Transferability and fine-mapping of glucose and insulin quantitative trait loci across populations: CARe, the Candidate Gene Association Resource

AIMS/HYPOTHESIS

Hyperglycaemia disproportionately affects African-Americans (AfAs). We tested the transferability of 18 single-nucleotide polymorphisms (SNPs) associated with glycaemic traits identified in European ancestry (EuA) populations in 5,984 non-diabetic AfAs.

METHODS

We meta-analysed SNP associations with fasting glucose (FG) or insulin (FI) in AfAs from five cohorts in the Candidate Gene Association Resource. We: (1) calculated allele frequency differences, variations in linkage disequilibrium (LD), fixation indices (F(st)s) and integrated haplotype scores (iHSs); (2) tested EuA SNPs in AfAs; and (3) interrogated within ± 250 kb around each EuA SNP in AfAs.

RESULTS

Allele frequency differences ranged from 0.6% to 54%. F(st) exceeded 0.15 at 6/16 loci, indicating modest population differentiation. All iHSs were <2, suggesting no recent positive selection. For 18 SNPs, all directions of effect were the same and 95% CIs of association overlapped when comparing EuA with AfA. For 17 of 18 loci, at least one SNP was nominally associated with FG in AfAs. Four loci were significantly associated with FG (GCK, p = 5.8 × 10(-8); MTNR1B, p = 8.5 × 10(-9); and FADS1, p = 2.2 × 10(-4)) or FI (GCKR, p = 5.9 × 10(-4)). At GCK and MTNR1B the EuA and AfA SNPs represented the same signal, while at FADS1, and GCKR, the EuA and best AfA SNPs were weakly correlated (r(2) <0.2), suggesting allelic heterogeneity for association with FG at these loci.

CONCLUSIONS/INTERPRETATION

Few glycaemic SNPs showed strict evidence of transferability from EuA to AfAs. Four loci were significantly associated in both AfAs and those with EuA after accounting for varying LD across ancestral groups, with new signals emerging to aid fine-mapping.

ADAM17_i33708A>G polymorphism interacts with dietary n-6 polyunsaturated fatty acids to modulate obesity risk in the Genetics of Lipid Lowering Drugs and Diet Network study

BACKGROUND AND AIMS

The disintegrin and metalloproteinase ADAM17, also known as tumor necrosis factor alpha converting enzyme, is expressed in adipocytes. Importantly, elevated levels of ADAM17 expression have been linked to obesity and insulin resistance. Therefore, the aim of this study was to evaluate the association of six ADAM17 single nucleotide polymorphisms (SNPs) (m1254A>G, i14121C>A, i33708A>G, i48827A>C, i53440C>T, and i62781G>T) with insulin-resistance phenotypes and obesity risk, and their potential interactions with dietary polyunsaturated fatty acids (PUFA).

METHODS AND RESULTS

ADAM17 SNPs were genotyped in 936 subjects (448 men/488 women) who participated in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study. Anthropometrical and biochemical measurements were determined by standard procedures. PUFA intake was estimated using a validated questionnaire. G allele carriers at the ADAM17_m1254A>G polymorphism exhibited significantly higher risk of obesity (P=0.003), were shorter (P=0.017), had higher insulin (P=0.016), and lower HDL-C concentrations (P=0.027) than AA subjects. For the ADAM17_i33708A>G SNP, homozygotes for the A allele displayed higher risk of obesity (P=0.001), were heavier (P=0.011), had higher BMI (P=0.005), and higher waist measurements (P=0.023) than GG subjects. A significant gene-diet interaction was found (P=0.030), in which the deleterious association of the i33708A allele with obesity was observed in subjects with low intakes from (n-6) PUFA (P<0.001), whereas no differences in obesity risk were seen among subjects with high (n-6) PUFA intake (P>0.5)

CONCLUSION

These findings support that ADAM17 (m1254A>G and i33708A>G) SNPs may contribute to obesity risk. For the ADAM17_i33708A>G SNP, this risk may be further modulated by (n-6) PUFA intake.

The effect of a novel intergenic polymorphism (rs11774572) on HDL-cholesterol concentrations depends on TaqIB polymorphism in the cholesterol ester transfer protein gene

BACKGROUND AND AIMS

Several genes have been shown to individually affect plasma lipoprotein metabolism in humans. Studies on gene-gene interactions could offer more insight into how genes affect lipid metabolism and may be useful in predicting lipid concentrations. We tested for gene-gene interactions between TaqIB SNP in the cholesterol ester transfer protein (CETP) and three novel single nucleotide polymorphisms (SNPs), namely rs11774572, rs7819412 and rs6995374 for their effect on metabolic syndrome (MetS) components and related traits.

