A sero-biochemical genetic study of Jalari and Brahmin caste populations of Andhra Pradesh, India

Blood specimens from Jalari and Brahmin caste populations of Andhra Pradesh, India, were examined for blood groups, red cell enzymes, and serum proteins. Of 33 genetic loci studied, 16 were observed to be invariant among both the castes, while common polymorphism or rare variants were observed in one or both populations for the other loci. Three rare heterozygotes at the phosphoglucoisomerase locus, two different peptidase A variants occurring once each and single cases of rare 6-phosphogluconate dehydrogenase and transferrin variants were recorded. Also a few cases of hemoglobin AS and anhaptoglobinemia were observed. The difference in rare variants between the two castes is conspicuous but large differences in their gene frequencies at the polymorphic loci were not observed. It is pointed out that the frequency of rare variants in the tribal and caste populations of Southern India appears to be higher than observed in temperate-dwelling civilized populations.     

Maternal footprints of Southeast Asians in North India

We have analyzed 7,137 samples from 125 different caste, tribal and religious groups of India and 99 samples from three populations of Nepal for the length variation in the COII/tRNA(Lys) region of mtDNA. Samples showing length variation were subjected to detailed phylogenetic analysis based on HVS-I and informative coding region sequence variation. The overall frequencies of the 9-bp deletion and insertion variants in South Asia were 1.9 and 0.6%, respectively. We have also defined a novel deep-rooting haplogroup M43 and identified the rare haplogroup H14 in Indian populations carrying the 9-bp deletion by complete mtDNA sequencing. Moreover, we redefined haplogroup M6 and dissected it into two well-defined subclades. The presence of haplogroups F1 and B5a in Uttar Pradesh suggests minor maternal contribution from Southeast Asia to Northern India. The occurrence of haplogroup F1 in the Nepalese sample implies that Nepal might have served as a bridge for the flow of eastern lineages to India. The presence of R6 in the Nepalese, on the other hand, suggests that the gene flow between India and Nepal has been reciprocal.     

Protein variants in Hiroshima and Nagasaki: tales of two cities.

The results of 1,465,423 allele product determinations based on blood samples from Hiroshima and Nagasaki, involving 30 different proteins representing 32 different gene products, are analyzed in a variety of ways, with the following conclusions: (1) Sibships and their parents are included in the sample. Our analysis reveals that statistical procedures designed to reduce the sample to equivalent independent genomes do not in population comparisons compensate for the familial cluster effect of rare variants. Accordingly, the data set was reduced to one representative of each sibship (937,427 allele products). (2) Both chi 2-type contrasts and a genetic distance measure (delta) reveal that rare variants (P less than .01) are collectively as effective as polymorphisms in establishing genetic differences between the two cities. (3) We suggest that rare variants that individually exhibit significant intercity differences are probably the legacy of tribal private polymorphisms that occurred during prehistoric times. (4) Despite the great differences in the known histories of the two cities, both the overall frequency of rare variants and the number of different rare variants are essentially identical in the two cities. (5) The well-known differences in locus variability are confirmed, now after adjustment for sample size differences for the various locus products; in this large series we failed to detect variants at only three of 29 loci for which sample size exceeded 23,000. (6) The number of alleles identified per locus correlates positively with subunit molecular weight. (7) Loci supporting genetic polymorphisms are characterized by more rare variants than are loci at which polymorphisms were not encountered. (8) Loci whose products do not appear to be essential for health support more variants than do loci the absence of whose product is detrimental to health. (9) There is a striking excess of rare variants over the expectation under the neutral mutation/drift/equilibrium theory. We suggest that this finding is primarily due to the relatively recent (in genetic time) agglomeration of previously separated tribal populations; efforts to test for agreement with the expectations of this theory by using data from modern cosmopolitan populations are exercises in futility. (10) All of these findings should characterize DNA variants in exons as more data become available, since the finding are the protein expression of such variants.     

Rare variants, private polymorphisms, and locus heterozygosity in Amerindian populations.

The results of 21,103 electrophoretic typings distributed across 28 polypeptides in members of 12 Amerindian tribes are reported, and the accumulated results of electrophoretic studies on these same polypeptides in 21 Amerindian tribes are then analyzed. Thus far 11 'private' polymorphisms have been identified in these tribes. When the tribal samples are combined and traits achieving polymorphic proportions in the total sample excluded from consideration, the average frequency of rare variants is 2.8 per 1,000 determinations. For a subset of 23 of these polypeptides also studied in Caucasians and Japanese, variant frequencies per 1,000 determinations are: Indians, 2.2; Caucasians (British), 1.6; and Japanese, 1.5. Average locus heterogeneity for these polypeptides (based on rare variants plus polymorphisms) is: Indians, .049; Caucasians, .078; and Japanese, .077. A higher proportion of loci are monomorphic within tribes than within civilized urban populations. It is argued that for inferences concerning the forces maintaining genetic variability within populations, studies on samples from tribespeople are much more appropriate than studies on samples from civilized urban populations.     

