Y chromosome polymorphisms in Native American and Siberian populations: identification of Native American Y chromosome haplotypes

We have initiated a study of ancient male migrations from Siberia to the Americas using Y chromosome polymorphisms. The first polymorphism examined, a C→T transition at nucleotide position 181 of the DYS199 locus, was previously reported only in Native American populations. To investigate the origin of this DYS199 polymorphism, we screened Y chromosomes from a number of Siberian, Asian, and Native American populations for this and other markers. This survey detected the T allele in all five Native American populations studied at an average frequency of 61%, and in two of nine native Siberian populations, the Siberian Eskimo (21%) and the Chukchi (17%). This finding suggested that the DYS199 T allele may have originated in Beringia and was then spread throughout the New World by the founding populations of the major subgroups of modern Native Americans. We further characterized Native American Y chromosome variation by analyzing two additional Y chromosome polymorphisms, the DYS287 Y Alu polymorphic (YAP) element insertion and a YAP-associated A→G transition at DYS271, both commonly found in Africans. We found neither African allele associated with the DYS199 T allele in any of the Native American or native Siberian populations. However, we did find DYS287 YAP+ individuals who harbored the DYS199 C allele in one Native American population, the Mixe, and in one Asian group, the Tibetans. A correlation of these Y chromosome alleles in Native Americans with those of the DYS1 locus, as detected by the p49a/p49f (p49a,f) probes on TaqI-digested genomic DNA, revealed a complete association of DYS1 alleles (p49a,f haplotypes) 13, 18, 66, 67 and 69 with the DYS199 T allele, while DYS1 alleles 8 and 63 were associated with both the DYS199 C and T allele. Received: 18 November 1996 / Accepted: 19 May 1997     

Genotype and allele frequency of human multidrug resistance (MDR1) gene C3435T polymorphism in Denizli province of Turkey

Human p-glycoprotein encoded by human multidrug resistance (MDR1) gene, is a transmembrane protein that serves as efflux pump for a wide variety of lipophilic compounds possessing a physiological role in protecting cells against the DNA damaging of certain xenobiotics. According to the published data, the frequency of C3435T polymorphism differs depending on the different ethnical populations such as Asian, African, and Caucasians populations. In our study, we identified the MDR1 C3435T polymorphism in 150 healthy volunteers in Denizli province of Turkey. DNA was extracted from peripheral blood samples by standard phenol/chloroform extraction method. Polymerase chain reaction–restriction fragment length polymorphism was used for the detection of C3435T single nucleotide polymorphism. We obtained CC, CT and TT genotype frequencies as 20, 53 and 27%, respectively. According to our results, the C allele in Turkish population (Denizli province, west of Turkey) is found 47% and this data shows similarity with Caucasian (UK and German) populations and significantly lower than African populations (p < 0.001). Our study is the first data on the genotype and allele frequency of the human multidrug resistance (MDR1) Gene C3435T Polymorphism in Denizli Province at regional basis in Turkey. Our results could serve as a basis for large-scale correlation studies on the relevance of C3435T genotype in cancer therapy and other diseases in Turkish population. Investigation of genotype frequencies related with p-glycoprotein substrates should be investigated in large scale at regional bases in Turkish population. The scaled-up data might help either to the use of p-glycoprotein substrates to be used for therapeutic applications and population genetics considering the genotype frequencies possibly occurring throughout the history in Anatolian basin.     

MDR1 C3435T polymorphism has no influence on developing Helicobacter pylori infection-related gastric cancer and peptic ulcer in Japanese

