Population Genetics and Structure of Buryats from the Lake Baikal Region of Siberia
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Population Genetics and Structure of Buryats from the Lake Baikal Region of Siberia A.G.NOVORADOVSKY,1'3 V.A. SPITSYN,1 R. DUGGIRALA,2 ANDM.H. CRAWFORD2 Abstract Geneticpolymorphisms of blood groups,serum pro- teins,red cell enzymes,PTC tasting,and cerumen types are reported forfive Mongoloidpopulations of Buryatsfrom the Lake Baikal regionof Siberia(Russia). These groupsare characterizedby rela- tivelyhigh frequencies of allelesABO*B, RH*D , cerumenD, GC*1F, ACP1*B, ESD*2, and PGD*C. Significantgenetic heterogeneity betweenpopulations was demonstratedfor the loci RH, MN, ce- rumen,PGD, ABO, GC, GLO, TF, and PGM1. Geneticdistance analysesusing five loci revealeda lowerlevel of geneticmicrodif- ferentiationwithin the Buryat populations compared with other na- tiveSiberian groups. The distributionof genemarkers in Buryatsis similarto thatfound in neighboringCentral Asian groups,such as theYakuts and theMongols. Intrapopulational analyses of thefive Buryatsubdivisions, based on R matrixand rihindicate that one of thesubdivisions is reproductivelymore isolated than the others and thattwo of thecommunities have receivedconsiderable gene flow. A nonlinearrelationship was demonstratedbetween geographic and geneticdistances of Buryatpopulation subdivisions. To date, thereis a paucity of informationon the distributionof genetic markersin the aboriginal populations of Siberia. The Buryats, one of the largestAsian populations of Russia, inhabitthe regions proximal to Lake Baikal. Linguistically,the Buryatsare closely related to the Mon- gols, who speak a language belonging to the Turkishsubdivision of the Altaic linguisticfamily (Hughes 1962). According to Alexseeva et al. (1970), the Buryatsanthropologically resemble a numberof native Mon- goloid groups that settledin an area fromnorthern Central Asia to east of the Ob River and includingnorthern China and Mongolia. 'RussianAcademy ofMedical Sciences, National Research Center of Medical Genetics, 1 MoskovrechieStreet, 115478 Moscow, Russia. 2Laboratory ofBiological Anthropology, University ofKansas, Lawrence, KS 66045. 3Present address: Laboratory ofNeurogenetics, National Institute ofAlcohol Abuse and Al- coholism,National Institutes ofHealth, Building 10/3C102, 9000 Rockville Pike, Bethesda, MD 20892. HumanBiology , October 1993, v. 65,no. 5, pp.689-710. Copyright© 1993 Wayne State University Press, Detroit, Michigan 48202 KEYWORDS: GENETIC POLYMORPHISMS, BURYATS, LAKE BAIKAL REGION, GE- NETICSTRUCTURE This content downloaded from 129.237.46.100 on Thu, 04 Jun 2015 12:57:36 UTC All use subject to JSTOR Terms and Conditions 690 / NOVORADOVSKYET AL. Figure1. Localizationofthe Buryat populations. In this articlewe presentdata on the geneticpolymorphisms of five geographicallyseparated Buryat populations residing in the vicinityof Lake Baikal. The gene frequenciesof these genetic markersare used to reconstructthe structureof the subdivided Buryat population, particu- larly with respect to the relative roles of systematicand nonsystematic evolutionarypressures in theirgenetic microdifferentiation. Materials and Methods Blood samples were collected fromBuryat settlements of the Chita region(Suduntui and Sakhurtasettlements), the Irkutskregion (Ust-Orda and Olhon Island on Lake Baikal), and the Kizhinga District (Mogso- hon). Figure 1 places these five communitiesgeographically. The populations were sampled randomly.Both males and females between the ages of 18 and 85 years were included. Serum samples and blood clots were immediatelyfrozen and stored in that condition until phenotypingat the National Research Center of Medical Genetics in Moscow. The ABO, MN, and RH(D) blood groups were typed using standardserological methods [see Alexseeva et al. (1972), Batsuur(1979), This content downloaded from 129.237.46.100 on Thu, 04 Jun 2015 12:57:36 UTC All use subject to JSTOR Terms and Conditions Population Genetics of Buryats / 691 and Batsuuret al. (1991)]. Anti-serafor the ABO and RH systemswere obtainedfrom the Moscow City Blood TransfusionCenter; MN anti-sera were providedby the Blood TransfusionInstitute of St. Petersburg,Rus- sia. Cerumentypes were scored into wet or drycategories by inspection. Phenylthiocarbamide(PTC) sensitivityto a concentratedsolution was testedduring the collection of blood specimens. The red cell enzymes acid phosphatase (ACPI), esterase D (ESD), and adenylate kinase (AK1) were phenotypedby horizontal starch gel electrophoresis,following the methodsof Harris and Hopkinson (1976) with some modifications.Tris-maleine-EDTA buffer(pH 7.2) was used in a horizontalgel, 35-40 V/cm at 4°C for 100-120 min. A specially designed semi-microelectrophoresisstarch gel box with a cooling jacket was