A surface protease and the invasive character of plague

A 9.5-kilobase plasmid of Yersinia pestis, the causative agent of plague, is required for high virulence when mice are inoculated with the bacterium by subcutaneous injection. Inactivation of the plasmid gene pla, which encodes a surface protease, increased the median lethal dose of the bacteria for mice by a millionfold. Moreover, cloned pla was sufficient to restore segregants lacking the entire pla-bearing plasmid to full virulence. Both pla+ strains injected subcutaneously and pla- mutants injected intravenously reached high titers in liver and spleen of infected mice, whereas pla- mutants injected subcutaneously failed to do so even though they establish a sustained local infection at the injection site. More inflammatory cells accumulated in lesions caused by the pla- mutants than in lesions produced by the pla+ parent. The Pla protease was shown to be a plasminogen activator with unusual kinetic properties. It can also cleave complement C3 at a specific site.

Preparation of poly(glycolic acid) bonded fiber structures for cell attachment and transplantation

A novel method was developed to prepare three-dimensional structures with desired shapes used as templates for cell transplantation. The produced biomaterials are highly porous with large surface/volume and provide the necessary space for attachment and proliferation of the transplanted cells. The processing technique calls for the formation of a composite material with nonbonded fibers embedded in a matrix followed by thermal treatment and the selective dissolution of the matrix. To evaluate the technique, poly(glycolic acid) (PGA) fiber meshes were bonded using poly(L-lactic acid) (PLLA) as a matrix. The bonded structures were highly porous with values of porosity up to 0.81 and area/volume ratios as high as 0.05 micron-1.

Identification and characterization of a prostaglandin transporter

Carrier-mediated prostaglandin transport has been postulated to occur in many tissues. On the basis of sequence homology, the protein of unknown function encoded by the rat matrin F/G complementary DNA was predicted to be an organic anion transporter. Expression of the matrin F/G complementary DNA in HeLa cells or Xenopus oocytes conferred the property of specific transport of prostaglandins. The tissue distribution of matrin F/G messenger RNA and the sensitivity of matrin F/G-induced prostaglandin transport to inhibitors were similar to those of endogenous prostaglandin transport. The protein encoded by the matrin F/G complementary DNA is thus preferably called PGT because it is likely to function as a prostaglandin transporter.

An improved Tn7-based system for the single-copy insertion of cloned genes into chromosomes of gram-negative bacteria

A system is described for the single-copy, stable insertion of cloned DNA sequences into the chromosomes of Gram- bacteria. Two narrow-host-range plasmids form the basis of this system: the 'carrier' plasmid contains the mini Tn7-Km transposon, into which foreign DNA can be cloned; the 'helper' plasmid provides the Tn7 transposition functions in trans. Both plasmids are readily transferred into Gram- bacteria by conjugation. The functionality of this system has been demonstrated in Rhodospirillum rubrum.

Conjugation position of quercetin glucuronides and effect on biological activity

Quercetin glycosides are common dietary antioxidants. In general, however, potential biological effects of the circulating plasma metabolites (e.g., glucuronide conjugates) have not been measured. We have determined the rate of glucuronidation of quercetin at each position on the polyphenol ring by human liver cell-free extracts containing UDP-glucuronosyltransferases. The apparent affinity of UDP-glucuronosyltransferase followed the order 4'- > 3'- > 7- > 3, although the apparent maximum rate of formation was for the 7-position. The 5-position did not appear to be a site for conjugation. After isolation of individual glucuronides, the inhibition of xanthine oxidase and lipoxygenase were assessed. The K(i) for the inhibition of xanthine oxidase by quercetin glucuronides followed the order 4'- > 3'- > 7- > 3-, with quercetin-4'-glucuronide a particularly potent inhibitor (K(i) = 0. 25 microM). The glucuronides, with the exception of quercetin-3-glucuronide, were also inhibitors of lipoxygenase. Quercetin glucuronides are metabolites of quercetin in humans, and these compounds can retain some biological activity depending on conjugation position at expected plasma concentrations.

