First reports of primary ciliary dyskinesia caused by a shared DNAH11 allele in Canadian Inuit

BACKGROUND

Primary ciliary dyskinesia (PCD) is typically an autosomal recessive disease characterized by recurrent infections of the lower respiratory tract, frequent and severe otitis media, chronic rhinosinusitis, neonatal respiratory distress, and organ laterality defects. While severe lower respiratory tract infections and bronchiectasis are common in Inuit, PCD has not been recognized in this population.

METHODS

We report a case series of seven Inuit patients with PCD identified by genetic testing in three Canadian PCD centers.

RESULTS

Patients ranged from 4 to 59 years of age (at time of last evaluation) and originated in the Qikiqtaaluk region (Baffin Island, n = 5), Nunavut, or Nunavik (northern Quebec, n = 2), Canada. They had typical features of PCD, including neonatal respiratory distress (five patients), situs inversus totalis (four patients), bronchiectasis (four patients), chronic atelectasis (six patients), and chronic otitis media (six patients). Most had chronic rhinitis. Genetic evaluation demonstrated that all had homozygous pathogenic variants in DNAH11 at NM_001277115.1:c.4095+2C>A.

CONCLUSIONS

The discovery of this homozygous DNAH11 variant in widely disparate parts of the Nunangat (Inuit homelands) suggests this is a founder mutation that may be widespread in Inuit. Thus, PCD may be an important cause of chronic lung, sinus, and middle ear disease in this population. Inuit with chronic lung disease, including bronchiectasis or laterality defects, should undergo genetic testing for PCD. Consideration of including PCD genetic analysis in routine newborn screening should be considered in Inuit regions.

Variation in biomarker levels of metals, persistent organic pollutants, and omega-3 fatty acids in association with genetic polymorphisms among Inuit in Nunavik, Canada

BACKGROUND

Biomarker measures of contaminant exposure and nutrient status can help increase understanding of the risks and benefits associated with the consumption of traditional foods by Inuit. While gene-environment and gene-nutrient interactions may help explain variations in biomarker measures, the role of genetic polymorphisms is largely understudied especially for vulnerable sub-populations.

OBJECTIVE

The aim of this study was to characterize the relationship between single nucleotide polymorphisms (SNPs) in key genes and blood concentrations of environmental chemicals and nutrients among Inuit.

METHODS

Blood samples from 665 individuals who participated in the Qanuippitaa Survey (Nunavik, Canada) in 2004 were analyzed for toxicants and nutrients. DNA was extracted and 140 SNPs in classes relevant to the toxicokinetics and/or toxicodynamics of the target contaminants and nutrients, and/or are involved in cardiovascular health and lipid metabolism were genotyped using the Sequenom iPLEX Gold platform.

RESULTS

Geometric means (μg/L) of mercury (Hg), cadmium (Cd), lead (Pb), DDE, PCB-153, and selenium (Se) were 11.1, 2.8, 39.9, 2.9, 1.1 and 301.2, respectively. Red blood cell membrane levels of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were 5.1%/total fatty acid (TFA) and 1.3%/TFA respectively. Out of 106 SNPs which met our inclusion criteria, biomarker levels for Hg, Cd, Pb, DDE, PCB-153, DHA, and EPA differed (p < 0.05) by genotype for 20, 13, 12, 19, 21, 9 and 8 SNPs, respectively. Following Bonferroni correction (p < 0.0005), only 9 SNPs remained significant (rs2274976 in MTHFR, rs174602 in FADS2, rs7115739 and rs74771917 in FADS3, rs713041 in GPX4, rs2306283 and rs4149056 in SLCO1B1, rs1885301 in ABCC2/MRP2, and rs4244285 in CYP2C19; 5 associated with Hg, 2 with Pb, 2 with DDE, 4 with PCB-153, 1 with DHA).

CONCLUSIONS

The findings suggest that polymorphisms in environmentally-responsive genes can influence biomarker levels of key toxicants and nutrients. While there are no immediate clinical or public health implications of these findings, we believe that such gene-environment and gene-nutrient studies provide a foundation that will inform and provide direction to future studies.

Physical activity attenuates postprandial hyperglycaemia in homozygous TBC1D4 loss-of-function mutation carriers

AIMS/HYPOTHESIS

The common muscle-specific TBC1D4 p.Arg684Ter loss-of-function variant defines a subtype of non-autoimmune diabetes in Arctic populations. Homozygous carriers are characterised by elevated postprandial glucose and insulin levels. Because 3.8% of the Greenlandic population are homozygous carriers, it is important to explore possibilities for precision medicine. We aimed to investigate whether physical activity attenuates the effect of this variant on 2 h plasma glucose levels after an oral glucose load.

METHODS

In a Greenlandic population cohort (n = 2655), 2 h plasma glucose levels were obtained after an OGTT, physical activity was estimated as physical activity energy expenditure and TBC1D4 genotype was determined. We performed TBC1D4-physical activity interaction analysis, applying a linear mixed model to correct for genetic admixture and relatedness.

RESULTS

Physical activity was inversely associated with 2 h plasma glucose levels (β[main effect of physical activity] -0.0033 [mmol/l] / [kJ kg-1 day-1], p = 6.5 × 10-5), and significantly more so among homozygous carriers of the TBC1D4 risk variant compared with heterozygous carriers and non-carriers (β[interaction] -0.015 [mmol/l] / [kJ kg-1 day-1], p = 0.0085). The estimated effect size suggests that 1 h of vigorous physical activity per day (compared with resting) reduces 2 h plasma glucose levels by an additional ~0.7 mmol/l in homozygous carriers of the risk variant.

CONCLUSIONS/INTERPRETATION

Physical activity improves glucose homeostasis particularly in homozygous TBC1D4 risk variant carriers via a skeletal muscle TBC1 domain family member 4-independent pathway. This provides a rationale to implement physical activity as lifestyle precision medicine in Arctic populations.

DATA REPOSITORY

The Greenlandic Cardio-Metabochip data for the Inuit Health in Transition study has been deposited at the European Genome-phenome Archive ( https://www.ebi.ac.uk/ega/dacs/EGAC00001000736 ) under accession EGAD00010001428.

Inuit metabolism revisited: what drove the selective sweep of CPT1a L479?

This article reassesses historical studies of Inuit metabolism in light of recent developments in evolutionary genetics. It discusses the possible selective advantage of a variant of CPT1a, which encodes the rate limiting enzyme in hepatic fatty acid oxidation. The L479 variant of CPT1a underwent one of the strongest known selective sweeps in human history and is specific to Inuit and Yu'pik populations. Recent hypotheses predict that this variant may have been selected in response to possible detrimental effects of chronic ketosis in communities with very low carbohydrate consumption. Assessing these hypotheses alongside several alternative explanations of the selective sweep, this article challenges the notion that the selection of L479 is linked to predicted detrimental effects of ketosis. Bringing together for the first time data from biochemical, metabolic, and physiological studies inside and outside the Inuit sphere, it aims to provide a broader interpretative framework and a more comprehensive way to understand the selective sweep. It suggests that L479 may have provided a selective advantage in glucose conservation as part of a metabolic adaptation to very low carbohydrate and high protein consumption, but not necessarily a ketogenic state, in an extremely cold environment. A high intake of n-3 fatty acids may be linked to selection through the mitigation of a detrimental effect of the mutation that arises in the fasted state. The implications of these conclusions for our broader understanding of very low carbohydrate metabolism, and for dietary recommendations for Inuit and non-Inuit populations, are discussed.

Palaeo-Eskimo genetic ancestry and the peopling of Chukotka and North America

Much of the American Arctic was first settled 5,000 years ago, by groups of people known as Palaeo-Eskimos. They were subsequently joined and largely displaced around 1,000 years ago by ancestors of the present-day Inuit and Yup'ik1-3. The genetic relationship between Palaeo-Eskimos and Native American, Inuit, Yup'ik and Aleut populations remains uncertain4-6. Here we present genomic data for 48 ancient individuals from Chukotka, East Siberia, the Aleutian Islands, Alaska, and the Canadian Arctic. We co-analyse these data with data from present-day Alaskan Iñupiat and West Siberian populations and published genomes. Using methods based on rare-allele and haplotype sharing, as well as established techniques4,7-9, we show that Palaeo-Eskimo-related ancestry is ubiquitous among people who speak Na-Dene and Eskimo-Aleut languages. We develop a comprehensive model for the Holocene peopling events of Chukotka and North America, and show that Na-Dene-speaking peoples, people of the Aleutian Islands, and Yup'ik and Inuit across the Arctic region all share ancestry from a single Palaeo-Eskimo-related Siberian source.