METHODS AND RESULTS

The aforementioned SNPs were genotyped in 1002 subjects who participated in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study. Lipids were measured by standard procedures and lipoprotein subfractions, by proton nuclear magnetic resonance spectroscopy. Polymorphism rs11774572 was significantly associated with MetS (P=0.020), mainly driven by the association of the C allele with lower HDL-C (P=0.043) and higher triglycerides (P=0.049) and insulin (P=0.040) concentrations than TT subjects. A significant interaction between SNPs rs11774572 and CETP-TaqIB SNPs was found for HDL-C concentrations (P=0.006) and for HDL (P=0.008) and LDL particle sizes (P=0.009), small LDL (P=0.004), and VLDL concentrations (P=0.021), in which TT homozygotes displayed higher HDL-C concentrations and for HDL and LDL particle sizes, and lower small LDL and VLDL concentrations than C carriers, if they were CETP B2 allele carriers (P values ranging from <0.001 to 0.001).

CONCLUSIONS

The rs11774572 polymorphism may play a role in the dyslipidemia that characterizes MetS. The interaction between rs11774572 and CETP-TaqIB SNPs on HDL-C concentrations provides some insights into the underlying mechanisms.

Common variants in the 5' region of the leptin gene are associated with body mass index in men from the National Heart, Lung, and Blood Institute Family Heart Study

Linkage of body mass index (BMI) to a broad region of chromosome 7q22-35 has been reported in multiple studies. We previously published a multipoint LOD score of 4.9 at D7S1804 for BMI from the National Heart, Lung, and Blood Institute Family Heart Study. Leptin (LEP), the human homolog of the mouse obesity (ob) gene, is positioned near the linkage peak and is the most prominent candidate gene in this region. Interest in LEP as a susceptibility gene for human obesity has led to numerous linkage and association studies, but the results of these studies are still controversial. In the present study, we employed family-based tests of association with both a quantitative measure of BMI adjusted for age and sex and a dichotomously defined obesity trait. We genotyped 29 single-nucleotide polymorphisms (SNPs) spanning 240 kb around the LEP gene in the 82 extended pedigrees with the strongest evidence for linkage. When the programs TRANSMIT and FBAT were used, a number of SNPs showed association in men but not women, for both the quantitative and qualitative trait definitions (P<.05). Five SNPs (H1328084, H1328083, H1328082, H1328081, and H1328080) positioned 2 kb beyond the previously defined promoter region showed strong association in single-marker and multiple-marker haplotype analysis. This five-marker haplotype (frequency 49% in this sample) is overtransmitted to obese offspring (P=.00005). All five of these SNPs are predicted to modify transcription-factor binding sites. This may indicate new functional variants in an extended promoter region of LEP.

Cytochrome P450 polymorphisms are associated with reduced warfarin dose

BACKGROUND

Warfarin use is complicated by an erratic dose response. Interpatient variability associated with warfarin therapy may be partly attributable to polymorphisms of the cytochrome P450 (CYP) complex. The purpose of this study was to ascertain the frequency and influence of CYP polymorphisms on warfarin dosing in our patient population.

METHODS

Patients receiving warfarin therapy were recruited from the inpatient divisions of our hospital. Genotyping for known polymorphic alleles of the CYP subfamilies CYP2C9 (CYP2C9*1, CYP2C9*2, and CYP2C9*3) and CYP2A6 (CYP2A6*1, CYP2A6*2) with the use of standard methods of polymerase chain reaction amplification was performed. An unpaired t test was used to statistically compare genotypes.

RESULTS

Genotype frequency in 38 patients is as follows: CYP2C9*1/CYP2C9*1, 71%; CYP2C9*1/CYP2C9*2, 21%; CYP2C9*2/CYP2C9*2, 3%; CYP2C9*1/CYP2C9*3, 5%; CYP2A6*1/CYP2A6*1, 95%; CYP2A6*1/CYP2A6*2, 5%. Compared to a wild-type genotype, the presence of the CYP2C9*2, CYP2C9*3, or CYP2A6*2 allele was associated with a significant reduction in weekly warfarin dose (mean weekly warfarin dose [+/- SE] for wild-type genotype was 0.397 +/- 0.024 mg/kg/wk vs 0.307 +/- 0.03 mg/kg/wk for carriers of CYP2C9*2, CYP2C9*3, or CYP2A6*2 polymorphism; P =.03).