A revised indirect estimate of mutation rates in Amerindians

We have previously raised the possibility that the mutation rate resulting in rare electrophoretic variants is higher in tribal/tropical-dwelling/nonindustrialized societies than in civilized/temperate-dwelling/industrialized societies. Here, we report the results of examining 11 additional proteins for the occurrence of rare electrophoretic variants in 10 Amerindian tribes, for a total of 8,968 determinations and a total of 17,648 locus tests. When these data are combined with the results of all our previous similar studies of Amerindians, a total of 272,298 polypeptides, the products of 43 different loci, have been examined for the occurrence of rare electrophoretic variants. On the assumption that these variants are maintained by mutation pressure and are essentially neutral in their phenotypic effects, we have calculated by three different approaches that it requires an average mutation rate of 1.3 X 10(-5)/locus per generation to maintain the observed variant frequency. Concurrently, we are reporting elsewhere that a direct estimate of the mutation rate resulting in electromorphs in various studies of civilized industrialized populations is 0.3 X 10(-5)/locus per generation. Although this difference appears to have statistical significance, the nonquantifiable uncertainties to both approaches are such that our enthusiasm for a true difference in mutation rates between the two types of populations has diminished. However, even the lower of these estimates, when corrected for all the types of genetic variation that electrophoresis does not detect, implies total locus and gametic mutation rates well above those which in the past have dominated genetic thinking.     

Insertion/deletion polymorphisms in tribal populations of southern India and their possible evolutionary implications

India has the unique distinction of having perhaps the largest diversities, both biological and cultural. The Nilgiri Hills of southern India, a home for several tribal pockets representing different genetic isolates, provides a genetic wealth to understand human evolution. We have analyzed eight widely distributed polymorphic insertion/deletion loci (AluAPO, AluACE, AluDI, AluPLAT, AluPV92, AluFXIIIB, CD4 del and mtNUC) in 250 unrelated individuals from five tribal populations (Badaga, Irula, Kota, Kurumba, and Toda). All loci were highly polymorphic except the CD4 del locus, at which the deletion allele was fixed in Kotas and Kurumbas. The levels of average heterozygosities were found to be high in all the populations. In most populations, they were also higher than those predicted by the island model of population structure. The gene diversity (GST = 8.3%) was found to be higher than that in populations of most global regions with the exception of Africa. It is clear from the present study that drift effects could have accentuated the process of genetic differentiation of the tribal populations. The possibility of an early demographic expansion of modern humans within south India also cannot be ruled out.     

Genetic Affinity of the Bhil,Kol and Gond Mentioned in Epic Ramayana

Kol, Bhil and Gond are some of the ancient tribal populations known from the Ramayana, one of the Great epics of India. Though there have been studies about their affinity based on classical and haploid genetic markers, the molecular insights of their relationship with other tribal and caste populations of extant India is expected to give more clarity about the the question of continuity vs. discontinuity. In this study, we scanned >97,000 of single nucleotide polymorphisms among three major ancient tribes mentioned in Ramayana, namely Bhil, Kol and Gond. The results obtained were then compared at inter and intra population levels with neighboring and other world populations. Using various statistical methods, our analysis suggested that the genetic architecture of these tribes (Kol and Gond) was largely similar to their surrounding tribal and caste populations, while Bhil showed closer affinity with Dravidian and Austroasiatic (Munda) speaking tribes. The haplotype based analysis revealed a massive amount of genome sharing among Bhil, Kol, Gond and with other ethnic groups of South Asian descent. On the basis of genetic component sharing among different populations, we anticipate their primary founding over the indigenous Ancestral South Indian (ASI) component has prevailed in the genepool over the last several thousand years.     

Double heterozygous hemoglobin Q India/hemoglobin D Punjab hemoglobinopathy: Report of two rare cases

Cation exchange high performance liquid chromatography (CE HPLC) provides an excellent tool for accurate and reliable diagnosis of various hemoglobin (Hb) disorders. HbQ India is a rare alpha chain variant that usually presents in the heterozygous state. Its presence in double heterozygous state with HbD Punjab is extremely rare. The double heterozygosity for α and β chain variants leads to formation of abnormal heterodimer hybrids, which can lead to diagnostic dilemmas. We report two rare cases of double heterozygous HbQ India/HbD Punjab where the hybrid Hb was seen to elute at retention time similar to HbC on CE HPLC. The first case had unconjugated hyperbilirubinemia at presentation; while, the second case was asymptomatic.     