Genetic determinants of glycated hemoglobin levels in the Greenlandic Inuit population

We previously showed that a common genetic variant leads to a remarkably increased risk of type 2 diabetes (T2D) in the small and historically isolated Greenlandic population. Motivated by this, we aimed at discovering novel genetic determinants for glycated hemoglobin (HbA1C) and at estimating the effect of known HbA1C-associated loci in the Greenlandic population. We analyzed genotype data from 4049 Greenlanders generated using the Illumina Cardio-Metabochip. We performed the discovery association analysis by an additive linear mixed model. To estimate the effect of known HbA1C-associated loci, we modeled the effect in the European and Inuit ancestry proportions of the Greenlandic genome (EAPGG and IAPGG, respectively). After correcting for multiple testing, we found no novel significant associations. When we investigated loci known to associate with HbA1C levels, we found that the lead variant in the GCK locus associated significantly with HbA1C levels in the IAPGG ([Formula: see text]). Furthermore, for 10 of 15 known HbA1C loci, the effects in IAPGG were similar to the previously reported effects. Interestingly, the ANK1 locus showed a statistically significant ancestral population differential effect, with opposing directions of effect in the two ancestral populations. In conclusion, we found only 1 of the 15 known HbA1C loci to be significantly associated with HbA1C levels in the IAPGG and that two-thirds of the loci showed similar effects in Inuit as previously found in European and East Asian populations. Our results shed light on the genetic effects across ethnicities.

Loss-of-function variants in ADCY3 increase risk of obesity and type 2 diabetes

We have identified a variant in ADCY3 (encoding adenylate cyclase 3) associated with markedly increased risk of obesity and type 2 diabetes in the Greenlandic population. The variant disrupts a splice acceptor site, and carriers have decreased ADCY3 RNA expression. Additionally, we observe an enrichment of rare ADCY3 loss-of-function variants among individuals with type 2 diabetes in trans-ancestry cohorts. These findings provide new information on disease etiology relevant for future treatment strategies.

Dietary and genetic influences on hemostasis in a Yup'ik Alaska Native population

Fish and marine animals are important components of the subsistence diet of Alaska Native people, resulting in a high ω3 PUFA intake. The historical record for circumpolar populations highlights a tendency for facile bleeding, possibly related to ω3 PUFA effects on platelet activation and/or vitamin K-dependent clotting factors. To evaluate these two scenarios in Yup'ik people of southwestern Alaska, we examined the association between dietary ω3 PUFA intake and activities of clotting factor II, V, fibrinogen, PT, INR, PTT, and sP-selectin in 733 study participants, using the nitrogen isotope ratio of red blood cells as a biomarker of ω3 PUFA consumption. sP-selectin alone correlated strongly and inversely with ω3 PUFA consumption. Approximately 36% of study participants exhibited PIVKA-II values above the threshold of 2 ng/ml, indicative of low vitamin K status. To assess genetic influences on vitamin K status, study participants were genotyped for common vitamin K cycle polymorphisms in VKORC1, GGCX and CYP4F2. Only CYP4F2*3 associated significantly with vitamin K status, for both acute (plasma vitamin K) and long-term (PIVKA-II) measures. These findings suggest: (i) a primary association of ω3 PUFAs on platelet activation, as opposed to vitamin K-dependent clotting factor activity, (ii) that reduced CYP4F2 enzyme activity associates with vitamin K status. We conclude that high ω3 PUFA intake promotes an anti-platelet effect and speculate that the high frequency of the CYP4F2*3 allele in Yup'ik people (~45%) evolved in response to a need to conserve body stores of vitamin K due to environmental limitations on its availability.

Archaic Adaptive Introgression in TBX15/WARS2

A recent study conducted the first genome-wide scan for selection in Inuit from Greenland using single nucleotide polymorphism chip data. Here, we report that selection in the region with the second most extreme signal of positive selection in Greenlandic Inuit favored a deeply divergent haplotype that is closely related to the sequence in the Denisovan genome, and was likely introgressed from an archaic population. The region contains two genes, WARS2 and TBX15, and has previously been associated with adipose tissue differentiation and body-fat distribution in humans. We show that the adaptively introgressed allele has been under selection in a much larger geographic region than just Greenland. Furthermore, it is associated with changes in expression of WARS2 and TBX15 in multiple tissues including the adrenal gland and subcutaneous adipose tissue, and with regional DNA methylation changes in TBX15.

[Haplotype Analysis of Oculopharyngeal Muscular Dystrophy (OPMD) Locus in Yakutia]

Oculopharyngeal muscular dystrophy (OPMD) is a hereditary neuromuscular disease with autosomal dominant and rarely with autosomal recessive inheritance types. This study included 50 patients with a clinical diagnosis of OPMD, 23 asymptomatic carriers of the mutation from 45 unrelated families, and 56 healthy relatives, as well as population samples of four ethnic groups of Yakutia: Yakuts, Evens, Evenks, Yukaghirs. It was found that the cause of OPMD development in all investigated families is the same increase in.GCN repeats to 14 copies in the PABPN1 gene. The molecular structure ofthe (GCN)₁₄ mutant allele is (GCG)₁₀(GCA)₃GCG. The genetic variability of ten SNPs at the OPMD locus was studied in patient families and population samples. The haplotypes of OPMD were determined by a segregation analysis technique using the EM algorithm in the groups of patients, mutation carriers, and population samples. Only one haplotype of four SNPs (ATCG) linked with the (GCN)₁₄ mutant allele was found in Yakuts and Russian patients and OPMD mutation carriers. Probably, this indicates the accumulation of mutations as a result of the founder effect.

Genomic study of the Ket: a Paleo-Eskimo-related ethnic group with significant ancient North Eurasian ancestry

The Kets, an ethnic group in the Yenisei River basin, Russia, are considered the last nomadic hunter-gatherers of Siberia, and Ket language has no transparent affiliation with any language family. We investigated connections between the Kets and Siberian and North American populations, with emphasis on the Mal'ta and Paleo-Eskimo ancient genomes, using original data from 46 unrelated samples of Kets and 42 samples of their neighboring ethnic groups (Uralic-speaking Nganasans, Enets, and Selkups). We genotyped over 130,000 autosomal SNPs, identified mitochondrial and Y-chromosomal haplogroups, and performed high-coverage genome sequencing of two Ket individuals. We established that Nganasans, Kets, Selkups, and Yukaghirs form a cluster of populations most closely related to Paleo-Eskimos in Siberia (not considering indigenous populations of Chukotka and Kamchatka). Kets are closely related to modern Selkups and to some Bronze and Iron Age populations of the Altai region, with all these groups sharing a high degree of Mal'ta ancestry. Implications of these findings for the linguistic hypothesis uniting Ket and Na-Dene languages into a language macrofamily are discussed.

Linkage and association analysis of obesity traits reveals novel loci and interactions with dietary n-3 fatty acids in an Alaska Native (Yup'ik) population

OBJECTIVE

To identify novel genetic markers of obesity-related traits and to identify gene-diet interactions with n-3 polyunsaturated fatty acid (n-3 PUFA) intake in Yup'ik people.

MATERIAL AND METHODS

We measured body composition, plasma adipokines and ghrelin in 982 participants enrolled in the Center for Alaska Native Health Research (CANHR) Study. We conducted a genome-wide SNP linkage scan and targeted association analysis, fitting additional models to investigate putative gene-diet interactions. Finally, we performed bioinformatic analysis to uncover likely candidate genes within the identified linkage peaks.

RESULTS

We observed evidence of linkage for all obesity-related traits, replicating previous results and identifying novel regions of interest for adiponectin (10q26.13-2) and thigh circumference (8q21.11-13). Bioinformatic analysis revealed DOCK1, PTPRE (10q26.13-2) and FABP4 (8q21.11-13) as putative candidate genes in the newly identified regions. Targeted SNP analysis under the linkage peaks identified associations between three SNPs and obesity-related traits: rs1007750 on chromosome 8 and thigh circumference (P=0.0005), rs878953 on chromosome 5 and thigh skinfold (P=0.0004), and rs1596854 on chromosome 11 for waist circumference (P=0.0003). Finally, we showed that n-3 PUFA modified the association between obesity related traits and two additional variants (rs2048417 on chromosome 3 for adiponectin, P for interaction=0.0006 and rs730414 on chromosome 11 for percentage body fat, P for interaction=0.0004).