CONCLUSIONS

Polymorphisms that impair warfarin metabolism are common, occurring in 34% of patients, and are associated with increased warfarin sensitivity. The use of genotypic information to prescribe more accurate doses of warfarin may increase the safety and efficacy of this medication.

Inheritance of the waist-to-hip ratio in the National Heart, Lung, and Blood Institute Family Heart Study

OBJECTIVE

Considering that waist-to-hip ratio (WHR) is a simple anthropometric measure of obesity and is a better predictor of coronary heart disease than body mass index (BMI), the genetic underpinnings of WHR are of interest. The inheritance pattern of WHR, before and after adjustment for BMI (WHR-BMI), was investigated in 2713 individuals from 1038 nuclear families in the National Heart, Lung, and Blood Institute Family Heart Study (NHLBI-FHS).

RESEARCH METHODS AND PROCEDURES

Waist and hip measurements were taken twice, and the means of the measurements were used to calculate the WHR. Adjustments for age were carried out separately by sex, using stepwise multiple regression procedures for WHR and WHR-BMI phenotypes. Segregation analysis was applied using the unified model as implemented in the computer program POINTER.

RESULTS

For age-adjusted WHR, the segregation results suggested an additive major gene that accounts for 35% of the phenotypic variance, and approximately 30% of the sample are homozygous for the "high" genotype. The results for age- and BMI-adjusted WHR were also compatible with a major gene; however, the multifactorial model provided the most parsimonious fit to the data.

DISCUSSION

Although the genetic mechanisms for several obesity traits have been studied, tests of Mendelian segregation on this simple anthropometric measure (WHR) have not been reported previously. This study provides evidence for the presence of a major gene for age-adjusted WHR, suggesting that it is an appropriate trait for further genetic analysis, especially because it has strong predictive value and probably relates biologically to cardiovascular risk.

Segregation analysis of serum uric acid in the NHLBI Family Heart Study

Segregation analysis was performed on the serum uric acid measurements from 523 randomly ascertained Caucasian families from the NHLBI Family Heart Study. Gender-specific standardized residuals were used as the phenotypic variable in both familial correlation and segregation analysis. Uric acid residuals were adjusted for age, age2, age3, body mass index (kg/m2), creatinine level, aspirin use (yes/no), total drinks (per week), HOMA insulin resistance index [(glucose * insulin)/22.5], diuretic use (yes/no), and triglyceride level. Sibling correlations (r=0.193) and parent-offspring correlations (r=0.217) were significantly different from zero, but these two familial correlations were not significantly different from one another. After adjustment for covariates, the heritability estimate for serum uric acid was 0.399. Segregation analysis rejected the "no major gene" model but was unable to discriminate between an "environmental" and a "Mendelian major gene" model. These results support the hypothesis that uric acid is a multifactorial trait possibly influenced by more than one major gene, modifying genes, and environmental factors.

Genomic scan for maximal oxygen uptake and its response to training in the HERITAGE Family Study

This study aimed to identify human genomic regions that are linked to maximal oxygen uptake (VO(2 max)) in sedentary individuals or to the responsiveness of VO(2 max) to a standardized endurance training program. The results of a genomic scan based on 289 polymorphic markers covering all 22 pairs of autosomes performed on the Caucasian families of the HERITAGE Family Study are presented. The mean spacing of the markers was 11 cM, and a total of 99 families and 415 pairs of siblings were available for the study. VO(2 max) in the sedentary state was adjusted for the effects of age, sex, body mass, fat mass, and fat-free mass, whereas the VO(2 max) response was adjusted for age and baseline level of the phenotype. Two analytic strategies were used: a single-point linkage procedure using all available pairs of siblings (SIBPAL) and a multipoint variance components approach using all the family data (SEGPATH). Results indicate that linkages at P values of 0.01 and better are observed with markers on 4q, 8q, 11p, and 14q for VO(2 max) before training and with markers on 1p, 2p, 4q, 6p, and 11p for the change in VO(2 max) in response to a 20-wk standardized endurance training program. These chromosomal regions harbor many genes that may qualify as candidate genes for these quantitative traits. They should be investigated in this and other cohorts.

