Genetic variations in regulatory pathways of fatty acid and glucose metabolism are associated with obesity phenotypes: a population-based cohort study.

BACKGROUND: As nuclear receptors and transcription factors have an important regulatory function in adipocyte differentiation and fat storage, genetic variation in these key regulators and downstream pathways may be involved in the onset of obesity. OBJECTIVE: To explore associations between single nucleotide polymorphisms (SNPs) in candidate genes from regulatory pathways that control fatty acid and glucose metabolism, and repeated measurements of body mass index (BMI) and waist circumference in a large Dutch study population. METHODS: Data of 327 SNPs across 239 genes were analyzed for 3575 participants of the Doetinchem cohort, who were examined three times during 11 years, using the Illumina Golden Gate assay. Adjusted random coefficient models were used to analyze the relationship between SNPS and obesity phenotypes. False discovery rate q-values were calculated to account for multiple testing. Significance of the associations was defined as a q-value < or = 0.20. RESULTS: Two SNPs (in NR1H4 and SMARCA2 in women only) were significantly associated with both BMI and waist circumference. In addition, two SNPs (in SIRT1 and SCAP in women only) were associated with BMI alone. A functional SNP, in IL6, was strongly associated with waist. CONCLUSION: In this explorative study among participants of a large population-based cohort, five SNPs, mainly located in transcription mediator genes, were strongly associated with obesity phenotypes. The results from whole genome and candidate gene studies support the potential role of NR1H4, SIRT1, SMARCA2 and IL6 in obesity. Although replication of our findings and further research on the functionality of these SNPs and underlying mechanism is necessary, our data indirectly suggest a role of GATA transcription factors in weight control.

Novel insight in the association between salmonellosis or campylobacteriosis and chronic illness, and the role of host genetics in susceptibility to these diseases.

We studied the role of host genetics in the susceptibility to severe Salmonella and Campylobacter infections and chronic sequelae of these infections. Participants of a previous case-control study were sent a buccal swab kit and a questionnaire about occurrence of chronic sequelae. Single nucleotide polymorphisms (SNPs) in the TLR4 (rs4986790), IFNG (rs2430561 and rs1861493), STAT1 (rs1914408), IL1B (rs16944), NRAMP (SLC11A1 rs2276631), JUN (rs11688) and VDR (rs10735810) genes were determined. In total, 687 controls, 457 Campylobacter cases and 193 Salmonella cases participated. None of the SNPs were associated with Campylobacter or Salmonella infections. None of the participants developed Guillain-Barré, Miller-Fisher or Reiter's syndrome. Reactive arthritis occurred in 5% and 2% of cases and controls, respectively. Campylobacter cases more frequently experienced gastroenteritis episodes than controls. Campylobacter or Salmonella infection in women, use of proton pump inhibitors and an SNP in the IFNG gene were independent risk factors for reactive arthritis. Another SNP in the IFNG gene and use of proton pump inhibitors were risk factors for recurrent episodes of gastroenteritis. In conclusion, reactive arthritis and recurrent gastroenteritis episodes are common after infection and host genetic factors play a role in susceptibility to these long-term health effects.

Genetic variation in the response to vaccination.

Vaccines are the most powerful means to prevent and diminish the burden of infectious disease. However, there are limitations to their use: vaccines are not yet available for all infectious diseases (including human immunodeficiency virus and respiratory syncytial virus), they sometimes lack efficacy, the response to vaccination is limited by maternal antibodies in very young infants, and the response to vaccination is variable or may even be absent in some individuals. This review focuses on genetic factors that determine the variable response to vaccination. The highly polymorphic human leukocyte antigen system, which is involved in antigen presentation, has been researched most in this aspect, and clearly affects the response to vaccination. Other, but less polymorphic pathways involved are the Toll-like receptor pathway, which is involved in antigen recognition and stimulation of the immune system, and the cytokine immunoregulatory network. The heritability, or the proportion of total variance that is due to additive genetic factors, appears to be particularly large for vaccine-induced antibody responses in young infants compared with cell-mediated responses and antibody responses in older, immunologically more mature individuals. Both antibody and cell-mediated responses are not only affected by loci within, but also strongly by loci outside the human leukocyte antigen system. Because most genes that are important in influencing immune responses to vaccination are still unknown, clearly more work is required. A better understanding of the factors that determine an effective response to vaccination may lead to the identification of specific genes and pathways as targets for the development of novel more uniformly effective vaccines.