CONCLUSIONS

This study presents evidence of novel genomic regions and gene-diet interactions that may contribute to the pathophysiology of obesity-related traits among Yup'ik people.

Increased missense mutation burden of Fatty Acid metabolism related genes in nunavik inuit population

Background

Nunavik Inuit (northern Quebec, Canada) reside along the arctic coastline where for generations their daily energy intake has mainly been derived from animal fat. Given this particular diet it has been hypothesized that natural selection would lead to population specific allele frequency differences and unique variants in genes related to fatty acid metabolism. A group of genes, namely CPT1A, CPT1B, CPT1C, CPT2, CRAT and CROT, encode for three carnitine acyltransferases that are important for the oxidation of fatty acids, a critical step in their metabolism.

Methods

Exome sequencing and SNP array genotyping were used to examine the genetic variations in the six genes encoding for the carnitine acyltransferases in 113 Nunavik Inuit individuals.

Results

Altogether ten missense variants were found in genes CPT1A, CPT1B, CPT1C, CPT2 and CRAT, including three novel variants and one Inuit specific variant CPT1A p.P479L (rs80356779). The latter has the highest frequency (0.955) compared to other Inuit populations. We found that by comparison to Asians or Europeans, the Nunavik Inuit have an increased mutation burden in CPT1A, CPT2 and CRAT; there is also a high level of population differentiation based on carnitine acyltransferase gene variations between Nunavik Inuit and Asians.

Conclusion

The increased number and frequency of deleterious variants in these fatty acid metabolism genes in Nunavik Inuit may be the result of genetic adaptation to their diet and/or the extremely cold climate. In addition, the identification of these variants may help to understand some of the specific health risks of Nunavik Inuit.

Genetic variation in alcohol metabolizing enzymes among Inuit and its relation to drinking patterns

BACKGROUND

Variation in genes involved in alcohol metabolism is associated with drinking patterns worldwide. We compared variation in these genes among the Inuit with published results from the general population of Denmark and, due to the Asian ancestry of the Inuit, with Han Chinese. We analyzed the association between gene variations and drinking patterns among the Inuit.

METHODS

We genotyped 4162 Inuit participants from two population health surveys. Information on drinking patterns was available for 3560. Seven single nucleotide polymorphisms (SNPs) were examined: ADH1B arg48his, ADH1C ile350val, ADH1C arg272gln, ALDH2 glu504lys, ALDH2 5'-UTR A-357G, ALDH1B1 ala86val and ALDH1B1 arg107leu.

RESULTS

The allele distribution differed significantly between Inuit and the general population of Denmark. A protective effect on heavy drinking was found for the TT genotype of the ALDH1B1 arg107leu SNP (OR=0.59; 95% CI 0.37-0.92), present in 3% of pure Inuit and 37% of Danes. The ADH1C GG genotype was associated with heavy drinking and a positive CAGE test (OR 1.34; 95% CI 1.05-1.72). It was present in 27% of Inuit and 18% of Danes. The Asian genotype pattern with a high frequency of the ADH1B A allele and an ALDH2 gene coding for an inactive enzyme was not present in Greenland.

CONCLUSIONS

ADH1C and ALDH1B1 arg107leu SNPs play a role in the shaping of drinking patterns among the Inuit in Greenland. A low frequency of the ALDH1B1 arg107leu TT genotype compared with the general population in Denmark deserves further study. This genotype was protective of heavy drinking among the Inuit.

CDKAL1 and HHEX are associated with type 2 diabetes-related traits among Yup'ik people

BACKGROUND

Genome-wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) associated with type 2 diabetes (T2D), mainly among individuals of European ancestry. In the present study, we examined the frequency of these SNPs and their association with T2D-related traits in an Alaska Native study population with a historically low prevalence of T2D. We also investigated whether dietary characteristics that may protect against T2D, such as n-3 polyunsaturated fatty acid (PUFA) intake, modify these associations.

METHODS

In 1144 Yup'ik people, we examined 17 SNPs repeatedly identified in GWAS for individual and cumulative associations with T2D-related traits. Cumulative associations were evaluated using a genetic risk score (GRS) calculated by summing risk alleles. Associations were tested for interactions with sex, body mass index (BMI), and n-3 PUFA intake.

RESULTS

The rs7754840 SNP in CDKAL1 is significantly associated with HbA1c (P = 0.00091). The rs5015480 SNP near HHEX is significantly associated (in opposite direction to that in Europeans) with a combined fasting glucose (FG) and HbA1c measure (P = 0.00046) and with homeostatic model assessment of β-cell function (HOMA-B; P = 0.0014). The GRS is significantly associated with FG and combined FG and HbA1c only when the HHEX SNP is dropped from the GRS. Associations are not modified by BMI or n-3 PUFA intake.

CONCLUSION

Our results highlight the potential importance of CDKAL1 and HHEX in glucose homeostasis in this Alaska Native population with a low prevalence of T2D, and suggest that these loci should be examined in greater detail in this population.

Polymorphisms in phase I and phase II genes and breast cancer risk and relations to persistent organic pollutant exposure: a case-control study in Inuit women

BACKGROUND

We have previously reported that chemicals belonging to the persistent organic pollutants (POPs) such as perfluorinated compounds (PFAS) and polychlorinated biphenyls (PCBs) are risk factors in Breast Cancer (BC) development in Greenlandic Inuit women. The present case-control study aimed to investigate the main effect of polymorphisms in genes involved in xenobiotic metabolism and estrogen biosynthesis, CYP1A1, CYP1B1, COMT and CYP17, CYP19 and the BRCA1 founder mutation in relation to BC risk and to explore possible interactions between the gene polymorphisms and serum POP levels on BC risk in Greenlandic Inuit women.

METHODS

The study population consisted of 31 BC cases and 115 matched controls, with information on serum levels of POPs. Genotyping was conducted for CYP1A1 (Ile462Val; rs1048943), CYP1B1 (Leu432Val; rs1056836), COMT (Val158Met; rs4680), CYP17A1 (A1> A2; rs743572); CYP19A1 (C> T; rs10046) and CYP19A1 ((TTTA)n repeats) polymorphisms and BRCA1 founder mutation using TaqMan allelic discrimination method and polymerase chain reaction based restriction fragment length polymorphism. The χ2 -test was used to compare categorical variables between cases and controls and the odds ratios were estimated by unconditional logistic regression models.

RESULTS

We found an independent association of CYP1A1 (Val) and CYP17 (A1) with BC risk.Furthermore, an increased BC risk was observed for women with high serum levels of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) and carriers of at least: one CYP1A1 variant Val allele; one variant COMT Met allele; or the common CYP17 A1 allele. No combined effects were seen between PFAS exposure and CYP1B1 and CYP19 polymorphisms. The risk of BC was not found significantly associated with exposure to PCBs and OCPs, regardless of genotype for all investigated SNPs. The frequency of the Greenlandic founder mutation in BRCA1 was as expected higher in cases than in controls.

CONCLUSIONS

The BRCA1 founder mutation and polymorphisms in CYP1A1 (Val) and CYP17 (A1) can increase the BC risk among Inuit women and the risk increases with higher serum levels of PFOS and PFOA. Serum PFAS levels were a consistent risk factor of BC, but inter-individual polymorphic differences might cause variations in sensitivity to the PFAS/POP exposure.

Non-linear association between androgen receptor CAG and GGN repeat lengths and reproductive parameters in fertile European and Inuit men

Recently the dogma that there is an inverse linear association between androgen receptor (AR) CAG and GGN polymorphisms and receptor activity has been challenged. We analysed the pattern of association between 21 male reproductive phenotypes and AR CAG/GGN repeat lengths in 557 proven-fertile men. A linear association was only found between sperm DNA fragmentation index (DFI) and CAG length, and between inhibin B and GGN length. Men with longer CAG then the reference (22-24), had higher oestradiol levels, whereas men with shorter CAG stretches had a higher DFI and a higher proportion of Fas-positive germ cells. Subjects with either short or long CAG had increased seminal levels of prostate-specific antigen and neutral α-glucosidase activity. Compared to men with the median GGN length of 23, those with shorter GGN repeats had higher levels of inhibin B, higher proportions of normal and progressive sperm, and a higher fraction of Fas-positive sperm, while men with longer GGN had higher oestradiol levels. These data indicate that at least for some markers of male reproductive function the association with CAG or GGN repeat length is curvilinear.