used to load 40 specimens per run. The red cell enzyme 6-phosphogluconatedehydrogenase (PGD) was typedusing verticalPolyacrylamide gels withTEB (tris-EDTA-boricacid) buffer(pH 8.6) (Peacock et al. 1965). Phosphoglucomutase-1(PGM1) enzyme was phenotypedusing isoelectric focusing on Polyacrylamide gels followingthe method of Goedde et al. (1981). Haptoglobinvariation was studiedusing a starchgel electrophoretic proceduredescribed by Spitsyn (1985). Alpha-1 -antitrypsin (PI), transferrin(TF), and group-specificcom- ponent (GC) were characterizedby isoelectricfocusing on agarose gels using the methodsof Righetti(1983) and Spitsynand Titenko (1990). Analytical Procedures. The blood genetic frequencydata were ana- lyzed using several differentapproaches. Genetic distances for native Siberianpopulations were computedby using Nei's (1972) method,which was also used to constructa dendrogram.A topographicdisplay of the populationaffinities was generatedby applyingthe Harpendingand Jen- kins (1973) method.The relativeroles of systematicversus nonsystemat- ic evolutionarypressures on subdivided populations were explored by the Harpendingand Ward (1982) method, which predictsthe existence of a linear relationshipbetween heterozygosityin a subgroup and its distance fromthe centroidof distribution.Extreme deviation fromthis expected relationshipis indicativeof the possible action of systematicor nonsystematicevolutionary pressures. To measure the probable relationshipbetween the genetic similarity of the subgroups and geography,we computed a product-momentcor- relationbetween the elementsof the genetic distance matrix(</? = ru + - rij 2rij) and of the straight-linegeographic distance matrix (Harpending and Jenkins1973). The significanceof this correlationis tested through the Mantel matrixpermutation procedure (Relethford 1990). Because our analysis consisted of five populations, all possible permutationswere used, which is 5! = 120. This content downloaded from 129.237.46.100 on Thu, 04 Jun 2015 12:57:36 UTC All use subject to JSTOR Terms and Conditions 692 / NOVORADOVSKYET AL. Results and Discussion Phenotypicand allelic frequencies in the Buryat populations are listed in Table 1. Chi-square testsfor Hardy-Weinberg equilibrium have revealed some isolated cases of disequilibriumat low levels of signifi- cance in the Suduntui,Olhon, and Mogsohon populations(see Table 2). Several cases of disequilibriumin the Ust-Orda population exhibit an excess of heterozygotesMN and TF C1,C2 and an excess of homo- zygotesPGM1 2A, 2A (see Table 2). No age or sex trendswere observed in the distributionof MN, TF, and PGM1 polymorphismswhen different age and sex cohorts fromUst-Orda were compared (data not shown). These negativefindings complicate the interpretationof the possible pop- ulation structuremechanisms responsible for the observed disequilibria. It is for this reason thatwe regressedmean per locus heterozygosityon the distance fromthe centroidof distribution;we found that Ust-Orda has medium levels of heterozygositybut low r„. These results suggest considerable gene flow and presentlittle evidence of the action of sto- chastic processes (see Figure 5). The testsfor the genetichomogeneity of the five Buryatpopulations are shown in Table 3. Significantheterogeneity (at p < 0.05 level) among the five Buryatgroups is demonstratedfor the loci RH, MN, cerumen, PGD, ABO, GC, GLOl, TF, and PGM1. These differencesby locus between the subdivisions are due to varyingdegrees of recent genetic admixture,a foundereffect in the original subdivision, or genetic mi- crodifferentiation.A previous physical anthropologicalstudy of Buryats by Alexseeva et al. (1970) also observed considerable genetic hetero- geneityamong othersubdivided populations. Compared with other indigenous populations of Siberia, the Bur- yats have relativelyhigh frequenciesof the alleles ABO*B, RH*D, ce- rumenD, GC*1F, ACP*B, ESD*2, and PGD*C. In the populationsof the Chita region(Suduntui and Sakhurta),the PGD*C allele has, to date, the highestfrequency observed in any native Siberian population. Because most of the genetic markerstudies of native Siberian pop- ulationswere publishedin Russian, a comparisonof the allelic frequency distributionsamong the Buryatvillages and withother ethnic groups may be useful(Alexseeva et al. 1972; Batsuuret al. 1985, 1991; Boeva 1988; Emialanova et al. 1976). Historically,the people of Siberia, as a result of relativegeographic isolation, evolved separatelyinto threeAsian lin- guistic groups: Samoyedic (Uralic-Western),Tungusic (North Asian- Central), and Paleo-Asiatic speakers (Northeastern).In addition, there are a numberof groups that speak unique languages (such as the Kets and Ngansan) whose linguisticaffiliation has perplexed linguists. The geneticvariability within the indigenousSiberian populationis high,