Cloning, in vitro expression, and tissue distribution of a human prostaglandin transporter cDNA(hPGT)

We recently identified a cDNA in the rat that encodes a broadly expressed PG transporter (PGT). Because PGs play diverse and important roles in human health and disease, we cloned human PGT (hPGT) from an adult human kidney cDNA library. A consensus sequence (4.0 kb) derived from several clones, plus 3' polymerase chain reaction amplification, exhibited 74% nucleic acid identity and 82% amino acid identity compared to rat PGT. When transiently expressed in HeLa cells, a full-length clone catalyzed the transport of PGE1, PGE2, PGD2, PGF2alpha, and, to a lesser degree, TXB2. Northern blotting revealed mRNA transcripts of many different sizes in adult human heart, placenta, brain, lung, liver, skeletal muscle, pancreas, kidney, spleen, prostate, ovary, small intestine, and colon. hPGT mRNAs are also strongly expressed in human fetal brain, lung, liver, and kidney. The broad tissue distribution and substrate profile of hPGT suggest a role in the transport and/or metabolic clearance of PGs in diverse human tissues.

Mapping of RNA accessible sites for antisense experiments with oligonucleotide libraries

Antisense experiments are often complicated by the lack of reliable methods for selecting effective antisense sequences. Chimeric oligodeoxynucleotide (ODN) libraries and ribonuclease H (RNase H) were used to identify regions on the 1253 nucleotide angiotensin type-1 receptor (AT1) mRNA that are accessible to hybridization with antisense ODNs. Phosphorothioate antisense ODNs targeted against accessible sites reduced AT1 receptor levels by at least 50% in cell culture. ODNs to 4 sites produced a 70% to 80% reduction. In contrast, most sequences targeted between accessible sites were ineffective. When injected into the brains of rats, ODNs targeted to accessible sites reduced AT1 (by 65%) but not AT2 receptor levels. Additionally, AT1 receptor function as measured by agonist-induced water intake, was significantly attenuated in these rats. ODNs directed between accessible sites were ineffective at suppressing water intake. RNA mapping can be applied to any RNA target to facilitate selection of multiple, active antisense sequences for cell culture and in vivo experiments.

Glucose-insulin-potassium solutions improve outcomes in diabetics who have coronary artery operations

BACKGROUND

This study was undertaken to determine whether glucose-insulin-potassium (GIK) would improve myocardial performance and limit morbidity after coronary artery bypass grafting in diabetic patients.

METHODS

Forty consecutive coronary artery bypass grafting patients with medically treated diabetes mellitus were prospectively randomly assigned to either a GIK group (n = 20; 500 mL D5W + 80 U regular insulin + 40 mEq KCl 30 mL/hour) or a no-GIK group (n = 20; D5W at 30 mL/hour). The GIK was begun at anesthetic induction and continued for 12 hours postoperatively.

RESULTS

Patients treated with GIK had higher postoperative cardiac indices (2.88 +/- 0.50 versus 2.20 +/- 0.39 L/minute per square meter; p < 0.0001), lower inotrope scores (0.40 +/- 0.68 versus 1.25 +/- 1.44; p = 0.05), less weight gain (5.80 +/- 3.76 versus 13.85 +/- 6.52 pounds; p < 0.0001), and had shorter times of ventilator support (8.35 +/- 2.60 versus 13.45 +/- 7.33 hours; p = 0.0128). They had a significantly lower prevalence of atrial fibrillation (15% versus 60%; p = 0.003), and shorter hospital stays (6.70 +/- 1.52 versus 10.15 +/- 6.62 days; p = 0.02).

CONCLUSIONS

Substrate enhancement with GIK in diabetic patients improved myocardial performance and resulted in faster recovery after coronary artery bypass grafting.

Phospholipid hydroperoxide glutathione peroxidase activity of human glutathione transferases

