies have suggested that midbrain and cerebellum development require different levels of FGF signaling. However, little is known about the extent to which specific regions within these two parts of the brain differ in their requirement for FGF signaling during embryogenesis. Here, we have explored the effects of inhibiting FGF signaling within the embryonic mouse midbrain (mesencephalon) and cerebellum (rhombomere 1) by misexpressing sprouty2 (Spry2) from an early stage. We show that such Spry2 misexpression moderately reduces FGF signaling, and that this reduction causes cell death in the anterior mesencephalon, the region furthest from the source of FGF ligands. Interestingly, the remaining mesencephalon cells develop into anterior midbrain, indicating that a low level of FGF signaling is sufficient to promote only anterior midbrain development. Spry2 misexpression also affects development of the vermis, the part of the cerebellum that spans the midline. We found that, whereas misexpression of Spry2 alone caused loss of the anterior vermis, reducing FGF signaling further, by decreasing Fgf8 gene dose, resulted in loss of the entire vermis. Our data suggest that cell death is not responsible for vermis loss, but rather that it fails to develop because reducing FGF signaling perturbs the balance between vermis and roof plate development in rhombomere 1. We suggest a molecular explanation for this phenomenon by providing evidence that FGF signaling functions to inhibit the BMP signaling that promotes roof plate development.

An FGF signaling loop sustains the generation of differentiated progeny from stem cells in mouse incisors

Rodent incisors grow throughout adult life, but are prevented from becoming excessively long by constant abrasion, which is facilitated by the absence of enamel on one side of the incisor. Here we report that loss-of-function of sprouty genes, which encode antagonists of receptor tyrosine kinase signaling, leads to bilateral enamel deposition, thus impeding incisor abrasion and resulting in unchecked tooth elongation. We demonstrate that sprouty genes function to ensure that enamel-producing ameloblasts are generated on only one side of the tooth by inhibiting the formation of ectopic ameloblasts from self-renewing stem cells, and that they do so by preventing the establishment of an epithelial-mesenchymal FGF signaling loop. Interestingly, although inactivation of Spry4 alone initiates ectopic ameloblast formation in the embryo, the dosage of another sprouty gene must also be reduced to sustain it after birth. These data reveal that the generation of differentiated progeny from a particular stem cell population can be differently regulated in the embryo and adult.

Inhibitors of collagenase IV and cell adhesion reduce the invasive activity of malignant tumour cells

The invasive activities of some malignant cells appear to be activated by contact with laminin. This protein occurs solely in basement membranes and the binding of malignant cells to the surface of this extracellular matrix initiates the invasion process. Passage of the cells across basement membrane requires degradative activity and laminin induces the production of collagenase IV which lyses the collagen IV network. The motility of the cells is enhanced by chemo-attractants and by matrix molecules. Peptides that inhibit the binding of tumour cells to laminin, inhibitors of collagenase IV, and inhibitors of specific pathways of arachidonic acid metabolism prevent invasion as well as the metastasis of malignant cells and could be employed to stop the spread of cancer.

The ECM protein nephronectin promotes kidney development via integrin alpha8beta1-mediated stimulation of Gdnf expression

Development of the metanephric kidney crucially depends on proper interactions between cells and the surrounding extracellular matrix. For example, we showed previously that in the absence of alpha8beta1 integrin, invasion by the ureteric bud into the metanephric mesenchyme is inhibited, resulting in renal agenesis. Here we present genetic evidence that the extracellular matrix protein nephronectin is an essential ligand that engages alpha8beta1 integrin during early kidney development. We show that embryos lacking a functional nephronectin gene frequently display kidney agenesis or hypoplasia, which can be traced to a delay in the invasion of the metanephric mesenchyme by the ureteric bud at an early stage of kidney development. Significantly, we detected no defects in extracellular matrix organization in the nascent kidneys of the nephronectin mutants. Instead, we found that Gdnf expression was dramatically reduced in both nephronectin- and alpha8 integrin-null mutants specifically in the metanephric mesenchyme at the time of ureteric bud invasion. We show that this reduction is sufficient to explain the agenesis and hypoplasia observed in both mutants. Interestingly, the reduction in Gdnf expression is transient, and its resumption presumably enables the nephronectin-deficient ureteric buds to invade the metanephric mesenchyme and begin branching. Our results thus place nephronectin and alpha8beta1 integrin in a pathway that regulates Gdnf expression and is essential for kidney development.

