D1S80 single-locus discrimination among African populations

The highly polymorphic D1S80 locus has no known genetic function. However, this variable number of tandem repeats (VNTR) locus has been highly valuable in forensic identification. In this study we report the allele and genotype frequencies of five African populations (Benin, Cameroon, Egypt, Kenya, and Rwanda), which can be used as databases to help characterize populations and identify individuals. The allele frequencies were used to infer genetic associations through phylogenetic, principal component, and G test statistical analyses. Compliance with Hardy-Weinberg equilibrium expectations was determined as were F(ST) estimates, theta p values, and power of discrimination assessment for each population. Our analyses of 28 additional populations demonstrate that the D1S80 locus alone can be used to discriminate geographic and ethnic groups. We have generated databases useful for human identification and phylogenetic studies.     

Allele frequency of VNTR locus D1S80 observed in Hb D-Los Angeles carrires

One of our previous studies presented the allele frequencies of D1S80 VNTR locus in province Denizli including the high frequencies of allele 24 and 18. In Denizli province of Turkey, the most common abnormal variant is Hb D-Los Angeles with a frequency of 57.8?% of the total abnormal Hbs. The aim of this study is to identify the allele frequencies of D1S80 VNTR locus in Hb D-Los Angeles carriers in Denizli province of Turkey. We studied unrelated 36 Hb D-Los Angeles carriers residing in Denizli province of Turkey. The size range of the D1S80 VNTR locus PCR products was determined first by agarose gel electrophoresis and then by a capillary electrophoresis system. For all subjects, DNA sequencing was performed. Allele frequency, theta (k) value, and observed and expected heterozygosity were calculated using Arlequin Software version 3.11. The most common alleles were the 24 (32?%), 18 (18.1?%) and 29 (16.7?%) alleles, and frequencies of these alleles were 0.329, 0.186 and 0.171 respectively. Other observed alleles percentages were 33, 2?%. We did not observe alleles 6, 15, 27 and 35, but we observed alleles 20 and 33. Results were in Hardy–Weinberg linkage disequilibrium. Observed heterozygosity was 0.889, and expected heterozygosity was 0.847. Theta (k) value was 4.91 (95?% confidence interval limits). According to our results, we concluded that Hb D-Los Angeles carriers have different allele frequencies in D1S80 VNTR and also have their own D1S80 VNTR locus divergence.     

The relevance of paternity analysis in Romanian population using the D1S80 locus

At present, DNA fingerprinting for human identification and paternity testing is a necessary and usual procedure. D1S80 is one of the best known polymorphic loci showing a VNTR, and exhibiting a high heterozygosity. This genetic locus, with a Tsp 509 I polymorphism of its 5' flanking sequence (1, 9), have been successfully amplified from human genomic DNA isolated from blood. The Tsp 509 I polymorphism was detected by restriction after PCR amplification. We tested the relevance of paternity analysis using the D1S80 locus considering the allele frequency distribution characteristic for our country. Paternal and maternal bands were compared with the children's DNA patterns. Our data include a comparison between D1S80 alleles amplified from mother, child and the supposed father for three tested families. This study was the first of this type made in Romania. We concluded a good power of discrimination and exclusion for this locus. It can be used successfully in the case of subtypes with low frequencies, and this is frequent for our population because of the high heterozygosity of D1S80 subtypes in Romanian population. We recommend the D1S80 use for exclusion paternity tests in Romanian population, as a very useful molecular tool, but we also recommend a complete set of molecular markers for confirmation paternity test in the same population.     

Characteristics of polymorphism at a VNTR locus 3' to the apolipoprotein B gene in five human populations.

We have analyzed the allele frequency distribution at the hypervariable locus 3' to the apolipoprotein B gene (ApoB 3' VNTR) in five well-defined human populations (Kacharis of northeast India, New Guinea Highlanders of Papua New Guinea, Dogrib Indians of Canada, Pehuenche Indians of Chile, and a relatively homogeneous Caucasian population of northern German extraction) by using the PCR technique. A total of 12 segregating alleles were detected in the pooled sample of 319 individuals. A fairly consistent bimodal pattern of allele frequency distribution, apparent in most of these geographically and genetically diverse populations, suggests that the ApoB 3' VNTR polymorphism predates the geographic dispersal of ancestral human populations. In spite of the observed high degree of polymorphism at this locus (expected heterozygosity levels 55%-78%), the genotype distributions in all populations (irrespective of their tribal or cosmopolitan nature) conform to their respective Hardy-Weinberg predictions. Furthermore, analysis of the congruence between expected heterozygosity and the observed number of alleles reveals that, in general, the allele frequency distributions at this locus are in agreement with the predictions of the classical mutation-drift models. The data also show that alleles that are shared by all populations have the highest average frequency within populations. These findings demonstrate the potential utility of highly informative hypervariable loci such as the ApoB 3' VNTR locus in population genetic research, as well as in forensic medicine and determination of biological relatedness of individuals.     

