Synergistic interactions between XPC and p53 mutations in double-mutant mice: neural tube abnormalities and accelerated UV radiation-induced skin cancer

The significance of DNA repair to human health has been well documented by studies on xeroderma pigmentosum (XP) patients, who suffer a dramatically increased risk of cancer in sun-exposed areas of their skin [1] and [2]. This autosomal recessive disorder has been directly associated with a defect in nucleotide excision–repair (NER) [1] and [2]. Like human XP individuals, mice carrying homozygous mutations in XP genes manifest a predisposition to skin carcinogenesis following exposure to ultraviolet (UV) radiation [3], [4] and [5]. Recent studies have suggested that, in addition to roles in apoptosis [6] and cell-cycle checkpoint control [7] in response to DNA damage, p53 protein may modulate NER [8]. Mutations in the p53 gene have been observed in 50% of all human tumors [9] and have been implicated in both the early [10] and late [11] stages of skin cancer. To examine the consequences of a combined deficiency of the XPC and the p53 proteins in mice, we generated double-mutant animals. We document a spectrum of neural tube defects in XPC p53 mutant embryos. Additionally, we show that, following exposure to UV-B radiation, XPC p53 mutant mice have more severe solar keratosis and suffer accelerated skin cancer compared with XPC mutant mice that are wild-type with respect to p53.     

Synthesis and secretion of the mouse whey acidic protein in transgenic sheep

The synthesis of foreign proteins can be targeted to the mammary gland of transgenic animals, thus permitting commercial purification of otherwise unavailable proteins from milk. Genetic regulatory elements from the mouse whey acidic protein (WAP) gene have been used successfully to direct expression of transgenes to the mammary gland of mice, goats and pigs. To extend the practical usefulness of WAP promoter-driven fusion genes and further characterize WAP expression in heterologous species, we introduced a 6.8 kb DNA fragment containing the genomic form of the mouse WAP gene into sheep zygotes. Two lines of transgenic sheep were produced. The transgene was expressed in mammary tissue of both lines and intact WAP was secreted into milk at concentrations estimated to range from 100 to 500 mg/litre. Ectopic WAP gene expression was found in salivary gland, spleen, liver, lung, heart muscle, kidney and bone marrow of one founder ewe. WAP RNA was not detected in skeletal muscle and intestine. These data suggest that unlike pigs, sheep may possess nuclear factors in a variety of tissues that interact with WAP regulatory sequences. Though the data presented are based on only two lines, these findings suggest WAP regulatory sequences may not be suitable as control elements for transgenes in sheep bioreactors.     

A block to efficient replication of simian immunodeficiency virus in C8166 cells can be overcome by duplication of the NF-κB binding site

Sequence analysis of the acutely lethal pbj14 strain of simian immunodeficiency virus (SIVpbj14) clone revealed among other differences from its less pathogenic counterparts a duplication of its binding site for nuclear factor kappa B (NF-B) in its long terminal repeats (LTR). We have investigated whether introducing a similar duplication into the pathogenic molecular clone SIVmac239 would alter its biological properties. We compared an SIV which possessed 2 NF-B sites to the wild type, a single NF-B site virus, with respect to its ability to replicate in vitro in established CD4+ T cell lines, primary peripheral blood mononuclear cells (PBMCs), and primary alveolar macrophages. The virus containing 2 NF-B sites exhibited no apparent difference from wild type in established cell lines 174×CEM, MT-2 and MT-4, or in primary PBMC or tissue macrophage cultures. However, the 2 B virus replicated well in the established cell line C8166, while the wild type, 1 B virus replicated very poorly in this cell type, suggesting that duplication of the NF-B site is capable of overcoming a block to efficient replication of SIVmac239 in C8166 cells. Interestingly, Em*, a macrophage tropic SIVmac that differs from SIVmac239 by 9 amino acids in the envelope region yet possesses only one NF-B binding site, also replicates well in C8166. The data suggest that the replication of wild type SIVmac239 is restricted in C8166 cells, but that this restriction can be overcome either by changes in the LTR or by changes in the envelope region.     

Isolation and propagation of yolk-sac-derived endothelial cells from a hypervascular transgenic mouse expressing a gain-of-functionFPS/FES proto-oncogene

Summary We report on the isolation and propagation of endothelial cells from the mouse embryonic yolk sac, the earliest site of blood vessel development, and on the advantages of a hypervascular transgenic mouse source of these cells. These transgenic mice express multiple copies of an activated allele of the humanfps/fes proto-oncogene and display hypervascularity progressing to multifocal hemangiomas. This phenotype suggested a role of thefps/fes proto-oncogene in vasculogenesis and angiogenesis and led us to investigate the growth characteristics of yolk-sac-derived endothelial cells from transgenicfps/fes embryos. We have established eight independent cell clones from a mixture of transgenic and control yolk sacs from Day 12 embryos. Southern blot hybridization analysis showed all eight clones to be derived from transgenic cells suggesting a growth advantage of cells carrying the activatedfps/fes gene. A cell line, Clone 166 (C166), established from one of these clones, was more fully characterized. C166 exhibits normal endothelial characteristics, such as rearrangement into tubelike structures when placed on Matrigel, expression of angiotensin converting enzyme, retention of cobblestone morphology at confluence, and the presence of cell surface receptors for acetylated low density lipoprotein. The cells constitutively express murine endothelial cell adhesion molecule VCAM-1 and the vascular addressin identified by antibody MECA-99. As expected, the cell line expresses high levels of the cytoplasmic protein-tyrosine kinase encoded by thefps/fes proto-oncogene. The clone we have described as well as other endothelial cell lines that we have established from the mouse embryonic yolk sac should prove useful for the study of endothelial cell differentiation and for the determination of the mechanisms underlying the establishment of organ-specific endothelial cell heterogeneity.     

