Characteristics of Mongoloid and neighboring populations based on the genetic markers of human immunoglobulins

Leukocyte immunoglobulin-like receptor A3 gene deletion in five Chinese populations and protective association with nasopharyngeal carcinoma

Among the thirteen leukocyte Ig-like receptor (LILR) loci located at 19q13.4, LILRA3 is unique in that it encodes a soluble protein lacking the transmembrane and cytoplasmic domains, and a 6.7 kb deletion spanning the first seven exons has been detected in some human individuals. Presently, there is a lack of data about the distribution of LILRA3 gene deletion in more diverse ethnic groups. Also, no previous studies have investigated the correlation between copy number variation (CNV) of LILRA3 and nasopharyngeal carcinoma (NPC). In this study, five populations from China mainland: two Southern Han populations, Hunan (N = 1478) and Guandong (N = 107); one Southeastern Han population, Fujian (N = 439); and two Northern populations, Inner Mongolia Han (N = 104) and Mongol population from Inner Mongolia (N = 158) were investigated for CNV of LILRA3 using polymerase chain reaction-sequence-specific priming (PCR-SSP) method. LILRA3 variants were also examined in a cohort of NPC cases (N = 1142) in Hunan Han population. The five Chinese populations demonstrated northward increase in frequency of the deleted form of LILRA3 gene (LILRA3*Del) (all corrected p values < 0.05). Inter-population comparison also uncovered significant differentiation in the distribution of CNV of LILRA3 among modern human populations. LILRA3*Del was found to confer significantly reduced risk to NPC in Hunan Han population (at allelic level: OR = 0.79, 95% CI = 0.71-0.89, p < 0.0001; at genotype level: OR = 0.63, 95% CI = 0.51-0.79, p < 0.0001). No interaction was found between LILRA3 variants and HLA-A*02:07, HLA-A*11:01, HLA-B*13 and HLA-B*46:01 alleles in susceptibility to NPC. Our study constitutes the first demonstration of LILRA3 gene as a locus linked to NPC susceptibility in a southern Chinese population. Future independent studies in other populations are warranted to confirm the findings reported in this study.

Association between interleukin 12B and interleukin 23R gene polymorphisms and systemic lupus erythematosus: a meta-analysis

OBJECTIVE

To determine whether polymorphisms of interleukin 12B (IL12B) and IL23 receptor genes (IL23R) confer susceptibility to systemic lupus erythematosus (SLE).

METHODS

A meta-analysis was conducted to analyze the associations between SLE and IL12B rs3212227 and rs17860508 and IL23R rs7517847, rs10489629, rs10889677, rs1004819, rs11209026, rs11209032, rs1343151, and rs1884444 polymorphisms using allele contrast, dominant, recessive, heterozygote, and homozygote models. Ten studies involving 1989 patients with SLE and 2394 controls were considered for the meta-analysis.

RESULTS

The meta-analysis using the homozygote model revealed that IL23R rs10889677 was significantly associated with SLE susceptibility in the overall population (AA vs. CC) (odds ratio = 0.70, 95% confidence interval = 0.50-0.98) but not in the Asian population. Other polymorphisms of IL12B and IL23R were not significantly associated with SLE protection.

CONCLUSIONS

These findings suggest that the IL23R rs10889677 polymorphism confers SLE susceptibility to individuals of certain ethnicities. (Research Registry number: 1268).

Populations dynamics in Northern Eurasian forests: a long-term perspective from Northeast Asia

The 'Northern Eurasian Greenbelt' (NEG) is the northern forest zone stretching from the Japanese Archipelago to Northern Europe. The NEG has created highly productive biomes for humanity to exploit since the end of the Pleistocene. This research explores how the ecological conditions in northern Eurasia contributed to and affected human migrations and cultural trajectories by synthesizing the complimentary viewpoints of environmental archaeology, Geographic Information Science (GIS), genetics and linguistics. First, the environmental archaeology perspective raises the possibility that the NEG functioned as a vessel fostering people to develop diverse cultures and engage in extensive cross-cultural exchanges. Second, geographical analysis of genomic data on mitochondrial DNA using GIS reveals the high probability that population dynamics in the southeastern NEG promoted the peopling of the Americas at the end of the Pleistocene. Finally, a linguistic examination of environmental- and landscape-related vocabulary of the proto-Turkic language groups enables the outline of their original cultural landscape and natural conditions, demonstrating significant cultural spheres, i.e. from southern Siberia to eastern Inner Mongolia during Neolithization. All of these results combine to suggest that the ecological complex in the southern edge of the NEG in northeast Asia played a significant role in peopling across the continents during prehistory.

The frequency of SLCO1B1*5 polymorphism genotypes among Russian and Sakha (Yakutia) patients with hypercholesterolemia

Introduction

Statins are the most commonly prescribed medicines for treatment of hypercholesterolemia. At the same time, up to 25% of patients cannot tolerate or have to discontinue the statin therapy due to statin-induced myopathy. In a majority of cases, statin-induced myopathy is attributed to SLCO1B1 gene polymorphism. The strongest association between statin-induced myopathy and SLCO1B1 gene polymorphism was described for simvastatin. Our research was focused on the frequency of SLCO1B1*5 genetic variant in the Russian population and in the native population of Sakha (Yakutia).

Materials and methods

A total of 1,071 hyperlipidemic Russian and 76 hyperlipidemic Sakha (Yakutian) patients were included in the study. Genotypes of SLCO1B1*5 (c.521T>C, rs4149056) were determined with polymerase chain reaction amplification. The results of our study were compared with data about hyperlipidemic patients in available publications.

Results

In the Russian population 665 (62%) patients had TT genotype of SLCO1B1*5, 346 (32%) patients had TC genotype, and in 60 patients (6%) CC variant was found (Hardy–Weinberg’s chi-square test was 3.1 P=0.21). In comparison with Brazil, France, the People’s Republic of China, Japan, and the native population of Sakha (Yakutia), C-allele, which causes an increased risk of statin-induced myopathy, was found significantly more often in the Russian population. In the native population of Sakha (Yakutia) SLCO1B1 polymorphism was TT – 62 (82%), TC – 11 (14%), CC – 3 (4%) (Hardy–Weinberg’s chi-square test was 5.13 P=0.077). In comparison with data from Brazil, France, the People’s Republic of China, and Japan, C-allele frequency in the Sakha (Yakutian) population was not significantly different.

Conclusion

Thus, we have studied the incidence of pathologic SLCO1B1 c.521C-allele in Russian and Sakha hyperlipidemic patients. The presence of SLCO1B1 C-allele in patients with hyperlipidemia forces us to be more careful in hypolipidemic drug prescription, especially statins, according to a higher risk of statin-induced myopathy development. The fact that SLCO1B1 C-allele is rarer among Sakha patients, could be interesting from the point of studying adverse drug effects frequency and statins’ effectiveness.