Apolipoprotein B signal peptide polymorphism in patients with myocardial infarction and controls

We report the allele frequencies of the apolipoprotein B (Apo B) signal peptide polymorphism in patients with myocardial infarction and compare them with controls. The first sample consists of 197 myocardial infarction patients and 168 controls from Belfast (UK). The second sample consists of 167 myocardial infarction patients and 205 controls from Strasbourg (France), and the third consists of 71 patients and 146 controls from Haute-Garonne (Toulouse, France). No significant differences were observed in the frequency distribution of genotypes among cases and controls or between populations. However, there were more rare homozygotes in the Belfast cases. Significant associations were observed between the Apo B signal peptide polymorphism and mean levels of total cholesterol, low density lipoprotein cholesterol, Apo B and lipoprotein particles containing Apo (a) [Lp(a)] in the Strasbourg control population. Individuals homozygous for the rare allele had higher levels of these lipid parameters. In Belfast, although not statistically significant, the Apo B signal peptide polymorphism had a similar effect on Apo-B-related parameters as seen in Strasbourg. No significant associations were observed in the Haute-Garonne population where the risk of myocardial infarction is three times lower than in Belfast. In all three populations, the average Lp(a) levels were consistently different among Apo B signal peptide genotypes. These data implicate the Apo B signal peptide in determining some of the risks of myocardial infarction in these populations. Regardless of the exact mechanism, the Apo B signal peptide is an important candidate locus for the study of potentially atherogenic lipid variants.     

The genetic architecture of selection at the human dopamine receptor D4 (DRD4) gene locus

Associations of the seven-repeat (7R) allele of the human dopamine receptor D4 (DRD4) gene with both the personality trait of novelty seeking and attention deficit/hyperactivity disorder have been reported. Recently, on the basis of the unusual DNA sequence organization of the DRD4 7R 48-bp tandem repeat (VNTR), we proposed that the 7R allele originated as a rare mutational event that increased to high frequency by positive selection. We now have resequenced the entire DRD4 locus from 103 individuals homozygous for 2R, 4R, or 7R variants of the VNTR, a method developed to directly estimate haplotype diversity. DNA from individuals of African, European, Asian, North and South American, and Pacific Island ancestry were used. 4R/4R homozygotes exhibit little linkage disequilibrium (LD) over the region examined, with more polymorphisms observed in DNA samples from African individuals. In contrast, the evidence for strong LD surrounding the 7R allele is dramatic, with all 7R/7R individuals (including those from Africa) exhibiting the same alleles at most polymorphic sites. By intra-allelic comparison at 18 high-heterozygosity sites spanning the locus, we estimate that the 7R allele arose prior to the upper Paleolithic era (approximately 40000-50000 years ago). Further, the pattern of recombination at these polymorphic sites is the pattern expected for selection acting at the 7R VNTR itself, rather than at an adjacent site. We propose a model for selection at the DRD4 locus consistent with these observed LD patterns and with the known biochemical and physiological differences between receptor variants.     

Nearly identical allelic distributions of xanthine dehydrogenase in two populations of Drosophila pseudoobscura

In a previous study, Keith (1983) showed by sequential gel electrophoresis of the esterase-5 protein in Drosophila pseudoobscura that a highly polymorphic locus with many alleles can have very similar frequency distributions in populations separated by 500 km. The present work studies another highly polymorphic locus, xanthine dehydrogenase, in the same California population samples, using the same technique to distinguish allelic classes. Twelve electromorphs were found in one population and 15 in the other. Both populations shared a single very frequent (approximately 60%) allele, as well as five other alleles in low but similar frequencies. In addition, each population had an array of unique alleles present only once in one population sample but absent in the other. A statistical test against the stationary distribution for neutral alleles shows that, if the populations are at equilibrium, then purifying selection is operating on xanthine dehydrogenase. The extremely close similarity in frequency distributions of the alleles between populations for both the xanthine dehydrogenase and esterase-5 loci, despite differences in allele frequency distribution between loci, strongly emphasizes the importance of migration in influencing genic diversity in these populations.     