Human glutathione transferases (GSTs) from Alpha (A), Mu (M) and Theta (T) classes exhibited glutathione peroxidase activity towards phospholipid hydroperoxide. The specific activities are in the order: GST A1-1>GST T1-1>GST M1-1>GST A2-2>GST A4-4. Using a specific and sensitive HPLC method, specific activities towards the phospholipid hydroperoxide,1-palmitoyl-2-(13-hydroper oxy-cis-9, trans-11 -octadecadienoyl)-l-3-phosphatidylcholine (PLPC-OOH) were determined to be in the range of 0.8-20 nmol/min per mg of protein. Two human class Pi (P) enzymes (GST P1-1 with Ile or Val at position 105) displayed no activity towards the phospholipid hydroperoxide. Michaelis-Menten kinetics were followed only for glutathione, whereas there was a linear dependence of rate with PLPC-OOH concentration. Unlike the selenium-dependent phospholipid hydroperoxide glutathione peroxidase (Se-PHGPx), the presence of detergent inhibited the activity of GST A1-1 on PLPC-OOH. Also, in contrast with Se-PHGPx, only glutathione could act as the reducing agent for GST A1-1. A GST A1-1 mutant (Arg15Lys), which retains the positive charge between the GSH- and hydrophobic binding sites, exhibited a decreased kcat for PLPC-OOH but not for CDNB, suggesting that the correct topography of the GSH site is more critical for the phospholipid substrate. A Met208Ala mutation, which gives a modified hydrophobic site, decreased the kcat for CDNB and PLPC-OOH by comparable amounts. These results indicate that Alpha, Mu and Theta class human GSTs provide protection against accumulation of cellular phospholipid hydroperoxides.

Hepatic and neuromuscular forms of glycogen storage disease type IV caused by mutations in the same glycogen-branching enzyme gene

Glycogen storage disease type IV (GSD-IV) is an autosomal recessive disease resulting from deficient glycogen-branching enzyme (GBE) activity. The classic and most common form is progressive liver cirrhosis and failure leading to either liver transplantation or death by 5 yr of age. However, the liver disease is not always progressive. In addition, a neuromuscular type of the disease has been reported. The molecular basis of GSD-IV is not known, nor is there a known reason for the clinical variability. We studied the GBE gene in patients with various presentations of GSD-IV. Three point mutations in the GBE gene were found in two patients with the classical presentation: R515C, F257L, and R524X. Transient expression experiments showed that these mutations inactivated GBE activity. Two point mutations, L224P and Y329S, were detected in two separate alleles of a patient with the nonprogressive hepatic form. The L224P resulted in complete loss of GBE activity, whereas the Y329S resulted in loss of approximately 50% of GBE activity. The Y329S allele was also detected in another patient with the nonprogressive form of GSD-IV but not in 35 unrelated controls or in patients with the more severe forms of GSD-IV. A 210-bp deletion from nucleotide 873 to 1082 of the GBE cDNA was detected in a patient with the fatal neonatal neuromuscular presentation. This deletion, representing the loss of one full exon, was caused by a 3' acceptor splicing site mutation (ag to aa). The deletion abolished GBE activity. Our studies indicate that the three different forms of GSD-IV were caused by mutations in the same GBE gene. The data also suggest that the significant retention of GBE activity in the Y329S allele may be a reason for the mild disease. Further study of genotype/phenotype correlations may yield useful information in predicting the clinical outcomes.

Mutations in exon 3 of the glycogen debranching enzyme gene are associated with glycogen storage disease type III that is differentially expressed in liver and muscle

Glycogen storage disease type HI (GSD-III), an autosomal recessive disease, is caused by deficient glycogen debranching enzyme (GDE) activity. Most GSD-III patients are GDE deficient in both liver and muscle (type IIIa), and some GSD-III patients have GDE absent in liver but retained in muscle (type IIIb). The molecular basis for this enzymatic variability is largely unknown. In the present study, the analysis of the GDE gene in three GSD-IIIb patients by single-strand conformation polymorphism (SSCP), DNA sequencing, restriction analysis, and family studies, revealed each of them as being a compound heterozygote for two different mutations. The first mutant alleles in all three patients involved mutations in exon 3 at amino acid codon 6 of the GDE protein. Two had an AG deletion at nucleotides 17 and 18 of the GDE cDNA (17delAG) which resulted in change of subsequent amino acid sequence and a truncated protein (25X); the other had a C to T transition at nucleotide 16 of the cDNA which changed a Glutamine codon to a stop codon (Q6X). The 17delAG mutation was also found in 8 of the 10 additional GSD-IIIb patients. The Q6X mutation was found in one of the remaining two GSD-IIIb patients. These two mutations were not found in any of the 31 GSD-IIIa patients, 2 GSD-IIId patients, nor 28 unrelated normal controls. The second mutant alleles in each of the three GSD-IIIb patients were R864X, R1228X, and W68OX. The R864X and R1228X were not unique for GSD-IIIb as they were also found in GSD-IIIa patients (frequency of 10.3% and 5.2% in Caucasian patients, respectively). Our data demonstrated that both IIIa and IIIb had mutations in the same GDE gene and established for the first time the molecular basis of GSD-III that differentially expressed in liver and muscle. The striking and specific association of exon 3 mutations with GSD-IIIb may provide insight into mechanisms controlling tissue-specific expression of the GDE gene. The identification of exon 3 mutations has clinical significance as well because it distinguished GSD-IIIb from IIIa hence permitting diagnosis from a blood sample rather than a more invasive muscle biopsy.