Preliminary trial to investigate temperature of the iPulse™ intense pulsed light (IPL) glass transmission block during treatment of Fitzpatrick II, IV, V, and VI skin types

The glass transmission block, a key component of all intense pulsed light (IPL) devices, is responsible for the delivery of IPL energy from the xenon discharge lamp to hair and skin structures during treatment. The purpose of this study was to investigate the variation in temperature of the quartz glass block used in the iPulse (CyDen, Swansea, UK) handset during typical hair removal treatments of Asian and Afro-Caribbean skin types. Initial results from four subjects indicated that the temperature of the glass transmission block did not exceed 45 degrees C during any of the treatments. Furthermore, the development of the temperature measurement methodology described in this paper will enable the comparison of data from different IPL systems to be undertaken in a subsequent larger scale trial.

Sprouty genes control diastema tooth development via bidirectional antagonism of epithelial-mesenchymal FGF signaling

Unlike humans, who have a continuous row of teeth, mice have only molars and incisors separated by a toothless region called a diastema. Although tooth buds form in the embryonic diastema, they regress and do not develop into teeth. Here, we identify members of the Sprouty (Spry) family, which encode negative feedback regulators of fibroblast growth factor (FGF) and other receptor tyrosine kinase signaling, as genes that repress diastema tooth development. We show that different Sprouty genes are deployed in different tissue compartments--Spry2 in epithelium and Spry4 in mesenchyme--to prevent diastema tooth formation. We provide genetic evidence that they function to ensure that diastema tooth buds are refractory to signaling via FGF ligands that are present in the region and thus prevent these buds from engaging in the FGF-mediated bidirectional signaling between epithelium and mesenchyme that normally sustains tooth development.

An FGF response pathway that mediates hepatic gene induction in embryonic endoderm cells

While particular combinations of mesodermal signals are known to induce distinct tissue-specific programs in the endoderm, there is little information about the response pathways within endoderm cells that control their specification. We have used signaling inhibitors on embryo tissue explants and whole-embryo cultures as well as genetic approaches to reveal part of an intracellular network by which FGF signaling helps induce hepatic genes and stabilize nascent hepatic cells within the endodermal epithelium. Specifically, we found that hepatic gene induction is elicited by an FGF/MAPK pathway. Although the PI3K pathway is activated in foregut endoderm cells, its inhibition does not block hepatic gene induction in explants; however, it does block tissue growth. We also found that at the onset of hepatogenesis, the FGF/MAPK and PI3K pathways do not crossregulate in the endoderm. The finding of separate pathways for endoderm tissue specification and growth provides insights for guiding cellular regeneration and stem cell differentiation.

Glucagon-like peptide-2 induces a specific pattern of adaptation in remnant jejunum

