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To identify plant defense components that are important in restricting the growth of virulent pathogens, we screened for Arabidopsis mutants in the accession Columbia (carrying the transgene BGL2-GUS) that display enhanced disease susceptibility to the virulent bacterial pathogen Pseudomonas syringae pv. maculicola (Psm) ES4326. Among six (out of a total of 11 isolated) enhanced disease susceptibility (eds) mutants that were studied in detail, we identified one allele of the previously described npr1/nim1/sai1 mutation, which is affected in mounting a systemic acquired resistance response, one allele of the previously identified EDS5 gene, and four EDS genes that have not been previously described. The six eds mutants studied in detail (npr1-4, eds5-2, eds10-1, eds11-1, eds12-1, and eds13-1) displayed different patterns of enhanced susceptibility to a variety of phytopathogenic bacteria and to the obligate biotrophic fungal pathogen Erysiphe orontii, suggesting that particular EDS genes have pathogen-specific roles in conferring resistance. All six eds mutants retained the ability to mount a hypersensitive response and to restrict the growth of the avirulent strain Psm ES4326/avrRpt2. With the exception of npr1-4, the mutants were able to initiate a systemic acquired resistance (SAR) response, although enhanced growth of Psm ES4326 was still detectable in leaves of SAR-induced plants. The data presented here indicate that eds genes define a variety of components involved in limiting pathogen growth, that many additional EDS genes remain to be discovered, and that direct screens for mutants with altered susceptibility to pathogens are helpful in the dissection of complex pathogen response pathways in plants.

Arabidopsis contains five isoenzymes of aspartate aminotransferase (AspAT) localized to the cytosol, chloroplast, mitochondria, or peroxisomes. To define the in vivo function of individual isoenzymes, we screened for Arabidopsis mutants deficient in either of the two major isoenzymes, cytosolic AAT2 or chloroplastic AAT3, using a native gel activity assay. In a screen of 8,000 [M.sub.2] seedlings, three independent mutants deficient in cytosolic AAT2 (aat2) and two independent mutants deficient in chloroplastic AAT3 (aat3) were isolated. Mapping of aat2 and aat3 mutations and the five AspAT genes (ASP1-ASP5) established associations as follows: the mutation affecting aat2 maps with and cosegregates with ASP2, one of two expressed genes for cytosolic AspAT; the mutation affecting aat3 maps to the same location as the ASP5 gene encoding chloroplastic AspAT. Phenotypic analysis of the aat2 and aat3 mutants revealed a dramatic aspartate-related phenotype in one of the mutants deficient in cytosolic AAT2. The aat2-2 mutant displays an 80% reduction in levels of aspartate transported in the phloem of light-grown plants, and a 50% reduction in levels of asparagine transported in dark-adapted plants. These results indicate that cytosolic AAT2 is the major isoenzyme controlling aspartate synthesized for nitrogen transport in the light, and that this aspartate pool is converted to asparagine when plants are dark adapted.

The arginine-rich motif provides a versatile framework for RNA recognition in which few amino acids other than arginine are needed to mediate specific binding. Using a mammalian screening system based on transcriptional activation by HIV Tat, we identified novel arginine-rich peptides from combinatorial libraries that bind tightly to the Rev response element of HIV. Remarkably, a single glutamine, but not asparagine, within a stretch of polyarginine can mediate high-affinity binding. These results, together with the structure of a Rev peptide-Rev response element complex, suggest that the carboxamide groups of glutamine or asparagine are well-suited to hydrogen bond to G-A base pairs and begin to establish an RNA recognition code for the arginine-rich motif. The screening approach may provide a relatively general method for screening expression libraries in mammalian cells.

A two-color genetic screen was used to determine mutations in lrp and to examine the participation of Lrp in coordinating Pap phase variation. The amino acid replacements in Lrp at position 126, 133 or 134 had a negligible influence on ilvIH transcription but significantly minimized the rate of Pap phase variation. In vitro analyses suggested that the T134A and E133G Lrp variants sustained affinities for pap and ilvIH DNAs in a manner which is identical to those of wild-type Lrp.

To the Editor: Yersinia pestis causes plague, which primarily affects rodents, but is an invasive and virulent pathogen among humans. Y. pestis infection is endemic in small rodent populations in [...]

A novel 111-amino acid polypeptide called beta3-endoxin was recently identified through the utilization of a yeast two-hybrid screening strategy. The polypeptide can be fused to the cytoplasmic tail of the beta3 integrin subunit in both yeast and in vitro, but it cannot bind to other integrin tails such as beta1, beta2, and alpha(sub IIb). The Chinese hamster ovary cell model system was used to express alpha(sub IIb)beta3 and beta3-endoxin, showing the protein's ability to strengthen the affinity state and adhesive function of alpha(sub IIb)beta3.

