Methods to Investigate the Roles of Progranulin in Angiogenesis Using In Vitro Strategies and Transgenic Mouse Models.

Endothelial cells activate the expression of progranulin during angiogenesis. Here we discuss methods to investigate progranulin activity on endothelial cells in vitro and on aortic explants. We then discuss methods to generate transgenic mice in which progranulin expression is targeted to endothelial cells. These mice can be used to study the influence of progranulin on angiogenesis during development in vivo. The transgenic strategy summarized here could be readily adapted to investigate the roles of progranulin in other cell types and tissues by use of appropriate targeting vectors to drive the expression of progranulin in the cell type of choice.

Horizontal mattress technique for anastomosis of size-mismatched vessels.

OBJECTIVE: To evaluate the horizontal mattress technique in microvascular anastomosis for size-mismatched vessels. METHODS: The present study involved cadaveric simulation using size-mismatched (1.5:1) Thiel-embalmed cadaveric arteries. The authors performed horizontal mattress anastomoses using 9-0 nylon suture and recorded the procedure. Vessel patency was evaluated by saline infusion. Vessels were cut open and photographed; histological slides were prepared and stained with hematoxylin and eosin. RESULTS: Four anastomoses were performed. Vessels were found to be patent in all cases, with grade 0 leaks. Intima-on-intima apposition with no intraluminal exposure of muscularis nor adventitia were observed. CONCLUSION: The present cadaveric study supports the technical feasibility of using horizontal mattress sutures in size-mismatched end-toend anastomoses.

OBJECTIF: Évaluer la technique de suture matelassée horizontale pour l'anastomose microvasculaire de vaisseaux de différentes dimensions. MÉTHODOLOGIE: La présente étude par simulation cadavérique portait sur des artères cadavériques de différentes dimensions (1,5:1), embaumées selon la méthode de Thiel. Les auteurs ont effectué des anastomoses par suture matelassée horizontale au moyen d'un fil de nylon 9-0 et ont vidéo-enregistré l'intervention. Ils ont évalué la perméabilité des vaisseaux au moyen d'une infusion de solution saline. Ils ont ouvert et photographié les vaisseaux et préparé des lames histologiques qu'ils ont colorées à l'hématoxyline et à l'éosine. RÉSULTATS: Quatre anastomoses ont été effectuées. Dans tous les cas, les vaisseaux étaient perméables et les fuites, de grade 0. Les chercheurs ont observé une apposition intima-sur-intima sans exposition intraluminale de la musculeuse ou de la séreuse. CONCLUSION: La présente étude cadavérique corrobore la faisabilité technique des sutures matelassées horizontales pour les anastomoses terminoterminales d'artères de dimensions différentes.

A new microsurgical research model using Thiel-embalmed arteries and comparison of two suture techniques.

PURPOSE: To assess the utility of the Thiel arterial model in microsurgical research, we compared interrupted horizontal mattress (HM) sutures to simple interrupted (SI) sutures in human vessels. METHODS: A microsurgical set-up using an operating microscope and Thiel-embalmed arteries was used to practice ten SI and HM anastomoses. Vessel patency, leak and stricture were evaluated using angiography, and vessel wall architecture was evaluated using light microscopy and scanning electron microscopy (SEM). The technique speed was also assessed. RESULTS: We have successfully evaluated all outcomes. All anastomoses were patent. The stricture rate was higher with HM than with SI (60% vs. 35% surface area reduction). Three minor leaks occurred with HM sutures versus one with SI sutures. Edges were evenly everted without any intimal flaps with HM compared to SI. The anastomoses were performed faster using HM than SI sutures (7:58 min vs. 12:41 min, respectively). CONCLUSION: This is the first study to evaluate the feasibility of a Thiel-embalmed artery model for research purposes. The HM microvascular suture is a promising technique that requires further in vivo validation.

Expression of the growth factor progranulin in endothelial cells influences growth and development of blood vessels: a novel mouse model.