The genetic heritage of the earliest settlers persists both in Indian tribal and caste populations

Two tribal groups from southern India--the Chenchus and Koyas--were analyzed for variation in mitochondrial DNA (mtDNA), the Y chromosome, and one autosomal locus and were compared with six caste groups from different parts of India, as well as with western and central Asians. In mtDNA phylogenetic analyses, the Chenchus and Koyas coalesce at Indian-specific branches of haplogroups M and N that cover populations of different social rank from all over the subcontinent. Coalescence times suggest early late Pleistocene settlement of southern Asia and suggest that there has not been total replacement of these settlers by later migrations. H, L, and R2 are the major Indian Y-chromosomal haplogroups that occur both in castes and in tribal populations and are rarely found outside the subcontinent. Haplogroup R1a, previously associated with the putative Indo-Aryan invasion, was found at its highest frequency in Punjab but also at a relatively high frequency (26%) in the Chenchu tribe. This finding, together with the higher R1a-associated short tandem repeat diversity in India and Iran compared with Europe and central Asia, suggests that southern and western Asia might be the source of this haplogroup. Haplotype frequencies of the MX1 locus of chromosome 21 distinguish Koyas and Chenchus, along with Indian caste groups, from European and eastern Asian populations. Taken together, these results show that Indian tribal and caste populations derive largely from the same genetic heritage of Pleistocene southern and western Asians and have received limited gene flow from external regions since the Holocene. The phylogeography of the primal mtDNA and Y-chromosome founders suggests that these southern Asian Pleistocene coastal settlers from Africa would have provided the inocula for the subsequent differentiation of the distinctive eastern and western Eurasian gene pools.     

Gc subtyping in south Indian tribal and caste populations

Seven tribal (Konda Kammara - 2 samples; Koya Dora - 3 samples; Lambadi) and caste (Madiga) populations from Andhra Pradesh (South India) have been analyzed for the distribution of Gc subtypes. The observed heterogeneity in the distribution of Gc1F, Gc1S and Gc2 alleles was found to be statistically significant. Comparisons are made with North Indian populations as well as with those of other racial affiliation. The anthropological impact of the Gc subtype polymorphism is discussed.     

A genetic study of the Konda Kapu tribe of coastal Andhra Pradesh, South India

Phenotype and gene frequencies of two blood group and four red cell enzyme systems were examined in a Konda Kapu tribal sample of Coastal Andhra Pradesh, South India. The gene frequencies for these systems in Konda Kapus indicate the middle range values for Andhra Pradesh tribal populations, excepting the ADA and Rh(D) systems, where extreme range values are found. Further, gene flow is indicated between the Konda Kapus under study and Plain Kapus, a neighbouring caste population by calculation of Fi estimates.     

Rare and Low Frequency Variant Stratification in the UK Population: Description and Impact on Association Tests

Although variations in allele frequencies at common SNPs have been extensively studied in different populations, little is known about the stratification of rare variants and its impact on association tests. In this paper, we used Affymetrix 500K genotype data from the WTCCC to investigate if variants in three different frequency categories (below 1%, between 1 and 5%, above 5%) show different stratification patterns in the UK population. We found that these patterns are indeed different. The top principal component extracted from the rare variant category shows poor correlations with any principal component or combination of principal components from the low frequency or common variant categories. These results could suggest that a suitable solution to avoid false positive association due to population stratification would involve adjusting for the respective PCs when testing for variants in different allele frequency categories. However, we found this was not the case both on type 2 diabetes data and on simulated data. Indeed, adjusting rare variant association tests on PCs derived from rare variants does no better to correct for population stratification than adjusting on PCs derived from more common variants. Mixed models perform slightly better for low frequency variants than PC based adjustments but less well for the rarest variants. These results call for the need of new methodological developments specifically devoted to address rare variant stratification issues in association tests.     

Fission Models of Population Variability

Most models in population genetics are models of allele frequency, making implicit or explicit assumptions of equilibrium or constant population size. In recent papers, we have attempted to develop more appropriate models for the analysis of rare variant data in South American Indian tribes; these are branching process models for the total number of replicates of a variant allele. The spatial distribution of a variant may convey information about its history and characteristics, and this paper extends previous models to take this factor into consideration. A model of fission into subdivisions is superimposed on the previous branching process, and variation between subdivisions is considered. The case where fission is nonrandom and the locations of like alleles are initially positively associated, as would happen were a tribal cluster or village to split on familial lines, is also analyzed. The statistics developed are applied to Yanomama Indian data on rare genetic variants. Due to insufficient time depth, no definitive new inferences can be drawn, but the analysis shows that this model provides results consistent with previous conclusions, and demonstrates the general type of question that may be answered by the approach taken here. In particular, striking confirmation of a higher-than-average growth rate, and hence smaller-than-previously-estimated age, is obtained for the Yan2 serum albumen variant.     

