Distribution of Transferrin Phenotypes in Selected Troops of Kenya Baboons JOHN BUETTNER-JANUSCH AND THOMAS J. OLIVIER Departments o f Anatomy, Zoology, and Sociology-Anthropology, Duke University, Durham, North Carolina 27706 ABSTRACT The distribution of transfenin alleles in a group of common baboons, Papio cynocephalus of East Africa, was determined after starch gel electrophoresis of plasma and autoradiography of electrophoretograms. Three alleles, T f A ,T f B ,and T f C , were found, i n agreement with results previously reported. The frequencies of these alleles are T f " = 0.276, T f B = 0.515, T f C= 0.209. The difference between the frequencies reported here and those reported by Buettner-Janusch (1963 Folia Primat., 1: 738 7 ) for the same species ( T f A= 0.205, T f " = 0.332, T f C: 1 8.463) is significant. Transferrin of P. cynocephalus contains four residues of sialic acid per molecule of transferrin, as determined by electrophoresis and autoradiography o€ plasma treated with neuraminidase. Although there is a wealth of information available on genetic variation in Homo sapiens, there are a limited number of genetic studies of socially or geographically separated populations of nonhuman primates. We know little about the distribution and range of genetic variation in natural populations of nonhuman primates and even less about the influences of behavior on genetic variation. Despite the paucity of data, we constantly make assumptions about kinds and degrees of genetic variation in the order Primates in our attempts to elucidate evolutionary processes. The available data on genetic traits of Anthropoidea come largely from studies of serum proteins, hemoglobins, and other erythrocytic proteins. We report here the distribution of transferrin phenotypes for selected groups of baboons, Papio cynocephalus. We compare these results with those reported in an earlier study that provided evidence for effective genetic isolation between baboon troops (BuettnerJanusch, '63, '65). Serum transferrins of nonhuman primates are excellent proteins for genetic studies. The transferrin phenotypes can be determined easily from small amounts of material. Surveys of transferrin phenotypes among the nonhuman primates indicate that many species of primates are polymorphic at the transferrin locus (Goodman et al., '65, '67; Barnicot et al., '67; Nute, '68). In those species for which AM. J. PHYS.ANTHROP.,33: 303-306. the inheritance of transferrin alleles has been studied, the alleles are inherited in a simple, nondominant, autosomal manner (Goodman and Riopelle, '63; Nute and Buettner-Janusch, '69; Nute et al., '69). MATERIALS AND METHODS Blood samples were obtained in Kenya in 1962 from 67 Papio cynocephalus, common baboons of East Africa. These 67 animals were captured in four well-defined trapping areas. The method of trapping has been described (Maxim and Buettner-Janusch, '63). We assume that the animals obtained in a single trapping area are members of a single troop (Maxim and Buettner-Janusch, '63; Buettner-Janusch, '65). These animals and the animals used in the previous study came from the large population of baboons in the Kibwezi-Darajani area of southeast Kenya (Buettner-Janusch, '63). Plasma and red cells were separated in the usual manner. Plasmas were frozen, packed in dry ice, and shipped by air to the United States where they were stored at -20°C. Starch-gel electrophoresis and autoradiography of plasma labelled with radioactive iron were carried out essentially as described previously (Nute and Buettner-Janusch, '68, '69). Transferrin bands were identified on the autoradiographs. The bands are named alphabetically in order of increasing mobility toward the anode. This is a different system from 303 304 JOHN BUETTNER-JANUSCH AND THOMAS J. OLIVIER that used earlier (Buettner-Janusch, '63). The three bands reported in 1963 as bands 1, 2, and 3 are bands B, C, and A, respectively, in the present system. Selected plasma samples were treated with neuraminidase (Coppenhaver and Buettner-Janusch, '70) in order to determine the number of sialic acid residues in baboon transferrin and to establish that multiple bands of heterozygotes do not result from variation in number of sialic acid residues present on a single transferrin (Chen and Sutton, '67; Nute et al., '69). Blood samples used as controls were obtained from the inbred colony of baboons at the Southwest Foundation for Research and Education, San Antonio, Texas. The animals in this colony are descendants of animals from the Kibwezi-Darajani area and are homozygous for transferrin B (Buettner-Janusch, '63). RESULTS AND DISCUSSION Three different transferrin bands were found on autoradiographs made after electrophoresis of labelled plasmas on starch gels (fig. 1). These three bands have been designated A, B, and C. Band B has the same mobility as band B found in plasmas used as controls. We cannot distinguish the three major bands from the three reported in the earlier study (Buettner-Janusch, '63). Barnicot and his colleagues reported a similar transferrin polyrnorphism in East African baboons (Barnicot et al., '65; Kitchin et al., '67). In addition to the three major bands seen on auto- I Origin - AA BB CC AB AC BC Human Fig. 1 Relative electrophoretic mobilities of transferrin phenotypes found in Papio cynocephalus. Human transferrin CC is shown as a reference. radiographs, faint bands appeared in some cases. The faint band moved either faster or slower than the major band with which it was associated. The samples in which these faint bands were evident had been stored for several years. The control samples had been freshly prepared and these faint bands were not seen on autoradiographs. We believe that the faint bands are artifacts that occur after prolonged storage of plasma. Treatment of five samples of plasma with neuraminidase indicated that