Genetic variation in thioredoxin interacting protein (TXNIP) is associated with hypertriglyceridaemia and blood pressure in diabetes mellitus.

AIMS: Thioredoxin interacting protein (TXNIP) is an attractive candidate gene for diabetes or diabetic dyslipidaemia, since TXNIP is the strongest glucose-responsive gene in pancreatic B-cells, TXNIP deficiency in a mouse model is associated with hyperlipidaemia and TXNIP is located in the 1q21-1q23 chromosomal Type 2 diabetes mellitus (DM) locus. We set out to investigate whether metabolic effects of TXNIP that were previously reported in a murine model are also relevant in human Type 2 DM. METHODS: The frequency distribution of a 3' UTR single nucleotide polymorphism (SNP) in TXNIP was investigated in subjects with normal glucose tolerance (NGT; n = 379), impaired glucose tolerance (IGT; n = 228) and Type 2 DM (n = 230). Metabolic data were used to determine the effect of this SNP on parameters associated with lipid and glucose metabolism. RESULTS: The frequency of the TXNIP variation did not differ between groups, but within the group of diabetic subjects, carriers of the TXNIP-T variant had 1.6-fold higher triglyceride concentrations (P = 0.015; n = 136) and a 5.5-mmHg higher diastolic blood pressure (P = 0.02; n = 212) than homozygous carriers of the common C-allele, whereas in non-diabetic subjects fasting glucose was 0.26 mmol/l lower (P = 0.002; n = 478) in carriers of the T-allele. Moreover, a significant interaction between plasma glucose concentrations and TXNIP polymorphism on plasma triglycerides was observed (P = 0.012; n = 544). CONCLUSION: This is the first report to implicate TXNIP in a human disorder of energy metabolism, Type 2 diabetes. The effect of TXNIP on triglycerides is influenced by plasma glucose concentrations, suggesting that the biological relevance of TXNIP variations may be particularly relevant in recurrent episodes of hyperglycaemia.

[Effect of genetic polymorphisms on the susceptibility to and course of infectious diseases]. / Invloed van genetische polymorfismen op de gevoeligheid voor en het beloop van infectieziekten.

The highly variable susceptibility to and course of infectious diseases are caused by variable environmental factors and by genetic differences in both the pathogens and the host. The genetic variability of the host is determined mainly by polymorphisms in genes that play a role in processes such as adhesion, specific and non-specific immunity, antigen presentation, and inflammation. These variations are important, for example, in infections with HIV or respiratory syncytial virus. It is important to combine genetic knowledge with knowledge about the functional properties of variant genes. Applications of knowledge about genetic variability can be found in the development of vaccines and therapeutic agents, prognostics, and the treatment of individual patients.

Host genetics of Bordetella pertussis infection in mice: significance of Toll-like receptor 4 in genetic susceptibility and pathobiology.

The susceptibility to and the severity of Bordetella pertussis infections in infants and children varies widely, suggesting that genetic differences between individuals influence the course of infection. We have previously identified three novel loci that influence the severity of whooping cough by using recombinant congenic strains of mice: Bordetella pertussis susceptibility loci 1, 2, and 3 (Bps1, -2, and -3). Because these loci could not account for all genetic differences between mice, we extended our search for additional susceptibility loci. We therefore screened 11 inbred strains of mice for susceptibility to a pertussis infection after intranasal infection. Susceptibility was defined by the number of bacteria in the lungs, being indicative of the effect between the clearance and replication of bacteria. The most resistant (A/J) and the most susceptible (C3H/HeJ) strains were selected for further genetic and phenotypic characterization. The link between bacterial clearance and chromosomal location was investigated with 300 F2 mice, generated by crossing A/J and C3H/HeJ mice. We found a link between the delayed clearance of bacteria from the lung and a large part of chromosome 4 in F2 mice with a maximum log of the odds score of 33.6 at 65.4 Mb, which is the location of Tlr4. C3H/HeJ mice carry a functional mutation in the intracellular domain of Tlr4. This locus accounted for all detectable genetic differences between these strains. Compared to A/J mice, C3H/HeJ mice showed a delayed clearance of bacteria from the lung, a higher relative lung weight, and increased body weight loss. Splenocytes from infected C3H/HeJ mice produced almost no interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha) upon ex vivo restimulation with B. pertussis compared to A/J mice and also showed a delayed gamma interferon (IFN-gamma) production. TNF-alpha expression in the lungs 3 days after infection was increased fivefold compared to uninfected controls in A/J mice and was not affected in C3H/HeJ mice. In conclusion, Tlr4 is a major host factor explaining the differences in the course of infection between these inbred strains of mice. Functional Tlr4 is essential for an efficient IL-1-beta, TNF-alpha, and IFN-gamma response; efficient clearance of bacteria from the lung; and reduced lung pathology.