Nurses should be prepared to deal with the ramifications of genetic testing, particularly regarding patients who may be identified as having hereditary cancer syndrome. Genetic testing is making identification of these individuals increasingly easier, so nurses will be called on to provide support and patient education. Nurses must assess the proper way to inform these patients of their genetic susceptibility and the pros and cons of genetic tests. Psychosocial and ethical issues must also be considered in determining the proper use of genetic testing.

Many Hong Kong women at risk of bearing a child with alpha- or beta-thalassemia are not receiving prenatal testing. Thalassemia is a genetic disorder that affects the synthesis of hemoglobin. Researchers in Hong Kong tested 1,812 high school students for alpha- or beta-thalassemia. Ninety students tested positive for alpha-thalassemia, 61 tested positive for beta-thalassemia and six tested positive for both. Generalizing these results to the remaining population shows that many pregnant women carrying these mutations are not being tested.

DNA library screening of TnphoA insertion mutants for iron-repressed fusions to phoA led to the selection and cloning of the Bordetella bronchiseptica ferric iron repressed outer-membrane protein (bfrA) gene. Sequence analysis of the 80-kDa gene product revealed that it is homologous to a number of bacterial proteins belonging to the family of Ton B-dependent outer membrane receptors. bfrA gene expression was found to be induced by low iron availability under the control of the promoter that is overlapped by a sequence resembling a consensus Fur-binding sequence.

Different mutations in the phenylalanine hydroxylase (PAH) gene appear to correlate with variations in the biochemical and clinical features of patients with phenylketonuria (PKU) and hyperphenylalaninemia (HPA). The buildup of phenylalanine that occurs in PKU and HPA usually results from a deficiency in the activity of the PAH enzyme. Researchers analyzed DNA samples taken from 35 patients with PKU or HPA and 1 carrier and identified a variety of mutations in the PAH gene, 5 of which were new. For 32 patients whose PAH genes were fully characterized, there was a strong association between the patients' phenylalanine levels and predictions of their PAH activity based on previous laboratory studies of the corresponding mutant PAH enzymes. A strong association was also found between the predicted PAH activity and the patients' tolerance for phenylalanine. The findings indicate that PAH genetic screening may be useful even in the variable American population from which the study participants were selected., Objective. To determine the molecular basis of phenylketonuria (PKU) and related hyperphenylalaninemia (HPA) and to establish correlations between phenylalanine hydroxylase (PAH) genotypes and biochemical and clinical phenotypes in an ethnically diverse US population, PAH genotypes were determined in 35 patients with PKU or HPA and 1 carrier from the Medical Genetics Clinic of the Emory University School of Medicine. Methodology. Patients were identified through Georgia's population-based newborn screening program. PAH genotypes in these individuals were determined from dried blood spots or whole-blood samples using a combination of polymerase chain reaction-mediated amplification, denaturing gradient gel electrophoresis, and direct-sequence analysis. The phenotypic severity of patients with PKU and HPA was based on pretreatment serum phenylalanine (PHE) levels during the neonatal period and on dietary tolerance of PHE later in life. Results. Sixty-eight (96%) of 71 mutant alleles were identified. Major mutations in this population included R408W (11 of 71), 165T (11 of 71), Y414C (6 of 71), L348V (4 of 71), and IVS10 (4 of 71). Five new nucleotide substitutions, E76A (1 of 71), R241L (1 of 71), Q304R (2 of 71), C334S (1 of 71), and R400R (2 of 71) were also detected. Thirty-two of the thirty-five nonrelated patients examined in this study were completely genotyped. Strong correlations were observed between the level of PAH activity predicted from the genotype, when known from previous in vitro expression studies of the mutant proteins, and pretreatment serum PHE levels (r = .841) or clinical severity (Kendall rank-order correlation coefficient, .936). Conclusions. These results demonstrate strong correlations between PAH genotype and biochemical and clinical phenotypes in this heterogeneous American sample population, extending our previous findings from relatively homogeneous European populations. These correlations further demonstrate the clinical utility of genotype analysis in the treatment of patients with PKU and HPA. Pediatrics 1996;97:512-516, phenylketonuria, hyperphenylalaninemia, phenylalanine hydroxylase, mutation, genotype-phenotype correlation., ABBREVIATIONS. PKU, phenylketonuria; PAH, phenylalanine hydroxylase; VNTR, variable number of tandem repeat; HPA, hyperphenylalaninemia; PHE, phenylalanine; PCR, polymerase chain reaction; DGGE, denaturing gradient gel electrophoresis. Phenylketonuria (PKU; McKusick's Mendelian inheritance [...]