Glucagon-like peptide-2 (GLP-2) is an enteroendocrine hormone which is uniquely trophic for the intestine; a physiological role in regulating nutrient absorptive capacity is becoming apparent. GLP-2, independent of enteral feeding, stimulates a classical pattern of intestinal adaptation in terminal ileum following resection. Herein we investigate the effects of GLP-2 on the jejunal remant using a rat model of short bowel syndrome (SBS). Juvenile 250- to 275-g SD rats underwent 80% distal small bowel resection, leaving 20 cm of proximal jejunum and venous catheterization. Animals were maintained with total parenteral nutrition (TPN) or TPN+10 microg/kg/hr GLP-2 (n=8 per group). After 7 days, intestinal permeability was assessed by urinary recovery of gavaged carbohydrate probes. Animals were euthanized, and the intestines taken for analysis of morphology, crypt cell proliferation, apoptosis, and expression of SGLT-1 and GLUT-5 transport proteins. GLP-2 treatment reduced intestinal permeability and increased in vivo glucose absorption, small intestinal weight, surface area, villus height, crypt depth, and microvillus height. Intestinal mucosal DNA and protein content per unit length of the small bowel were increased (P < 0.05 for all comparisons). However, in contrast to previous studies examining GLP-2's effects on remnant ileum, the jejunal crypt apoptotic index was increased in GLP-2-treated animals, with no increase in SGLT-1 or GLUT 5 expression. These results show that exogenous GLP-2 treatment of animals with jejunal remnant reduces intestinal permeability, increases glucose absorption, and stimulates morphological features of intestinal adaptation including increased micovillus height and surface area. However, the pattern of changes seen is different from that in remnant ileum. This suggests that GLP-2's effects are specific to different regions of the bowel. Nonetheless, remnant jejunum is responsive to GLP-2 in the absence of enteral nutrition. Further studies are warranted to establish the mechanisms of action and therapeutic potential of GLP-2 in modulating nutrient absorptive capacity.

A common progenitor for haematopoietic and endothelial lineages in the zebrafish gastrula

It has been proposed that haematopoietic and endothelial cells share a common progenitor, termed the haemangioblast. This idea was initially conceived as a result of the observation that these two cell types develop in close proximity to each other within the embryo. Support for this hypothesis was provided by studies on single-cell-derived colonies that can produce both haematopoietic and endothelial cells in vitro. Although these data point towards the existence of a common progenitor for these two lineages, the presence of a bipotential progenitor cell has yet to be demonstrated in vivo. Through the construction of single-cell-resolution fate maps of the zebrafish late blastula and gastrula, we demonstrate that individual cells can give rise to both haematopoietic and endothelial cells. These bipotential progenitors arise along the entire extent of the ventral mesoderm and contribute solely to haematopoietic and endothelial cells. We also find that only a subset of haematopoietic and endothelial cells arise from haemangioblasts. The endothelial descendants of the haemangioblasts all clustered in a specific region of the axial vessels regardless of the location of their progenitors. Our results provide in vivo evidence supporting the existence of the haemangioblast and reveal distinct features of this cell population.

Loss of Aif function causes cell death in the mouse embryo, but the temporal progression of patterning is normal

Apoptosis-inducing factor (AIF) is an evolutionarily conserved, ubiquitously expressed flavoprotein with NADH oxidase activity that is normally confined to mitochondria. In mammalian cells, AIF is released from mitochondria in response to apoptotic stimuli and translocates to the nucleus where it is thought to bind DNA and contribute to chromatinolysis and cell death in a caspase-independent manner. Here we describe the consequences of inactivating Aif in the early mouse embryo. Unexpectedly, we found that both the apoptosis-dependent process of cavitation in embryoid bodies and apoptosis associated with embryonic neural tube closure occur in the absence of AIF, indicating that Aif function is not required for apoptotic cell death in early mouse embryos. By embryonic day 9 (E9), loss of Aif function causes abnormal cell death, presumably because of reduced mitochondrial respiratory chain complex I activity. Because of this cell death, Aif null embryos fail to increase significantly in size after E9. Remarkably, patterning processes continue on an essentially normal schedule, such that E10 Aif null embryos with only approximately 1/10 the normal number of cells have the same somite number as their wild-type littermates. These observations show that pattern formation in the mouse can occur independent of embryo size and cell number.

Dose-dependent functions of Fgf8 in regulating telencephalic patterning centers

Mouse embryos bearing hypomorphic and conditional null Fgf8mutations have small and abnormally patterned telencephalons. We provide evidence that the hypoplasia results from decreased Foxg1 expression,reduced cell proliferation and increased cell death. In addition, alterations in the expression of Bmp4, Wnt8b, Nkx2.1 and Shh are associated with abnormal development of dorsal and ventral structures. Furthermore, nonlinear effects of Fgf8 gene dose on the expression of a subset of genes, including Bmp4 and Msx1, correlate with a holoprosencephaly phenotype and with the nonlinear expression of transcription factors that regulate neocortical patterning. These data suggest that Fgf8 functions to coordinate multiple patterning centers, and that modifications in the relative strength of FGF signaling can have profound effects on the relative size and nature of telencephalic subdivisions.