there are four sialic acid residues per molecule of baboon transferrin. After enzymatic digestion, plasma from two heterozygous animals yielded two transferrin bands; plasma from three homozygous animals, including one from the control group, yielded a single transferrin band. The sialic acid content of transferrin of Papio cynocephalus is the same as that of P. geladn and P . hamadryas (Coppenhaver and Buettner-Janusch, ' 7 0 ) . We assume that the transferrins of Papio cynocephalus are inherited as nondominant autosomal alleles. Thus, one band seen on an autoradiograph designates one allele. This distribution of phenotypes in the sample of 67 Papio cynocephalus from four troops is presented in table 1. The allele frequencies are: T f * = 0.276, Tf" = 0.515, TfC = 0.209. The observed frequencies of genotypes do not fit the Hardy-Weinberg model; x* = 12.98, P < 0.01. In order to compare these data with results of the earlier study on Kibwezi-Darajani baboons, we reproduce in table 2 the data from the previous study (BuettnerJanusch, '63). The f m t study was based on a group of animals trapped in 1960; the present one based on a group of animals trapped in 1962. The differences in frequencies of alleles in these two sets of data are significant (table 3 ) . Among the baboons examined in 1960, there were many more homozygotes than the HardyWeinberg model predicted; x2 = 264.4, P < 0.01. Among those sampled in 1962, there was an excess of heterozygotes. In each of the troops sampled in 1960, only two of the three transferrin alleles were present. In the 1962 sample, all three al. leles were present in each troop. 305 TRANSFERRINS OF BABOONS TABLE I Distribution of transferrin phenotypes of baboons from various trapping areas (1962 sample) Transfemn phenotype Area AA BB cc AB BC AC Total Kitui Bridge Kibwezi River Kibwezi Springs-2 North Darajani 1 0 0 0 6 3 4 5 22 2 3 3 1 1 7 1 0 1 5 1 1 0 46 7 8 6 Total 1 16 6 28 9 7 67 0 0 TABLE 2 Distribution o f transferrin phenotypes of baboons f r o m selected troops (1960 sample) Transferrin phenotype Troop AA BB cc AB BC AC Total 8 0 0 20 40 35 47 17 0 0 0 0 E 0 11 10 9 2 0 5 11 2 0 0 0 0 0 10 5 0 0 45 68 32 34 53 Total 32 68 99 16 2 15 232 A B C D 1 Data from Buettner-Janusch ('63). TABLE 3 Frequencies of trunsferrin alleles i n t w o samples o f baboon populations Allele TfA TP Tf C Number Frequency Number Frequency Number Frequency Sample 1960 1962 95 37 0.205 0.276 x2 = 28.30 1 Calculated 154 69 0.332 0.515 D.F. = 2 215 28 0.463 0.209 Total Number Frequency 464 134 1.000 1.000 P < 0.001 on basis of number of alleles. There is no obvious explanation for these data. We suggest that interpretations must be sought in one or all of the following. It is possible that the selective pressures were not identical for the two groups of animals sampled. This explanation is in keeping with classical concepts of adaptation and does not demand the modification of a general theory to fit phenomena occurring in a particular species. Alternatively, the observed frequencies of transferrin alleles may be the result of sampling error. The trapping procedures used for obtaining the animals were essentially unchanged from 1960 to 1962. These trapping methods may have led to the biases seen in the allele frequencies in both sets of data. It j s also possible that our trapping areas did not define troops, although we consider this unlikely. If we assume that the trapping procedure did not bias the sample, then sampling error may be a consequence of the structure of baboon populations in the Kibwezi-Darajani area. Many baboon troops appear to be stable in composition, relatively small, and with many more adult females than males. The effective breeding population may be further limited, for mating may be restricted to two or three males and may not be random in a troop (DeVore and Washburn, '63; DeVore, '65; Buettner-Janusch, '65; Rowell, '66). Random processes are believed to have their greatest effect in small closed or semiclosed breeding isolates, and baboon troops may often be such isolates. The distribution of transferrin alleles suggests that there is effective genetic isolation between neighboring troops of baboons (Buettner- 306 JOHN BUETTNER-JANUSCH AND THOMAS J. OLIVIER Janusch, '65), and it seems plausible that territoriality of a troop causes effective reproductive isolation. Thus, we can interpret both the differences between the allele frequencies in the two samples and the deviations from the Hardy-Weinberg model in each of the samples as results of random processes such as genetic drift. Although this interpretation does not completely explain the failure of the alleles at the transferrin locus to assort according to HardyWeinberg predictions, there is evidence from behavioral studies (DeVore and Washburn, '63; DeVore, '65; Buettner-Janusch, '65; Rowell, '66) to support in part this interpretation of the observed results. It should be pointed out that random processes and natural selection are not mutually exclusive phenomena (Dobzhansky and Pavlovsky, '57; Wright, '48). The frequencies of alleles possessing adaptive values may well be influenced by random processes. The relative importance of these processes in the genus Papio is unknown and may be better understood with further studies of the population dynamics and genetics of this group. ACKNOWLEDGMENTS We thank the Southwest Foundation for Research and Education (SFRE) for supplying much of the material used in this study. Our special thanks go to Dr. William R. Maples, resident manager of the SFRE Darajani station in 1962, for obtaining the wild baboons; and to Dr. Robert Hummer, Director, Animal Resources and Facilities, SFRE, for his cooperation. The work reported here was supported in part by GM 06053 and GM 13222 of the United States Public Health Service. 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