Apoptosis of chondrocytes in transgenic mice lacking collagen II

Previous work demonstrated that collagen fibrils were not detectable in the cartilage of transgenic mice homozygous for targeted inactivation of the collagen II gene. In the present work, we used the same mice to show that chondrocytes undergo apoptosis in the absence of collagen II, the major component of the extracellular matrix of cartilage. The chondrocytes in the homozygous mice had condensed nuclei, fragmentation of nuclear DNA, and decreased levels of the Bcl-2 protein. These results provide direct evidence that cartilage extracellular matrix lacking collagen II cannot support the survival of chondrocytes. In addition, the results suggest that apoptosis may play a role in degenerative connective tissue diseases such as osteoarthritis in which there is extensive tissue loss.

Correlation of lens density measured using the Pentacam Scheimpflug system with the Lens Opacities Classification System III grading score and visual acuity in age-related nuclear cataract

AIMS

To investigate the relationship between lens density measured with the Pentacam Scheimpflug System and grading score using the Lens Opacities Classification System (LOCS) III as well as that between lens density and visual acuity in age-related nuclear cataract patients.

METHODS

Lens density and grading score were evaluated in 138 cases (180 eyes) with age-related nuclear cataract. LogMAR visual acuity was tested with the Early Treatment Diabetic Retinopathy Study chart. The correlations between lens density value and LOCS III nuclear opacity (NO) and nuclear colour (NC) grading score and that between lens density value and logMAR visual acuity were analysed.

RESULTS

There was a linear increasing relationship between lens density value and LOCS III grading score in nuclear cataract patients. Lens density value had a stronger significant correlation with LOCS III NO score than that with NC score. The correlation between the nuclear lens density value and logMAR visual acuity was stronger than that between NO score and logMAR visual acuity or between NC score and logMAR visual acuity.

CONCLUSION

Lens density as a quantitative and objective parameter can present the degree of NO and associated visual impairment due to nuclear cataract. The LOCS III criterion as an economic cataract grading system provides data that are in satisfactory concordance with the results obtained using the Pentacam Scheimpflug system.

Enhanced ZAG production by subcutaneous adipose tissue is linked to weight loss in gastrointestinal cancer patients

Background:

Profound loss of adipose tissue is a hallmark of cancer cachexia. Zinc-α2-glycoprotein (ZAG), a recently identified adipokine, is suggested as a candidate in lipid catabolism.

Methods:

In the first study, eight weight-stable and 17 cachectic cancer patients (weight loss ⩾5% in previous 6 months) were recruited. Zinc-α2-glycoprotein mRNA and protein expression were assessed in subcutaneous adipose tissue (SAT), subcutaneous adipose tissue morphology was examined and serum ZAG concentrations were quantified. In the second cohort, ZAG release by SAT was determined in 18 weight-stable and 15 cachectic cancer patients. The effect of ZAG on lipolysis was evaluated in vitro.

Results:

Subcutaneous adipose tissue remodelling in cancer cachexia was evident through shrunken adipocytes with increased fibrosis. In cachectic cancer patients, ZAG mRNA was upregulated (2.7-fold, P=0.028) while leptin mRNA decreased (2.2-fold, P=0.018); serum ZAG levels were found to be unaffected. Zinc-α2-glycoprotein mRNA correlated positively with weight loss (r=0.51, P=0.01) and serum glycerol levels (r=0.57, P=0.003). Zinc-α2-glycoprotein release by SAT was also elevated in cachectic patients (1.5-fold, P=0.024) and correlated with weight loss (r=0.50, P=0.003). Recombinant ZAG stimulated lipolysis in human adipocytes.

Conclusions:

Zinc-α2-glycoprotein expression and secretion by adipose tissue is enhanced in cachectic cancer patients. Given its lipid-mobilising effect, ZAG may contribute to adipose atrophy associated with cancer cachexia in human beings.