AIMS: P-glycoprotein, the gene product of multidrug-resistant transporter-1 (MDR1), confers multidrug resistance against antineoplastic agents but also affects the kinetic disposition of some drugs and carcinogens. MDR1 C3435T polymorphism influences the development of colon cancer and adult acute myeloid leukemia by the association with transporting carcinogen. The aim of this study was to clarify the association of MDR1 C3435T polymorphism with susceptibility to gastric cancer and peptic ulcers in patients with Japanese H. pylori infection. MAIN METHODS: We assessed the MDR1 C3435T polymorphism in H. pylori-positive gastritis alone patients (n=150), gastric cancer (n=292), gastric ulcer (n=215), and duodenal ulcer (n=163) and H. pylori-negative subjects (n=168) as control by a PCR-based method. KEY FINDINGS: No significant difference existed in frequencies of MDR1 C3435T polymorphisms between H. pylori-negative controls and H. pylori-positive gastritis alone patients. Moreover, MDR1-3435 T allele carriage didn't affect the risk of gastric cancer or peptic ulcer development. The age- and sex-adjusted odds ratios (ORs) of MDR1 3435 T allele carriers relative to the C/C genotype group for gastric cancer, gastric ulcer and duodenal ulcer risk were 0.96 (95%CI: 0.56-1.66), 1.16 (95%CI: 0.72-1.84) and 1.00 (95%CI: 0.61-1.62), respectively. SIGNIFICANCE: In this preliminary data, the association with MDR1 C3435T polymorphism and risk for developing H. pylori-related gastric cancer and peptic ulcer in Japanese was low. P-glycoprotein might not be involved in the carcinogenesis of H. pylori-related gastric cancer.     

The drug-transporter gene MDR1 C3435T and G2677T/A polymorphisms and the risk of multidrug-resistant epilepsy in Turkish children

One-third of all individuals with epilepsy are resistant to antiepileptic drug (AED) treatment. Antiepileptic treatment response has been suggested to be modulated by genetic polymorphisms of drug efflux transporters. Several polymorphic variants within the multidrug resistance 1 (MDR1) gene, which encodes the major transmembrane efflux transporter P-glycoprotein, have been proposed to be associated with AED resistance in epilepsy patients. The aim of this study was to evaluate the effect of C3435T and G2677T/A polymorphisms of MDR1 on AED resistance in Turkish children with epilepsy. MDR1 C3435T and G2677T/A were genotyped in 152 patients with epilepsy, classified as drug-resistant in 69 and drug-responsive in 83. Genotypes of the C3435T and G2677T/A polymorphisms were determined by polymerase chain reaction followed by restriction fragment length polymorphism. Genotype and allele frequencies of C3435T and G2677T/A polymorphisms of the MDR1 gene did not differ between drug-resistant and drug-responsive epilepsy patients. Our results suggest that MDR1 C3435T and G2677T/A polymorphisms are not associated with AED resistance in Turkish epileptic patients. To clarify the exact clinical implication of the MDR1 polymorphisms on the multidrug resistance in epilepsy, further investigations in various ethnic populations would be necessary.     

The role of Multidrug Resistance-1 (MDR1) variants in response to atorvastatin among Jordanians

The MDR1 gene encodes for P-glycoprotein (P-gp), which is an efflux transporter at the cell membrane. The P-gp has wide substrate specificity for multiple medications including the lipid lowering drug, atorvastatin. In this study, we investigated the possible association between three common MDR1 gene polymorphisms (G2677T, C3435T, and C1236T), and the lipid lowering effect of atorvastatin among Jordanians. Lipid and lipoproteins were measured in blood samples collected from patients (n = 201) at baseline and during atorvastatin treatment. MDR1 polymorphisms were genotyped using polymerase chain reaction–restriction fragment length polymorphism. Both the TT genotype of G2677T and the TT genotype of the C3435T polymorphisms were associated with lower levels of low-density lipoproteins after atorvastatin treatment. However, the effects of atorvastatin on the levels of total cholesterol, triglycerides, and high-density lipoprotein, were not correlated with any of the genotypes in both polymorphisms. Finally, the C1236T polymorphism was not associated with the lipid lowering effect of atorvastatin. In conclusion, the MDR1 gene polymorphisms G2677T, and C3435T, but not C1236T were associated with the lipid lowering effect of atorvastatin among Jordanians.     

