Genetic basis for nongroupable Neisseria meningitidis

Nongroupable Neisseria meningitidis may constitute one-third or more of meningococcal isolates recovered from the nasopharynx of human carriers. The genetic basis for nongroupability was determined in isolates obtained from a population-based study in which 60 (30.9%) of 194 meningococcal isolates from asymptomatic carriers were not groupable. Forty-two percent of nongroupable isolates were related to serogroup Y ET-508/ST-23 clonal complex strains, the most common groupable carrier isolate from the study population. Nongroupable isolates were all rapidly killed by 10% normal human serum. The capsule loci of 6 of the ET-508/ST-23 complex strains and of 25 other genetically diverse nongroupable meningococci were studied in detail. Serogroup A or novel capsule biosynthesis genes were not found. Nongroupable isolates were genetically serogroup Y, B, or C isolates that did not express capsule but were related to groupable isolates found in the population (class I); capsule deficient because of insertion element-associated deletions of capsule biosynthesis genes (class II); or isolates that lacked all capsule genes and formed a distinct genetic cluster not associated with meningococcal disease (class III).     

Genetic basis in plants for interactions with disease-suppressive bacteria

Plant health depends, in part, on associations with disease-suppressive microflora, but little is known about the role of plant genes in establishing such associations. Identifying such genes will contribute to understanding the basis for plant health in natural communities and to new strategies to reduce dependence on pesticides in agriculture. To assess the role of the plant host in disease suppression, we used a genetic mapping population of tomato to evaluate the efficacy of the biocontrol agent Bacillus cereus against the seed pathogen Pythium torulosum. We detected significant phenotypic variation among recombinant inbred lines that comprise the mapping population for resistance to P. torulosum, disease suppression by B. cereus, and growth of B. cereus on the seed. Genetic analysis revealed that three quantitative trait loci (QTL) associated with disease suppression by B. cereus explained 38% of the phenotypic variation among the recombinant inbred lines. In two cases, QTL for disease suppression by B. cereus map to the same locations as QTL for other traits, suggesting that the host effect on biocontrol is mediated by different mechanisms. The discovery of a genetic basis in the host for interactions with a biocontrol agent suggests new opportunities to exploit natural genetic variation in host species to enhance our understanding of beneficial plant-microbe interactions and develop ecologically sound strategies for disease control in agriculture.     

Surface hydrocarbons of queen eggs regulate worker reproduction in a social insect

A hitherto largely unresolved problem in behavioral biology is how workers are prevented from reproducing in large insect societies with high relatedness. Signals of the queen are assumed to inform the nestmates about her presence in the colony, which leads to indirect fitness benefits for workers. In the ant Camponotus floridanus, we found such a signal located on queen-laid eggs. In groups of workers that were regularly provided with queen-laid eggs, larvae, and cocoons, with larvae and cocoons alone, or with no brood, only in the groups with queen-laid eggs did workers not lay eggs. Thus, the eggs seem to inform the nestmates about the queen's presence, which induces workers to refrain from reproducing. The signal on queen-laid eggs is presumably the same that enables workers to distinguish between queen- and worker-laid eggs. Despite their viability, the latter are destroyed by workers when given a choice between both types. Queen- and worker-laid eggs differ in their surface hydrocarbons in a way similar to the way fertile queens differ from workers in the composition of their cuticular hydrocarbons. When we transferred hydrocarbons from the queen cuticle to worker-laid eggs, the destruction of those eggs was significantly mitigated. We conclude that queen-derived hydrocarbon labels inform workers about the presence of a fertile queen and thereby regulate worker reproduction.     

Genetic basis of arterial calcification for diabetes mellitus

Frequency of arterial calcification is high in diabetic patients, particularly in those with end-stage renal disease. A familial syndrome of aortic calcification, difference in the prevalence of arterial calcification among different races and different strains of mice suggest the contribution of genetic factor to arterial calcification. Among candidate genes, a common polymorphism in the promoter of Matrix matalloproteinase 3 gene (MMP3) has been reported to be associated with arterial calcification. Elucidation of genetic basis of arterial calcification will contribute to develop effective methods for prediction, prevention and intervention of this complication.     