Most of the extant mtDNA boundaries in South and Southwest Asia were likely shaped during the initial settlement of Eurasia by anatomically modern humans

Background

Recent advances in the understanding of the maternal and paternal heritage of south and southwest Asian populations have highlighted their role in the colonization of Eurasia by anatomically modern humans. Further understanding requires a deeper insight into the topology of the branches of the Indian mtDNA phylogenetic tree, which should be contextualized within the phylogeography of the neighboring regional mtDNA variation. Accordingly, we have analyzed mtDNA control and coding region variation in 796 Indian (including both tribal and caste populations from different parts of India) and 436 Iranian mtDNAs. The results were integrated and analyzed together with published data from South, Southeast Asia and West Eurasia.

Results

Four new Indian-specific haplogroup M sub-clades were defined. These, in combination with two previously described haplogroups, encompass approximately one third of the haplogroup M mtDNAs in India. Their phylogeography and spread among different linguistic phyla and social strata was investigated in detail. Furthermore, the analysis of the Iranian mtDNA pool revealed patterns of limited reciprocal gene flow between Iran and the Indian sub-continent and allowed the identification of different assemblies of shared mtDNA sub-clades.

Conclusions

Since the initial peopling of South and West Asia by anatomically modern humans, when this region may well have provided the initial settlers who colonized much of the rest of Eurasia, the gene flow in and out of India of the maternally transmitted mtDNA has been surprisingly limited. Specifically, our analysis of the mtDNA haplogroups, which are shared between Indian and Iranian populations and exhibit coalescence ages corresponding to around the early Upper Paleolithic, indicates that they are present in India largely as Indian-specific sub-lineages. In contrast, other ancient Indian-specific variants of M and R are very rare outside the sub-continent.     

Rare variants of blood proteins in human populations

Rare variants of blood proteins occur, due to mutations (mutant alleles) in monomorphic loci encoding various proteins. A number of authors studied the distribution of these variants in human populations using the method of electrophoresis. The population of USA, South America, Japan, Europe was analysed. 1334 rare variants (1.0.10(-3)) were discovered out of 1,329,558 alleles (test locus in 664,779 individuals). 7 mutant alleles (3.6.10(-6)) were found among 1,957,305 alleles. The low frequency of occurrence of mutations in the loci encoding rare blood protein variants, when testing the speed of mutagenicity and its alteration, necessitates electrophoresis of blood proteins to be done in large scales. A method was proposed, based on accounting rare variants in children with congenital disorders, which are supposed to have a heavy load of mutations. The data collected demonstrated that the majority of rare variants in a given generation were obtained from parents. Accumulation of rare protein variants at low concentrations, as neutral alleles, in conditions of low mutation frequency in monomorphic loci takes place in the population. Comparison of frequencies of rare variants among healthy newborns and the children with congenital disorders revealed their identity (1.0.10(-3)), as compared to 1.05.10(-3)). Simplification of the method for scoring mutations judging by rare blood protein variants, which is necessary for monitoring for gene mutations in human populations, stimulates development of novel approaches.     

The genetics of an electrophoretic variant of an erythrocytic protein in the house mouse (Mus musculus)

An electrophoretic mobility variant of a protein band anodal to haemoglobin in alkaline starch gels was found in wild house mouse populations in South Australia. Most wild mice and all inbred lines examined are homozygous for the Erp-1 ^a allele at the locus controlling this variation. The rare allele Erp-1 ^b, which has a frequency of about 1% in South Australia, produces a protein band of slower mobility in alkaline gels. Homozygotes show one protein band whilst the heterozygote has three bands. The Erp-1 protein does not appear to be haemoglobin or carbonic anhydrase. The Erp-1 locus is closely linked to Es-1 on chromosome 8 with a recombination fraction of 6.04 ± 1.32%.     

Identification of a rare blood group, "Bombay (Oh) phenotype," in Bhuyan tribe of Northwestern Orissa, India

BACKGROUND:

Blood group serology plays a vital role in transfusion medicine. The Bombay (Oh) phenotype is characterized by the absence of A, B, and H antigens on red cells and occurs rarely, especially in tribal populations of India.