Polymorphisms in the NPY and AGRP genes and body fatness in Dutch adults.

OBJECTIVE: To investigate the association between DNA polymorphisms in the NPY and AGRP genes and body fatness. DESIGN AND METHODS: The association between the AGRP Ala67Thr or the NPY Leu7Pro polymorphisms and indicators of body fatness (baseline leptin levels, body mass index (BMI) values and prevalence of overweight) are investigated in 582 participants of two large cohorts in The Netherlands (total 18 500 adult men and women), aged 20-40 years whose weight remained relatively constant or whose weight increased substantially (range 5.5-47 kg) during a mean follow-up of 7 years. RESULTS: No consistent associations were found for the indicators of body fatness for men and women. Among women, BMI values, leptin levels and prevalence of overweight were not statistically different for carriers of the mutant alleles compared to that of the non-carriers. Among men, carriers of the Thr67-allele of the AGRP gene had similar leptin levels, but higher BMI values compared to those with the genotyping Ala67/Ala67: mean adjusted BMI 25.6 kg/m2 (95% CI 24.3-27.0) vs 23.9 kg/m2 (23.6-24.3). Also, the risk of being overweight at baseline tended to be higher for male carriers of the Thr67-allele of the AGRP gene (OR 2.52; 95% CI 0.86-7.4). Furthermore, male carriers of the Pro7-allele of the NPY gene had on average higher leptin levels and BMI values vs non-carriers of this allele: 4.7 microg/l (95% CI 3.7-6.0) and 25.7 kg/m2 (95% CI 24.4-27.0) vs 3.1 microg/l (95% CI 2.9-3.4) and 23.9 kg/m2 (95% CI 23.5-24.3), respectively. These male carriers had also a higher risk on being overweight at baseline (OR 3.3 (95% CI 1.2-8.9)) compared to non-carriers of the Pro7-allele. CONCLUSION: The consistent findings among men suggest that the NPY Leu7Pro polymorphism (or another linked marker) might be involved in the development of obesity at younger ages. The findings for the AGRP Ala67Thr were less consistent and need further investigation. Among women, these polymorphisms do not play an important role.

Influence of beta(2)-adrenoceptor gene polymorphisms on diet-induced thermogenesis.

The sympathetic nervous system is involved in the control of energy metabolism and expenditure. Diet-induced thermogenesis is mediated partly by the ss-adrenergic component of this system. The aim of the present study was to investigate the role of genetic variation in the beta(2)-adrenoceptor in diet-induced thermogenesis. Data from twenty-four subjects (fourteen men and ten women; BMI 26.7(sem 0.8) kg/m(2); age 45.2(sem1.4) years) with different polymorphisms of the beta(2)-adrenoceptor at codon 16 (Gly16Gly, Gly16Arg or Arg16Arg) were recruited for this study. Subjects were given a high-carbohydrate liquid meal, and the energy expenditure, respiratory exchange ratio, and plasma concentrations of NEFA, glycerol, glucose, insulin and catecholamines were measured before and over 4 h after the meal. The AUC of energy expenditure (diet-induced thermogenesis) was not significantly different between polymorphism groups, nor was the response of any of the other measured variables to the meal. In a multiple regression model, the only variable that explained a significant proportion (32 %) of the variation in diet-induced thermogenesis was the increase in plasma adrenaline in response to the meal (P<0.05). The beta(2)-adrenoceptor codon16 polymorphisms did not contribute significantly. In conclusion, an independent contribution of the codon 16 polymorphism of the beta(2)-adrenoceptor gene to the variation in thermogenic response to a high-carbohydrate meal could not be demonstrated. The interindividual variation in thermogenic response to the meal was correlated with variations in the plasma adrenaline response to the meal.