Increasing Fgf4 expression in the mouse limb bud causes polysyndactyly and rescues the skeletal defects that result from loss of Fgf8 function

A major function of the limb bud apical ectodermal ridge (AER) is to produce fibroblast growth factors (FGFs) that signal to the underlying mesenchyme. Previous studies have suggested that of the four FGF genes specifically expressed in the mouse AER, Fgf8 is unique not only in its expression pattern, but also because it is the only such FGF gene that causes limb skeletal abnormalities when individually inactivated. However, when both Fgf8 and Fgf4 are simultaneously inactivated in the AER, the limb does not develop. One possible explanation for these observations is that although both of these FGF family members contribute to limb development, Fgf8 has functions that Fgf4 cannot perform. To test this hypothesis, we used a novel method to substitute Fgf4 for Fgf8 expression in the developing limb bud by concomitantly activating a conditional Fgf4 gain-of-function allele and inactivating an Fgf8 loss-of-function allele in the same cells via Cre-mediated recombination. Our data show that when Fgf4 is expressed in place of Fgf8, all of the skeletal defects caused by inactivation of Fgf8 are rescued, conclusively demonstrating that FGF4 can functionally replace FGF8 in limb skeletal development. We also show that the increase in FGF signaling that occurs when the Fgf4 gain-of-function allele is activated in a wild-type limb bud causes formation of a supernumerary posterior digit (postaxial polydactyly), as well as cutaneous syndactyly between all the digits. These data underscore the importance of controlling the level of FGF gene expression for normal limb development.

The epidemiology of Kawasaki disease in an urban hospital: does African American race protect against coronary artery aneurysms?

The etiology and pathogenesis of Kawasaki disease (KD) is largely unknown. Certain demographic factors and laboratory findings are predictive of the development of coronary artery (CA) aneurysms. The objectives of this study were to determine the epidemiology of KD patients in an urban hospital and determine risk factors associated with their development of CA abnormalities. A longitudinal case series of KD patients admitted to Children's National Medical Center from 1990 to 2002 was examined. Age, sex, ethnic background, duration of fever prior to diagnosis, address, month diagnosed, and CA abnormalities (ectasia or aneurysms) on echocardiography were recorded. Median household income was obtained from the U.S. Census Bureau Web site. The Student t-test, logistic regression analyses, and the Kruskal-Wallis test were used, with significance assumed at p < 0.05. A total of 302 patients were evaluated. CA abnormalties were found in 27 patients (9%), with aneurysms identified in 13 patients (4%). Age was 2.9 +/- 2.4 years (range, 2 months to 14 years). A total of 51 patients (16%) were < or =1 year and 35 patients (12%) were > or =5 years. Ethnic distribution was 54% (164) African American, 24% (72) Caucasian, 9% (29) Asian/Pacific Islander, 8% (23) Hispanic, and 5% (14) Middle Eastern. Only 2/164 (1.2%) African Americans developed CA aneurysms. Neighborhood median income of the cohort was $45,400 +/- $21,200 ($52,200 +/-$25,800 for patients with aneurysms). A total of 28% of cases clustered between December and January. Cases doubled annually in 1999-2001 compared to 1990-1998 (39 vs 19). Multivariate logistic regression found age between 1 and 5 years [p = 0.045; odds ratio, 0.31; 95% confidence interval (CI), 0.10-0.97] and African American race (p = 0.014; odds ratio, 0.15; 95% CI, 0.03-0.68) to be independently protective against CA aneurysms. Duration of fever prior to diagnosis, considered in 210 patients, was different between patients with and without aneurysms (11 +/- 5.3 vs 6.5 +/- 3.8 days, respectively, p = 0.0007). Multivariate logistic regression found fever longer than 5 days to be the only predictive factor associated with the development of aneurysms and any abnormality. African Americans had a shorter duration of fever than the rest of the cohort (6.03 vs 7.31 days), (p = 0.0087). The epidemiology of KD at our hospital is similar to that at other centers except for the predominance of African Americans with a shorter duration of fever prior to diagnosis and a decreased incidence of CA aneurysms compared to other ethnicities. The protective nature of African American ethnicity against the development of CA aneurysms raises speculation about the role of genetics and its interaction with immunity in the pathogenesis of KD.