Comparison of VNTR allele frequencies and inclusion probabilities over six populations

There is considerable debate about the methodologies used to estimate VNTR (Variable Number of Tandem Repeats) multi-locus genotype frequencies or odds of inclusion in forensic cases. To compare two of the methods in use, allele frequency distributions among six populations were compared and the effect of population heterogeneity on VNTR multi-locus genotype frequency estimation was examined. Genotype frequencies estimated from single population data were one or two orders of magnitude smaller than those estimated by picking the highest allele frequency in a group of subpopulations to estimate genotype frequencies using a ceiling principle. The average change does not appear to be very sensitive to the set of subpopulations used; four locus frequencies still give inclusion odds of one in a million or less. We think that use of the ceiling principle solves both the statistical problem engendered by subpopulation heterogeneity and the legal problem of assuming that the prepetrator and suspect belong to the same subpopulation. The counterintuitive fact of human genetic polymorphism is that it is easier to identify an individual than it is to identify the subpopulation, ethnic group or race to which that individual belongs.     

Estimation of allele frequencies for VNTR loci

VNTR loci provide valuable information for a number of fields of study involving human genetics, ranging from forensics (DNA fingerprinting and paternity testing) to linkage analysis and population genetics. Alleles of a VNTR locus are simply fragments obtained from a particular portion of the DNA molecule and are defined in terms of their length. The essential element of a VNTR fragment is the repeat, which is a short sequence of basepairs. The core of the fragment is composed of a variable number of identical repeats that are linked in tandem. A sample of fragments from a population of individuals exhibits substantial variation in length because of variation in the number of repeats. Each distinct fragment length defines an allele, but any given fragment is measured with error. Therefore the observed distribution of fragment lengths is not discrete but is continuous, and determination of distinct allele classes is not straightforward. A mixture model is the natural statistical method for estimating the allele frequencies of VNTR loci. In this article we develop nonparametric methods for obtaining the distribution of allele sizes and estimates of their frequencies. Methods for obtaining maximum-likelihood estimates are developed. In addition, we suggest an empirical Bayes method to improve the maximum-likelihood estimates of the gene frequencies; the empirical Bayes procedure effects a local smoothing. The latter method works particularly well when measurement error is large relative to the repeat size, because the estimated distribution of allele frequencies when maximum likelihood is used is unreliable because of an alternating pattern of over- and underestimation. We define alleles and estimate the allele frequencies for two VNTR loci from the human genome (D17S79 and D2S44), from data obtained from Lifecodes, Inc.     

Population-genetic structure of Chuvashia (from data on eight DNA loci in the nuclear genome)

Population-genetic study of indigenous populations representing three ethnic Chuvash group: highland (Cheboksarsk and Morgaush district), lowland (Kanash district) and mid-lowland (Marposad district). Eight polymorphic DNA loci of the nuclear genome (VNTR/PAH, STR/PAH, VNTR/ApoB, VNTR/DAT1, APF, VNTR/eNOS, IVS6aGATT, and KM.19/PstI) were examined in the population of each district. For each of the four population, we estimated the allele and genotype frequency distributions at each polymorphic system, heterozygosities HS and between-population differences FST. In the combined Chuvash sample, HS = 0.464 and FST = 0.006. Loci VNTR(DAT) and VNTR(ApoB) showed highest between-population differentiation (0.009 < or = FST < or = 0.012), and loci IVS6aGATT, APF, VNTR/eNOS, and D7S23 (KM.19), lowest differentiation (0.001 < or = FST < or = 0.003). Analysis of genetic distances revealed somewhat higher genetic similarity between the Cheboksarsk and Morgaush populations belonging to the highland Chuvash group, whereas the highland Chuvash population from the Marposad district, which belong to the mid-lowland group, was more distant from the former populations.     

广东汉族人载脂蛋白B(apoB)基因3′端VNTR的遗传多态性研究

随机抽提100例无血缘关系的广东汉族人的血痕DNA,用PCR法扩增载脂蛋白B(apolipoprotein B apoB)基因3′端的VNTR,共检出19个等位基因,片段大小分布在510～1200bp之间,等位基因频率为0.005—0.195,杂合度为88.80％,父权排除率为0.6395,其等位基因数目及频率分布均与英国白种人的有差异。家系分析表明扩增片段按孟德尔方式遗传。本实验证实了apoB基因3′端VNTR的高度多态性和高度杂合性。     