The Na(+)-K(+)-ATPase alpha2 gene and trainability of cardiorespiratory endurance: the HERITAGE family study

The Na(+)-K(+)-ATPase plays an important role in the maintenance of electrolyte balance in the working muscle and thus may contribute to endurance performance. This study aimed to investigate the associations between genetic variants at the Na(+)-K(+)-ATPase alpha2 locus and the response (Delta) of maximal oxygen consumption (VO(2 max)) and maximal power output (W(max)) to 20 wk of endurance training in 472 sedentary Caucasian subjects from 99 families. VO(2 max) and W(max) were measured during two maximal cycle ergometer exercise tests before and again after the training program, and restriction fragment length polymorphisms at the Na(+)-K(+)-ATPase alpha2 (exons 1 and 21-22 with Bgl II) gene were typed. Sibling-pair linkage analysis revealed marginal evidence for linkage between the alpha2 haplotype and DeltaVO(2 max) (P = 0.054) and stronger linkages between the alpha2 exon 21-22 marker (P = 0.005) and alpha2 haplotype (P = 0.003) and DeltaW(max). In the whole cohort, DeltaVO(2 max) in the 3.3-kb homozygotes of the exon 1 marker (n = 5) was 41% lower than in the 8.0/3.3-kb heterozygotes (n = 87) and 48% lower than in the 8.0-kb homozygotes (n = 380; P = 0.018, adjusted for age, gender, baseline VO(2 max), and body weight). Among offspring, 10.5/10.5-kb homozygotes (n = 14) of the exon 21-22 marker showed a 571 +/- 56 (SE) ml O(2)/min increase in VO(2 max), whereas the increases in the 10.5/4.3-kb (n = 93) and 4.3/4.3-kb (n = 187) genotypes were 442 +/- 22 and 410 +/- 15 ml O(2)/min, respectively (P = 0.017). These data suggest that genetic variation at the Na(+)-K(+)-ATPase alpha2 locus influences the trainability of VO(2 max) in sedentary Caucasian subjects.

Association and linkage between an insulin-like growth factor-1 gene polymorphism and fat free mass in the HERITAGE Family Study

OBJECTIVE

To investigate the relationship between a DNA microsatellite marker in the insulin-like growth factor-1 (IGF-1) gene and body composition phenotypes before and following exposure to 20 weeks of aerobic exercise training in the HERITAGE Family Study.

DESIGN

A controlled intervention study: fat mass (FM), percentage body fat (%FAT), fat free mass (FFM), body mass index (BMI) and abdominal visceral fat (AVF) at baseline (B) and in response to training (delta=post minus pre-training value) were measured. Association and sib-pair linkage studies were undertaken.

SUBJECTS

A maximum of 502 Caucasian individuals (99 families; 190 parents and 312 adult offspring).

MEASUREMENTS

The polymorphism was typed by polymerase chain reaction and DNA sequencer. The body composition phenotypes were determined from the underwater weighing method, and AVF was assessed by computerized tomography scan.

RESULTS

11 alleles were found: the lengths ranged from 189 to 209 base pairs (bp), and the frequency of the most common allele, 189 bp, reached 0.71. In association studies, significant differences for B-FM, B-FFM and B-%FAT among the three genotypes (189 bp homozygotes, heterozygotes and non-carriers) were detected. The B-FM for 189 bp homozygotes was 19.7+/-0.6 kg, but 21.6+/-0.7 and 21.3+/-1.5 kg for the 189 bp heterozygotes and the non-189 bp carriers respectively (P=0.03 after adjustment for age, sex and generation). Differences among the three genotypes were also observed for B-%FAT (25.9+/-0.5 versus 27.4+/-0.6 and 26.6+/-1.2 kg; P<0.05) and B-FFM (53.7+/-0.4 versus 54.9+/-0.5 kg and 54.4+/-1.0 kg; P<0.05). No significant difference for B-AVF was found among the three genotypes. Following 20 weeks of endurance exercise, the 189 bp homozygotes gained only about half the amount of FFM compared with the other two IGF-1 genotypes (0.3+/-0.1 vs 0.7+/-0.1 and 0.5+/-0.2 kg; P=0.005). A strong linkage was observed between the IGF-1 marker and the changes in FFM (308 pairs of full sibs, P=0.0002) but only a suggestive linkage with B-AVF (352 pairs of full sibs, P<0.02)

CONCLUSION

Associations were detected between the IGF-1 gene marker and FM, %FAT and FFM at baseline, and a strong association with the changes in FFM in response to training. Moreover, the IGF-1 gene marker was found to be strongly linked to the changes in FFM in response to 20 weeks of endurance exercise and weakly linked to abdominal visceral fat in the sedentary state.