AIMS AND OBJECTIVES:

This is a field-based random population study in the Bhuyan tribal community. The study reports three cases of the rare Bombay (Oh) phenotype for the first time in the Bhuyan tribe of Sundargarh district in North-Western Orissa.

MATERIALS AND METHODS:

Taking informed consent, red blood cells of 836 Bhuyan subjects were tested with three antisera, i.e., anti-A, anti-B, and anti-H (lectin) for forward reaction. Agglutinations of plasma with A, B, and O (H) red cells (reverse reaction) were also tested for the presence or absence of antibodies in the serum. Specialized tests like absorption-elution, titration of naturally occurring antibodies at different temperatures, inhibition of anti-H by O saliva secretor, and determination of secretor status were performed.

RESULTS:

Three cases of a rare blood group, Bombay (Oh) phenotype, (2 out of 244 Khandayat Bhuyan and 1 out of 379 Paudi Bhuyan from Hemgiri and Lahunipara blocks, respectively) in the Bhuyan tribe of Sundargarh district in North-Western Orissa were detected, giving an incidence of 1 in 122 in Khandayat Bhuyan and 1 in 379 in Paudi Bhuyan, with an average of 1 in 278 among the Bhuyan tribal population. This incidence is high in comparison to earlier studies reported from India.

CONCLUSIONS:

The practice of tribal and territorial endogamy in a smaller effective populations (for example, there are only 3,521 individuals in Paudi Bhuyan) results in smaller marital distance and inbreeding, leading to increased homozygous expression of rare recessive genetic characters like the Bombay (Oh) phenotype. This study further testifies that the incidence is higher in those states of India where the consanguinity is a common practice.     

Hemoglobin Fontainebleau [a21(B2)Ala>Pro]: The second report from India

Structural hemoglobin (Hb) variants are mainly due to point mutations in the globin genes resulting in single amino acid substitutions. Until date, about 200 alpha chain variants have been identified and they are usually detected during the hemoglobinopathy screening programs. Under a community control program for hemoglobinopathies, which involved screening of antenatal cases followed by prenatal diagnosis if indicated. Here, we report a rare alpha globin gene variant Hb Fontainebleau [a21(B2)Ala>Pro] detected in the heterozygous condition in a 35-year-old pregnant lady screened during this program. This is the second report of this alpha globin variant from India. Unlike the earlier case from India where Hb Fontainebleau was reported in a neonate who was also a carrier of Hb Sickle and had no clinical problems, this case presented with a bad obstetric history associated with the secondary infertility. However, the presence of the variant and the obstetric complications may be unrelated.     

Patterns of social and geographical distribution of transferrin subtype polymorphism in India

Transferrin subtypes have been determined by isoelectric focussing of sera from 536 individuals belonging to 9 South Indian populations: Vaidic Brahmins and Vaysya from Andhra Pradesh; Havik Brahmin, Lingayat and Jenu Kuruba from Karnataka; Namboodri Brahmin, Ezhava and Urali from Kerala; and Kallan from Tamil Nadu. C1 and C2 alleles are present in all the populations, whereas C4 is totally lacking and D1 occurs only in 3 populations. The highest frequency of C1 gene (0.814) is found in Havik Brahmins while C2 shows highest incidence among the tribe Urali. C1 occurs in slightly higher frequencies among the Hindu castes (range 0.724-0.814) than the tribal populations (range 0.698-0.703). C2 is more common in the tribes (range 0.281-0.290) compared to the castes (range 0.186-0.269). Strikingly the C3 allele is absent in all the 3 Brahmin samples but is present in 3 non-Brahmin castes and a tribal population. An examination of all the available data on Tf subtypes in India reveals no clear-cut decreasing north-south gradient in C1 gene as suggested by Walter et al. (1983). Interestingly, however, the same is observed when tribal populations are considered separately. Among the castes, in fact, the opposite trend (increasing north to south) is seen. It is suggested that the basic postulate of Walter et al. (1983) will hold good only among the tribal populations of the country. The data do not fully support the observation of Kamboh and Kirk (1983) that C3 is a specific marker of European (Caucasian) populations.     

Two more "private" polymorphisms of Amerindian tribes: LDHb GUA-1 and ACP1 B GUA-1 in the Guaymi in Panama.

A survey of Guaymi Indians of Panama for the occurrence of genetic variants of 25 proteins of the erythrocytes and sera have revealed, in addition to seven well-known genetic polymorphisms, four rare variants and two "private polymorphisms," the latter involving erythrocyte acid phosphatase and lactate dehydrogenase. The significance of such private polymorphisms in tribal populations to the interpretation of rare variants in civilized populations is emphasized.