Common variants in the ATP-sensitive K+ channel genes KCNJ11 (Kir6.2) and ABCC8 (SUR1) in relation to glucose intolerance: population-based studies and meta-analyses.

AIMS: To evaluate the relation between common variants in the ATP-sensitive K+ channel genes and glucose intolerance. METHODS: We conducted a meta-analysis of reported association studies in Caucasian populations for common variants in the ABCC8 (exons 16 and 18) and the KCNJ11 (E23K) gene and examined sources of heterogeneity in the results. The meta-analysis was based on 7768-10216 subjects (depending on the gene variant), and included two new population-based studies in the Netherlands with 725 cases and 742 controls. RESULTS: For the KCNJ11 variant, the summary odds ratio (OR) for glucose intolerance was 1.12 (1.01-1.23, P=0.03) for the EK genotype and 1.44 (1.17-1.78, P=0.0007) for the KK genotype, as compared with the EE genotype. For the ABCC8 exon 16 variant, the OR was 1.06 (0.94-1.19, P=0.34) for ct and 0.93 (0.71-1.20, P=0.56) for tt, as compared with the cc genotype. For ABCC8 exon 18, the OR was 1.20 (0.97-1.49, P=0.10) for CT/TT, as compared with the CC genotype. Studies of the ABCC8 variants that were published first or had smaller sample sizes (for the exon 18 variant) showed stronger associations, which may indicate publication bias. For the ABCC8 exon 18 and the KCNJ11 variant, associations were stronger for studies of clinical diabetes than newly detected glucose intolerance. The population attributable risk for clinical Type 2 diabetes was 6.2% for the KCNJ11 KK genotype and 10.1% for the KCNJ11 EK and KK genotype combined. CONCLUSIONS: The common KCNJ11 E23K gene variant, but not the ABCC8 exon 16 or exon 18 variant, was consistently associated with Type 2 diabetes.

beta2-adrenergic receptor polymorphisms and salbutamol-stimulated energy expenditure.

The beta-adrenergic system is involved in the control of energy metabolism and expenditure. The beta2-adrenergic receptor (beta2-AR) gene shows polymorphisms that have been associated with obesity in several studies. In vitro and in vivo studies suggest differences in beta2-AR-mediated function between these polymorphisms. The aim of this study was to investigate the influence of genetic variation in codon 16 of the beta2-AR gene on energy metabolism in humans. Thirty-four subjects were recruited [Gly16Gly (n = 13), Gly16Arg (n = 16), or Arg16Arg (n = 5)]. The beta2-AR was stimulated with two doses of salbutamol (50 and 100 ng/kg fat-free mass per minute) after blockade of the beta1-adrenergic receptors with atenolol. Energy expenditure and plasma substrate and hormone concentrations were measured. The increase in energy expenditure (DeltaEE) was significantly different among groups in which the Arg16Arg group showed the lowest increase (P < 0.05 vs. Gly carriers). In a multiple regression model, variations in the increase in nonesterified fatty acid concentration during salbutamol infusion (partial r = 0.51) and the polymorphism contributed significantly to the variation in DeltaEE. Thirty-five percent of the variation in DeltaEE was explained by these two factors. We conclude that subjects with the Arg16Arg polymorphism of the beta2-AR gene have a reduced thermogenic response to beta2-adrenergic stimulation. Although this relatively small study needs confirmation, the findings support a role for this polymorphism in the development and maintenance of overweight and obesity.

Genetic control of Bordetella pertussis infection: identification of susceptibility loci using recombinant congenic strains of mice.