Genotyping of the c.1423C>T (p.P475S) polymorphism in the ADAMTS13 gene by APLP and HRM assays: Northeastern Asian origin of the mutant

ADAMTS13 is a von Willebrand factor-cleaving protease. The mutant types of p.P475S (c.1423C>T) polymorphism in ADAMTS13 have a reduced activity in comparison with the wild type. In the present study, we investigated the frequency of the C-to-T substitution in 2584 genomic DNA samples from 25 Asian, European, and African populations using APLP (amplified product length polymorphism) and/or HRM (high-resolution melting) assays. Allele T (ADAMTS13(∗)T) was detected only in Asian populations and its frequency was observed to decrease gradually from north to south in 24 East Asian populations. Almost all ADAMTS13(∗)T were associated with ABO(∗)O. These results suggested that ADAMTS13(∗)T had occurred on a chromosome with ABO(∗)O in a northern part of East Asia. This SNP is useful as an ancestry-informative marker, and the present genotyping techniques are applicable to the investigation of an association between this SNP and aortic dissection (Kobayashi et al., 2012).

Founder haplotype analysis of Fanconi anemia in the Korean population finds common ancestral haplotypes for a FANCG variant

A common ancestral haplotype is strongly suggested in the Korean and Japanese patients with Fanconi anemia (FA), because common mutations have been frequently found: c.2546delC and c.3720_3724delAAACA of FANCA; c.307+1G>C, c.1066C>T, and c.1589_1591delATA of FANCG. Our aim in this study was to investigate the origin of these common mutations of FANCA and FANCG. We genotyped 13 FA patients consisting of five FA-A patients and eight FA-G patients from the Korean FA population. Microsatellite markers used for haplotype analysis included four CA repeat markers which are closely linked with FANCA and eight CA repeat markers which are contiguous with FANCG. As a result, Korean FA-A patients carrying c.2546delC or c.3720_3724delAAACA did not share the same haplotypes. However, three unique haplotypes carrying c.307+1G>C, c.1066C > T, or c.1589_1591delATA, that consisted of eight polymorphic loci covering a flanking region were strongly associated with Korean FA-G, consistent with founder haplotypes reported previously in the Japanese FA-G population. Our finding confirmed the common ancestral haplotypes on the origins of the East Asian FA-G patients, which will improve our understanding of the molecular population genetics of FA-G. To the best of our knowledge, this is the first report on the association between disease-linked mutations and common ancestral haplotypes in the Korean FA population.

SLC25A13 gene analysis in citrin deficiency: sixteen novel mutations in East Asian patients, and the mutation distribution in a large pediatric cohort in China

Background

The human SLC25A13 gene encodes citrin, the liver-type mitochondrial aspartate/glutamate carrier isoform 2 (AGC2), and SLC25A13 mutations cause citrin deficiency (CD), a disease entity that encompasses different age-dependant clinical phenotypes such as Adult-onset Citrullinemia Type II (CTLN2) and Neonatal Intrahepatic Cholestasis caused by Citrin Deficiency (NICCD). The analyses of SLC25A13 gene and its protein/mRNA products remain reliable tools for the definitive diagnoses of CD patients, and so far, the SLC25A13 mutation spectrum in Chinese CD patients has not been well-characterized yet.

Methods and Results

By means of direct DNA sequencing, cDNA cloning and SNP analyses, 16 novel pathogenic mutations, including 9 missense, 4 nonsense, 1 splice-site, 1 deletion and 1 large transposal insertion IVS4ins6kb (GenBank accession number KF425758), were identified in CTLN2 or NICCD patients from China, Japan and Malaysia, respectively, making the SLC25A13 variations worldwide reach the total number of 81. A large NICCD cohort of 116 Chinese cases was also established, and the 4 high-frequency mutations contributed a much larger proportion of the mutated alleles in the patients from south China than in those from the north (χ² = 14.93, P<0.01), with the latitude of 30°N as the geographic dividing line in mainland China.

Conclusions

This paper further enriched the SLC25A13 variation spectrum worldwide, and formed a substantial contribution to the in-depth understanding of the genotypic feature of Chinese CD patients.

Y-chromosome O3 haplogroup diversity in Sino-Tibetan populations reveals two migration routes into the eastern Himalayas

The eastern Himalayas are located near the southern entrance through which early modern humans expanded into East Asia. The genetic structure in this region is therefore of great importance in the study of East Asian origins. However, few genetic studies have been performed on the Sino-Tibetan populations (Luoba and Deng) in this region. Here, we analyzed the Y-chromosome diversity of the two populations. The Luoba possessed haplogroups D, N, O, J, Q, and R, indicating gene flow from Tibetans, as well as the western and northern Eurasians. The Deng exhibited haplogroups O, D, N, and C, similar to most Sino-Tibetan populations in the east. Short tandem repeat (STR) diversity within the dominant haplogroup O3 in Sino-Tibetan populations showed that the Luoba are genetically close to Tibetans and the Deng are close to the Qiang. The Qiang had the greatest diversity of Sino-Tibetan populations, supporting the view of this population being the oldest in the family. The lowest diversity occurred in the eastern Himalayas, suggesting that this area was an endpoint for the expansion of Sino-Tibetan people. Thus, we have shown that populations with haplogroup O3 moved into the eastern Himalayas through at least two routes.

Molecular characterization of phenylketonuria and tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency in Japan

Phenylketonuria (PKU) is a heterogeneous metabolic disorder caused by a deficiency in hepatic phenylalanine hydroxylase (PAH). On the basis of phenotype/genotype correlations, determination of phenylketonuric genotype is important for classification of the clinical phenotype and treatment of PKU, including tetrahydrobiopterin therapy. We characterized the genotypes of 203 Japanese patients with PKU and hyperphenylalaninemia using the following systems: (1) denaturing high-performance liquid chromatography with a GC-clamped primer; (2) direct sequencing; and, (3) multiplex ligation-dependent probe amplification. Of 406 mutant alleles, 390 (96%) were genotyped; 65 mutations were identified, including 22 new mutations. R413P, R241C, IVS4-1g>a, R111X and R243Q were prevalent mutations. Mutations prevalent in the Japanese cohort are also common in Korean and Northern Chinese populations, suggesting same origin. The spectrum of prevalent mutations was not significantly different among six Japanese districts, indicating that Japan comprises a relatively homogeneous ethnic group. We classified the mutations by clinical phenotypes and in vivo PAH activity and estimated the mutations with potential tetrahydrobiopterin (BH(4)) responsiveness. The frequency of BH(4) responsiveness based on the genotype was 29.1% in Japanese PKU patients. A catalog of PKU genotypes would be useful for predicting clinical phenotype, deciding on the subsequent treatment of PKU including BH(4) therapy, and genetic counseling in East Asia.