A QTL for genotype by sex interaction for anthropometric measurements in Alaskan Eskimos (GOCADAN Study) on chromosome 19q12-13

Variation in anthropometric measurements due to sexual dimorphism can be the result of genotype by sex interactions (G×S). The purpose of this study was to examine the sex-specific genetic architecture in anthropometric measurements in Alaskan Eskimos from the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) study. Maximum likelihood-based variance components decomposition methods, implemented in SOLAR, were used for G×S analyses. Anthropometric measurements included BMI, waist circumference (WC), waist/height ratio, percent body fat (%BF), and subscapular and triceps skinfolds. Except for WC, mean values of all phenotypes were significantly different in men and women (P < 0.05). All anthropometric measures were significantly heritable (P < 0.001). In a preliminary analysis not allowing for G×S interaction, evidence of linkage was detected between markers D19S414 and D19S220 on chromosome 19 for WC (logarithm of odds (lod) = 3.5), %BF (lod = 1.7), BMI (lod = 2.4), waist/height ratio (lod = 2.5), subscapular (lod = 2.1), and triceps skinfolds (lod = 1.9). In subsequent analyses which allowed for G×S interaction, linkage was again found between these traits and the same two markers on chromosome 19 with significantly improved lod scores for: WC (lod = 4.5), %BF (lod = 3.8), BMI (lod = 3.5), waist/height ratio (lod = 3.2), subscapular (lod = 3.0), and triceps skinfolds (lod = 2.9). These results support the evidence of a G×S interaction in the expression of genetic effects resulting in sexual dimorphism in anthropometric phenotypes and identify the chromosome 19q12-13 region as important for adiposity-related traits in Alaskan Eskimos.

Carnitine palmitoyltransferase 1A (CPT1A) P479L prevalence in live newborns in Yukon, Northwest Territories, and Nunavut

Carnitine palmitoyltransferase 1A (CPT1A), encoded by the gene CPT1A, is the hepatic isoform of CPT1 and is a major regulatory point in long-chain fatty acid oxidation. CPT1A deficiency confers risk for hypoketotic hypoglycaemia, hepatic encephalopathy, seizures, and sudden unexpected death in infancy (SUDI). It remains controversial whether the CPT1A gene variant, c.1436C>T (p.P479L), identified in Inuit, First Nations, and Alaska Native infants, causes susceptibility to decompensation, in particular during times of fever and intercurrent illness. Although newborn screening for the P479L variant occurs in some jurisdictions, background knowledge about the presence of the variant in Canadian Aboriginal populations is lacking. In an effort to understand the population implications of the variant in northern Canada, overall frequencies of the variant were assessed. Further studies are underway to determine associated risk. Ethics approval was obtained from university REBs, local research institutes, and with consultation with territorial Aboriginal groups. Newborn screening blood spots from all infants born in 2006 in the three territories were genotyped for the p.P479L variant. p.P479L (c.1436C>T) allele frequencies in the three territories were 0.02, 0.08, and 0.77 in Yukon (n=325), Northwest Territories (n=564), and Nunavut (n=695), respectively. Homozygosity rates were 0%, 3%, and 64%. Aboriginal status was available only in NWT, with allele frequencies of 0.04, 0.44, 0.00, and 0.01 for First Nations, Inuvialuit/Inuit, Métis, and non-Aboriginal populations. Although individual blood spots were not identified for Aboriginal ethnicity in Nunavut infants, ~90% of infants in Nunavut are born to Inuit women. The allele frequency and rate of homozygosity for the CPT1A P479L variant were high in Inuit and Inuvialuit who reside in northern coastal regions. The variant is present at a low frequency in First Nations populations, who reside in areas less coastal than the Inuit or Inuvialuit in the two western territories. The significance of the population and geographic distribution remains unclear, but the high population frequencies of the variant suggest a historically low penetrance for adverse outcomes. Further evidence is needed to determine if there is an increased risk for infant mortality and morbidity and whether newborn screening will be indicated on a population basis.

Identification of a novel BRCA1 nucleotide 4803delCC/c.4684delCC mutation and a nucleotide 249T>A/c.130T>A (p.Cys44Ser) mutation in two Greenlandic Inuit families: implications for genetic screening of Greenlandic Inuit families with high risk for breast and/or ovarian cancer

Germ-line mutations in the tumour suppressor proteins BRCA1 and BRCA2 predispose to breast and ovarian cancer. We have recently identified a Greenlandic Inuit BRCA1 nucleotide 234T>G/c.115T>G (p.Cys39Gly) founder mutation, which at that time was the only disease-causing BRCA1/BRCA2 mutation identified in this population. Here, we describe the identification of a novel disease-causing BRCA1 nucleotide 4803delCC/c.4684delCC mutation in a Greenlandic Inuit with ovarian cancer. The mutation introduces a frameshift and a premature stop at codon 1572. We have also identified a BRCA1 nucleotide 249T>A/c.130T>A (p.Cys44Ser) mutation in another Greenlandic individual with ovarian cancer. This patient share a 1-2 Mb genomic fragment, containing the BRCA1 gene, with four Danish families harbouring the same mutation, suggesting that the 249T>A/c.130T>A (p.Cys44Ser) mutation originates from a Danish ancestor. We conclude that screening of Greenlandic Inuits with high risk of breast or ovarian cancer should include sequencing of the entire BRCA1 gene.

The importance of environment on respiratory genotype/phenotype relationships in the Inuit

BACKGROUND

Genetic and environmental influences and their interactions are central to asthma pathogenesis. This study aimed to investigate the effects of different macro-environments on asthma genotype-phenotype associations in two geographically separated populations with common ancestry.

METHODS

To accomplish this, two unselected populations of Inuit were recruited, one living in Greenland (n = 618) and the other in Denmark (n = 739). Subjects were genotyped for CD14 C-159T, SCGB1A1 A38G, ADRB2 Arg16Gly and Gln27Glu. The resulting genetic data were analysed for relationships with asthma-related parameters including lung function, ever asthma, atopy, rhinitis and dermatitis.

RESULTS

The results showed contrasting magnitude and direction of genetic associations between the two geographically separate Inuit populations. In Greenland, the ADRB2 16Arg allele was associated with male-specific lower lung function, but in Denmark the same allele was associated with male-specific higher lung function. This allele was also associated with higher incidence of ever asthma in Denmark but not in Greenland. The SCGB1A1 38A allele was associated with lower rhinitis prevalence in Greenland but not in Denmark.

CONCLUSIONS

These associations suggest that environment interacts with candidate asthma genes to modulate asthma pathogenesis in the Inuit.

APOEpolymorphism distribution among Native Americans and related populations

BACKGROUND

Apolipoprotein E (apoE, protein; APOE, gene) plays a central role in lipid metabolism. Three common alleles, E*2, E*3 and E*4 have quantitative effects on lipid and lipoproteins levels, which are major risk determinants of cardiovascular diseases in several populations. Given their clinical significance, it is of interest to know the distribution of APOE variants in populations from diverse ethnic groups, as well as to determine if this polymorphism presents variations that might be associated with given evolutionary factors.

AIM

We report the distribution of APOE polymorphisms in Native American populations from South America, comparing it with other native populations of the Americas and Siberia.

SUBJECTS AND METHODS

The sample consisted of 315 individuals from nine Native American populations living at subtropical latitudes of Argentina, Brazil and Paraguay. The extended analysis included 50 populations across South and North America, Greenland and Siberia. The geographic patterns of the variation were investigated through correlation analysis, spatial autocorrelation and analysis molecular of variance (AMOVA).