Susceptibility to and severity of Bordetella pertussis infection in infants and children vary widely. The spectrum of clinical symptoms ranges from subclinical infection to mild disease, severe whooping cough, and death. The aims of this study were to examine genetic susceptibilities of mice to B. pertussis and to identify genetic loci in the mouse genome that are involved in susceptibility to B. pertussis infection. For this purpose we screened two sets of recombinant congenic strains (RCS) of mice, HcB and CcS, for differences in the numbers of bacteria in the lung 7 days after inoculation. For both CcS and in HcB mice, a wide range in numbers of bacteria in the lung was found, suggesting that the course of infection is under multigenic control. From both RCS sets of mice, we selected one strain to identify possible susceptibility loci in F(2) hybrid mice. The degree of lung colonization 7 days postinoculation in these F(2) mice was evaluated in relation to genetic markers by linkage analysis. We found three novel loci that are involved in the control of B. pertussis infection. One locus, designated B. pertussis susceptibility locus 1 (Bps-1), was identified on chromosome 12. The presence of the C57BL/10 genome on this locus instead of the C3H genome significantly decreased the number of B. pertussis bacteria in the lung. Bps-1 has a dominant-positive effect on the clearance of B. pertussis from the lung. The function of most genes in this region is unknown. Two other loci, Bps-2 and Bps-3, showed genetic interaction and are located on chromosomes 5 and 11. We aim to identify the gene(s) in these regions which modify susceptibility to B. pertussis.

The insulin receptor substrate-1 Gly972Arg polymorphism is not associated with Type 2 diabetes mellitus in two population-based studies.

AIMS: The insulin receptor substrate-1 (IRS-1) gene is among the most frequently studied candidate genes for Type 2 diabetes, but findings have been inconsistent. This may have been due to generally small study sizes, or to interaction with body fatness as suggested by studies of insulin sensitivity. The aim of this study was to test the hypothesis that the IRS-1 Gly972Arg variant increases risk of Type 2 diabetes. METHODS: We conducted two large population-based studies including a total of 725 cases and 742 control subjects, who were Caucasian Dutch men and women aged 40-70 years. We calculated odds ratios adjusted for body mass index, study centre, sex and age. RESULTS: Carriers of the Arg allele did not have a higher prevalence of newly detected (OR 0.49, 95% CI 0.24-1.01) or treated (OR 0.71, 0.37-1.35) Type 2 diabetes in the first study, or a higher prevalence of glucose intolerance (OR 1.07, 0.71-1.59) in the second study. The summary odds ratio was 0.86 (0.62-1.17) for carrying the Arg allele as compared with the Gly/Gly genotype. Associations did not differ appreciably by degree of obesity. Also, the Arg variant was not associated with detrimental values for body mass index, waist circumference, plasma HDL-and total cholesterol or hypertension. CONCLUSIONS: Our findings indicate that the IRS-1 Gly972Arg variant does not substantially increase risk of common Type 2 diabetes, or Type 2 diabetes in obese persons.

Genetic factors as predictors of weight gain in young adult Dutch men and women.

OBJECTIVE: To investigate the association between DNA polymorphisms in several candidate genes for obesity and weight gain. Polymorphisms in these genes may contribute to weight gain through effects on energy intake, energy expenditure or adipogenesis. DESIGN AND METHODS: From two large cohorts in The Netherlands (total 17,500 adult men and women), we compared 286 subjects aged 20-40 y who gained an average of 12.8 kg (range 5.5-47 kg) during a mean follow-up of 6.8 y with 296 subjects who remained relatively constant over the same period with respect to occurrence of several polymorphisms in candidate genes of obesity and some lifestyle factors. Subjects who were dieting, were high alcohol consumers, were pregnant, changed their smoking status recently, or those who suffered from serious illnesses were excluded. Polymorphisms were determined in the LEPR-gene (LEPR Lys109Arg, LEPR Gln223Arg, LEPR Lys656Asn), in the UCP1 gene (A-G mutation at position-3826 5' region), in the UCP2 gene (Ala55Val, 45 bp Ins/Del), in the PPARG2 gene (Pro12Ala) and in the ADRB2 gene (Gly16Arg and Gln27Glu). RESULTS: With the exception of the Gly16Arg polymorphism in the ADRB2 gene in men (P = 0.04) and women (P = 0.05), and the Lys109Arg polymorphism in the LEPR gene in women, no statistically significant differences in the genotype and allele frequencies were observed between weight gainers and non-weight gainers. Weight gainers differed in some aspects of dietary habits and physical activity patterns: weight gainers consumed relatively more savory snacks and were less active during leisure time compared with non-weight gainers. CONCLUSION: Only variations in the ADRB2 gene and LEPR gene, may contribute to susceptibility to weight gain. None of the other studied genetic markers were clearly associated with weight gain. Further research is necessary to establish the role of lifestyle factors, or interactions between genes or between genes and lifestyle factors on weight gain with age.