Disruption of microfilaments alters laminin synthesis but not laminin trafficking in NHEKin vitro

Summary Laminin synthesis and deposition are concomitant with the development of a basal lamina between the human epidermis and the underlying dermis. One of the challenges in tissue engineering of human epidermal models is to develop substrates and conditions that encourage the development of a basement membrane. The purpose of this study was to determine if actin filaments and/or microtubules are involved in the synthesis/secretion of laminin by normal human epidermal keratinocytes (NHEK)in vitro. NHEK synthesize and secrete laminin subunits B1, B2, and M but little, if any, of laminin subunit A. Data indicate that disruption of microfilaments by the destabilizing agent, cytochalasin D, had no apparent effect on the relative synthesis rates of most cytosolic proteins as, revealed by one-dimensional sodium dodecyl sulfate (SDS) gel electrophoresis. This drug, however, increased laminin B2 synthesis several fold over untreated controls. This enhanced synthetic rate was independent of the type of collagen, matrix on which the NHEK were grown. Similar increases in synthesis of the M and B1 laminin chains were not observed. To determine if this increase in synthesis lead to increases in laminin B2 secretion, laminin B2 was immunoprecipitated from both the apical and basal domains of NHEK cells grown on microporous membranes. While more laminin B1, B2, and M were secreted basally than apically, an observation consistent with laminin’s role in basal lamina formation, cytochalasin D had no apparent effect on either basal or apical laminin B2 secretion. Experiments with the microtubule destabilizer, nocodazole, showed no similar effects on laminin synthesis and/or secretion. We conclude that (a) disruption of the actin network in NHEK selectively increases the synthesis of laminin B2, (b) the secretion of laminin B2 from NHEK cells is not governed by either the microfilamentous cytoskeleton or the amount of laminin synthesized by NHEK, and (c) disruption of the microtubular network does not alter laminin synthesis or secretion.     

The Total Chemical Synthesis of Monocyte Chemotactic Protein-1 (MCP-1)

The affinity-based N^α-amino protecting group tetrabenzo [a,c,g,i]fluorenyl-17-methoxycarbonyl (Tbfmoc) has been utilized as a hydrophobic probe to allow the simple, quick and highly effective isolation of a 76 residue cysteine-containing protein (MCP-1). The base-labile Tbfmoc group can be removed under very mild conditions, which preserve the thiol-con taining protein in the reduced state. Oxidative folding was then used to furnish the biologically active β-chemokine MCP-1.     

Production, Purification, and Characterization of Recombinant Human Hemoglobin Rainier Expressed inSaccharomyces cerevisiae

Hemoglobin Rainier is a naturally occurring hemoglobin variant in which the β145 tyrosine is substituted with cysteine. The α and β^Rainierglobin cDNAs were cloned in a high copy number vector and expressed inSaccharomyces cerevisiaeunder the control of galactose-regulated hybrid promoters. Using this system, we have expressed individual α and β^Rainierglobin chains. Coexpression of both α and β^RainiercDNAs resulted in the production of a functional hemoglobin molecule. Purification of the recombinant protein was accomplished by ion exchange chromatography. The N-termini of the α and β chains were correctly processed, and the molecular mass, as determined by mass spectrometry, indicated amino acid composition identical to that of natural hemoglobin Rainier. The chromatographic properties of the recombinant hemoglobin Rainier were similar to human-derived hemoglobin A₀. The purified recombinant hemoglobin molecule was shown to have an elevated oxygen affinity and a reduced cooperativity as previously reported for natural hemoglobin Rainier. Production of recombinant hemoglobin and especially hemoglobin variants like hemoglobin Rainier has the potential to facilitate use of hemoglobin as a blood substitute as well as in specific applications, such as for use as a therapeutic agent in the treatment of hypotension associated with septic shock.     

The Best Gastric Site for Obtaining a Positive Rapid Urease Test

Background Rapid urease tests (RUTs) provide a simple, sensitive method of detecting Helicobacter pylori infection.
Objectives. Our aim, therefore, was to determine whether the yield of detecting H. pylori infection by RUT varied depending on the site of gastric biopsy.
Materials and Methods. Gastric biopsies were obtained from 50 patients for RUT by use of hp fast (GI Supply, Camp Hill, PA). Biopsies were taken from the prepyloric greater curve antrum, from the gastric angle, and from the greater curve in mid-corpus. One biopsy specimen was placed in the RUT gel, and the biopsy from the adjacent mucosa was placed in formalin for subsequent histological evaluation by using the Genta stain. RUTs were examined and scored at intervals of 5, 10, 15, 30, and 45 minutes and after 1, 2, 4, and 24 hours.
Results. Fifty patients were entered in the test (150 RUTs), 32 having H. pylori infection. There were no false-positive RUTs (specificity, 100%). The gastric angle site was positive in 100%. The prepyloric site was positive in 87%, and the corpus site was positive in 84.4% ( p < .052 for angle or prepyloric antrum versus corpus). The most common pattern was for all to be positive (74%). The median time to positivity was similar with angle and prepyloric sites (37.5 and 60 minutes, respectively, p = not significant) and shorter than the corpus biopsy (180 minutes); ( p < .05 for angle or prepyloric antrum versus corpus).
Conclusion. The maximum probability for detecting H. pylori infection using a RUT is to obtain a biopsy from the gastric angle. To prevent missing a positive result when intestinal metaplasia is present, we recommend that (at a minimum) biopsies be taken from both the angle and the corpus.