Relationship of human pancreatic cholesterol esterase gene structure with lipid phenotypes

Pancreatic cholesterol esterase is one of the enzymes that plays a pivotal role in cholesterol absorption. Differences in the genotype of this enzyme could affect the susceptibility of individuals to dyslipidemia and/or cardiovascular disease. We undertook this study to investigate if any correlation exists between restriction fragment length polymorphism in the human pancreatic cholesterol esterase gene and serum lipid levels. DNA from 96 healthy adults was restricted with Stu I, Southern blotted, and probed with cDNA of human pancreatic cholesterol esterase. Results revealed six distinct patterns which were classified as A, B, C, D, E, and F which had a population frequency of 1%, 34.5%, 49%, 12.5%, 1% and 2% respectively. Correlation of the distribution of lipid and lipoprotein levels by pattern and sex revealed a significant interaction between pattern type and HDL (p=0.03) in the most common group (group C) for males. Male patients of pattern C tended to have a lower LDL cholesterol than non-pattern C males (p=0.07); in addition, 80% of all males in the study population with LDL cholesterol under 100 mg/dl were found in pattern C. Thus, the most common Stu I RFLP genotype is associated with a favorable lipid phenotype. This report shows an association between the human pancreatic cholesterol esterase genotype and serum lipid levels. Further analysis of a larger study group with Stu I and alternative polymorphic restriction enzymes is warranted, to confirm this biologically plausible result.

Linkage and association of the sodium potassium-adenosine triphosphatase alpha2 and beta1 genes with respiratory quotient and resting metabolic rate in the Québec Family Study

The purpose of this study was to examine the relationship between the alpha2 (exon 1 and exon 21-22 with BglII) and beta1 (MspI and PvuII) genes of the sodium potassium adenosine triphosphatase and resting metabolic rate (RMR) and respiratory quotient (RQ). The sample included 582 participants from 171 families of the Québec Family Study. RMR and RQ were adjusted for age, sex, fat mass, and fat free mass. Sib-pair analyses indicated a significant linkage between RQ and the alpha2 exon 1 marker (P = 0.03) and the alpha2 exon 21-22 marker (P = 0.02). No linkage was detected between the beta1 markers and either RMR or RQ, whereas RMR was not linked with the alpha2 makers. There was a significant interaction (P < 0.0003) between alpha2 exon 1 carrier status and age group [younger (< 45 yr) vs. older (> or = 45 yr) adults] for RQ. The association between carrier status and RQ was significant in younger adults (RQ = 0.76 in carriers vs. 0.80 in noncarriers, P < 0.0001) but was not in older adults (RQ = 0.81 in carriers vs. 0.80 in noncarriers). The alpha2 exon 1 gene accounted for approximately 9.1% and 0.3% of the variance in RQ in younger and older adults, respectively. The results suggest that the sodium potassium adenosine triphosphatase alpha2 gene may play a role in fuel oxidation, particularly in younger individuals.

Relation between dietary fiber consumption and fibrinogen and plasminogen activator inhibitor type 1: The National Heart, Lung, and Blood Institute Family Heart Study

Considerable evidence suggests that high plasma concentrations of plasminogen activator inhibitor type 1 (PAI-1) and fibrinogen increase the risk of cardiovascular disease. Recent studies report beneficial effects of dietary fiber on coronary artery disease, although the mechanisms by which high fiber intake reduces the risk of heart disease are not well understood. This study examined the relation of dietary fiber intake to PAI-1 and fibrinogen concentrations in 883 men and 1116 women aged 50.4 +/- 13.8 and 52.1 +/- 13.7 y, respectively, in the National Heart, Lung, and Blood Institute Family Heart Study. Diet was assessed with a semiquantitative food-frequency questionnaire. The natural logarithm was used to transform PAI-1 because of a skewed distribution. In the first through fifth age- and energy-specific quintiles of fiber intake, mean (ln)PAI-1 was 6.09, 5.91, 5.88, 5.82, and 5.67 pmol/L, respectively, for men and 5.50, 5.37, 5.39, 5.23, and 5.18 pmol/L, respectively, for women. Multiple regression showed that when the lowest was compared with the second, third, fourth, and fifth age- and energy-specific quintiles of fiber intake, (ln)PAI-1 was 0.21, 0.25, 0.22, and 0.32 pmol/L lower in men (P for trend = 0.009) and 0.08, 0.06, 0.14, and 0.20 pmol/L lower in women (P for trend = 0.037), respectively, with anthropometric, lifestyle, and metabolic factors adjusted for. No significant association was found between fiber intake and fibrinogen. Waist-hip ratio did not modify the relation of fiber intake to PAI-1 (P for interaction = 0.39 for men and 0.36 for women). These data suggest that higher fiber intake is inversely associated with PAI-1, but not with fibrinogen concentration.