Apolipoprotein E genotyping among the healthy Kuwaiti population

Apolipoproteins (lipid-free) are lipid-binding proteins that circulate in the plasma of human blood and are responsible for the clearance of lipoproteins. Apolipoprotein E (ApoE) is one of the several classes of this protein family. It acts as a ligand for the low-density lipid (LDL) receptors and is important for the clearance of very low-density lipid (VLDL) and chylomicron remnants. The APOE gene locus is polymorphic, with three major known alleles, APOE*3, *4, and *2. We investigated the distribution of the allele frequency of the APOE gene locus and describe here the genetic variation in four Kuwaiti subpopulations: Arab origin (Arabian peninsula), Arab Bedouin tribes, Iranian origin, and the heterogeneous population. We also describe the use of Spreadex gels in resolving the amplified and digested products of the APOE gene locus. DNA was extracted from whole blood and subjected to PCR and then to RFLP analysis. Allele and genotype frequencies were estimated for the total population and for each subpopulation. Statistical analysis showed no difference in the allele frequencies between the four groups. The frequency of APOE*3 in the Kuwaiti population was highest (88.4%) followed by the frequency of APOE*4 (6.5%) and APOE*2 (5.1%). The genotype and allele frequencies obtained for the Kuwaiti population fell within the reported worldwide distribution for the APOE gene locus. Moreover, the results obtained in this study showed no statistical difference (p > 0.05) between the APOE allele and genotype frequencies between the subgroups for all six genotypes and three alleles, supporting the assumption of admixture in the Kuwaiti population and that the obtained frequencies were in Hardy-Weinberg equilibrium. Finally, we found that the distribution of the APOE alleles in Kuwait differs somewhat from those reported in other Arab populations, suggesting that the Arabs originating from the Arabian peninsula are different from those of Lebanon, Morocco, and Sudan.     

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.     

Genetic structure of the Sardinian population at the D1S80 VNTR locus and population diversity

We typed the Sardinian population at the D1S80 VNTR locus. Nineteen alleles were detected in a sample of 92 unrelated individuals, allele frequency distribution showing a modal pattern mostly in agreement with other Caucasoid populations. A high degree of heterozygosity (observed value=80.4%) was present. Goodness-of-fit tests demonstrated no departure from Hardy-Weinberg expectations. Data regarding heterozygosity, number of alleles and singletons appeared in accordance with the IAM mutation-drift equilibrium model and showed no evidence of hidden substructuring. Allele 34 exhibited in Sardinians the highest frequency never observed in Caucasians. Nonetheless, the comparison with other European populations did not disclose Sardinian genetic peculiarity. Indeed, measures of genetic divergence among Europeans demonstrated definitely smaller values at the D1S80 locus in comparison with those calculated over a high number of (pre-DNA) polymorphic loci. High mutation rate and selective neutrality typical of VNTRs could account for the observed moderate genetic divergence. Isolation and genetic drift, on the other hand, may have determined certain deviations in allele frequency distribution, as occurred to allele 34 in the Sardinian population.     

VNTR-polymorphism of the PAH, e-NOS genes and deletion of the CCR5 gene in populations in the northern Caucasus

VNTR allelic polymorphism at the phenylalanine hydroxilase (PAH) and endothelial constitutive nitric oxide synthase (eNOS) genes and the prevalence of the CCR5 chemokine receptor gene 32-bp deletion were examined in four indigenous populations of Northern Caucasus, Adygs, Kumyks, Karachais, and Nogais (Kuban and Karanogais). Population-specific features of the allele and genotype frequency distribution patterns of the polymorphisms examined were described. The data obtained were compared to those obtained from literature. The results of the study confirmed that the frequency and occurrence of the PAH polymorphic alleles exhibit substantial interpopulation differences. In the populations of Northern Caucasus, the eNOS minisatellite polymorphism alleles and genotypes frequency distribution patterns were close to those described earlier for populations of the Volga-Ural region (VUR), and also for the Australian Caucasoids, Japanese, and Turks. In the populations examined, the mean frequency of the CCR5 gene deletion was 0.055, which was somewhat lower than in the populations of VUR (0.07) and Europe (0.081), and practically identical to that in Asian populations (0.050). For each population observed and expected heterozygosities at each locus were calculated. In general, the gene pool of Northern Caucasian populations showed substantial differentiation at the loci examined: the GST value was 0.0274. The data for individual loci showed that the greater contribution to the interpopulation diversity was made by the differences in the PAH VNTR allele frequencies (GST = 0.04), while the differences at the eNOS and CCR5 loci were small (GST = 0.0025 and GST = 0.0039, respectively).     

Effects of intragenic variability at 3 polymorphic sites of the apolipoprotein B gene on serum lipids and lipoproteins in a multiethnic Asian population.