RESULTS

The incidence of the most common allele (APOE*3) in the sample analysed ranged from 0.78 to 0.98. The second allele in prevalence, APOE*4, varied from 0.00 to 0.17. The rare allele APOE*2 was found in five of the nine populations investigated. This variant was found in a male with both maternal and paternal Native American lineages, suggesting that this allele is present in Native Americans and hence should not be used as an indicator of admixture. APOE*3 and APOE*4 present, respectively, positive and negative associations with latitude, although the pattern is much more pronounced in the Northern Hemisphere than in South America. APOE*2 increases its frequency with latitude but this pattern is statistically significant only in South America.

CONCLUSION

The overall APOE spatial pattern seems, in general, compatible with a directional demographic expansion which occurred in north-eastern Asia and much of the New World. The APOE*2 allele shows this pattern in South America but a random distribution in the Northern Hemisphere, suggesting that the possibility of selection should not be discarded.

A novel oculo-oto-facial dysplasia in a Native Alaskan community with autosomal recessive inheritance

We describe a novel autosomal recessive malformation syndrome in four related individuals from a geographically isolated Native Alaskan community, who have facial defects similar to those of individuals with Treacher Collins (TCS) and Miller syndrome. Distinctive findings include malar and mandibular hypoplasia, lower eyelid coloboma, choanal atresia, orofacial clefting, and external ear malformation with preauricular tags. Intellect is normal and profound mixed hearing loss has been observed in affected adults. Variable extracranial findings include atrioseptal defect, renal dysplasia, and imperforate anus, however, no limb defects have been observed. Cranial imaging studies demonstrate relative prominence of the zygoma, inferior orbital maxillary hypoplasia, and lateral orbital wall defects with an accessory superior bony projection off the zygoma lateral to the orbital rim. We propose that these individuals have inherited a novel autosomal recessive condition we have termed oculo-oto-facial dysplasia (OOFD) with unique radiographic findings.

Genomic anthropology: coming in from the cold?

By rendering obsolete the theoretical opposition of nature and culture, the study of the human genome has given rise to fresh networks among anthropologists and other scholars. These developments, in turn, invite a refashioning of anthropology. Because genomic studies are directly concerned with the constitution of personhood, they must engage with local notions of personhood and belonging, thus undermining the distinction between experts and laypersons and demonstrating the need for new frameworks for collaboration between anthropologists and their subjects. These trends are illustrated by research in Nunavut (Canada) and Greenland, in particular an examination of the similarities and differences between modern gene talk about the constitution of the individual and "Inuit epigenetics"--local notions of naming, subjectivity, and relatedness.

Generation time and effective population size in Polar Eskimos

North Greenland Polar Eskimos are the only hunter-gatherer population, to our knowledge, who can offer precise genealogical records spanning several generations. This is the first report from Eskimos on two key parameters in population genetics, namely, generation time (T) and effective population size (Ne). The average mother-daughter and father-son intervals were 27 and 32 years, respectively, roughly similar to the previously published generation times obtained from recent agricultural societies across the world. To gain an insight for the generation time in our distant ancestors, we calculated maternal generation time for two wild chimpanzee populations. We also provide the first comparison among three distinct approaches (genealogy, variance and life table methods) for calculating Ne, which resulted in slightly differing values for the Eskimos. The ratio of the effective to the census population size is estimated as 0.6-0.7 for autosomal and X-chromosomal DNA, 0.7-0.9 for mitochondrial DNA and 0.5 for Y-chromosomal DNA. A simulation of alleles along the genealogy suggested that Y-chromosomal DNA may drift a little faster than mitochondrial DNA in this population, in contrast to agricultural Icelanders. Our values will be useful not only in prehistoric population inference but also in understanding the shaping of our genome today.

Growth hormone (GH) insensitivity and insulin-like growth factor-I deficiency in Inuit subjects and an Ecuadorian cohort: functional studies of two codon 180 GH receptor gene mutations

CONTEXT

Among more than 250 cases of GH insensitivity syndrome (GHIS) reported to date, the largest cohort was identified in southern Ecuador. In the Ecuadorian GHIS cohort, a sense mutation (GAA>GAG) at codon E180 of GH receptor [GHR (E180sp)] results in deletion of codons 181-188. No functional studies of this mutation have been performed, nor have different mutations at codon 180 been reported.

OBJECTIVE

We now report identification of a novel GHR mutation, also within codon E180, in two distantly related GHIS subjects of Inuit origin and provide mechanistic insights into the defects caused by the Inuit and Ecuadorian GHR mutations.

PATIENTS

The two Inuit subjects, with heights of -5 sd score and -7 sd score, respectively, had elevated circulating levels of GH but low levels of GH-binding protein, IGF-I, and IGF-binding protein-3.

RESULTS

Both Inuit subjects carry the same novel nonsense homozygous GHR mutation at codon E180 (GAA->TAA, E180X). In vitro reconstitution experiments demonstrated that GHR (E180sp), but not GHR (E180X), could be stably expressed. GHR (E180sp), however, could not bind GH and could neither activate signal transducer and activator of transcription-5b nor induce -5b-dependent gene expression on GH treatment. Furthermore, the GHR (E180sp), which has a deletion of eight amino acid residues within the GHR dimerization domain, although retaining the ability to homodimerize, was defective in trafficking to the cell surface.

CONCLUSIONS

The E180X mutation identified in two Inuit patients resulted in a truncated, unstably expressed GHR variant, whereas the E180 splicing mutation previously identified in the Ecuadorian cohort, affected both GH binding and GHR trafficking and rendered the abnormal GHR nonfunctional.

HLA genes of Aleutian Islanders living between Alaska (USA) and Kamchatka (Russia) suggest a possible southern Siberia origin

Aleuts HLA profile has been compared with that of neighboring and worldwide populations. Thirteen thousand one hundred and sixty-four chromosomes have been used for this study. Computer programs have obtained HLA allele frequencies, genetic distances between populations, NJ relatedness dendrograms, correspondence analysis and most frequent HLA extended haplotypes. Aleuts have inhabited Aleutian Islands since about 9000 years BP according to fossil and genetic (mtDNA) records. They are genetically different to Eskimo, Amerindian and Na-Dene speakers according to their HLA profile; this correlates with cultural and anthropological Aleut distinctiveness. No typical Amerindian HLA alleles have been found in a significant frequency. Their HLA relatedness to Saami (or Lapps, northern Scandinavians), Finns and Pomors (North-West Russia) indicates an ancient possible origin from the Baikal Lake Area (southern Siberia) around the present day Buryat peopling area; other origins are not discarded. Aleuts characteristic HLA profile may influence future transplantation programs in the region and be useful to study diseases linked to HLA epidemiology.

Population based study of health and living conditions in areas with both Sámi and Norwegian populations--the SAMINOR study

OBJECTIVES

The overall aim of the SAMINOR project was to study health and diseases in relation to living conditions among the Sámi population and to compare these with the Norwegian population in the same area. This article provides an overview of the background of the study and a description of the methods employed for the data collection. We give sample characteristics and elaborate on different definitions of ethnicity.

STUDY DESIGN

Cross-sectional, population-based study, including questionnaires, a clinical examination and analyses of blood samples.

METHODS

All individuals 30 or 36 to 79 years of age who were living in defined municipalities or specified local areas with a known Sámi population were invited to a cardiovascular screening program. The data were collected during 2003-2004. The questionnaires focused on living conditions, health, Sámi traditions and ethnicity. The eligible population consisted of 27,987 individuals and 16,865 (60.6%) participated by answering at least one questionnaire. Analyses were restricted to the 36 to 79 year-old age group which had 16,538 participants. The screening program comprised a blood sample, measurements of blood pressure, height, weight, and waist and hip ratio. Different definitions of Sámi ethnicity were explored.

RESULTS

Of the sample, 35.6% reported Sámi background, and 13.2% reported that they, their parents and their grandparents had Sámi as their domestic language. This stringent definition of Sámi produced clearer differences between Sámi and Norwegians, as shown for some measures of socioeconomic status.