Variations in KCNQ1 are associated with type 2 diabetes and beta cell function in a Chinese population

AIMS/HYPOTHESIS

Recent genome-wide association studies in East Asian populations reported that single nucleotide polymorphisms (SNPs) in KCNQ1 are associated with type 2 diabetes. The aim of this study was to validate this finding in a Chinese population.

METHODS

We genotyped four SNPs, rs2074196, rs2237892, rs2237895 and rs2237897, in a group of 3,503 Shanghai Chinese individuals, comprising 1,769 type 2 diabetic patients and 1,734 normoglycaemic controls. Both the cases and the controls were extensively phenotyped for anthropometric and biochemical traits related to glucose metabolism. Arginine stimulation tests under fasting conditions were performed in a subgroup of 466 cases.

RESULTS

All four of the SNPs were associated with type 2 diabetes, with rs2237892 showing strongest evidence for association (OR 1.532, 95% CI 1.381-1.698, p = 5.0 x 10(-16)). The SNP rs2237897 was associated with both acute insulin and C-peptide response after arginine stimulation in a subgroup of cases (p = 0.0471 and p = 0.0156, respectively). The SNP rs2237895 was associated with both first- and second-phase insulin secretion in the controls (p = 0.0334 and p = 0.0002, respectively).

CONCLUSIONS/INTERPRETATION

In this study we found that KCNQ1 was associated with type 2 diabetes susceptibility in a Chinese population, possibly through its effect on beta cell function.

Position-dependent ATT initiation during plant pararetrovirus rice tungro bacilliform virus translation

The expression of the rice tungro bacilliform virus open reading frame I was studied in transiently transfected protoplasts. Expression occurs despite the presence of a long leader sequence and the absence of a proper ATG initiation codon. Translation is initiated at an ATT codon. The efficiency of initiation in rice protoplasts depends strongly on the mechanism by which ribosomes reach this codon. From the effects of scanning-inhibiting structures inserted into different leader regions, it can be deduced that this mechanism is related to the ribosome shunt described for cauliflower mosaic virus 35S RNA. The process delivers initiation-competent ribosomes to the region downstream of the leader and is so precise that only the second of two potential start codons only 12 nucleotides apart is recognized. The ATT codon that is used when it is present downstream of the leader is hardly recognized as a start codon by ribosomes that reach it by scanning.

Genome-wide association study in a Chinese population identifies a susceptibility locus for type 2 diabetes at 7q32 near PAX4

AIMS/HYPOTHESIS

Most genetic variants identified for type 2 diabetes have been discovered in European populations. We performed genome-wide association studies (GWAS) in a Chinese population with the aim of identifying novel variants for type 2 diabetes in Asians.

METHODS

We performed a meta-analysis of three GWAS comprising 684 patients with type 2 diabetes and 955 controls of Southern Han Chinese descent. We followed up the top signals in two independent Southern Han Chinese cohorts (totalling 10,383 cases and 6,974 controls), and performed in silico replication in multiple populations.

RESULTS

We identified CDKN2A/B and four novel type 2 diabetes association signals with p < 1 × 10(-5) from the meta-analysis. Thirteen variants within these four loci were followed up in two independent Chinese cohorts, and rs10229583 at 7q32 was found to be associated with type 2 diabetes in a combined analysis of 11,067 cases and 7,929 controls (p meta = 2.6 × 10(-8); OR [95% CI] 1.18 [1.11, 1.25]). In silico replication revealed consistent associations across multiethnic groups, including five East Asian populations (p meta = 2.3 × 10(-10)) and a population of European descent (p = 8.6 × 10(-3)). The rs10229583 risk variant was associated with elevated fasting plasma glucose, impaired beta cell function in controls, and an earlier age at diagnosis for the cases. The novel variant lies within an islet-selective cluster of open regulatory elements. There was significant heterogeneity of effect between Han Chinese and individuals of European descent, Malaysians and Indians.

CONCLUSIONS/INTERPRETATION

Our study identifies rs10229583 near PAX4 as a novel locus for type 2 diabetes in Chinese and other populations and provides new insights into the pathogenesis of type 2 diabetes.