FGF8 is required for cell survival at distinct stages of nephrogenesis and for regulation of gene expression in nascent nephrons

During kidney morphogenesis, the formation of nephrons begins when mesenchymal nephron progenitor cells aggregate and transform into epithelial vesicles that elongate and assume an S-shape. Cells in different regions of the S-shaped body subsequently differentiate into the morphologically and functionally distinct segments of the mature nephron. Here, we have used an allelic series of mutations to determine the role of the secreted signaling molecule FGF8 in nephrogenesis. In the absence of FGF8 signaling, nephron formation is initiated, but the nascent nephrons do not express Wnt4or Lim1, and nephrogenesis does not progress to the S-shaped body stage. Furthermore, the nephron progenitor cells that reside in the peripheral zone, the outermost region of the developing kidney, are progressively lost. When FGF8 signaling is severely reduced rather than eliminated, mesenchymal cells differentiate into S-shaped bodies. However, the cells within these structures that normally differentiate into the tubular segments of the mature nephron undergo apoptosis, resulting in the formation of kidneys with severely truncated nephrons consisting of renal corpuscles connected to collecting ducts by an abnormally short tubular segment. Thus, unlike other FGF family members, which regulate growth and branching morphogenesis of the collecting duct system, Fgf8 encodes a factor essential for gene regulation and cell survival at distinct steps in nephrogenesis.

Sprouty2, a mouse deafness gene, regulates cell fate decisions in the auditory sensory epithelium by antagonizing FGF signaling

The auditory sensory epithelium (organ of Corti), where sound waves are converted to electrical signals, comprises a highly ordered array of sensory receptor (hair) cells and nonsensory supporting cells. Here, we report that Sprouty2, which encodes a negative regulator of signaling via receptor tyrosine kinases, is required for normal hearing in mice, and that lack of SPRY2 results in dramatic perturbations in organ of Corti cytoarchitecture: instead of two pillar cells, there are three, resulting in the formation of an ectopic tunnel of Corti. We demonstrate that these effects are due to a postnatal cell fate transformation of a Deiters' cell into a pillar cell. Both this cell fate change and hearing loss can be partially rescued by reducing Fgf8 gene dosage in Spry2 null mutant mice. Our results provide evidence that antagonism of FGF signaling by SPRY2 is essential for establishing the cytoarchitecture of the organ of Corti and for hearing.

Sprouty1 is a critical regulator of GDNF/RET-mediated kidney induction

Intercellular signaling molecules and their receptors, whose expression must be tightly regulated in time and space, coordinate organogenesis. Regulators of intracellular signaling pathways provide an additional level of control. Here we report that loss of the receptor tyrosine kinase (RTK) antagonist, Sprouty1 (Spry1), causes defects in kidney development in mice. Spry1(-/-) embryos have supernumerary ureteric buds, resulting in the development of multiple ureters and multiplex kidneys. These defects are due to increased sensitivity of the Wolffian duct to GDNF/RET signaling, and reducing Gdnf gene dosage correspondingly rescues the Spry1 null phenotype. We conclude that the function of Spry1 is to modulate GDNF/RET signaling in the Wolffian duct, ensuring that kidney induction is restricted to a single site. These results demonstrate the importance of negative feedback regulation of RTK signaling during kidney induction and suggest that failures in feedback control may underlie some human congenital kidney malformations.