CONCLUSIONS

The findings that are related to more strict definitions of Sámi ethnicity have important implications for the interpretation of earlier works and for future studies.

mtDNA from hair and nail clarifies the genetic relationship of the 15th century Qilakitsoq Inuit mummies

The 15th century Inuit mummies excavated at Qilakitsoq in Greenland in 1978 were exceptionally well preserved and represent the largest find of naturally mummified specimens from the Arctic. The estimated ages of the individuals, their distribution between two adjacent graves, the results of tissue typing, and incomplete STR results led researchers to conclude that the eight mummies formed two distinct family groups: A grandmother (I/5), two daughters (I/3, I/4), and their two children (I/1, I/2) in one grave, and two sisters (II/6, II/8) and a daughter (II/7) of one of them in the other. Using mtDNA from hair and nail, we have reanalyzed the mummies. The results allowed the unambiguous assignment of each of the mummies to one of three mtDNA haplogroups: A2b (I/5); A2a (I/2, I/3, II/6, II/8); A2a-311 (I/1, I/4, II/7), excluded some of the previous relations, and pointed to new ones. I/5 is not the grandmother/mother of the individuals in Grave I, and she is not maternally related to any of the seven other mummies; I/3 and I/4 are not sisters and II/7 is neither the daughter of II/6 nor of II/8. However, I/1 may be the child of either I/4 or II/7 and these two may be sisters. I/2 may be the son of I/3, who may be the daughter of either II/6 or II/8, and these two may be sisters. The observation of haplogroups A2a and A2b amongst the 550-year-old Inuit puts a lower limit on the age of the two lineages in Greenland.

Polymorphisms in genes regulating androgen activity among prostate cancer low-risk Inuit men and high-risk Scandinavians

In Greenland, with a male population of approximately 30 000 individuals, the incidence of prostate cancer is extremely low with only three cases described during the period 1988-1997. Polymorphisms related to high androgen metabolism and/or response in the 5alpha-reductase type 2 (SRD5A2) and the androgen receptor (AR) genes, respectively, have been linked to prostate cancer. Our objective was to analyse whether the distribution of these polymorphisms differed between the prostate cancer low-risk population from Greenland and the relatively high-risk Swedish male population. The SRD5A2 polymorphisms A49T, V89L and R227Q, and the CAG and GGN repeats in the AR gene were genotyped in leucocyte DNA from 196 Greenlanders and 305 Swedish military conscripts. All subjects had the wild-type R/R genotype of the R227Q marker. The high-activity variants A49T A/T and V89L V/V occurred less frequently (2% vs. 5%, p = 0.048 and 33% vs. 46%, p = 0.0027) in Greenland compared with Sweden, whereas the low-activity L/L genotype was more frequent in Greenland (24% vs. 13%, p = 0.0024). Greenlanders also had longer AR CAG repeats than the Swedish population (median 24 vs 22, p < 0.0005). Greenlanders also had a higher frequency of the GGN = 23 allele (85% vs. 54%, p < 0.0001). Our results suggest that Greenlanders are genetically predisposed to a lower activity in testosterone to 5alpha-dihydrotestosterone turnover and to lower AR activity, which, at least partly, could explain their low incidence of prostate cancer.

HLA genes in Cubans and the detection of Amerindian alleles

Caribbean Islands including Cuba were first inhabited by Meso-American and later by Arawak-speaking Amerindians from nowadays Venezuela. Spanish invaders brought to almost extinction to the Amerindian population after 1492. Black slaves from West Africa were taken into Cuba by Europeans. The degree of admixture among populations is approached. HLA alleles were studied by DNA techniques. Comparison with other worldwide populations (a total of 14.094 chromosomes) included genetic distances, Neighbour-Joining dendrograms, correspondence analyses and calculation of extended haplotypes. While African-European HLA features were clearly found, Amerindian HLA characteristics are less evident, indicating that Amerindian devastation was particularly marked after 1492 AD. However, typical Amerindian alleles have been found in our Cuban sample, i.e. DRB1*0403, DRB1*0404, DRB1*0407, DRB1*0411, DRB1*0802 and DRB1*1602. The presence of Amerindian alleles in Cubans [corrected] may have a bear in the making up of transplantation registries (both for bone marrow and solid organ transplantation) at the regional level and also be important for epidemiological studies of diseases linked to HLA.

Deficiency of mannan-binding lectin associated serine protease-2 due to missense polymorphisms

Mannan-binding lectin (MBL) and ficolins distinguish between self, non-self and altered-self by recognizing patterns of ligands on the surface of microorganisms or aberrant cells. When this happens MBL-associated serine protease-2 (MASP-2) is activated and cleaves complement factors to start inflammatory actions. We examined human populations for MASP-2 levels, MASP-2 function and for the presence of mutations in coding exons of MASP2. The MASP-2 levels were lowest in Africans from Zambia (median, 196 ng/ml) followed by Hong Kong Chinese (262 ng/ml), Brazilian Amerindians (290 ng/ml) and Danish Caucasians (416 ng/ml). In the Chinese population, we uncovered a novel four amino-acid tandem duplication (p.156_159dupCHNH) associated with low levels of MASP-2. The frequency of this mutation as well as the SNPs p.R99C, p.R118C, p.D120G, p.P126L and p.V377A were analyzed. The p.156_159dupCHNH was only found in Chinese (gene frequency 0.26%) and p.D120G was found only in Caucasians and Inuits from West-Greenland. The p.P126L and p.R99Q were present in Africans and Amerindians only, except for p.R99Q in one Caucasian. The MASP-2 levels were reduced in individuals with p.V377A present. The MASP-2 present in individuals homozygous for p.377A or p.99Q had a normal enzyme activity whereas MASP-2 in individuals homozygous for p.126L was non-functional.

Variations in ADH and ALDH in Southwest California Indians

Native Americans as a group have the highest rates of alcohol-related deaths of all ethnicities in the United States; however, it remains unclear how and why a greater proportion of individuals in some Native American communities develop alcohol-related problems and alcohol use disorders (AUDs). One potential factor that can influence responses to alcohol are variations in alcohol-metabolizing enzymes. Researchers have analyzed the frequencies of variants in the alcohol-metabolizing enzymes alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) in some Native American populations. So far the studies have yielded no evidence that an ALDH2 variant, which has shown protective effects in other populations, is found in either American Indians or Alaska Natives. A variant of the ALDH1 enzyme that is encoded by the ALDH1A1*2 allele, however, was found in a small proportion of a group of Southwest California Indians and had a protective effect against alcoholism in that population. Furthermore, a variant of the ADH1B enzyme that is encoded by the ADH1B*3 allele was found in a similar proportion of Southwest California Indians and also was associated with a protective effect. However, these findings do not explain the high prevalence of alcoholism in the tribes investigated.

DNA on loan: issues to consider when carrying out genetic research with aboriginal families and communities

In the current research milieu where genetic etiology is considered a critical component in the discovery of pathogenesis, aboriginal families and communities affected with genetic conditions may be considered as research participants. However, because of concerns about the impact of genetic information and historical harmful research practices, some aboriginal communities have considerable unease when faced with this prospect. Therefore, in the circumstance that genetics is considered an important part of research inquiry by aboriginal families and communities, there needs to be assurance that the research will be carried out according to mutual expectations. A research relationship that respects aboriginal individuals and communities within their culture and is in keeping with their values is essential. This respect extends to the use of biological samples, considering the DNA to be 'on loan' to the researcher for the purpose of the research for which consent was obtained. This paper will explore practical ways of maintaining a respectful research relationship when genetics research with aboriginal people is undertaken.

Disparities in Lung Cancer: Focus on Asian Americans and Pacific Islanders, American Indians and Alaska Natives, and Hispanics and Latinos

Significant population changes in the United States are expected over the next few decades. The changing demographics inclusive of native and newly native individuals will significantly impact health care because racial and ethnic groups vary widely in their risks for disease and approach to medical care. For lung cancer specifically, racial and ethnic groups differ in smoking habits, metabolism of nicotine, presentation, stage at diagnosis, treatment received, and outcomes. This article summarizes current information on lung cancer for American and Pacific Islanders, American Indians and Alaska natives,and Hispanics and Latinos with an emphasis on tobacco use, epidemiologic issues sur-rounding acculturation and assimilation, genetic epidemiology, and disparities in treatment outcomes.

Lifestyle modifies obesity-associated risk of cardiovascular disease in a genetically homogeneous population

BACKGROUND

The association between obesity and cardiovascular disease risk differs across populations. Whether such differences in obesity-related risk factors exist within population groups of the same genetic origin but with differences in lifestyle remains to be determined.

OBJECTIVE

The aim was to analyze whether obesity was associated with the same degree of metabolic disturbances in 2 groups of genetically homogeneous Inuit who were exposed to considerable differences in lifestyle.