ABCB_1基因C3435T多态性与耐药性癫痫的关系

目的：探讨中国粤西地区汉族人群ABCB1基因C3435T（rs1045642）的单核苷酸多态性与耐药性癫痫的关系。方法：研究对象128例,包括正常对照组60例和癫痫组68例。根据患者对抗癫痫药物的反应性将癫痫组分为耐药组（30例）和药物敏感组（38例）。提取所有研究对象外周血基因组DNA,采用PCR扩增后基因测序鉴定ABCB1基因C3435T多态性。测定该位点基因型频率和等位基因频率,并进行统计学分析。结果：各组ABCB1基因C3435T基因型频率的分布符合Hardy-Weinburg平衡,提示其来自同一孟德尔群体。正常对照组与药物敏感组及耐药组,药物敏感组与耐药组间基因型频率比较,差异均无统计学意义（P〉0.05）。正常对照组与药物敏感组及耐药组,药物敏感组与耐药组间等位基因型频率比较,差异亦无统计学意义（P〉0.05）。结论：本研究结果初步证实ABCB1基因C3435T位点多态性分布与耐药性癫痫之间无相关性。     

Lactase persistence in central Asia: phenotype, genotype, and evolution

The aim of the present study is to document the evolution of the lactase persistence trait in Central Asia, a geographical area that is thought to have been a region of long-term pastoralism. Several ethnic groups co-exist in this area: Indo-Iranian speakers who are traditionally agriculturist (Tajik) and Turkic speakers who used to be nomadic herders (Kazakh, Karakalpak, Kyrgyz, Turkmen). It was recently demonstrated that horse milking practice existed in the Botai culture of Kazakhstan as early as 5,500 BP ( Outram et al. 2009 ). However, the frequency of the lactase persistence trait and its genetic basis in Central Asian populations remain largely unknown. We propose here the first genotype-phenotype study of lactase persistence in Central Asia based on 183 individuals, as well as the estimation of the time of expansion of the lactase-persistence associated polymorphism. Our results show a remarkable genetic-phenotypic correlation, with the causal polymorphism being the same than in Europe (-13.910C>T, rs4988235). The lactase persistence trait is at low frequency in these populations: between 25% and 32% in the Kazakh population (traditionally herders), according to phenotype used, and between 11% and 30% in the Tajiko-Uzbek population (agriculturalists). The difference in lactase persistence between populations, even if small, is significant when using individuals concordant for both excretion of breath hydrogen and the lactose tolerance blood glucose test phenotypes (P = 0.018, 25% for Kazakh vs. 11% for Tajiko-Uzbeks), and the difference in frequency of the -13.910*T allele is almost significant (P = 0.06, 30% for Kazakhs vs. 19% for Tajiko-Uzbeks). Using the surrounding haplotype, we estimate a date of expansion of the T allele around 6,000-12,000 yrs ago, which is consistent with archaeological records for the emergence of agropastoralism and pastoralism in Central Asia.     

The investigation of allele and genotype frequencies of human C3 (rs2230199) in south Iranian population

The complement system is an important mediator of natural and acquired immunity. The complement system genes coding complement proteins have polymorphisms. Hereditary deficiencies of this system predispose to autoimmune conditions such as age-dependent macular degeneration or impairment of immunity against microorganisms. When different populations are compared, the frequency of complement polymorphism shows a very marked geographical distribution. The frequency of the functional polymorphism rs2230199 (Arg80Gly; C > G) in the C3 gene was determined in population from south of Iran (n = 200), using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). One hundred thirty-eight persons (69 %) were homozygous for C allele (CC or SS); fifty-six person (28 %) heterozygote GC (FS) and six people were homozygous for G allele (GG or FF) (3 %). The allele frequency was 82 % for C3S and 18 % for C3F. A distribution of C3C allele frequency in our population is different from the reports of Asians (100 %); Indians (90-98 %); African-American (93 %); Africans (99 %) and south Brazilian (97 %). However, this finding is similar with the findings Caucasian (80-82 %) ( http://www.ncbi.nlm.nih.gov/SNP ); Americans (80 %); Pushtoon, Hazaras, Osbek and Tajik ethnic groups in Afghanistan (88-90 %) and Tunisian population (84 %). Our study confirmed significant inter-ethnic differences in C3 (rs2230199) frequencies between south Iranians and other ethnic groups. The analysis of genetic variation in complement genes is a tool to provide new insights into the evolution of the human immune system.     