Mutational spectrum of phenylketonuria in the Chinese Han population: a novel insight into the geographic distribution of the common mutations

The absence of a comprehensive analysis for phenylketonuria (PKU) mutations in the Chinese Han population has resulted in continued studies during the past 18 y to elucidate the mutational spectrum in patients from virtually all Chinese regions. Our study systematically investigated 13 exons and their surrounding introns of the phenylalanine hydroxylase (PAH) gene in 212 unrelated patients using PCR and direct sequencing. A total of 79 different mutations were identified in 405 of 424 mutant PAH alleles including 15 novel ones. Eight mutations, R243Q, Ex6-96A>G, IVS4 - 1G>A, R413P, Y356X, R111X, R241C, and V399V, with a relative frequency of 3% or more, accounted for two thirds of the identified ones. The data presented in this study indicates that the total pool of mutant PAH alleles in China consisted of a small number of common mutations and a very high number of rare mutations. Moreover, by merging the findings of previous studies to generate a more composite data set for the Chinese mainland, it is shown that there are no significant differences of the common mutations between southern and northern except for R413P statistically, raising questions about the previous hypothesis that great variations on mutation frequencies exist between above regions.

Development of two murine monoclonal antibodies recognizing human nG1m(a)-like isoallotypic markers

Antigenic determinants of immunoglobulin molecules are categorized into three groups: idiotypes, isotypes, and allotypes. An isoallotype is defined as an isotypic determinant in one or more subclasses and an allotype in another subclass of a given isotype. The isoallotype nG1m(a), formerly called non-a, is an allotype located on human IgG1 molecules lacking the G1m(a) allotype. This marker, however, is also detectable on all human IgG2 and IgG3 molecules. Anti-isoallotypic antibodies are useful tools for structural studies of immunoglobulins, forensic science, and epidemiological demographic investigations. In this study, two murine monoclonal antibodies (MAbs) recognizing nG1m(a)-like epitope(s) were generated against a human IgG myeloma protein. These MAbs are produced by hybridoma clones (4F18B12 and 6F18D1) obtained by fusion of SP2/0 myeloma cells with splenocytes from BALB/c mice immunized with heavy chain of a human IgG3 myeloma protein. These MAbs reacted with Fc, but not Fab fragment of the immunizing IgG3 paraprotein. Specificity of the MAbs was further analyzed using a panel of purified myeloma proteins and polyclonal IgG3, including IgG1 (n = 9), IgG2 (n = 4), IgG3 (n = 8), and IgG4 (n = 6) subclasses. Our results demonstrated that these MAbs reacted with linear epitope(s) located on heavy chain of all IgG2 and IgG3 molecules tested and some paraproteins of IgG1 subclass, but none of the IgG4 molecules. So these MAbs seem to recognize nG1m(a)-like isoallotypic marker. These MAbs showed no cross-reactivity with serum of other species tested. Both MAbs belonged to IgG1 subclass with affinity constants of 4.5 x 10(9) mol(-1) (4F18B12) and 3.46 x 10(9) mol(-1) (6F18D1), respectively. These MAbs might be used as a tool to detect nG1m(a) + IgG molecules.

The origin of the Japanese race based on genetic markers of immunoglobulin G

This review addresses the distribution of genetic markers of immunoglobulin G (Gm) among 130 Mongoloid populations in the world. These markers allowed the populations to be clearly divided into 2 groups, the northern and southern groups. The northern group is characterized by high frequencies of 2 marker genes, ag and ab3st, and an extremely low frequency of the marker gene afb1b3; and the southern group, in contrast, is indicated by a remarkably high frequency of afb1b3 and low frequencies of ag and ab3st. Based on the geographical distribution of the markers and gene flow of Gm ag and ab3st (northern Mongoloid marker genes) from northeast Asia to the Japanese archipelago, the Japanese population belongs basically to the northern Mongoloid group and is thus suggested to have originated in northeast Asia, most likely in the Baikal area of Siberia.

Frequency of the G/G genotype of resistin single nucleotide polymorphism at -420 appears to be increased in younger-onset type 2 diabetes

OBJECTIVE

Resistin is an adipocyte-secreted cytokine associated with insulin resistance in mice. We previously reported that the G/G genotype of a resistin single nucleotide polymorphism (SNP) at -420 increases type 2 diabetes susceptibility by enhancing its promoter activity. The aim of the present study was to determine the relevance of SNP -120 in a large number of subjects.

RESEARCH DESIGN AND METHODS

We examined 2,610 type 2 diabetic case and 2,502 control subjects. The relation between SNP -420 and the age of type 2 diabetes onset was further analyzed by adding 237 type 2 diabetic subjects with age of onset <or=40 years.

RESULTS

When analyzed without considering subject age, the SNP -420 genotype was not associated with type 2 diabetes. Since we reported that the onset of type 2 diabetes was earlier in G/G genotype, we analyzed the data using a trend test for age intervals of 10 years. The frequency of G/G genotype differed among age grades in type 2 diabetes (P = 0.037) and appeared to be higher in younger grades. In type 2 diabetes, G/G genotype was more frequent in subjects aged <40 years than in those aged >or=40 years (G/G vs. C/C, P = 0.003). In a total of 2,430 type 2 diabetic subjects with age of onset <60 years, the trend test showed that the G/G genotype had an increasing linear trend as the age grade of type 2 diabetes onset became younger (P = 0.0379). In control subjects, the frequency of C/G genotype showed an increasing linear trend with increasing age (P = 0.010).

CONCLUSIONS

The G/G genotype frequency of resistin SNP -420 appears to be increased in younger-onset type 2 diabetic subjects.