Familial resemblance for resting blood pressure with particular reference to racial differences: preliminary analyses from the HERITAGE Family Study

Resting blood pressure in both white and black families participating in the HERITAGE Family Study was analyzed using a simple familial correlation model to assess familial influences. The two samples of black and white families were analyzed separately and together, providing an opportunity to test for heterogeneity in the familial resemblance. Maximal heritability was 46% for systolic blood pressure (SBP) and 31% for diastolic blood pressure (DBP) in the pooled sample. Noticeably higher heritabilities were found in the black sample (68% for SBP and 56% for DBP) than in the white sample (43% for SBP and 24% for DBP). The patterns of familial correlations were similar in blacks and whites, with the exception that spouse resemblance was significant in white families but not in black families. These results along with the finding that the magnitude of the familial correlations was higher in the black sample than in the white sample suggest that the effects of host and familial environmental factors differ between the races.

Genetic epidemiology of the Mitsuda reaction in leprosy

This study comprised 544 nuclear families with 2,925 individuals tested for the Mitsuda reaction, from the Campinas region in Brazil. Segregation analyses suggest the segregation of a major gene (chi 2(1) = 0.07 - 0.07 = 0, p = 1), by failing to reject the hypothesis of Mendelian transmission and by rejecting the hypothesis of nontransmission of a major gene (chi 2(3) = 0.07 - 0.0 = 0.07, p > 0.99; chi 2(2) = 198.28 - 0.0 = 198.28, p < 0.0001).

The genetic epidemiology of leprosy in a Brazilian population

Data on leprosy patients have been obtained from the Dispensary of Leprosy of Campinas, São Paulo, where records on practically all cases of leprosy in the Campinas area during the period 1960-70 are filed. The whole sample comprises 10,886 individuals, distributed among 1,568 families. Complex segregation analysis was utilized to determine the nature of the genetic factors that may operate on leprosy and its subtypes. The results suggest the presence of a recessive major gene controlling susceptibility to leprosy per se, with frequency of approximately .05, although there are deviations from the expected Mendelian segregation proportions. Possible etiologic heterogeneity was examined by considering two subtypes separately: for lepromatous leprosy and tuberculoid leprosy there are suggestions for a segregating major effect; however, Mendelian transmission could not be demonstrated in either case. Therefore, there is no evidence to suggest unique genetic determinants for leprosy subtypes.

Linkage analysis of the human insulin receptor gene and maturity onset diabetes of the young

The cloning of the insulin receptor cDNA has permitted the definition of restriction fragment length polymorphisms at that locus. These polymorphisms were used to study the role of the insulin receptor in four pedigrees with maturity onset diabetes of the young through linkage analyses. When each pedigree was individually analysed, no linkage was demonstrated in the two larger pedigrees, implying that an insulin receptor defect was not responsible for the predisposition to diabetes in these pedigrees. One of these pedigrees was known to be hypoinsulinaemic, while insulin levels were unavailable in the second pedigree. In the two smaller pedigrees, however, a single haplotype cosegregated with diabetes. One of these pedigrees is known to be hyperinsulinaemic. The small size of the pedigrees which demonstrated cosegregation precluded statistical proof of linkage. Nonetheless, the presence of an uncommon insertional polymorphism which cosegregated with diabetes in both pedigrees was improbable and suggested that this insertion could be responsible for diabetes in these families. This study thus may be additional evidence for heterogeneity in maturity onset diabetes of the young. For the two larger pedigrees, the insulin gene and HLA region have already been eliminated as genetic markers. This study provides data which eliminate a third candidate gene in these two pedigrees.

[International surveillance of some viral diseases (author's transl)]

During a period of more than fifteen years the WHO international surveillance system for selected viral diseases has been modified on several occasions. The aims of the surveillance programme on viral diseases are two-fold: to make available world-wide epidemiological information and to contribute to the development of public health laboratories in countries where this is necessary.