The yeast, Saccharomyces cerevisiae, recapitulates retroviral -1 frameshifting, as detected by the assays in the yeast that screen host mutants. A two-times increase in -1 frameshifting levels in yeast mutants is noticed, by using a model substrate of the mouse mammary tumor virus gag-pro frameshift site. The haploid cells devoid of 82% of the IFSI open reading frame are viable and phenotypically similar to isf1-1 mutants.

Screening procedure applied to a novel set of temperature sensitive (ts) mutants of Aspergillus nidulans for strains unable to develop septa at the restrictive temperature, but capable of completing early nuclear division, provides fine new genes termed sep E, G, H, I and J and another allele of an already established separation gene. Separation is absent for the mutants that cannot proceed beyond the third nuclear division. A regulatory process in A. nidulans guarantees the progression of nuclear division after cytokinesis begins.

This past spring, Christian Schaaf sat back and watched seven-year-old Lily play in his office at the Baylor College of Medicine in Houston. She looked just like any other girl [...]

Protein and gene expression tests may aid in the molecular diagnosis of familial adenomatous polyposis. Familial adenomatous polyposis is an inherited disorder characterized by multiple tumors in the colon and rectum. Researchers developed tests detecting the protein product of genes and the expression of gene pairs involved in polyposis to screen 62 unrelated polyposis patients for gene mutations. The protein test identified mutations in 51 of these patients. Researchers evaluated the 11 remaining patients and some normal subjects with the gene expression test to detect abnormalities. Seven patients and six healthy subjects tested positive for the expression of at least one of the two genes. Three of the polyposis patients had reduced expression of one gene. A family member of one patient also had a reduction in gene expression, indicating an inheritance pattern. The protein and gene expression tests identified mutations in 87% of the patients tested.

Pairwise cooperative binding reveals the likely deformations in the genetic screen of a lambda repressor mutant with the help of a hybrid operator promoter region, OsPs. The C-terminal area of the repressor allows the separation of four mutations by using the genetic screen. The cooperativity-defective phenotype of the mutation of the transformation of Gly 147 to Asp is observed by in vitro examination of the other repressor mutants. Cooperative interactions are required to steady the repressor dimer which binds at the weak operator site Os2. The interaction requires a repressor dimer which is bound at the strong operator site Os1.

Some women may inherit an increased risk of developing breast or ovarian cancer. This increased susceptibility to breast and ovarian cancer is caused by mutations in the BRCA1 gene located on chromosome 17. Both male and female carriers of the altered form of the BRCA1 gene can be identified by undergoing genetic screening. This type of screening can have a significant affect on the lives of women from families with a high incidence of breast and ovarian cancer. Women from these families often live in fear of developing these types of cancer at a young age. Genetic screening can enable earlier diagnosis of breast or ovarian cancer in women who are carriers of the altered gene. Some individuals who are carriers may choose to undergo a preventative mastectomy or ovariectomy. Insurance companies may be reluctant to pay for this type of screening despite its benefits.

Genetic screening may be an effective method for identifying women at risk for developing breast or ovarian cancer. Some women may have a higher susceptibility to breast or ovarian cancer as a result of mutations in the BRCA1 gene on chromosome 17. These mutations in these women may cause an estimated 85% lifetime risk of developing breast or ovarian cancer. Women with BRCA1 mutations are also more likely to develop breast cancer before the age of 50 than other individuals. Several families have been identified as having a linkage between the development of breast or ovarian cancer and the BRCA1 gene. Genetic analysis has identified several members of one family as probable carriers of the BRCA1 mutation. Individuals who undergo screening for the BRCA1 mutation may require different types of psychological and social support. This type of screening is not yet available on a widespread basis., Efforts are under way to isolate a gene (BRCA1) on chromosome 17912-21. Mutations in this gene predispose women to breast and ovarian cancer. Women with germline mutations in BRCA1 are estimated to have an 85% lifetime risk of developing breast cancer and an increased but as yet undetermined risk of ovarian cancer. It is estimated that one in 200 to 400 American women may be carriers of BRCA1 mutations. We have identified several families that show nkage between breast and/or ovarian cancer and genetic markers that flank BRCA1. It is now possible, within these linked families, to prospectively identify family members likely to be carrying BRCA1 mutations. Because of profound and immediate clinical ramifications, we offered to provide this information to one such extended family. To provide information to this family, we developed a protocol to address the many issues that arise in the delivery of these services. Although testing for BRCA1 mutation carriers is currently limited to very rare families being analyzed for research purposes, this experience presages the complexities of the much larger scale availability of population screening for BRCA1 mutations, which is likely to become a reality in the next few years. (JAMA. 1993;269:1970-1974)

The article discusses the increasing focus being given to age-related macular degeneration (AMD), which is on the rise. Genetic research has helped provide great insights into the predisposition of AMD, which can be of great assistance in helping such people ward off the illness before it happens.