Association of the colorectal cancer and <Emphasis Type="Italic">MDR1</Emphasis> gene polymorphism in an Iranian population

The human multidrug resistance (MDR1) gene product P-glycoprotein is highly expressed in intestinal epithelial cells, where it constitutes a barrier against xenobiotics, bacterial toxins, drugs and other biologically active compounds, possibly carcinogens. In this study, an association of MDR1 gene polymorphism and the occurrence of colorectal cancer were evaluated. In this case-control-designed 118 unrelated colorectal cancer and 137 sex-and-ages matched healthy controls were enrolled. The C3435T MDR1 gene polymorphism was identified using the polymerase chain reaction-restriction fragment length polymorphism method. Significantly increased frequencies of the 3435T allele and the 3435TT were observed in patients with colorectal cancer compared with controls (P = 0.03; OR, 95% CI; 1.46 for 3435T allele and P = 0.003; OR, 95% CI; 2.2 for 3435TT genotype). In contrast, frequency of genotype TT was significantly higher in controls compared to colorectal cancer (P = 0.006; OR, 95% CI; 0.49 for TC genotype). In this study suggest that C3435T MDR1 polymorphism has an association with colorectal cancer. The results support that the presence of allele C results in decreased susceptibility to colorectal cancer.     

The interleukin-6 (-174) G/C promoter polymorphism is associated with type-2 diabetes mellitus in Native Americans and Caucasians

Chronic low-grade activation of the immune system may play a role in the pathogenesis of type-2 diabetes mellitus (T2DM). Interleukin-6 (IL6), a powerful inducer of hepatic acute phase response, has been implicated in the etiology of insulin resistance and T2DM. Recently, an IL6 promoter polymorphism (G/C) at position -174 was found to be associated with measures of insulin sensitivity. Because we have previously found an association between high IL6 levels and insulin resistance in both Pima Indians - a population with high rates of insulin resistance and T2DM - and Caucasians, we aimed to assess whether the IL6 promoter polymorphism is associated with T2DM in these populations. We genotyped the IL6 (-174) G/C polymorphism using pyrosequencing in 463 Native Americans and by PCR-RFLP in 329 Spanish Caucasians. Among the Spanish Caucasian subjects, there was a significant difference in genotypic distribution between diabetic and non-diabetic subjects (P=0.028); the GG genotype was more common in diabetic (0.40) than in non-diabetic (0.29) subjects. The G allele was much more frequent in the Native American sample, and among a sample of 143 cases and 145 controls, the GG genotype was significantly more common in diabetic subjects (P=0.019). When this sample population was stratified according to ethnic heritage, all 211 subjects who were of full Pima Indian heritage had the GG genotype, whereas in the 77 American Indian subjects with non-Pima admixture, T2DM was associated with IL6 genotype (P=0.001). These findings are consistent with a role for genetic determinants of inflammation in the development of T2DM in both Native Americans and Caucasians.     

Mexican American ancestry-informative markers: examination of population structure and marker characteristics in European Americans, Mexican Americans, Amerindians and Asians

Markers with large differences in allele frequencies between ethnicities provide ancestry information that can be applied to genetic studies. We identified over 100 biallelic ancestry informative markers (AIMs) with large allele frequency differences between European Americans (EA) and Pima Amerindians from laboratory and database screens. For 35 of these markers, Mayan, Yavapai and Quechuan Amerindians were genotyped and compared with EA and Pima allele frequencies. Markers with large allele frequency differences between EA and one Amerindian tribe showed only small differences between the Amerindian tribes. Examination of structure in individuals demonstrated a clear separation of subjects of European from those of Amerindian ancestry, and similarity between individuals from disparate Amerindian populations. The AIMs demonstrated the variation in ancestral composition of individual Mexican Americans, providing evidence of applicability in admixture mapping and in controlling for structure in association tests. In addition, a high percentage of single-nucleotide polymorphisms (SNPs) selected on the basis of large frequency differences between EA and Asian populations had large allele frequency differences between EA and Amerindians, suggesting an efficient method for greatly expanding AIMs for use in admixture mapping/structure analysis in Mexican Americans. Together, these data provide additional support for the practical application of admixture mapping in the Mexican American population.Electronic Supplementary Material Supplementary material is available in the online version of this article at     

Inter and intra-ethnic differences in the distribution of the molecular variants of TPMT, UGT1A1 and MDR1 genes in the South Indian population