Molecular basis for the resistance of an insect chymotrypsin to a potato type II proteinase inhibitor

Plants produce a variety of proteinase inhibitors (PIs) that have a major function in defense against insect herbivores. In turn, insects have developed strategies to minimize the effect of dietary PIs on digestion. We have discovered that Helicoverpa larvae that survive consumption of a multidomain serine PI from Nicotiana alata (NaPI) contain high levels of a chymotrypsin that is not inhibited by NaPI. Here we describe the isolation of this NaPI-resistant chymotrypsin and an NaPI-susceptible chymotrypsin from Helicoverpa larvae, together with their corresponding cDNAs. We investigated the mechanism of resistance by mutating selected positions of the NaPI-susceptible chymotrypsin using the corresponding amino acids of the NaPI-resistant chymotrypsin. Four critical residues that conferred resistance to NaPI were identified. Molecular modeling revealed that a Phe→Leu substitution at position 37 in the chymotrypsin results in the loss of important binding contacts with NaPI. Identification of the molecular mechanisms that contribute to PI resistance in insect digestive proteases will enable us to develop better inhibitors for the control of lepidopteran species that are major agricultural pests worldwide.     

Cross-reactivity between Trypanosoma cruzi and insect trypanosomatids as a basis for the diagnosos of Chagas' disease

Immunological cross-reactivity between Trypanosoma cruzi and insect trypanosomatids was demonstrated by immunofluorescence and confirmed by complement fixation, direct agglutination and cross-absorption experiments. As antigens, the following organisms were surveyed: Crithidia deanei, Crithidia fasciculata, Crithidia luciliae, Herpetomonas samuelpessoai, Herpetomonas megaseliae, Herpetomonas muscarum muscarum, Leptomonas seymouri and Blastocrithidia culicis. Sera from patients with Chagas' disease or sera from rabbits immunized against various trypanosomatids were used as sources of antibodies. The demonstration of cross-reactivity was followed by a survey of 500 human sera (from normal persons or Chagas' disease patients) by immunofluorescence using insect trypanosomatids (H. muscarum muscarum, C. fasciculata and L. seymouri) as antigens. With H. muscarum muscarum 98.7% coincident positive results and 100% of coincident negative results were obtained. These findings may validate the use of insect trypanosomatids as an alternative source of antigen in the serodiagnosis of Chagas' disease by indirect immunofluorescence.     

The development of immunity in a social insect: evidence for the group facilitation of disease resistance

The extraordinary diversity and ecological success of the social insects has been attributed to their ability to cope with the rich and often infectious microbial community inhabiting their nests and feeding sites. Mechanisms of disease control used by eusocial species include antibiotic glandular secretions, mutual grooming, removal of diseased individuals from the nest, and the innate and adaptive immune responses of colony members. Here we demonstrate that after a challenge exposure to the entomopathogenic fungus Metarhizium anisopliae, dampwood termites Zootermopsis angusticollis have higher survivorship when individuals develop immunity as group members. Furthermore, termites significantly improve their ability to resist infection when they are placed in contact with previously immunized nestmates. This "social transfer" of infection resistance, a previously unrecognized mechanism of disease control in the social insects, could explain how group living may improve the survivorship of colony members despite the increased risks of pathogen transmission that can accompany sociality.     

Genetic basis of pancreatic cancer

Because in the normal state, cells of the pancreas show a very low rate of proliferation, entering the cell cycle is assumed to be the initial event during tumorigenesis. So-called checkpoints monitor cell cycle progression and guarantee the proper duplication of the entire genome. Loss of one or more checkpoints causes subsequent accumulation of genetic alterations which finally results in cancer. Cancer cells are characterized by unrestricted growth, invasion of adjacent tissue and metastasis. All of these features can be explained in terms of genetic changes and the functional consequence of these changes. Activation of the proto-oncogene K-Ras and inactivation of the tumour suppressor gene loci INK4a, p53 and SMAD4 are characteristic for pancreatic cancer. The progression model of pancreatic cancer proposes that pancreatic intraepithelia neoplasia is the pre-cancerous lesion. A preferred genetic pathway has started to evolve. Germ-line mutations in specific genes are responsible for cases in which there is a familial predisposition to pancreatic cancer.     

Genetic basis of ankylosing spondylitis

Ankylosing spondylitis (AS) is a common rheumatic condition, highly heritable. Much of the genetic contribution to the disease lies in the major histocompatibility complex (MHC). The association with the allele group HLA-B*27 has been described worldwide for 30 years. On the other hand, genome wide scans have provided some interesting results showing that other MHC and non-MHC genes could be implicated either in disease susceptibility and phenotypic manifestations. Different hypothesis for disease pathophysiology have been investigated which contribute for a better understanding of the genetic basis of AS. This review aims to summarize the status of the knowledge in this exciting area. New data may, in a near future, change the screening of patients and generate new insights for the emergence of novel therapies.     