DESIGN

We studied obesity and cardiovascular disease risk factors in a cross-sectional population survey of 2311 Inuit living in Denmark (n = 995) or Greenland (n = 1316). The participants received an oral-glucose-tolerance test. Blood tests were supplemented by structured interviews and anthropometric and blood pressure measurements.

RESULTS

The trend in the association between obesity and metabolic effects was not significantly different in the Inuit populations, but the values of several risk factors were significantly different. At any given level of obesity, Inuit residents in Greenland had lower blood pressure and lower concentrations of triacylglycerol and postchallenge plasma glucose and insulin than did the Inuit migrants in Denmark. The trend in the association with obesity categories was different only for HDL cholesterol, with higher concentrations observed in women Inuit migrants in Denmark than in women Inuit residents in Greenland.

CONCLUSIONS

The health risk associated with obesity clearly varies within groups of Inuit living in Greenland and Inuit migrants living in Denmark. The findings indicate that lifestyle factors modify the cardiovascular disease risk associated with obesity.

Impact of PCB and p,p'-DDE contaminants on human sperm Y:X chromosome ratio: studies in three European populations and the Inuit population in Greenland

OBJECTIVE

Recent studies indicate that persistent organohalogen pollutants (POPs) may contribute to sex ratio changes in offspring of exposed populations. Our aim in the present study was to investigate whether exposure to 2,2 ,4,4 ,5,5 -hexachlorobiphenyl (PCB-153) and dichlorodiphenyldichloroethene (p,p -DDE) affects sperm Y:X chromosome distribution.

SUBJECTS AND METHODS

We obtained semen and blood for analysis of PCB-153 and p,p -DDE levels from 547 men from Sweden, Greenland, Poland (Warsaw), and Ukraine (Kharkiv), with regionally different levels of POP exposure. The proportion of Y- and X-chromosome-bearing sperm in the semen samples was determined by two-color fluorescence in situ hybridization analysis.

RESULTS

Swedish and Greenlandic men had on average significantly higher proportions of Y sperm (in both cohorts, 51.2%) and correspondingly higher lipid-adjusted concentrations of PCB-153 (260 ng/g and 350 ng/g, respectively) compared with men from Warsaw (50.3% and 22 ng/g) and Kharkiv (50.7% and 54 ng/g). In the Swedish cohort, log-transformed PCB-153 and log-transformed p,p -DDE variables were significantly positively associated with Y-chromosome fractions (p-values 0.04 and <0.001, respectively). On the contrary, in the Polish cohort PCB-153 correlated negatively with the proportion of Y-bearing fraction of spermatozoa (p=0.008).

CONCLUSIONS

The present study indicates that POP exposure might be involved in changing the proportion of ejaculated Y-bearing spermatozoa in human populations. Intercountry differences, with different exposure situations and doses, may contribute to varying Y:X chromosome ratios.

Genetic structure of the Aleuts and Circumpolar populations based on mitochondrial DNA sequences: A synthesis

The mtDNA variation of 198 Aleuts, as well as North American and Asian populations drawn from the literature, were analyzed to reconstruct the Aleuts' genetic prehistory and to investigate their role in the peopling of the Circumarctic region. From median-joining network analysis, three star-like clusters were identified in the Aleuts within the following subhaplogroups: A3, A7 (an Aleut-specific subclade of A3), and D2. Mismatch analyses, neutrality test scores, and coalescent time estimates for these three components provided evidence of two expansion events, one occurring at approximately 19,900 B.P. and the other at 5,400 B.P. Based on these findings and evidence from the archaeological data, four general models for the genetic prehistory of the Aleutian Island chain are proposed: 1) biological continuity involving a kin-structured peopling of the archipelago; 2) intrusion and expansion of a non-native biface-producing population dominated by subhaplogroup D2; 3) amalgamation of Arctic Small Tool tradition peoples characterized by D2 with an older Anangula substratum; and 4) biological continuity with significant gene flow from neighboring populations of the Alaskan mainland and Kodiak Island. The Aleut mtDNAs are consistent with the Circumarctic pattern by the fixation of A3 and D2, and the exhibition of depressed diversity levels relative to Amerind and Siberian groups. The results of this study indicate a broad postglacial reexpansion of Na-Dene and Esko-Aleuts from reduced populations within northern North America, with D2 representing a later infusion of Siberian mtDNAs into the Beringian gene pool.

Common set of genes regulates low-density lipoprotein size and obesity-related factors in Alaskan Eskimos: Results from the GOCADAN Study

Increasing incidence of cardiovascular disease in traditionally low-risk Alaskan Eskimos is a cause for concern. The purpose of this study was to examine the genetic and environmental correlations of low-density lipoprotein (LDL) subfractions with obesity-related factors in Alaskan Eskimos, using data from the first 954 participants of the Genetics of Coronary Artery Disease in Alaska Natives Study. Estimates of genetic and environmental influence were calculated using a maximum likelihood variance component method implemented in SOLAR. Mean values of weight, body mass index (BMI), and waist were 73.4 +/- 0.5 kg, 27.6 +/- 0.2 kg/m2, and 88.0 +/- 0.4 cm, respectively. LDL, and its small (LDL1), medium (LDL2), and large (LDL3) subfractions, had mean values of 115.8 +/- 1.2 mg/dl, 8.3 +/- 0.4 mg/dl, 19.6 +/- 0.8 mg/dl, and 71.5 +/- 1.5 mg/dl, respectively. Bivariate analysis displayed significant genetic correlations between LDL subfractions and obesity-related factors: LDL1 with BMI (rhoG = 0.67, P < 0.05), waist (rhoG = 0.80, P < 0.001), and subscapular and tricep skinfolds (rhoG = 0.93, P < 0.005, and rhoG = 0.78, P < 0.05, respectively); LDL2 with BMI (rhoG = 0.52, P < 0.05), waist (rhoG = 0.46, P < 0.05), and tricep skinfold (rhoG = 0.60, P < 0.05); and mean LDL size with BMI (rhoG = -0.36), waist (rhoG = -0.42,), and subscapular and tricep skinfolds (rhoG = -0.44 and -0.43, respectively) (P < 0.005). These results show that a common set of genes is influencing LDL size and obesity-related factors in Alaskan Eskimos.

mtDNA variation in Inuit populations of Greenland and Canada: Migration history and population structure

We examined 395 mtDNA control-region sequences from Greenlandic Inuit and Canadian Kitikmeot Inuit with the aim of shedding light on the migration history that underlies the present geographic patterns of genetic variation at this locus in the Arctic. In line with previous studies, we found that Inuit populations carry only sequences belonging to haplotype clusters A2 and D3. However, a comparison of Arctic populations from Siberia, Canada, and Greenland revealed considerable differences in the frequencies of these haplotypes. Moreover, large sample sizes and regional information about birthplaces of maternal grandmothers permitted the detection of notable differences in the distribution of haplotypes among subpopulations within Greenland. Our results cast doubt on the prevailing hypothesis that contemporary Inuit trace their all of their ancestry to so-called Thule groups that expanded from Alaska about 800-1,000 years ago. In particular, discrepancies in mutational divergence between the Inuit populations and their putative source mtDNA pool in Siberia/Alaska for the two predominant haplotype clusters, A2a and A2b, are more consistent with the possibility that expanding Thule groups encountered and interbred with existing Dorset populations in Canada and Greenland.

Inter-population variations in concentrations, determinants of and correlations between 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p'-DDE): a cross-sectional study of 3161 men and women from Inuit and European populations

BACKGROUND

The study is part of a collaborative project (Inuendo), aiming to assess the impact of dietary persistent organochlorine pollutants (POPs) on human fertility. The aims with the present study are to analyze inter-population variations in serum concentrations of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p'-DDE), to assess inter-population variations in biomarker correlations, and to evaluate the relative impact of different determinants for the inter-individual variations in POP-biomarkers.

METHOD

In study populations of 3161 adults, comprising Greenlandic Inuits, Swedish fishermen and their wives, and inhabitants from Warsaw, Poland and Kharkiv, Ukraine, serum concentrations of CB-153 and p,p'-DDE, were analysed by gas chromatography-mass spectrometry.