Molecular variants of polymorphic drug metabolizing enzymes and drug transporters are attributed to differences in individual's therapeutic response and drug toxicity in different populations. We sought to determine the genotype and allele frequencies of polymorphisms for major phase II drug-metabolizing enzymes (TPMT, UGT1A1) and drug transporter (MDR1) in South Indians. Allelic variants of TPMT (*2,*3A,*3B,*3C & *8), UGT1A1 (TA)6>7 and MDR1 (2677G>T/A & 3435C>T) were evaluated in 450-608 healthy South Indian subjects. Genomic DNA was extracted by phenol-chloroform method and genotype was determined by PCR-RFLP, qRT-PCR, allele specific PCR, direct sequencing and SNaPshot techniques. The frequency distributions of TPMT, UGT1A1 and MDR1 gene polymorphisms were compared between the individual 4 South Indian populations viz., Tamilian, Kannadiga, Andhrite and Keralite. The combined frequency distribution of the South Indian populations together, was also compared with that of other major populations. The allele frequencies of TPMT*3C, UGT1A1 (TA)7, MDR1 2677T, 2677A and 3435T were 1.2, 39.8, 60.3, 3.7, and 61.6% respectively. The other variant alleles such as TPMT*2, *3A, *3B and *8 were not identified in the South Indian population. Sub-population analysis showed that the distribution of UGT1A1 (TA)6>7 and MDR1 allelic variants differed between the four ethnic groups. However, the frequencies of TPMT*3C allele were similar in the four South Indian populations. The distribution of TPMT, UGT1A1 and MDR1 gene polymorphisms of the South Indian population was significantly different from other populations.     

The association of the <Emphasis Type="Italic">TP53</Emphasis> polymorphisms Pro72Arg and C(−594)CC with diabetic polyneuropathy in Russian Muscovites with type 1 diabetes mellitus

The allele and genotype frequency distributions of the Pro72Arg and C(?594)CC polymorphisms of the TP53 gene were studied in type 1 diabetes mellitus (T1DM) patients, ethnic Russians from Moscow, with a T1DM record of no more than 5 years and diabetic polyneuropathy (DPN) or a T1DM record of more than 10 years but without DPN. The Pro72Arg polymorphism was associated with DPN, a higher risk of DPN being determined by allele Arg (OR = 1.96, CI 1.32?2.90) and genotype Arg/Arg (OR = 2.14, CI 1.23?3.73). Allele Pro was associated with a lower risk of DPN (OR = 0.51, CI 0.34?0.76). No association with DPN was observed for the C(?594)CC polymorphism.     

MDR1 C3435T polymorphism and cancer risk: a meta-analysis based on 39 case–control studies

Multidrug resistance 1 (MDR1) gene encodes the ATP-dependent cellular efflux pump P-glycoprotein (P-gp) which efflux of a variety of substances across the membrane. P-gp could serve a role in cancer etiology based on its physiological role of protecting cells from xenobiotics or metabolites. The C3435T (rs1045642) polymorphism of the MDR1 gene which could influence the P-gp expression and function have been implicated in the cancer risk. However, the results from the published studies on the association between this polymorphism and cancer risk are conflicting. To drive a more precise estimation of this association, we performed a meta-analysis of 39 case-control studies, including a total of 9,265 cancer cases and 13,502 controls. We used odds ratios (ORs) with their 95% confidence intervals (CIs) to assess the strength of the association. Overall, individuals with the MDR1 3435TT genotype were associated with an increased cancer risk than those with the CC (OR = 1.29, 95% CI: 1.10-1.51) or CT/CC (OR = 1.18, 95% CI: 1.04-1.34) genotypes, similar to the CT or CT/TT compared with the CC genotype. In the stratified analyses, the increased risks were more pounced among hematologic malignances (OR = 1.27, 95% CI: 1.10-1.46, P (heterogeneity) = 0.415), breast cancer (1.42, 1.04-1.94, 0.018), renal cancer (1.77, 1.28-2.46, 0.307), Caucasians (1.21, 1.07-1.38, 0.000) and population-based studies (1.20, 1.05-1.36, 0.000) in a dominant model. The results suggested that the MDR1 C3435T polymorphism may contribute to cancer risk.     