Genetic link between Chaoshan and other Chinese Han populations: Evidence from HLA-A and HLA-B allele frequency distribution

The genetic polymorphism of HLA-A and HLA-B loci was investigated in 505 Chaoshanese using PCR-SSP method. Among the HLA-A alleles detected, A*11 (35.64%) was most frequent, followed by A*02 (31.78%). Of 34 HLA-B alleles tested, 30 were observed, in which B*60 (21.68%), B*46 (14.46%), and B*58 (10.69%) were highly predominant. Comparison was made with other nine Chinese Han ethnic groups covering the Mainland China, Taiwan, Hong Kong, and Singapore. The high frequent alleles found in Chaoshanese were also common in other Chinese groups compared though the frequency levels varied from group to group. The phylogenic tree analysis based on the HLA-A and -B allele frequencies of all the 10 Chinese ethnic groups revealed that Chaoshanese, while clustering in general with the southern China-related Han Chinese, had the highest affinity to the Mainland Minnanese, but separated distinctively from the northern Han Chinese. The study, however, was yet to confirm the hypothesis of the Central Plains Han origin of Chaoshanese. Interestingly, the alleles (B*46, B*38, and B*58) and the related haplotypes (A*02-B*46 and A*33-B*58) that are positively associated with nasopharyngeal carcinoma (NPC), a disease prevailing predominantly among southern Chinese, were always at much higher frequencies among southern Chinese than among northern Chinese, whereas A*31 and B*13, the two alleles with highly protective effects for NPC, and the associated haplotype A*30-B*13 were predominantly high in northern Chinese. The different genetic background between northern and southern China may explain, at least partially, the prevalence of NPC among southern Chinese.

Type 1 diabetes in Japan

Type 1 diabetes is a multifactorial disease which results from a T-cell-mediated autoimmune destruction of the pancreatic beta cells in genetically predisposed individuals. The risk for individuals of developing type 1 diabetes varies remarkably according to country of residence and race. Japan has one of the lowest incidence rates of type 1 diabetes in the world, and recognises at least three subtypes of the condition: acute-onset ('classical'), slow-onset, and fulminant type 1 diabetes. The incidence rate of type 1 diabetes in children aged 0-14 years in Japan increased over the period from 1973-1992, but remained constant over the last decade, averaging 2.37 cases per 100,000 persons per year; the incidence does not appear to have increased in older age groups. Although there are few reports regarding the incidence and prevalence of type 1 diabetes in adult-onset patients, it appears that the prevalence of type 1 diabetes in adults is more than twice that in childhood-onset patients and that two-thirds of them have a slow-onset form of type 1 diabetes. Differences and similarities in the association of MHC and non-MHC genes with type 1 diabetes are observed in Japan and in countries with Caucasoid populations. Highly susceptible class II HLA haplotypes identified in patients of Caucasoid origin are rarely seen in Japanese patients, whereas protective haplotypes are universal. Non-MHC genes associated with susceptibility to type 1 diabetes in both Japanese and Caucasoid patients include polymorphisms in the insulin gene, the cytotoxic T-lymphocyte antigen 4 (CTLA4) gene, the interleukin-18 (IL18) gene and the major histocompatibility complex class I chain-related gene A (MICA) gene. Fulminant type 1 diabetes is a unique subtype of type 1 diabetes that accounts for about 20% of acute-onset type 1 diabetes, and is seen mainly in adults. The challenge for the future is to investigate the underlying pathogenesis of beta cell destruction, including the genetic or environmental factors that may modify the form of onset for each subtype of Japanese type 1 diabetes.

Phylogenetic relationship of the populations within and around Japan using 105 short tandem repeat polymorphic loci

We have analyzed 105 autosomal polymorphic short tandem repeat (STR) loci for nine East and South-eastern Asian populations (two Japanese, five Han Chinese, Thai, and Burmese populations) and a Caucasian population using a multiplex PCR typing system. All the STR loci are genomewide tetranucleotide repeat markers of which the total number of observed alleles and the observed heterozygosity were 756 and 0.743, respectively, for Japanese populations. Phylogenetic analysis for these allele frequency data suggested that the Japanese populations are more closely related with southern Chinese populations than central and/or northern ones. STRUCTURE program analysis revealed the almost clearly divided and accountable population structure at K=2-6, that the two Japanese populations always formed one group separated from the other populations and never belong to different groups at K> or =3. Furthermore, our new allele frequency data for 91 loci were analyzed with those for 52 worldwide populations published by previous studies. Phylogenetic and multidimensional scaling (MDS) analyses indicated that Asian populations with large population size (six Han Chinese, three Japanese, two Southeast Asia) formed one distinct cluster and are closer to each other than other ethnic minorities in east and Southeast Asia. This pattern may be the caviar of comparing populations with greatly differing population sizes when STR loci were analyzed.

Frequency and distribution in East Asia of 12 mutations identified in the SLC25A13 gene of Japanese patients with citrin deficiency

Deficiency of citrin, a liver-type mitochondrial aspartate-glutamate carrier (AGC), encoded by the SLC25A13 gene on chromosome 7q21.3, causes autosomal recessive disorders: adult-onset type II citrullinemia (CTLN2) and neonatal hepatitis associated with intrahepatic cholestasis (NICCD). So far, we have described 12 SLC25A13 mutations: 11 were from Japan and one from Israel. Three mutations found in Chinese and Vietnamese patients were the same as those in Japanese patients. In the present study, we identified a novel mutation IVS6+1G>C in a Japanese CTLN2 patient and widely screened 12 SLC25A13 mutations found in Japanese patients in control individuals from East Asia to confirm our preliminary results that the carrier frequency was high in Asian populations. Mutations 851-854del and 1638-1660dup were found in all Asian countries tested, and 851-854del associated with 290-haplotype in microsatellite marker D7S1812 was especially frequent. Other mutations frequently detected were IVS11+1G>A in Japanese and Korean, S225X in Japanese, and IVS6+5G>A in Chinese populations. We found a remarkable difference in carrier rates in China (including Taiwan) between north (1/940) and south (1/48) of the Yangtze River. We detected many carriers in Chinese (64/4169 = 1/65), Japanese (20/1372 = 1/69) and Korean (22/2455 = 1/112) populations, suggesting that over 80,000 East Asians are homozygotes with two mutated SLC25A13 alleles.

GM haplotype diversity of 82 populations over the world suggests a centrifugal model of human migrations

This study investigates the GM genetic relationships of 82 human populations, among which 10 represent original data, within and among the main broad geographic areas of the world. Different approaches are used: multidimensional scaling analysis and test for isolation by distance, to assess the correlation between genetic variation and spatial distributions; analysis of variance, to investigate the genetic structure at different hierarchical levels of population subdivision; genetic similarity map (geographic map distorted by available genetic information), to identify regions of high and low genetic variation; and minimal spanning network, to point out possible migration routes across continental areas. The results show that the GM polymorphism is characterized by one of the highest amounts of genetic variation observed so far among populations of different continents (Fct=0.3915, P < 0.0001). GM diversity can be explained by a model of isolation by distance (IBD) at most continental levels, with a particularly significant fit to IBD for the Middle East and Europe. Five peripheral regions of the world (Europe, west and south sub-Saharan Africa, Southeast Asia, and America) exhibit a low level of genetic diversity both within and among populations. By contrast, East and North African, Southwest Asian, and Northeast Asian populations are highly diverse and interconnected genetically by large genetic distances. Therefore, the observed GM variation can be explained by a "centrifugal model" of modern humans peopling history, involving ancient dispersals across a large intercontinental area spanning from East Africa to Northeast Asia, followed by recent migrations in peripheral geographic regions.