RESULTS

The median serum concentrations of CB-153 were for male and female Inuits 200 and 110, for Swedish fishermen 190 and their wives 84, for Kharkiv men and women 44 and 27, and for Warsaw men and women 17 and 11 ng/g lipids, respectively. The median serum concentrations of p,p'-DDE were for Kharkiv men and women 930 and 650, for male and female Inuits 560 and 300, for Warsaw men and women 530 and 380, and for Swedish fishermen 240 and their wives 140 ng/g lipids, respectively. The correlation coefficients between CB-153 and p,p'-DDE varied between 0.19 and 0.92, with the highest correlation among Inuits and the lowest among men from Warsaw. Men had averagely higher serum concentrations of CB-153 and p,p'-DDE, and there were positive associations between age and the POP-biomarkers, whereas the associations with BMI and smoking were inconsistent. Dietary seafood was of importance only in the Inuit and Swedish populations.

CONCLUSION

CB-153 concentrations were much higher in Inuits and Swedish fishermen's populations than in the populations from Eastern Europe, whereas the pattern was different for p,p'-DDE showing highest concentrations in the Kharkiv population. The correlations between the POP-biomarkers varied considerably between the populations, underlining that exposure sources differ and that the choice of representative biomarkers of overall POP exposure has to be based on an analysis of the specific exposure situation for each population. Age and gender were consistent determinants of serum POPs; seafood was of importance only in the Inuit and Swedish populations.

Intra- and intercontinental molecular variability of an Alu insertion in the 3' untranslated region of the LDLR gene

One-hundred three individuals from two Mongolian, two Siberian, and ten native American populations were studied in relation to a 340-bp sequence from an Alu insertion located in the 3' untranslated region of the LDLR gene. Seven haplotypes have been determined, and haplotype B1 was the most common, accounting for about half the sequences found. In general, diversity values are quite high, about 2.5 times higher than those found in other autosomal Alu sequences. Almost all (93%) of the variability occurs at the intrapopulation level, but the greatest among-group differentiation (6-8%) was found when we grouped in a single population all Native Americans plus Siberian Eskimos and Chukchi and compared them with Mongolians. This result is compatible with earlier mtDNA and Y-chromosome suggestions of a single origin for the first colonizers of the American continent. With this nuclear locus it was not possible to broadly distinguish between Central and South American natives. No evidence of selection or marked demographic changes was obtained with these data.

Spondylolytic spondylolisthesis: a study of pelvic and lumbosacral parameters of possible etiologic effect in two genetically and geographically distinct groups with high occurrence

STUDY DESIGN

An anatomic and radiographic study of archeological skeletal remains from two genetically and geographically distinct groups with high occurrence rates of spondylolytic spondylolisthesis was done. Specimens were Aleut (27% known occurrence rate, n = 48) and Arikara Plains Indians (9% occurrence, n = 250+ of 1,062).

OBJECTIVE

To evaluate three radiographic parameters highly correlated with spondylolisthesis (pelvic incidence [PI], sacral table angle [STA], and lumbar index [LI]) in genetically homogeneous populations to determine which may be etiologic or most predictive for lysis.

SUMMARY OF BACKGROUND DATA

LI has been known to vary with the percentage of slip in lytic spondylolisthesis. Recent clinical studies have shown that PI is also significantly higher in high-grade slips, and a possible etiologic effect has been ascribed to this association. STA has also been shown to vary between normals, those with only lysis, and those with lysis and slip. The etiologic significance of STA is unknown.

METHODS

Radiographic and direct morphologic measurement of PI, LI, and STA was done on L5 and reassembled sacra and ilia. Statistical analysis of these three parameters among all groups was done.

RESULTS

1) There is a genetically determined difference in the upper sacral tilt (STA) that may be etiologic. 2) Genetically homogeneous groups with a lower STA in normal specimens have an increased occurrence rate of spondylolysis. 3) When there has been pars lysis, changes in the STA occur as well as deformity more caudal in the sacrum. 4) These changes are likely related to remodeling with epiphyseal growth related to changed axial stresses secondary to pars lysis. 5) PI is not a primary etiologic factor in the process.

CONCLUSIONS

The STA in the normal population for each genetic group varies and relates significantly to the occurrence rate and is thus probably etiologic. STA is more highly associated with the occurrence of pars defect than is PI. Upper sacral deformities appear due to the growth plate response to the changed pressure gradients across the epiphyseal plate rather than interosseous remodeling of the ilium and acetabular area. Thus, changes in PI would be secondary.

Serum lipids of Greenland Inuit in relation to Inuit genetic heritage, westernisation and migration

BACKGROUND

The reputed low prevalence of cardiovascular disease among the Inuit has recently been challenged. Studies have shown total cholesterol among the Inuit to differ little from that of western populations and the association between cholesterol and atherosclerosis to be inconsistent.

METHODS

We studied serum lipids in a population survey among 2114 Inuit living in Denmark or in West Greenland. Blood tests were supplemented by structured interviews, anthropometry and measurements of blood pressure.

FINDINGS

Compared with the general population of Denmark, total cholesterol was higher among Inuit women, while HDL-cholesterol was higher among Inuit men. Triglyceride was lower among Inuit of both sexes. Cholesterol and triglyceride varied according to westernisation, diet, alcohol consumption and smoking. In a multivariate analysis, serum lipids also differed significantly between pure and genetically mixed Inuit: HDL-cholesterol was higher among the genetically pure Inuit, while among men triglyceride was lower and among women total and LDL-cholesterol were higher.

INTERPRETATION

Among the Inuit, serum lipids are significantly associated with westernisation and genetic heritage. The effect of westernisation is to some extent due to dietary changes. From a cardiovascular health point of view, westernisation within Greenland is associated with unfavourable lipid changes while migration to Denmark is associated with favourable lipid changes.

Blondes, lost and found: representations of genes, identity, and history

Research carried out during recent decades has revealed our genome not only to be a unique mine of information about health, disease and the human condition, but also about the origin and dispersal history of the species. In this context, the genome is simply an additional source of information about human history, epistemologically no different from other historical sources. However, media and public interpretation of genetic studies of human history are complicated by the wider connotations of genes as the determinants of hereditary features and identity. We discuss two examples of media and public fascination with the interrelated themes of history, identity and heredity, pointing out some implications of historical research using genetic data in the context of our own ongoing study of Inuit groups in Greenland and Victoria Island, Canada.

Patterns of mtDNA Diversity in Northwestern North America

The mitochondrial DNA (mtDNA) haplogroups of 54 full-blooded modern and 64 ancient Native Americans from northwestern North America were determined. The control regions of 10 modern and 30 ancient individuals were sequenced and compared. Within the Northwest, the frequency distribution for haplogroup A is geographically structured, with haplogroup A decreasing with distance from the Pacific Coast. The haplogroup A distribution suggests that a prehistoric population intrusion from the subarctic and coastal region occurred on the Columbia Plateau in prehistoric times. Overall, the mtDNA pattern in the Northwest suggests significant amounts of gene flow among Northwest Coast, Columbia Plateau, and Great Basin populations.

[Genetic history of Aleuts of the Komandor islands from results of analyzing variability of class II HLA genes]

Variability of the HLA class II genes (alleles of the DRB1, DQA1, and DQB1 loci) was investigated in a sample of Aleuts of the Commanders (n = 31), whose ancestors inhabited the Commander Islands for many thousand years. Among 19 haplotypes revealed in Aleuts of the Commanders, at most eight were inherited from the native inhabitants of the Commander Islands. Five of these haplotypes (DRB1*0401-DQA1*0301-DQB1*0301, DRB1*1401-DQA1*0101-DQB1*0503, DRB1*0802-DQA1*0401-DQB1*0402, DRB1*1101-DQA1*0501-DQB1*0301, and DRB1*1201-DQA1*0501-DQB1*0301) were typical of Beringian Mongoloids, i.e., Coastal Chukchi and Koryaks, as well as Siberian and Alaskan Eskimos. Genetic contribution of the immigrants to the genetic pool of proper Aleuts constituted about 52%. Phylogenetic analysis based on Transberingian distribution of the DRB1 allele frequencies favored the hypothesis on the common origin of Paleo-Aleuts, Paleo-Eskimos, and the Indians from the northwestern North America, whose direct ancestors survived in Beringian/southwestern Alaskan coastal refugia during the late Ice Age.