Population Genetic Characteristics of the D1S80 locus in seven human populations

We have analyzed the allele frequency distribution at the highly polymorphic variable number of tandem repeat (VNTR) locus D1S80 (pMCT118) in seven ethnic populations (namely, New Guinea Highlanders of Papua New Guinea, Dogrib Indians of Canada, Pehuenche Indians of Chile, American and Western Samoans, Kacharis of Northeast India, and German Caucasians) using the polymerase chain reaction (PCR) technique. In the pooled sample of 443 unrelated individuals 20 segregating alleles were detected. A trimodal pattern of allelic distribution is present in the majority of populations and is indicative of the evolutionary antiquity of the polymorphism at this locus. In spite of the observed high degree of polymorphism (expected heterozygosity 56%–86%), with a single exception — the marginally significant P value (0.04) of the exact test in American Samoans — the genotype distributions in all populations conform to their respective Hardy-Weinberg expectations. Summary statistics indicate that, in general, the allele frequency distribution at this locus may be approximated by the infinite allele model. The data also demonstrate that alleles that are shared by all populations have the highest average frequency within populations. Furthermore, the kinship bioassay analysis demonstrates that the extensive variation observed at the D1S80 locus is at the interindividual within population level, which dwarfs any interpopulation allele frequency variation, consistent with the population dynamics of hypervariable polymorphisms. These characteristics of the D1S80 locus make it a very useful marker for population genetic research, genetic linkage studies, forensic identification of individuals, and for determination of biological relatedness of individuals.     

Brief communication: Molecular characterization of O alleles at the ABO locus in Chilean Aymara and Huilliche Indians

A molecular characterization of alleles O1, O1variant (O1v), and the mutation G542A of the ABO blood group was performed in two Amerindian populations of Chile, the Aymara (n = 84) and the Huilliche (n = 75). In addition, a sample of 82 individuals of Santiago belonging to the mixed Chilean population was typed for comparative purposes. The polymorphisms which allow for molecular differentiation of different alleles of the O blood group were studied in genomic DNA. The mutations G188, G261-, G542A, T646A, and C771T, described for alleles O1, O1v, and G542A, were determined using the PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) technique. All individuals studied were group O homozygotes for the deletion G261-, which defines the O1 alleles. Results obtained indicate that allele O1v exhibits frequencies of 0.65, 0.81, and 0.60 in Aymara, Huilliche, and Santiago populations, respectively. The frequencies of allele O1(G542A) were 0.119, 0.113, and 0.079 in the same populations. Frequencies for alleles O1 and O1v obtained in the Chilean populations studied concur with the results obtained by other authors, respecting the greater frequency of allele O1v as well as with its heterogeneous distribution in aboriginal South American populations. In Chilean populations, Allele G542A exhibits lower frequencies than those described for indigenous populations from Brazil and may be used as an Amerind admixture marker.     

Characterization of pharmacogenetically relevant CYP2D6 and ABCB1 gene polymorphisms in a Portuguese population sample

Differences in metabolism of drugs can lead to severe toxicity or therapeutic failure. In addition to cytochrome P450 2D6, which plays a critical role in drug metabolism, ABCB1 encoded P‐glycoprotein (PGP) is also an important determinant in drug bioavailability. The genes encoding these molecules are highly variable among populations and, given their clinical importance in drug therapy, determining CYP2D6 and ABCB1 allele frequencies in specific populations is very important for useful application in clinical settings. In this study the frequency of the pharmacologically relevant CYP2D6*3, *4, *5, *6 allelic variants and gene duplication, and ABCB1 C1236T and C3435T gene polymorphisms and their haplotypes was determined in a population sample of 100 Portuguese healthy subjects. CYP2D6 allele frequencies were 1.4% (*3), 13.3% (*4), 2.8% (*5), 1.8% (*6) and 6.1% (gene duplication), with 5% of the individuals classified as PM and 8.4% as UM. The frequencies obtained for the non‐functional alleles and for the CYP2D6 gene duplication are in agreement with other South European populations, and reinforce the previously suggested south/north gradient of CYP2D6 duplications. Allelic frequencies for the ABCB1 polymorphisms were 52% (3435C) and 54% (1236C) and the most common haplotype (1236C‐3435C) occurred with a frequency of 45.5%. Although allele and haplotype frequency data for ABCB1 in Southern Europe is limited, some discrepancies were found with other European populations, with possible therapeutic implications for PGP substrate drugs. Copyright © 2009 John Wiley & Sons, Ltd.     