Mitochondrial genome variation in eastern Asia and the peopling of Japan

To construct an East Asia mitochondrial DNA (mtDNA) phylogeny, we sequenced the complete mitochondrial genomes of 672 Japanese individuals (http://www.giib.or.jp/mtsnp/index_e.html). This allowed us to perform a phylogenetic analysis with a pool of 942 Asiatic sequences. New clades and subclades emerged from the Japanese data. On the basis of this unequivocal phylogeny, we classified 4713 Asian partial mitochondrial sequences, with <10% ambiguity. Applying population and phylogeographic methods, we used these sequences to shed light on the controversial issue of the peopling of Japan. Population-based comparisons confirmed that present-day Japanese have their closest genetic affinity to northern Asian populations, especially to Koreans, which finding is congruent with the proposed Continental gene flow to Japan after the Yayoi period. This phylogeographic approach unraveled a high degree of differentiation in Paleolithic Japanese. Ancient southern and northern migrations were detected based on the existence of basic M and N lineages in Ryukyuans and Ainu. Direct connections with Tibet, parallel to those found for the Y-chromosome, were also apparent. Furthermore, the highest diversity found in Japan for some derived clades suggests that Japan could be included in an area of migratory expansion to Continental Asia. All the theories that have been proposed up to now to explain the peopling of Japan seem insufficient to accommodate fully this complex picture.

Dental morphology of the Dawenkou Neolithic population in North China: implications for the origin and distribution of Sinodonty

We compare the incidence of 25 nonmetric dental traits of the people of the Neolithic Dawenkou culture (6300-4500 BP) sites in Shandong Province, North China with those of other East Asian populations. The Dawenkou teeth had an overwhelmingly greater resemblance to the Sinodont pattern typical of Northeast Asia than to the Sundadont pattern typical of Southeast Asia. Multidimensional scaling using Smith's mean measure of divergence (MMD) statistic place the Dawenkou sample near the Amur and the North China-Mongolia populations in the area of the plot indicating typical Sinodonty. The existence of the Sinodont population in Neolithic North China suggests a possible continuity of Sinodonty from the Upper Cave population at Zhoukoudian (about 34000-10000 BP) to the modern North Chinese. The presence of Sinodonty in Shandong Province shows that the Japan Sea and East China Sea were strong barriers to gene flow for at least 3000 years, because at this time the Jomonese of Japan were fully Sundadont. In addition, we suggest that the descendants of the Dawenkou population cannot be excluded as one of the source populations that contributed to sinodontification in Japan.

Evidence of a founder effect for the 235delC mutation of GJB2 (connexin 26) in east Asians

Mutations in the GJB2 gene encoding connexin 26 (Cx26) are a major cause of autosomal recessive and sporadic cases of congenital deafness in most populations. The 235delC mutation of GJB2 is the most frequent known mutation in some east Asian populations, with a carrier frequency of approximately 1%. In order to study the origin of 235delC among east Asians, we analyzed single-nucleotide polymorphisms (SNPs) within the coding region of GJB2 and flanking the 235delC mutation. We observed significant linkage disequilibrium between 235delC and five linked polymorphic markers, suggesting that 235delC arose from a common founder. The detection of 235delC only in east Asians, but not in Caucasians, and the small chromosomal interval of the shared haplotype suggest that 235delC is an ancient mutation that arose after the divergence of Mongoloids and Caucasians. Similarly, the finding that this mutation appears on a single haplotype provides no support for the possibility that recurrent mutation is the explanation for the high frequency of the allele.

Founder effect of the C9 R95X mutation in Orientals

A nonsense mutation at codon 95 (R95X) in the C9 gene is responsible for most Japanese C9 deficiency (C9D) cases, with a carrier frequency of 6.7%. Upon analysis of microsatellite markers and newly identified dinucleotide repeat number polymorphisms in the 3' flanking region of the C9 gene, a founder effect was demonstrated for the R95X mutation of the C9 gene in Japanese. Screening for the R95X mutation in Korean and Chinese individuals showed that the R95X carrier frequencies in Koreans and Chinese were 2.0% and 1.0%, respectively. Although homozygotes for the R95X mutation were not found in Korea or China, the shared haplotype of the dinucleotide repeat number polymorphisms appeared to be associated with the R95X mutation in the heterozygotes in Korea and China. The founder effect found in East Asians (Japanese, Koreans and Chinese) but not in Caucasians, as well as the haplotype sharing in only a small chromosomal interval, suggested that the R95X mutation of C9 gene was ancient and had occurred after the divergence of East Asians and Caucasians, and before migration of the Yayoi people to Japan. Since the mortality of meningococcal infections in complement-deficient patients is lower than that in normal individuals, a founder effect and a selective advantage in isolation might be the main reasons for the high frequency of the R95X mutation in Japan.

GM polymorphism and the evolutionary history of modern humans

Present human populations show a complex network of genetic relationships, which reflects mainly their unique origin and their migration and isolation history since the recent creation of modern man. The scrutiny of their genetic characteristics, according to GM polymorphism, shows that the continuity of the genetic variation between populations from neighbouring continents, assured by intermediate world part populations, is against any attempt to divide present human populations into major groups. GM polymorphism analysis also shows three remarkable levels of genetic differentiation, which would have appeared, respectively, within populations of sub-Saharan Africa, Europe and East Asia. The first small groups of people that split from the common ancestral population gave the sub-Saharan Africans. On the other hand, Asians diverged mainly from Europeans and Near East populations during a later period. The confrontation between the phylogeny and the frequency distribution of GM haplotypes shows that the ancestral population of actual South-Arabia people could be a candidate for a common ancestral population. The first major expansions of modern humans were proposed in a hypothetical scenario, which will open a new track in the research of our geographic origin.