The article discusses the various challenges that lie in the way of genomic medicine and the increasing prevalence of direct-to-consumer (DTC) genetic testing. However, consumers need to be protected from unrealistic claims and misrepresentations of complex, dynamic genomic information.

The various benefits of genome sequencing in studying the various genetic variants in different disorders caused in human body are discussed. The new technology is shown to be extremely efficient and cheap approach for the required diagnostic purposes.

Scientists plan to map the entire human genome - the complete set of genes - within the next few years. This project promises to vastly improve our ability to detect genetic predispositions for many diseases. There are some possible abuses such advances could bring, however. Employers might use genetic tests to identify employees or potential employees at risk for certain diseases and to deny such people jobs. There are a few situations for which such screening might be justified, but it could also lead to unwarranted discrimination. An employer might use genetic screening to identify workers who are predisposed to early disabling disease. This use of genetic screening is not justifiable, particularly since the screening indicates only an increased risk, not a definite likelihood, for certain diseases. Employers might also use the screening in an effort to cut health care costs. Such a policy would not alter society's overall health care costs, it would deny society the benefit of certain individuals' productivity, and it would unduly burden other employers with higher health care costs. Genetic testing for public safety is also of little use. It only identifies possible future risks, not present functioning. An employer might ask for such tests to identify people at risk for exposure to certain elements of a particular job. Again, in most cases, the testing would only identify a possible risk, not a definite outcome. An employer would need to show that a certain genetic test is highly accurate in predicting adverse effects from the particular exposure of the job. It is important that the legal rights of employees be protected and that the use of genetic testing by employers remain extremely limited. (Consumer Summary produced by Reliance Medical Information, Inc.)

Dopamine is a chemical substance that plays an important role in the transmission of certain nerve signals to and from the brain. Abnormalities of the D2 dopamine receptors have been suggested as a cause or a partial cause of some neurological and psychiatric disorders. Previous researchers have reported that a variation of the D2 dopamine receptor gene (DRD2) known as the A1 allele was present at a significantly higher rate in alcoholics than in nonalcoholics. Other studies have reported similar findings, while yet others have reported no association between the A1 allele and alcoholism. To further examine this issue, the allele at the DRD2 gene locus was determined in 44 alcoholics and 68 control subjects. All subjects were white and none were biologically related. The A1 allele was found in 35 percent of the control subjects and in 45 percent of the alcoholic subjects. Differences between alcoholics and controls in overall frequencies of the A1 and A2 alleles at DRD2 were not considered statistically significant. When the subjects in the alcoholic group were further subdivided into groups based on family history of alcoholism, age at onset, and consumption, the prevalence of the A1 allele was not significantly different for any of these subgroups compared with that of the control group. It is concluded that there is no association between the A1 allele of the DRD2 and alcoholism. (Consumer Summary produced by Reliance Medical Information, Inc.)

Dopamine is a chemical substance that plays an important role in the transmission of certain nerve signals. It is thought that abnormalities related to dopamine and its actions could be responsible or partially responsible for some neurological and psychiatric disorders. A few studies have reported an association between alcoholism and the presence of a variation of a gene associated with the expression of the dopamine D2 (DRD2) receptor, labelled the A1 allele. Other studies have not found such an association. These conflicting results could be explainable if the A1 allele is a modifying gene related to alcoholism as opposed to being a gene specifically responsible for alcoholism. To test this hypothesis, the prevalence of the A1 allele in various groups of people was measured. A total of 853 subjects were examined, including 314 healthy control subjects, 147 subjects with Tourette's syndrome (TS), 104 with attention deficit hyperactivity disorder (ADHD), 33 with autism, 104 who were alcoholics, 35 who suffered from posttraumatic stress syndrome, 13 who suffered panic attacks, 17 who had Parkinson's disease, and 10 who were obese. The A1 allele was found in 24.5 percent of the control subjects. It was found in 44.9 percent of subjects with TS, 46.2 percent of subjects with ADHD, 54.4 percent of the autistic patients, and 42.3 percent of the chronic alcoholics The prevalence for all of these groups was significantly greater than that in the control group. The differences in prevalence between the control group and the other groups studied were not statistically different. These results indicate that the A1 allele is related to, but not the direct cause of, a number of neuropsychiatric disorders. (Consumer Summary produced by Reliance Medical Information, Inc.)