Reduced expression of alpha-tubulin genes in Arabidopsis thaliana specifically affects root growth and morphology, root hair development and root gravitropism

Different alpha-tubulin cDNA sequences fused in an antisense orientation to a CaMV 35S promoter were introduced into Arabidopsis thaliana plants. Several independent transgenic lines that showed a moderate but clear reduction of alpha-tubulin gene expression (TUA6/AS lines) were obtained and phenotypically characterized. Although no apparent abnormalities were detected in the aerial parts of TUA6/AS plants, root development was severely affected. Cells in TUA6/AS root tips were found to contain aberrant microtubular structures, to expand abnormally and to be unable to undergo regular cell division. These cellular defects caused a dramatic radial expansion of the root tip and inhibited root elongation. In addition, TUA6/AS roots displayed ectopic formation of root hairs, root hair branching and a reduced ability to respond to gravitropic challenges. Our results contribute to an improved understanding of the different roles microtubules play during root development and demonstrate that reverse genetics is a powerful tool to analyze cytoskeletal functions during plant organogenesis.

Human glycogen debranching enzyme gene (AGL): complete structural organization and characterization of the 5' flanking region

Glycogen debranching enzyme (gene symbol, AGL) is a multifunctional enzyme acting as 1,4-alpha-D-glucan:1,4-alpha-D-glucan 4-alpha-D-glycosyltransferase and amylo-1,6-glucosidase in glycogen degradation. Genetic deficiency of AGL activity causes glycogen storage disease type III (GSD-III). To determine the molecular basis of GSD-III and elucidate the mechanisms for controlling tissue-specific gene expression, we report the isolation and structural organization of the human chromosomal AGL gene. The gene is 85 kb in length and is composed of 35 exons, encoding a 7.0-kb mRNA. The first 2 exons and 68 bp of exon 3 contain 5' untranslated region. Translation begins in exon 3, which encodes the first 27 amino acids of the AGL. Exons 4 to 35 encode the remaining 1505 amino acids. Among the 6 isoforms identified, the major isoform (isoform 1) starts with exon 1 and is widely expressed, including expression in both liver and muscle. Muscle-specific isoforms (2, 3, and 4) begin with exon 2. Isoforms 5 and 6 are minor isoforms that begin further within the gene. Reporter assays revealed that promoter region 1 (for isoform 1) was functional in liver (HepG2 cells), muscle (C2C12 cells), and ovary (Chinese hamster ovary cells), and promoter region 2 (for muscle-specific isoforms) was active only in muscle. These results suggest that the human AGL gene contains at least 2 promoter regions that confer differential expression of isoform mRNAs in a tissue-specific manner.

Downregulation of zinc-{alpha}2-glycoprotein in adipose tissue and liver of obese ob/ob mice and by tumour necrosis factor-alpha in adipocytes

Zinc-alpha2-glycoprotein (ZAG, also listed as AZGP1 in the MGI Database), a lipid-mobilising factor, has recently been suggested as a potential candidate in the modulation of body weight. We investigated the effect of increased adiposity on ZAG expression in adipose tissue and the liver and on plasma levels in obese (ob/ob) mice compared with lean siblings. The study also examined the effect of the pro-inflammatory cytokine tumour necrosis factor-alpha (TNFalpha) on ZAG expression in adipocytes. Zag mRNA levels were significantly reduced in subcutaneous (fourfold) and epididymal (eightfold) fat of ob/ob mice. Consistently, ZAG protein content was decreased in both fat depots of ob/ob mice. In the liver of obese animals, steatosis was accompanied by the fall of both Zag mRNA (twofold) and ZAG protein content (2.5-fold). Plasma ZAG levels were also decreased in obese mice. In addition, Zag mRNA was reduced in epididymal (fivefold) and retroperitoneal (fivefold) adipose tissue of obese (fa/fa) Zucker rats. In contrast to Zag expression, Tnfalpha mRNA levels were elevated in adipose tissue (twofold) and the liver (2.5-fold) of ob/ob mice. Treatment with TNFalpha reduced Zag gene expression in differentiated adipocytes, and this inhibition was chronic, occurring at 24 and 48 h following TNFalpha treatment. It is concluded that ZAG synthesis in adipose tissue and the liver is downregulated, as are its circulating levels, in ob/ob mice. The reduced ZAG production may advance the susceptibility to lipid accumulation in these tissues in obesity, and this could be at least in part attributable to the inhibitory effect of TNFalpha.