Paternal population history of East Asia: sources, patterns, and microevolutionary processes

Asia has served as a focal point for human migration during much of the Late Pleistocene and Holocene. Clarification of East Asia's role as a source and/or transit point for human dispersals requires that this region's own settlement history be understood. To this end, we examined variation at 52 polymorphic sites on the nonrecombining portion of the Y chromosome (NRY) in 1,383 unrelated males, representing 25 populations from southern East Asia (SEAS), northern East Asia (NEAS), and central Asia (CAS). The polymorphisms defined 45 global haplogroups, 28 of which were present in these three regions. Although heterozygosity levels were similar in all three regions, the average pairwise difference among haplogroups was noticeably smaller in SEAS. Multidimensional scaling analysis indicated a general separation of SEAS versus NEAS and CAS populations, and analysis of molecular variance produced very different values of Phi(ST) in NEAS and SEAS populations. In spatial autocorrelation analyses, the overall correlogram exhibited a clinal pattern; however, the NEAS populations showed evidence of both isolation by distance and ancient clines, whereas there was no evidence of structure in SEAS populations. Nested cladistic analysis demonstrated that population history events and ongoing demographic processes both contributed to the contrasting patterns of NRY variation in NEAS and SEAS. We conclude that the peopling of East Asia was more complex than earlier models had proposed-that is, a multilayered, multidirectional, and multidisciplinary framework is necessary. For instance, in addition to the previously recognized genetic and dental dispersal signals from SEAS to NEAS populations, CAS has made a significant contribution to the contemporary gene pool of NEAS, and the Sino-Tibetan expansion has left traces of a genetic trail from northern to southern China.

The origin of Minnan and Hakka, the so-called "Taiwanese", inferred by HLA study

The Minnan and Hakka people groups, the so-called "Taiwanese", are the descendants of early settlers from the southeast coast of China during the last few centuries. Genetically they showed affinities to southern Asian populations, as determined by phylogenetic trees and correspondence analysis calculated from HLA allele frequencies. This corresponds historically with the fact that they are the descendants of the southeast coastal indigenous population (Yueh) of China and should therefore not be considered as descendants of "pure" northern Han Chinese. A33-B58-DRB1*03 (A33-Cw10-B58-DRB1*03-DQB1*02), the most common HLA haplotype among "Taiwanese", with a haplotype frequency of 6.3%, has also been found to be the most common haplotype among Thai-Chinese and Singapore Chinese, two other populations also originating from the southeast coast of China. These observations suggests that this haplotype is the most well-conserved ancient haplotype of the Yueh.

Population structure and history in East Asia

Archaeological, anatomical, linguistic, and genetic data have suggested that there is an old and significant boundary between the populations of north and south China. We use three human genetic marker systems and one human-carried virus to examine the north/south distinction. We find no support for a major north/south division in these markers; rather, the marker patterns suggest simple isolation by distance.

Frequent mutation in Chinese patients with infantile type of GSD II in Taiwan: evidence for a founder effect

Glycogen storage disease type II (GSD II, Pompe's disease), an autosomal recessive inherited disease, is caused by the deficiency of acid alpha-D-glucosidase, which results in the impaired glycogen degradation in lysosome and causes excess glycogen accumulation in lysosome. In Taiwan, the infantile form of GSD II is the most common type of glycogen storage diseases. The frequency of C1935A mutant allele is 0.8 in these Chinese patients. In this study, we analyzed four single point polymorphic markers (324, 1203, 2065, 2338) by ACRS-based RFLP We observed that the alleles possessing the C1935A mutation in 19 of 25 Chinese patients who were heterozygous or homozygous have conserved polymorphic markers, and all of C1935A mutant alleles in these patients are linked to a specific haplotype. The allele frequency of this specific haplotype in 19 Chinese patients and in 42 normal individuals is 0.95 and 0.17, respectively (P<0.005, chi2 = 66.018). This result suggests that the C1935A mutation in Chinese patients with infantile form of GSD II is due to the founder effect.

GM and KM immunoglobulin allotypes in a Spanish Pyrenean population: Val d'Aran

Four hundred and thirteen unrelated individuals (202 autochthonous and 211 non-autochthonous) of Val d'Aran (Catalan Pyrenees) have been analysed for the GM and KM immunoglobulin genetic system using the inhibition haemagglutination method. This population was defined by eight GM haplotypes (GM*3 23 5*, GM*3 5*, GM*1,17 21,28, GM*1,2,17 21,28, GM*1,17 5*, GM*1,17 5,6,11,24, GM*1,17 10,11,13,15 and GM*1,17 10,11,13,15,16) inferred from the 17 observed phenotypes. The Val d'Aran population frequencies conform to Hardy-Weinberg expectations. The frequencies of phenotypes and haplotypes show a definite homogeneity between the autochthonous and non-autochthonous people of Val d'Aran and 11 other Pyrenean populations (Mauléon, Macaye, St. Jean Pied de Port, Vallée de L'Ouzom, Gavarnie, Barèges, Luz St. Sauveur, Esparros, Camurac, Capcir and Pays de Sault) that have already been studied for the same allotypes. A factorial correspondence analysis was performed for the 12 autochthonous Pyrenean populations, showing a high frequency of the GM*3 23 5* haplotype in the three Pyrenean regions (Western, Central and Eastern), while the GM*1,17 21,28 haplotype is mainly found in the Central region, GM*3 5* in the Eastern and Western zones, and the GM*1,2,17 21,28 is mainly present in the Central and Eastern populations. The results show a relative regional homogeneity, so there is no evidence of a frequency gradient in the Pyrenean populations for the GM and KM genetic systems. It may, however, be noticed that the Central Pyrenean populations form a group, with one population (Vallée de l'Ouzom) isolated from the rest, probably because of its particular model of inheritance by which the heritage is passed to the first born without sex consideration. It has been possible to point out some differences in the genetic structure of the autochthonous and non-autochthonous Val d'Aran population and to place the autochthonous Aranese group among its Pyrenean neighbours.

Immunoglobulin allotype gene polymorphisms in systemic sclerosis: interactive effect of MHC class II and KM genes on anticentromere antibody production

OBJECTIVE

To examine potential interactions between immunoglobulin (Ig)-allotype gene polymorphisms and susceptibility to systemic sclerosis (SSc) as well as serological expression in SSc patients.

METHODS

IgG heavy chain allotypes G1M(f, z), G2M(n+, n-), G3M(b, g) and Ig light chain allotype KM(1, (1, 2), 3) were genotyped in 105 Japanese SSc patients and 47 race matched normal controls using polymerase chain reaction (PCR) based methods. Associations of each Ig allotype with SSc related antinuclear antibodies were examined in combination with or without MHC class II alleles.

RESULTS

GM/KM genotypic and allelic frequencies were similar in SSc patients and in normal controls. Frequencies of G1M(f) and G2M(n+) were significantly decreased in anticentromere antibody (ACA) positive SSc patients compared with ACA negative SSc patients (p = 0.04 and 0.02, respectively). Conversely, the presence of DQB1*0501 and KM(1, 2) significantly increased the risk of ACA positivity.

CONCLUSION

Ig allotype gene polymorphisms were not associated with susceptibility to SSc. Instead, the results suggested that MHC class II and KM genes are associated with autoimmune responses by interactively promoting the production of ACA.