In vivo cytokinesis blocked micronucleus assay with carbendazim in rat fibroblasts and comparison with in vitro assays.

A successful in vivo application of the cytokinesis blocked micronucleus assay for the detection of aneuploidy induced by carbendazim (CARB) was carried out in the granuloma pouch assay. This was performed in two ways: (i) in vivo exposure of the skin fibroblasts to cytochalasin B (cytB) and CARB, by simultaneous injection of both substances into the pouch; (ii) in vivo exposure to CARB followed by in vitro culturing of the fibroblasts in the presence of cytB. Only the first assay was successful. Injection of cytB (with or without the test compound) into the pouch resulted in the induction of binucleate cells in vivo, up to a maximum of 5% at 1 mg cytB/pouch. After injection of CARB (0-50 or 0-10 mg/pouch) and cytB (1 mg) into the pouch, aneuploidy was determined in the isolated binucleate fibroblasts by fluorescence in situ hybridization with a general centromeric probe and combinations of chromosome-specific probes (19p + 19q, 4q + Yq). With all probes, the induction of chromosome loss and/or non-disjunction by CARB was very pronounced; at 10 mg CARB/pouch the total malsegregation frequency of chromosomes 4, 19 and Y was approximately 300/1000 binucleate cells. In an in vitro cytokinesis block assay with CARB (0-2.5 microg/ml) in primary skin fibroblasts the induced aneuploidy frequencies were as high as observed in the in vivo assay. The use of two probes for chromosome 19, which enabled the scoring of chromosome breaks in addition to aneuploidy, revealed no significant induction of chromosome breaks by CARB. The frequency of polyploid mononucleate and binucleate cells was decreased after CARB treatment, in both the in vivo and in vitro assays. However, in an additional in vitro assay without cytB a major induction of polyploidy from 2.5 microg/ml CARB and above was observed, showing that cytB may interfere with polyploidy induction.

Isolation of DNA probes specific for rat chromosomal regions 19p, 19q and 4q and their application for the analysis of diethylstilbestrol-induced aneuploidy in binucleated rat fibroblasts.

DNA probes specific for rat chromosomes 19p, 19q and 4q were isolated, characterized and used for the detection and analysis of diethylstilbestrol(DES)-induced aneuploidy. By denaturing and partially reassociating total genomic DNA a new rat repetitive DNA family was isolated, which was located on chromosome 19p21. Sequencing of a number of subclones from cos76-1 and other clones of this so-called 76-family revealed that the repeat units are interrupted with large areas of other (unique) DNA. Consequently, after fluorescence in situ hybridization (FISH) the signals in interphase nuclei are large and spread out. The other two probes, cos25 (chromosome 4q) and cos42-47 (chromosome 19q), were isolated by screening cosmid libraries with probes isolated previously in our laboratory. The repeat unit of cos25 is a 2174 bp long EcoRI unit that contains three Sau3A sites and is tandemly organized. Sequencing of subclones of cos42-47 revealed that this probe was in fact the 5S RNA gene, located on 19q12. In order to determine if these probes were suitable probes for aneuploidy detection, two series of dual colour FISH with the combinations cos25/cos76-1 (4q/19p) and cos42-47/cos76-1 (19q/19p) were carried out on slides from an in vitro micronucleus assay with DES. With all three probes used, an increase in binucleated cells with non-disjunction or chromosome loss was observed in the DES-treated cultures. Scoring of additional micronucleated cells on slides hybridized with the cos25/cos76-1 (4q/19p) probes revealed that the hybridization signal of probe cos25 (4q) was over-represented in the micronuclei of the control cultures. The simultaneous use of the 19q and 19p probes is a particularly valuable tool for the detection of aneuploidy, since it allows distinction between aneugenic and clastogenic events in binucleated cells. Results of this analysis showed that apart from aneuploidy, DES also induced structural chromosome aberrations, although to a lesser extent.

Increased frequencies of diploid sperm detected by multicolour FISH after treatment of rats with carbendazim without micronucleus induction in peripheral blood erythrocytes.