Nutrient-stimulated GLP-2 release and crypt cell proliferation in experimental short bowel syndrome

Glucagon-like peptide-2 (GLP-2) is an enteroendocrine peptide that is released in response to luminal nutrients and has unique trophic actions in the gastrointestinal tract. These features suggest GLP-2 may be important in controlling intestinal adaptation. We examined the relationship over time of GLP-2 production and adaptation to intestinal resection, the effects of resection-induced malabsorption on GLP-2 production, and the correlation of endogenous serum GLP-2 levels with adaptation as measured by crypt-cell proliferation (CCP). We initially examined the effect of nutrient malabsorption, induced by a 90% resection of the proximal intestine studied on day 4, on the time course and levels of GLP-2 release. Secondly, the degree of malabsorption was varied by performing intestinal transection or 50, 75, or 90% resection of proximal small intestine. Finally, the relationship of GLP-2 levels over time with adaptation to a 90% resection was examined by determining GLP-2 levels on days 7, 14, and 28, and correlating this with intestinal adaptation, as assessed by morphology and CCP rate. A 90% resection significantly increased basal and postprandial GLP-2 levels, with a net increase in nutrient-stimulated exposure over 90 min; GLP-2 exposure (integrated levels vs. time) increased 12.7-fold in resected animals (P < 0.001). Basal and postprandial GLP-2 levels significantly correlated with the magnitude of intestinal resection (r(2) = 0.71; P < 0.001), CCP (r(2) = 0.48; P < 0.005), and nutrient malabsorption (protein, P < 0.001; fat, P < 0.005). The increase in CCP was maintained to 28 days after small bowel resection and was associated with an ongoing elevation in GLP-2 release. These findings suggest that GLP-2 is important in initiating and maintaining the small intestinal adaptive response to resection.

Zolmitriptan:a new acute treatment for migraine

Zolmitriptan is a new oral acute treatment for migraine. It is a selective and potent agonist at the serotonin (5-HT)(1B/1D) receptor and was developed to improve on the oral bioavailability, tissue selectivity and CNS penetration of earlier compounds. Animal studies confirmed that these objectives had been attained. In man, zolmitriptan is rapidly absorbed after oral administration, with at least 75% of the eventual C(max) reached within 1 h. Oral bioavailability is approximately 40%. The elimination half-life of zolmitriptan is approximately 2.5 h and the primary route of elimination is metabolism, with one of the metabolites being pharmacologically active. A consistent 2-h headache response rate of 60-70% was observed at doses of 2.5 mg and above. Long-term treatment response is high (> 80%) and consistent. In addition, there is evidence from electrophysiology in migraineurs that zolmitriptan has a central action not shared by sumatriptan. Zolmitriptan is well-tolerated. The nature and incidence of the most frequently reported adverse events are similar to those of other 5-HT(1B/1D) agonists. Long-term zolmitriptan usage was associated with an improvement in quality of life. Zolmitriptan is a suitable first-line drug for acute treatment for migraine.

SLIT2-mediated ROBO2 signaling restricts kidney induction to a single site

Kidney development occurs in a stereotypic position along the body axis. It begins when a single ureteric bud emerges from the nephric duct in response to GDNF secreted by the adjacent nephrogenic mesenchyme. Posterior restriction of Gdnf expression is considered critical for correct positioning of ureteric bud development. Here we show that mouse mutants lacking either SLIT2 or its receptor ROBO2, molecules known primarily for their function in axon guidance and cell migration, develop supernumerary ureteric buds that remain inappropriately connected to the nephric duct, and that the SLIT2/ROBO2 signal is transduced in the nephrogenic mesenchyme. Furthermore, we show that Gdnf expression is inappropriately maintained in anterior nephrogenic mesenchyme in these mutants. Thus our data identify an intercellular signaling system that restricts, directly or indirectly, the extent of the Gdnf expression domain, thereby precisely positioning the site of kidney induction.