Mapping nucleotides in the 126-kDa protein gene that control the differential symptoms induced by two strains of tobacco mosaic virus

The differential symptom determinants of the Holmes' masked (M) and U1 strains of tobacco mosaic virus previously were mapped to the 5'-coterminal open reading frame (ORF) encoding the 126-kDa protein and the N-terminal two-thirds of the 183-kDa protein. Both proteins influence viral RNA accumulation, but the function of, and impact on, symptom formation by large domains within the 126-kDa gene, which are not conserved with sequences in analogous ORFs from other related viruses, are unknown. In the current study, cDNA clones representing each strain (i.e., MIC-TMV and U1-TMV) were mutated in these nonconserved domains to further define the nucleotides responsible for mosaic symptom induction on Nicotiana tabacum. Progeny virus of a mutant containing only eight nucleotide substitutions from the MIC-TMV sequence to the U1-TMV sequence within the 126-kDa protein ORF of MIC-TMV induced U1-TMV-like symptoms. Single or multiple substitutions among these eight nucleotides further defined residues critical for symptom modulation. Complementary substitutions in the MIC-TMV and U1-TMV sequences did not always yield progeny virus that induced complementary visual symptoms. Progeny of some mutants contained second-site spontaneous mutations at specific positions shown to influence symptom phenotype. For a subset of the stable site-directed mutants, there was no correlation between severity of systemic symptoms and chlorotic lesion size or virus accumulation in these chlorotic lesions on inoculated leaves.

Transgenic mice with inactive alleles for procollagen N-proteinase (ADAMTS-2) develop fragile skin and male sterility

Transgenic mice were prepared with inactive alleles for procollagen N-proteinase (ADAMTS-2; where ADAMTS stands for a disintegrin and metalloproteinase with thrombospondin repeats). Homozygous mice were grossly normal at birth, but after 1-2 months they developed thin skin that tore after gentle handling. Although the gene was inactivated, a large fraction of the N-propeptides of type I procollagen in skin and the N-propeptides of type II procollagen in cartilage were cleaved. Therefore the results suggested the tissues contained one or more additional enzymes that slowly process the proteins. Electron microscopy did not reveal any defects in the morphology of collagen fibrils in newborn mice. However, in two-month-old mice, the collagen fibrils in skin were seen as bizarre curls in cross-section and the mean diameters of the fibrils were approx. half of the controls. Although a portion of the N-propeptides of type II procollagen in cartilage were not cleaved, no defects in the morphology of the fibrils were seen by electron microscopy or by polarized-light microscopy. Female homozygous mice were fertile, but male mice were sterile with a marked decrease in testicular sperm. Therefore the results indicated that ADAMTS-2 plays an essential role in the maturation of spermatogonia.

Sebaceous carcinoma. Tumor progression through mutational inactivation of p53

BACKGROUND

Sebaceous carcinoma may masquerade for years as an inflammatory condition. In many cases, this may be because of the presence of longstanding intraepithelial disease (e.g., dysplasia or carcinoma in situ), which eventually progresses to invasive carcinoma recognized through tumefaction and a worsening clinical presentation. The mechanism for this tumor progression is unknown. In the Far East, human papilloma virus (HPV) has been suggested to play a role in the development of sebaceous carcinoma by inactivating tumor suppressor gene p53. Here, the authors explore the molecular basis of the progression of ocular sebaceous carcinoma.

METHODS

Cases of sebaceous carcinoma seen at the University of Virginia, Department of Ophthalmology, during the period from 1989 to 1996 were analyzed for HPV infection by in situ hybridization and polymerase chain reaction. The expression of p53, p21WAF-1, Bcl-2, and epithelial membrane antigen was examined by immunohistochemistry. In one of the cases, frozen tumor was available, allowing exons 5 through 9 of the p53 gene to be sequenced.

RESULTS

Seven cases were identified, all of which were from women. All were negative for HPV. In cases in which disease was restricted to dysplasia (carcinoma in situ), p53 but not p21WAF-1 was negative. In contrast, cases that contained a component of invasive or metastatic carcinoma showed striking hyperexpression of nuclear p53 in all of the malignant cells. In one of these cases, a G:C-->T:A transversion was found in the p53 gene. This mutation, characteristic of bulky carcinogens, substituted phenylalanine for cysteine 277, a residue that participates in hydrogen bonding to the p53 DNA binding consensus sequence.

CONCLUSIONS

Mutational inactivation of p53 may be involved in the progression of sebaceous carcinoma.