Polymorphism of the (CTG)n Repeat of the Myotonin Protein Kinase Gene in Populations of the Sakha Republic (Yakutia) and Central Asia

The allele frequency distribution of the (CTG)_n repeat located in the 3′-terminal region of the myotonin protein kinase gene (DMPK) was compared for populations of Yakutia (three ethnogeographic groups of Yakuts, Evenks, Evens, Yukaghirs, and Dolgans) and Central Asia (Kazakhs, Uzbeks, and Uighurs) and other ethnic groups. The populations of the two regions proved to considerably differ from each other: features characteristic of Asian Mongoloids were more distinct in the populations of Yakutia, while the Central Asian populations were closer to European populations. The (CTG)_n allele spectrum of Yakuts was considered in connection with the high incidence of myotonic dystrophy in Yakutia. The results support the hypothesis of the founder effect for the spread of myotonic dystrophy in Yakuts. Data on the (CTG)_n polymorphism were used to estimate the phylogenetic relationships of the populations under study.__________Translated from Molekulyarnaya Biologiya, Vol. 39, No. 3, 2005, pp. 385–393.Original Russian Text Copyright © 2005 by Fedorova, Khusainova, Kutuev, Sukhomyasova, Nikolaeva, Kulichkin, Akhmetova, Salimova, Svyatova, Berezina, Platonov, Khusnutdinova.     

Implications of <Emphasis Type="Italic">XRCC1</Emphasis>, <Emphasis Type="Italic">XPD</Emphasis> and <Emphasis Type="Italic">APE1</Emphasis> gene polymorphism in North Indian population: a comparative approach in different ethnic groups worldwide

Identifying risk factors for human cancers should consider combinations of genetic variations and environmental exposures. Several polymorphisms in DNA repair genes have impact on repair and cancer susceptibility. We focused on X-ray repair cross-complementing group 1 (XRCC1), Xeroderma pigmentosum D (XPD) and apurinic/apyrimidinic endonuclease (APE1) as these are most extensively studied in cancer. Present study was conducted to determine distribution of XRCC1 C26304T, G27466A, G23591A, APE1 T2197G and XPD A35931C gene polymorphisms in North Indian population and compare with different populations globally. PCR-based analysis was conducted in 209 normal healthy individuals of similar ethnicity. Allelic frequencies in wild type of XRCC1 C26304T were 91.1% C(Arg); G27466A 62.9% G(Arg); G23591A 60.3% G(Arg); APE1 T2197G 75.1% T(Asp) and XPD A35931C 71.8% A(Lys). The variant allele frequency were 8.9% T(Trp) in XRCC1 C26304T; 37.1% A(His) in G27466A; 39.7% A(Gln) in G23591A; 24.9% G(Glu) in APE1 and 28.2% C(Gln) in XPD respectively. We further compared frequency distribution for these genes with various published studies in different ethnicity. Our results suggest that frequency in these DNA repair genes exhibit distinctive pattern in India that could be attributed to ethnicity variation. This could assist in high-risk screening of humans exposed to environmental carcinogens and cancer predisposition in different ethnic groups.     

Association between MDR1 C3435T polymorphism and risk of breast cancer

The C3435T (rs1045642) polymorphism, located in multi-drug resistance gene 1 (MDR1), has demonstrated its role in decreasing the P-gp activity level which is related to the carcinogenesis. Many published studies have evaluated the association between the MDR1 C3435T polymorphism and breast cancer risk. However, the results remain conflicting rather than conclusive. To derive a more precise estimation of the association between MDR1 C3435T polymorphism and risk of breast cancer, we performed a meta-analysis comprised of 10 case–control studies, including 5282 breast cancer cases and 7703 controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the strength of the association. The overall results indicated that the variant genotypes were associated with a significantly increased risk of breast cancer (TT versus CC: OR = 1.45, 95% CI = 1.14–1.30, TT versus CT/CC: OR = 1.13, 95% CI = 1.04–1.23, TT/CT versus CC: OR = 1.22, 95% CI = 1.02–1.46). Our results suggest that the MDR1 C3435T polymorphism may contribute to individual susceptibility to breast cancer.