The isthmic organizer signal FGF8 is required for cell survival in the prospective midbrain and cerebellum

Numerous studies have demonstrated that the midbrain and cerebellum develop from a region of the early neural tube comprising two distinct territories known as the mesencephalon (mes) and rostral metencephalon (met; rhombomere 1), respectively. Development of the mes and met is thought to be regulated by molecules produced by a signaling center, termed the isthmic organizer (IsO), which is localized at the boundary between them. FGF8 and WNT1 have been implicated as key components of IsO signaling activity, and previous studies have shown that in Wnt1(-/-) embryos, the mes/met is deleted by the 30 somite stage ( approximately E10) (McMahon, A. P. and Bradley, A. (1990) Cell 62, 1073-1085). We have studied the function of FGF8 in mouse mes/met development using a conditional gene inactivation approach. In our mutant embryos, Fgf8 expression was transiently detected, but then was eliminated in the mes/met by the 10 somite stage ( approximately E8.75). This resulted in a failure to maintain expression of Wnt1 as well as Fgf17, Fgf18, and Gbx2 in the mes/met at early somite stages, and in the absence of the midbrain and cerebellum at E17.5. We show that a major cause of the deletion of these structures is ectopic cell death in the mes/met between the 7 and 30 somite stages. Interestingly, we found that the prospective midbrain was deleted at an earlier stage than the prospective cerebellum. We observed a remarkably similar pattern of cell death in Wnt1 null homozygotes, and also detected ectopic mes/met cell death in En1 null homozygotes. Our data show that Fgf8 is part of a complex gene regulatory network that is essential for cell survival in the mes/met.

Deciphering skeletal patterning: clues from the limb

Even young children can distinguish a Tyrannosaurus rex from a Brontosaurus by observing differences in bone size, shape, number and arrangement, that is, skeletal pattern. But despite our extensive knowledge about cartilage and bone formation per se, it is still largely a mystery how skeletal pattern is established. Much of what we do know has been learned from studying limb development in chicken and mouse embryos. Based on the data from such studies, models for how limb skeletal pattern is established have been proposed and continue to be hotly debated.

Dosage of Fgf8 determines whether cell survival is positively or negatively regulated in the developing forebrain

FGF8 is known to be an important regulator of forebrain development. Here, we investigated the effects of varying the level of Fgf8 expression in the mouse forebrain. We detected two distinct responses, one that was proportionate with Fgf8 expression and another that was not. The latter response, which led to effects on cell survival, displayed a paradoxical relationship to Fgf8 dosage. Either eliminating or increasing Fgf8 expression increased apoptosis, whereas reducing Fgf8 expression had the opposite effect. To explain these counterintuitive observations, we suggest that an FGF8-dependent cell-survival pathway is negatively regulated by intracellular inhibitors produced in proportion to FGF8 concentration. Our data provide insight into the function of FGF8 in forebrain development and underscore the value of using multiple alleles and different experimental approaches to unravel the complexities of gene function in vertebrate development.

Functions of FGF signalling from the apical ectodermal ridge in limb development

To determine the role of fibroblast growth factor (FGF) signalling from the apical ectodermal ridge (AER), we inactivated Fgf4 and Fgf8 in AER cells or their precursors at different stages of mouse limb development. We show that FGF4 and FGF8 regulate cell number in the nascent limb bud and are required for survival of cells located far from the AER. On the basis of the skeletal phenotypes observed, we conclude that these functions are essential to ensure that sufficient progenitor cells are available to form the normal complement of skeletal elements, and perhaps other limb tissues. In the complete absence of both FGF4 and FGF8 activities, limb development fails. We present a model to explain how the mutant phenotypes arise from FGF-mediated effects on limb bud size and cell survival.

Ostrich ocular optics

The optical structure of the eyes of ostriches (Struthio camelus; Struthionidae; Struthioniformes) was determined by the construction of a schematic eye model for paraxial optics. The eye is large (axial length = 38 mm) and of globose shape with an anterior focal length (posterior nodal distance) of 21.8 mm. The optical design of the eye is such that the lens and cornea contribute equally to its total optical power. Interspecific comparison shows that optically the ostrich eye is a larger scaled version of the eyes of common starlings (Sturnus vulgaris) and an owl (Strix aluco).