Progranulin is a secreted glycoprotein that regulates cell proliferation, migration and survival. It has roles in development, tumorigenesis, wound healing, neurodegeneration and inflammation. Endothelia in tumors, wounds and placenta express elevated levels of progranulin. In culture, progranulin activates endothelial proliferation and migration. This suggested that progranulin might regulate angiogenesis. It was, however, unclear how elevated endothelial progranulin levels influence vascular growth in vivo. To address this issue, we generated mice with progranulin expression targeted specifically to developing endothelial cells using a Tie2-promoter/enhancer construct. Three Tie2-Grn mouse lines were generated with varying Tie2-Grn copy number, and were called GrnLo, GrnMid, and GrnHi. All three lines showed increased mortality that correlates with Tie2-Grn copy number, with greatest mortality and lowest germline transmission in the GrnHi line. Death of the transgenic animals occurred around birth, and continued for three days after birth. Those that survived beyond day 3 survived into adulthood. Transgenic neonates that died showed vascular abnormalities of varying severity. Some exhibited bleeding into body cavities such as the pericardial space. Smaller localized hemorrhages were seen in many organs. Blood vessels were often dilated and thin-walled. To establish the development of these abnormalities, we examined mice at early (E10.5-14.5) and later (E15.5-17.5) developmental phases. Early events during vasculogenesis appear unaffected by Tie2-Grn as apparently normal primary vasculature had been established at E10.5. The earliest onset of vascular abnormality was at E15.5, with focal cerebral hemorrhage and enlarged vessels in various organs. Aberrant Tie2-Grn positive vessels showed thinning of the basement membrane and reduced investiture with mural cells. We conclude that progranulin promotes exaggerated vessel growth in vivo, with subsequent effects in the formation of the mural cell layer and weakening of vessel integrity. These results demonstrate that overexpression of progranulin in endothelial cells influences normal angiogenesis in vivo.

Tissue, cellular and sub-cellular localization of the Vangl2 protein during embryonic development: effect of the Lp mutation.

Loop-tail (Lp) mice show a very severe neural tube defect, craniorachischisis, which is caused by mis-sense mutations in the Vangl2 gene. The membrane protein Vangl2 belongs to a highly conserved group of proteins that regulate planar polarity in certain epithelia, and that are also important for convergent extension movements during gastrulation and neurulation. A specific anti-Vangl2 antiserum was produced and used to examine the tissue, cell type, and sub-cellular localization of Vangl2 during embryogenesis. Vangl2 protein is expressed at high levels in the neural tube and shows a dynamic expression profile during neurulation. After neural tube closure, robust Vangl2 staining is detected in several neural and neurosensory tissues, including cerebral cortex, dorsal root ganglia, olfactory epithelium, retina, mechanosensory hair cells of the cochlea, and optic nerve. Vangl2 is also expressed during organogenesis in a number of tubular epithelia, including the bronchial tree, intestinal crypt/villus axis, and renal tubular segments derived from ureteric bud and from metanephric mesenchyme. Examination of Vangl2 localization in the neural tubes and cochleas of the normal and Lp/Lp embryos shows disruption of normal membrane localization of Vangl2 in independent alleles at Lp (Lp, Lp(m1Jus)) as well as overall decrease in the expression level.

Respiratory distress and neonatal lethality in mice lacking Golgi alpha1,2-mannosidase IB involved in N-glycan maturation.

There are three mammalian Golgi alpha1,2-mannosidases, encoded by different genes, that form Man5GlcNAc2 from Man(8-9)GlcNAc2 for the biosynthesis of hybrid and complex N-glycans. Northern blot analysis and in situ hybridization indicate that the three paralogs display distinct developmental and tissue-specific expression. The physiological role of Golgi alpha1,2-mannosidase IB was investigated by targeted gene ablation. The null mice have normal gross appearance at birth, but they display respiratory distress and die within a few hours. Histology of fetal lungs the day before birth indicate some delay in development, whereas neonatal lungs show extensive pulmonary hemorrhage in the alveolar region. No significant histopathological changes occur in other tissues. No remarkable ultrastructural differences are detected between wild type and null lungs. The membranes of a subset of bronchiolar epithelial cells are stained with lectins from Phaseolus vulgaris (leukoagglutinin and erythroagglutinin) and Datura stramonium in wild type lungs, but this staining disappears in lungs from null mice. Mass spectrometry of N-glycans from different tissues shows no significant changes in global N-glycans of null mice. Therefore, only a few glycoproteins required for normal lung function depend on alpha1,2-mannosidase IB for maturation. There are no apparent differences in the expression of several lung epithelial cell and endothelial cell markers between null and wild type mice. The alpha1,2-mannosidase IB null phenotype differs from phenotypes caused by ablation of other enzymes in N-glycan biosynthesis and from other mouse gene disruptions that affect pulmonary development and function.

Essential function of PTP-PEST during mouse embryonic vascularization, mesenchyme formation, neurogenesis and early liver development.

PTP (protein-tyrosine phosphatase)-PEST is a ubiquitously expressed cellular regulator of integrin signalling. It has been shown to bind several molecules such as Shc, paxillin and Grb2, that are involved downstream of FAK (focal adhesion kinase) pathway. Through its specific association to p130cas and further dephosphorylation, PTP-PEST plays a critical role in cell-matrix interactions, which are essential during embryogenesis. We report here that ablation of the gene leads to early embryonic lethality, correlating well with the high expression of the protein during embryonic development. We observed an increased level of tyrosine phosphorylation of p130cas protein in E9.5 PTP-PEST(-/-) embryos, a first evidence of biochemical defect leading to abnormal growth and development. Analysis of null mutant embryos revealed that they reach gastrulation, initiate yolk sac formation, but fail to progress through normal subsequent developmental events. E9.5-10.5 PTP-PEST(-/-) embryos had morphological abnormalities such as defective embryo turning, improper somitogenesis and vasculogenesis, impaired liver development, accompanied by degeneration in both neuroepithelium and somatic epithelia. Moreover, in embryos surviving until E10.5, the caudal region was truncated, with severe mesenchyme deficiency and no successful liver formation. Defects in embryonic mesenchyme as well as subsequent failure of proper vascularization, liver development and somatogenesis, seemed likely to induce lethality at this stage of development, and these results confirm that PTP-PEST plays an essential function in early embryogenesis.