GM and KM allotypes in nine population samples of Sicily

Serum samples of 864 unrelated healthy male and female individuals belonging to nine provinces of Sicily were types for Glm (1,2,3,17), G3m (5,10,11,13,14,15,16,21), and KM (1). With the exception of the Trapani sample these samples are characterized by the presence of five GM haplotypes: GM*1,17;21,26; GM*1,2,17;21,26; GM*1,3;5,10,11,13,14,26; GM*3;5,10,13,14,26; and GM*1,17;10,11,13,15,16. The interpopulation variability in the distribution of these haplotypes is considerable, which is especially due to haplotypes GM*1,3;5,10,11,13,14,26, and GM*3;5,10,13,14,26. However, no clear-cut clustering of the samples according to historical or geographical facts could be shown. Comparisons with other Italian populations reveal the considerable genetic difference of the Sicilians, which is in particular caused by the presence of the haplotypes GM*1,3;5,10,11,13,14,26, and GM*1,17;10,11,13,15,16. These haplotypes are quite uncommon in Europeans and may reflect gene flow from the Middle East. The KM phenotype and allele frequencies also show a considerable interpopulation variability among the nine Sicilian samples, but as for GM no distinction between eastern and western provinces of Sicily is present.

Genetic origins of the Japanese: a partial support for the dual structure hypothesis

Based on the morphological characteristics of the skull and teeth, Hanihara ([1991] Japan Review 2:1-33) proposed the "dual structure model" for the formation of modern Japanese populations. We examine this model by dividing it into two independent hypotheses: 1) the Upper Paleolithic population of Japan that gave rise to the Neolithic Jomon people was of southeast Asian origin, and 2) modern Ainu and Ryukyuan (Okinawa) populations are direct descendants of the Jomon people, while Hondo (Main Island)-Japanese are mainly derived from the migrants from the northeast Asian continent after the Aeneolithic Yayoi period. Our aim is to examine the extent to which the model is supported by genetic evidence from modern populations, particularly from Japan and other Asian areas. Based on genetic distance analyses using data from up to 25 "classic" genetic markers, we find first that the three Japanese populations including Ainu and Ryukyuan clearly belong to a northeast Asian cluster group. This negates the first hypothesis of the model. Then, we find that Ainu and Ryukyuans share a group contrasting with Hondo-Japanese and Korean, supporting the second hypothesis of the model. Based on these results, we propose a modified version of the dual structure model which may explain the genetic, morphological, and archaeological evidence concerning the formation of modern Japanese populations.

GM and KM allotypes in eight tribal populations of Madyha Pradesh and Orissa, India

Serum samples from eight endogamous Indian tribal populations of Madhya Pradesh (Dhurwa, Halba, Bhatra, Muria, Maria) and Orissa (Deshia Khond, Binjhal, Kisan) with a total of n = 731 unrelated individuals were typed for G1M (1,2,3,17), G3M (5,10,11,13,14,15,16,21, 26), and KM (1). In seven of these populations five different GM haplotypes were found: GM* 1,17;21,26; GM* 1,17;10,11,13,15,16; GM* 1,2, 17;21,26; GM* 1,3;5,10,11,13,14,26; and GM* 3;5,10,11,13,14,26. In the Kisan sample the haplotype GM* 1,2,17;21,26 is absent. The intergroup variability in the distribution of these haplotypes is considerable and statistically highly significant. The reasons for that can be attributed to the ethnohistory and to the genetic isolation of these eight endogamous tribal populations. The GM haplotype distribution pattern of all these groups is quite different from that of the non-tribal populations of India, whereas it is in good agreement with that of the so far tested other tribal populations from India. This can be explained by different origin and history of the Indian tribal and non-tribal populations. In the KM system, too, remarkable variability is seen in the distribution of phenotype and allele frequencies among the eight tribal populations under study.

Nuclear DNA polymorphism in a Mandenka population from Senegal: comparison with eight other human populations

A large and ethnically well defined Mandenka sample from Senegal is analysed for 80 nuclear DNA RFLPs, and compared with eight previously studied human populations. A high level of genetic diversity is found in this sample, comparable to that observed in two African Pygmy samples, but lower than that of a European sample. High population variation is observed for most markers. A neutrality test reveals that the markers used in this study can be considered as neutral. A high correlation is found between genetic and geographic distances (r = 0.62), suggesting that geography does also affect long range population genetic relationships and is an important factor behind differentiation among human populations.

Population genetics of phenylketonuria

Phenylketonuria (PKU) is an autosomal recessive disorder caused by a large number of mutations at the phenylalanine hydroxylase (PAH) locus, most of which are strongly associated with specific RFLP or VNTR haplotypes. One of the major questions remaining in PKU research is why this apparently maladaptive disorder has been maintained at a frequency of approximately 1 in 10,000 among Caucasians. A growing number of studies have provided evidence that both the relatively high frequency of PKU and the strong mutation/haplotype associations might reflect the existence of multiple founding populations for PKU. Examples of putative founding populations for PKU in both Europe and Asia will be presented. Some PAH mutations are associated with multiple haplotypes, suggesting recurrence. Evidence for and against recurrence as the mechanism responsible for the association of the R408W mutation with RFLP haplotypes 1 and 2 will be discussed.

Gm and Km allotypes in Wayampi, Wayana and Emerillon Indians from French Guiana

We have studied 506 Amerindians from three French Guiana groups: 194 Wayampi, living in Trois-Sauts, and 100 in the Camopi area; 47 Emerillon also living in the Camopi area and 165 Wayana on the Litani and Maroni rivers. All samples were tested for G1m(1,2,3,17), G3m(5,6,10,11,13,14,15,16,21,24,28) and Km(1) by the classical method of hemaglutination inhibition. The phenotype and haplotype distributions are presented and have been subjected to factorial correspondence analysis. Two Gm haplotypes are common: Gm1,17;21,28, and Gm1,2,17;21,28, but with an important variation in frequency. A rare haplotype, probably the result of a genetic anomaly: Gm1,17;21R,28, is frequent in the Emerillon (17%). These populations show no evidence of Black or Caucasian admixtures.

A new approach for interpreting the genetic diversity in space: 'Mobile Site Method'. Application to Gm haplotype distribution of twenty-seven Amerindian tribes from North and Central America

We present a new approach, called 'Mobile Site Method' (MSM), to the construction of 'genetic similarity maps' more efficient than that described in a preceding paper (Hazout et al. 1991). After building a triangular mesh between the geographical sites, the method consists of moving these locations at each iteration to reduce the overall differences between the geographic and genetic distances. The genetic similarity map, i.e. the final distorted map, allows the interpretation of the genetic diversity of a population set. We have applied this method to the study of Gm immunoglobulin allotypes of twenty-seven Amerindian groups from North and Central America. By a local weighted linear regression, we have reconstituted the distorted contour of America. This representation completes the observations of the sites during the map distortion. In this study, we have defined a large geographical factor in the genetic data (84% of the variability explained), related to a linguistic factor.