We determined the allelic (X+/X-, M+/M-, and E+/E-) distribution frequencies of the XbaI, MspI, and EcoRI restriction fragment length polymorphisms (RFLPs) in the apolipoprotein B gene in a control group of 374 healthy Chinese, Malays, and Indians and in a hyperlipidemic cohort of 131 Chinese patients. Covariability between the RFLPs and serum lipid, lipoprotein, and apolipoprotein concentrations was also studied. We found a lower frequency (average 0.0829) of the X+ allele and higher frequencies of the E+ (average 0.9452) and M+ (average 0.9772) alleles in our study population compared with frequencies reported in other populations. The 3 polymorphic sites did not contribute to significant variations in lipid levels (p > 0.1 in all cases). Also, there was no significant variation in genotype frequencies between the control subjects and the hyperlipidemic subjects. Despite their relative close proximity within the APOB gene sequence, the 3 polymorphic sites did not show any significant linkage disequilibrium. However, the presence of the X+ cutting site was in linkage disequilibrium with the Del allele of the 5' insertion-deletion polymorphism and the E-allele was in linkage disequilibrium with the 3' VNTR located near the 3' end of the coding region of the APOB gene.     

Nondetectability of restriction fragments and independence of DNA fragment sizes within and between loci in RFLP typing of DNA.

We provide experimental evidence showing that, during the restriction-enzyme digestion of DNA samples, some of the HaeIII-digested DNA fragments are small enough to prevent their reliable sizing on a Southern gel. As a result of such nondetectability of DNA fragments, individuals who show a single-band DNA profile at a VNTR locus may not necessarily be true homozygotes. In a population database, when the presence of such nondetectable alleles is ignored, we show that a pseudodependence of alleles within as well as across loci may occur. Using a known statistical method, under the hypothesis of independence of alleles within loci, we derive an efficient estimate of null allele frequency, which may be subsequently used for testing allelic independence within and across loci. The estimates of null allele frequencies, thus derived, are shown to agree with direct experimental data on the frequencies of HaeIII-null alleles. Incorporation of null alleles into the analysis of the forensic VNTR database suggests that the assumptions of allelic independence within and between loci are appropriate. In contrast, a failure to incorporate the occurrence of null alleles would provide a wrong inference regarding the independence of alleles within and between loci.     

Recurrence of the R408W Mutation in the Phenylalanine Hydroxylase Locus in Europeans

The relative frequency of the common phenylalanine hydroxylase (PAH) mutation R408W and its associations with polymorphic RFLP, VNTR, and short-tandem-repeat (STR) sites in the PAH gene were examined in many European populations and one representative North American population of defined European descent. This mutation was found to cluster in two regions: in northwest Europe among Irish and Scottish peoples, and in eastern Europe, including the Commonwealth of Independent States. This allele was significantly less frequent in intervening populations. In eastern European populations, the R408W mutation is strongly associated with RFLP haplotype 2, the three-copy VNTR allele (VNTR 3), and the 240-bp STR allele. In northwestern European populations, it is strongly associated with RFLP haplotype 1, the VNTR allele containing eight repeats (VNTR 8), and the 244-bp STR allele. An examination of the linkage between the R408W mutation and highly polymorphic RFLP, VNTR, and STR haplotypes suggests that recurrence is the most likely mechanism to account for the two different major haplotype associations of R408W in Europe.     

Characterization of a highly polymorphic region near the first exon of the human MAOA gene containing a GT dinucleotide and a novel VNTR motif.

The genes encoding the A and B forms of the human monoamine oxidase enzymes (MAOA and MAOB) are localized at Xp11.23-Xp11.4. We report the characterization of a highly informative polymorphic region within a 2.9-kb cloned fragment containing the first exon of the MAOA gene. The polymorphic region consists of a GT microsatellite directly adjacent to an imperfectly duplicated novel 23-bp VNTR motif. DNA sequencing within and flanking the repeated segment allowed the design of specific amplification primers. In 56 unrelated females, 15 different alleles were identified with sizes ranging from 285 to 388 bp. The alleles differed in both the number of dinucleotide and the number of VNTR repeats, yielding a highly informative polymorphic marker locus with a calculated heterozygosity value of 75%.     

Amplification of reproducible allele markers for amplified fragment length polymorphism analysis.

A procedure for amplification by PCR of reproducible allele markers for amplified fragment length polymorphism (Amp-FLP) analysis is presented. We have prepared markers for the allelic products of the VNTR loci D1S80 (MCT118) and D17S30 (YNZ22) and for the hypervariable VNTR locus close to the 3' end of the apolipoprotein B gene (apoB) by re-amplifying a mixture of PCR products from individuals with known alleles. These allele markers allow precise and discrete determination of the VNTR alleles at these loci using the Amp-FLP technique that should prove suitable in forensic analyses, paternity testing and population studies.