Cardiac failure in C5-deficient A/J mice after Candida albicans infection.

The effect of a deficiency in the C5 component of complement on the pathophyisology of infection with the fungal pathogen Candida albicans was studied by using the A/J inbred mouse strain and the BcA17 congenic mouse strain. Acute infection caused by intravenous injection of C. albicans blastospores is associated with rapid fungal replication in the heart, brain, and, in particular, kidneys of C5-deficient mice. Histological studies and analysis of markers for tissue damage indicated that the heart is the organ that is most affected and that it ultimately fails in C5-deficient mice. In A/J and BcA17 mice, tissue damage is associated with (i) cellular infiltration in the heart, which is not seen in the kidney despite the higher fungal load in the latter organ, and (ii) a very strong inflammatory response, including elevated levels of many cytokines and chemokines. This results in cardiomyopathy, which is associated with elevated levels of creatine kinase and cardiac troponin I in the circulation. Damage to the cardiac muscle is associated with metabolic changes, including hypoglycemia, decreased lipid utilization resulting in elevated levels of cardiac triglycerides, and unproductive glucose utilization linked to a dramatic increase in the level of pyruvate dehydrogenase kinase 4 (Pdk4), a negative regulator of the pyruvate dehydrogenase complex.

The persisting pneumatoenteric recess and the infracardiac bursa: possible role in the pathogenesis of right hydrothorax complicating peritoneal dialysis.

Hydrothorax, an uncommon complication of peritoneal dialysis (PD), results from the migration of dialysis fluid under pressure from the peritoneal cavity into the pleural space. The exact site of the transdiaphragmatic fluid leak remains obscure, but the right-sided predominance of the hydrothorax points to the presence of abnormalities in the right hemidiaphragm. Such abnormalities have occasionally been described. In a recent case of acute massive right hydrothorax at the start of PD, the autopsy revealed extensive changes of amyloidosis that were comparable in both hemidiaphragms, prompting us to revisit the accepted explanation for right hydrothorax. We propose that an embryonic remnant--namely, the persisting pneumatoenteric recess and the infracardiac bursa--provides a passage connecting the peritoneal cavity to the right pleural space. The potential presence of this mechanism is consistent with the recognized clinical features of right hydrothorax complicating PD. This proposed route for dialysis fluid to form a right hydrothorax during PD can be investigated by currently available high-definition imaging techniques. This novel mechanism may also be involved in the pathogenesis of right hydrothorax observed in other medical conditions with tense ascites (liver cirrhosis, Meigs syndrome).

Subcellular localization of multiple PREP2 isoforms is regulated by actin, tubulin, and nuclear export.

The PREP, MEIS, and PBX families are mammalian members of the TALE (three amino acid loop extension) class of homeodomain-containing transcription factors. These factors have been implicated in cooperative DNA binding with the HOX class of homeoproteins, but PREP and MEIS interact with PBX in apparently non-HOX-dependent cooperative DNA binding as well. PREP, MEIS, and PBX have all been reported to reside in the cytoplasm in one or more tissues of the developing vertebrate embryo. In the case of PBX, cytoplasmic localization is due to the modulation of nuclear localization signals, nuclear export sequences, and interaction with a cytoplasmic anchoring factor, non-muscle myosin heavy chain II B. Here we report that murine PREP2 exists in multiple isoforms distinguished by interaction with affinity-purified antibodies raised to N- and C-terminal epitopes and by nuclear versus cytoplasmic localization. Alternative splicing gives rise to some of these PREP2 isoforms, including a 25-kDa variant lacking the C-terminal half of the protein and homeodomain and having the potential to act as dominant-negative. We further show that cytoplasmic localization is due to the concerted action of nuclear export, as evidenced by sensitivity to leptomycin B, and cytoplasmic retention by the actin and microtubule cytoskeletons. Cytoplasmic PREP2 colocalizes with both the actin and microtubule cytoskeletons and coimmunoprecipitates with actin and tubulin. Importantly, disruption of either cytoskeletal system redirects cytoplasmic PREP2 to the nucleus. We suggest that transcriptional regulation by PREP2 is modulated through the subcellular distribution of multiple isoforms and by interaction with two distinct cytoskeletal systems.