Origin of the Koreans: a population genetic study

A population genetic study was undertaken to investigate the origin of Koreans. Thirteen polymorphic and 7 monomorphic blood genetic markers (serum proteins and red cell enzymes) were studied in a group of 437 Koreans. Genetic distance analyses by both cluster and principal components models were performed between Koreans and eight other populations (Koreans in China, Japanese, Han Chinese, Mongolians, Zhuangs, Malays, Javanese, and Soviet Asians) on the basis of 47 alleles controlled by 15 polymorphic loci. A more detailed analysis using 65 alleles at 19 polymorphic loci was performed on six populations. Both analyses demonstrated genetic evidence of the origin of Koreans from the central Asian Mongolians. Further, the Koreans are more closely related to the Japanese and quite distant from the Chinese. The above evidence of the origin of Koreans fits well with the ethnohistoric account of the origin of Koreans and the Korean language. The minority Koreans in China also maintained their genetic identity.

Frequency and distribution of phenylketonuric mutations in Orientals

The frequency and distribution of eight mutations (R111X, IVS4nt-1, Y204C, R243Q, IVS7nt-2, W326X, Y356X, and R413P) in the phenylalanine hydroxylase gene of Orientals in Japan and Korea were examined by allele-specific oligonucleotide hybridization. The mutant alleles comprised 54 and 55% of the phenylketonuria (PKU) chromosomes examined in 36 patients in Japan and 10 patients in Korea, respectively. The spectrum of PKU mutations in Japan was similar to that in China, particularly in northern China, but different from that in Korea. The IVS4nt-1 mutation had a high frequency in Korea and southern China, due to the result of the founder effect and genetic drift. The R413P mutation, which may have originated in the regions surrounding the Baikal, expanded to northern China and Japan. We did not find Caucasian mutations in the Japanese or Korean PKU chromosomes. Thus, PKU mutations occurred after racial divergence between Caucasians and Mongoloids, and there were different founding populations for PKU in the two populations.

Missense mutations prevalent in Orientals with phenylketonuria: molecular characterization and clinical implications

Two missense mutations in the phenylalanine hydroxylase (PAH) genes of Orientals with phenylketonuria (PKU) have been identified. A G-to-A transition in exon 7 of the gene results in the substitution of Gln243 for Arg243 (R243Q) and accounts for 18% of all PKU chromosomes among Chinese. An A-to-G transition in exon 6 of the gene results in the substitution of Cys204 for Tyr204 (Y204C) and identifies about 13 and 5% of all PKU chromosomes in the Chinese and Japanese populations, respectively. The R243Q construct produced less than 10% of normal PAH activity in in vitro expression analysis in a eukaryotic cell system, and patients homozygous for this substitution exhibit a severe clinical phenotype. These results are consistent with previous findings in this expression system. The Y204C construct, however, produced near normal levels of PAH enzyme activity and immunoreactivity in this in vitro expression system. Because this substitution is present only on PKU chromosomes, it is a valuable marker for identifying the corresponding mutant allele for carrier screening of PKU. With the characterization of these two substitutions, about 60% of PKU alleles in China can now be identified. The continuing search for additional PKU mutations will permit effective carrier screening and prenatal gene diagnosis of PKU in East Asia.

A key amino acid determining G3m(b) allotypic markers

A key amino acid substitution specific for allotypic Gm b markers, b0, b3, b5, were determined through sequence analyses of the pFc' fragments of IgG1 (Su) and IgG3 (Ba[Gm(g)], Bu[Gm(b1b3)], and Kam[Gm(b3st)]) myeloma proteins. The results indicate that serine at position 384 is responsible for the specificities. It is considered from crystallographic data of IgG-Fc [Deisenhofer et al. (1981) Biochemistry 20:2361] that two residues, the serine and isoleucine specific for IgG3 subclass at position 422, cause the structural change responsible for b markers. The two residues are close to each other in the CH3 domain. The allocations of the epitopes are estimated to be on two bends (residue no. 382-392, 411-424) between the beta-strands, whose amino acid residues are present in wide contact area [Novotny et al. (1987) Immunol. Today 8:26).

Founder effect of a prevalent phenylketonuria mutation in the Oriental population

A missense mutation has been identified in the human phenylalanine hydroxylase [PAH; phenylalanine 4-monooxygenase; L-phenylalanine, tetrahydrobiopterin:oxygen oxidoreductase (4-hydroxylating), EC 1.14.16.1] gene in a Chinese patient with classic phenylketonuria (PKU). A G-to-C transition at the second base of codon 413 in exon 12 of the gene results in the substitution of Pro413 for Arg413 in the mutant protein. This mutation (R413P) results in negligible enzymatic activity when expressed in heterologous mammalian cells and is compatible with a classic PKU phenotype in the patient. Population genetic studies reveal that this mutation is tightly linked to restriction fragment length polymorphism haplotype 4, which is the predominant haplotype of the PAH locus in the Oriental population. It accounts for 13.8% of northern Chinese and 27% of Japanese PKU alleles, but it is rare in southern Chinese (2.2%) and is absent in the Caucasian population. The data demonstrate unambiguously that the mutation occurred after racial divergence of Orientals and Caucasians and suggest that the allele has spread throughout the Orient by a founder effect. Previous protein polymorphism studies in eastern Asia have led to the hypothesis that "northern Mongoloids" represented a founding population in Asia. Our results are compatible with this hypothesis in that the PKU mutation might have occurred in northern Mongoloids and subsequently spread to the Chinese and Japanese populations.

A BF subtype "Fb1" is a marker gene of some Mongoloid populations

A factor B subtype, BF*Fb1, was first detected in Japanese by using isoelectric focusing or agarose gel electrophoresis in Tris/glycine/Veronal buffer. Our previous studies suggested that BF*Fb1 may be characteristic of some of Mongoloid populations. To investigate further distribution of BF*Fb1, samples randomly collected from Japanese in Yonaguni island of Japan and Cambodian were tested. BF*Fb1 was not observed in a Cambodian population whereas in a Japanese population of Yonaguni island, BF*Fb1 occurred at a frequency five times as high as those in main islands of Japan. In paternity cases, a Korean family with three offsprings was shown to transmit BF*Fb1 from the accused man to one of the offsprings. These data strongly indicate that BF*Fb1 is a marker gene for some of Mongoloid populations.