The purpose of the present study was to determine the effect of a single oral dose of carbendazim (CARB) on the frequencies of numerical chromosome aberrations in sperm and on micronuclei in peripheral blood erythrocytes of rats. Dual colour FISH on epididymal sperm of rats treated 31 days before sacrifice (0, 50, 150, 450 and 800 mg/kg body wt CARB in corn oil), corresponding to exposure during late pachytene, revealed a clear induction of diploid sperm. Induction of aneuploid sperm was not observed. Although the absolute frequencies of diploidy were low, ranging from 0.03% in the control group to 0.22% in the highest dose group, the observed dose-response relationship was highly significant. In sperm of rats killed 50 days after treatment with CARB (corresponding to exposure of spermatogonial stem cells) the effect was no longer apparent. In a second experiment, in addition to more dose groups in the low dose range, the peripheral blood micronucleus assay was incorporated. Results of triple colour FISH on epididymal sperm of rats treated with CARB (0-800 mg/kg body wt) again showed induction of diploid, but not of aneuploid sperm. Induction was less prominent than in the first experiment, but the dose-response relationship for diploidy was again significant. In blood samples drawn from the tail vein 48 h after treatment with CARB induction of micronuclei in peripheral blood erythrocytes was not observed, whereas the micronucleus frequency was significantly increased after a single i. p. dose of mitomycin C (3 mg/kg body wt). In conclusion, the present results show that CARB induces diploidy in sperm, without an accompanying induction of micronuclei in erythrocytes. This finding suggests that in rats the peripheral blood micronucleus assay is a less sensitive indicator for the genotoxic potential of CARB than the epididymal sperm aneuploidy/diploidy assay.

Improved linkage map and thirty new microsatellite markers for rat Chromosome 10.

An improved linkage map for rat Chromosome (Chr) 10 with two F2 populations was constructed. Thirty new microsatellite markers were generated from a Chr 10-specific, small-insert genomic library and mapped to rat Chr 10. Among them were the rat homologs for the mouse gene for light and heavy chains of myeloperoxidase and human neurofibromatosis 1. Eight newly generated markers (D10Mco62, D10Mco63, D10Mco64, D10Mco65, D10Mco67, D10Mco68, D10Mco70, and D10Mco74) were mapped to the region of the rat Chr 10 blood pressure QTL. The availability of such markers may be instrumental in the search for genes responsible for the hypertension.

Rat Chromosome 2: assignment of the genes encoding cyclin B1, interleukin 6 signal transducer, and proprotein convertase 1 to the Mcs1-containing region and identification of new microsatellite markers.

The rat Chromosome (Chr) 2 harbors several genes controlling tumor growth or development, blood pressure, and non-insulin-dependent diabetes mellitus. We report that the region (2q1) containing the mammary susceptibility cancer gene Mcs1 also harbors the genes encoding cyclin B1, interleukin 6 signal transducer (gp130), and proprotein convertase 1. We also generated 13 new anonymous microsatellite markers from Chr 2-sorted DNA. These markers, as well as a microsatellite marker in the cyclin B1 gene, were genetically mapped in combination with known markers. A cyclin B1-related gene was also cytogenetically assigned to rat Chr 11q22-q23.

Linkage mapping of fifty-eight new rat microsatellite markers.

Fifty-eight new anonymous simple sequence repeats (SSR) were generated and mapped to various rat chromosomes. Among them two genes (rat homologs for human cadherin-14 and mouse fibroblast growth factor-related protein) were mapped on Chromosomes (Chrs) 2 and 11 respectively. The majority of markers were generated from a small insert genomic library specific to Chr 11, 13, 14, and 15. Twenty new markers were mapped to Chr 13, which is known to contain a blood pressure quantitative trait locus (QTL). Several approaches to obtain microsatellite markers are described. The protocols and newly generated markers should be useful for ongoing rat genome project.

Linkage analysis and construction of a congenic strain for a blood pressure QTL on rat chromosome 9.

A blood pressure quantitative trait locus was found (LOD = 5.0) on rat chromosome 9 using a large F2 population (N = 233) derived from Dahl salt-sensitive (S) and Dahl salt-resistant (R) rats. The F2 rats were fed 8% NaCl diet for 8 weeks. A congenic strain introgressing the R low-blood-pressure QTL allele on chromosome 9 into the S strain was constructed. The congenic strain, designated S.R(chr 9), had a lower blood pressure (19 mm Hg, P < 0.0001) and lower heart weight (112 mg, P < 0.0001) than S rats (2% NaCl diet for 24 days), proving the existence of a blood pressure QTL in the congenic region of about 21 cM.