Progranulin (acrogranin/PC cell-derived growth factor/granulin-epithelin precursor) is expressed in the placenta, epidermis, microvasculature, and brain during murine development.

The growth factor progranulin (acrogranin/PC-derived growth factor/granulin-epithelin precursor) promotes onset of blastocyst cavitation and is required for neonatal hypothalamic sexual differentiation. Little is known, however, of the range of developmental processes in which it is involved. We used in situ hybridization to investigate progranulin expression in murine embryos. Progranulin mRNA is expressed in maternal and embryonic components during early establishment of pregnancy. Abundant expression is observed in the early decidualizing uterine stroma and glands. In the embryo, the trophoblast giant cells at the interface of placental exchange sites (both choriovitelline and chorioallantoic placenta) show strong expression. The gastrulating epiblast and mesenchyme (intraembryonic and extraembryonic mesenchyme) all revealed activity. The allantois and yolk sac mesenchyme (site of early hemopoiesis) were positive, as were later phases of active vessel formation (pia mater of brain, epicardium of the heart). In the urogenital system, it was expressed in Sertoli cells and in kidney tubules. It was highly expressed in proliferating epidermal cells. During epidermal appendage formation, the early epithelial bud was positive, but the forming duct and differentiating adjacent mesenchyme was negative. It is widely distributed during central nervous system development and the peripheral nervous system (dorsal root ganglia and sympathetic ganglia). Based on the pattern of progranulin gene expression, we propose proliferative and developmental roles for progranulin in establishing pregnancy, during gastrulation, and during embryonic development of the epidermis, nervous system, blood vessel, formation, and spermatogenesis.

Expression of the Wdr9 gene and protein products during mouse development.

Human WDR9 has been mapped to chromosome 21, within one of the Down syndrome (DS) critical regions. Here, we study the expression pattern of the murine Wdr9 gene and its protein product. We show that Wdr9 is broadly expressed in the mouse embryo by means of in situ hybridization and immunohistochemistry. Wdr9 expression levels are dynamic during embryonic development as revealed by Northern blot analysis. We further show that WDR9 is a nuclear protein associated with BRG1, a SWI/SNF complex component. We also demonstrate that a polyglutamine-containing region of the protein functions as a transcriptional activation domain. We propose that WDR9 is a transcriptional regulator involved in chromatin remodeling through the action of two bromodomains and contacts to the SWI/SNF complex. These results may provide a molecular basis for the association of WDR9 with DS.

Prep2: cloning and expression of a new prep family member.

We describe Prep2, a new murine homeobox-containing gene closely related to Prep1. The PREP2 protein belongs to the three amino acid loop extension (TALE) superclass of homeodomain-containing proteins and encodes a polypeptide of 462 residues. As for PREP1, PREP2 binds an appropriate site on DNA as a heterodimer with PBX1A. Northern analysis, immunoblotting, immunohistochemistry, and in situ hybridization show widespread Prep2 expression during organogenesis and in the adult. The data suggest that Prep2 functions to varying degrees in a broad array of tissues and developmental processes.

Comparison of expression patterns and cell adhesion properties of the mouse biliary glycoproteins Bgp1 and Bgp2.

Biliary glycoproteins are members of the carcinoembryonic antigen (CEA) family and behave as cell adhesion molecules. The mouse genome contains two very similar Bgp genes, Bgp1 and Bgp2, whereas the human and rat genomes contain only one BGP gene. A Bgp2 isoform was previously identified as an alternative receptor for the mouse coronavirus mouse hepatitis virus. This isoform consists of two extracellular immunoglobulin domains, a transmembrane domain and a cytoplasmic tail of five amino acids. In this report, we have examined whether the Bgp2 gene can express other isoforms in different mouse tissues. We found only one other isoform, which has a long cytoplasmic tail of 73 amino acids. The long cytodomain of the Bgp2 protein is highly similar to that of the Bgp1/4L isoform. The Bgp2 protein is expressed in low amounts in kidney and in a rectal carcinoma cell line. Antibodies specific to Bgp2 detected a 42-kDa protein, which is expressed at the cell surface of these samples. Bgp2 was found by immunocytochemistry in smooth muscle layers of the kidney, the uterus, in gut mononuclear cells and in the crypt epithelia of intestinal tissues. Transfection studies showed that, in contrast with Bgp1, the Bgp2 glycoprotein was not directly involved in intercellular adhesion. However, this protein is found in the proliferative compartment of the intestinal crypts and in cells involved in immune recognition. This suggests that the Bgp2 protein represents a distinctive member of the CEA family; its unusual expression patterns in mouse tissues and the unique functions it may be fulfilling may provide novel clues about the multiple functions mediated by a common BGP protein in humans and rats.