Genetic basis of Fanconi anemia

Fanconi anemia is a rare autosomal recessive disease characterized by bone marrow failure, developmental anomalies, a high incidence of myelodysplasia and acute nonlymphocytic leukemia, and cellular hypersensitivity to cross linking agents. Five of the seven known Fanconi anemia proteins bind together in a complex and influence the function of a sixth, FANCD2, which colocalizes with BRCA1 in nuclear foci after genotoxic stress. Carboxy-terminal truncating mutations of the seventh Fanconi anemia gene, BRCA2, are hypomorphic and lead to FA-D1 and possibly FA-B. Because the Fanconi anemia alleles of BRCA2 fail to bind to Rad51 in response to genotoxic stress and Rad51 therefore fails to localize to nuclear damage foci, many investigators in the field suspect that the Fanconi anemia pathway supports the integrity of the Rad51 and BRCA1 and BRCA2 pathways as they function in homologous recombination repair. Because these abnormalities are common to all somatic cells, it is unlikely that dysfunction of this particular pathway results in tissue-specific apoptosis of hematopoietic cells. Indeed, at least one of the Fanconi anemia proteins, FANCC, exhibits functions in hematopoietic cells in addition to its role in the complex. Because FANCC protects hematopoietic cells from apoptotic cues in ways that do not require an intact heteromeric Fanconi anemia complex, it is reasonable to expect that the other Fanconi anemia gene products will have independent cytoplasmic and nuclear functions, particularly in hematopoietic and germ cells that seem to rely so substantially on an intact portfolio of Fanconi anemia proteins.     

Genetic basis of cardiomyopathy.

The molecular basis of cardiac growth and development is a fundamental question that has intrigued many investigators in cardiovascular research. Adult cardiomyocytes are terminally differentiated and lose their ability to proliferate shortly after birth; however, in response to injury, myocytes have the capacity to synthesize new DNA and exhibit plasticity by a compensatory growth response, as is shown by re-expression of the fetal isoforms of many muscle-specific genes, which is characteristic of the proliferative response. The long-term effects of these compensatory responses may lead to the development and progression of diseases such as hypertrophic cardiomyopathy and dilated cardiomyopathy, because of a single point mutation. This concept has engaged scientists to investigate human models to explore the molecular basis of hypertrophy or dilation of the myocardium.     

Genetic basis of ventricular arrhythmias

Sudden cardiac death caused by malignant ventricular arrhythmias is the most important cause of death in the industrialized world. Most of these lethal arrhythmias occur in the setting of ischemic heart disease. A significant number of sudden deaths, especially in young individuals, are caused by inherited ventricular arrhythmic disorders, however. Genetically induced ventricular arrhythmias can be divided in two subgroups: the primary electrical disorders or channelopathies, and the secondary arrhythmogenic cardiomyopathies. This article focuses on the genetic background of these electrical disorders and the current knowledge of genotype-phenotype interactions.     

心房颤动的遗传学研究

心房颤动多见于老年人,通常伴有器质性心脏病,也可无心脏病基础的称为孤立性房颤或特发性房颤,少部分呈家族遗传倾向。随着分子生物学技术的深入研究,发现家族性房颤的比例较以往增高,现针对心房颤动的遗传学研究作一综述。     

Genetic basis of chronic pancreatitis

BACKGROUND: Pancreatitis has a proven genetic basis in a minority of patients. METHODS: Review of the literature on genetics of pancreatitis. RESULTS: Ever since the discovery that in most patients with hereditary pancreatitis a mutation in the gene encoding for cationic trypsinogen (R122H) was found that results in a gain of trypsin function', many other mutations in the cationic trypsinogen gene, as well as in the gene encoding for pancreatic secretory trypsin inhibitor, have been found in patients with chronic pancreatitis. Furthermore, mutations in other genes, like the mucoviscoidosis-gene encoding for a chloride channel, and in genes encoding for enzymes involved in the metabolism of ethanol, have been linked to chronic pancreatitis. This article reviews the highlights that have been achieved in this field of pancreatic research. CONCLUSIONS: Recent data suggest that genetics may play a role in the pathogenesis of pancreatitis.     

自发性心室颤动的基因基础和分子机制

目的 通过研究心脏钠离子通道基因SCN5A的突变来了解是否离子通道的失常能够引起自发性心室颤动(IVF)，以帮助IVF的基因诊断和合理治疗。方法 我们用单链构型多态性(SSCP)和DNA序列分析法对伴有IVF的六个小家系和两个散发的病人的血样，在已知离子通道基因，包括心脏钠离子通道基因SCN5A上进行了识别突变的研究。并通过测试突变通道和正常通道在卵母细胞中的电生理活动来判定突变对IVF发生机制的影响。结果 我们已经在三个IVF家族中从SCN5A密码范围内识别了一个错义突变和一个读码突变。电生理研究显示含有错义突变的钠离子通道比正常通道从静止中恢复的更快，而读码突变使钠离子通道失去功能。结论 我们的工作显示了伴有RBBB和ST段抬高的IVF是一种明显的综合症，并且心脏钠通道基因SCN5A与IVF的发生密切相关。