Of the Chamorros of Guam CHRIS C
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Blood Group and Haptoglobin Frequencies of the Chamorros of Guam CHRIS C. PLATO' AND MANUEL CRUZ2 National Institute of Neurological Diseases and Blindness, National Institutes of Health, Bethesda, Maryland 20014. 2 National Institute of Neurological Diseases and Blindness Research Center, Guam Memorial Hospital, Agana, Guam. THE ISLAND of Guam recently has been the center for the investigation of two rare neurological diseases, amyotrophic lateral sclerosis (ALS) and Park- inson's dementia (Kurland and Mulder, 1954; Reed et al., 1966; Elizan et al., 1966; Plato et al., 1967). The incidence of ALS on Guam is almost one hun- dred times higher than that of the continental United States and other parts of the world. As an adjunct to the neurological studies, a series of limited sero- logical and hematological surveys have been conducted (Myrianthopoulos and Pieper, 1959; Tashian et al., 1963; Plato et al., 1964, 1966). The object of the present study is (1) to determine the blood group and haptoglobin frequencies among the Chamorros of Guam and (2) to relate the serological results with the available historical data, in an effort to estimate the magnitude of Spanish, Filipino, and Mexican contribution to the genetic structure of the present hybrid Chamorro population. Historical Notes Guam with an area of 215 square miles is the largest of the Mariana islands in the Western Pacific (Fig. 1). In 1960, the population of Guam was 67,044 (U. S. census report, 1960). Of these, 34,762 were Chamorros, 8,580 Filipinos, 20,724 Caucasians (mostly Americans), and about 3,000 Carolinians from the U. S. Trust Territory of the Pacific. The original Chamorros are presumed to have immigrated to Guam from the Philippines and the Malaysian region in general as early as 1527 ± 200 B.C. (Spoehr, 1957). Their first encounter with the Europeans was in 1521 when Magellan landed in the village of Umatac. In 1565, Guam was officially proclaimed a Spanish territory by Lopez de Legazpi. During the following one hundred years, the island remained in relative obscurity with only occa- sional visits by Spanish and other maritime groups. In 1668, Father Sanvitores and his helpers arrived from Acapulco, Mexico, and established a Jesuit mission. They were accompanied by a few laymen and 32 Spanish and Filipino soldiers. At the time of his arrival, Father Sanvi- tores estimated the native population to have been about 50,000. In 1680, Don Jose DeQuiroga ("the tyrant") was appointed governor of Guam. The arrival of Received June 6, 1967. 722 AMERICAN JOURNAL OF HUMAN GENETICS, VOL. 19, No. 6 (NOVEMBER), 1967 PLATO AND CRUZ 723 FIG. 1. Western Pacific and Guam (from United States Populations Census for Guam, 1961). DeQuiroga and his subsequent treatment of the natives sparked a series of Chamorro uprisings in which thousands of the island's inhabitants lost their lives. The Chamorro-Spanish wars together with two strong typhoons and a smallpox epidemic in 1688 contributed to the reduction of the Chamorro pop- ulation from 50,000 in 1668 to fewer than 5,000 by 1691. The first official census taken by the Spanish in 1710 reported only 3,678 natives living. The popula- tion of Guam continued to decline (Fig. 2) until 1783, when there were only 1,500 Chamorros alive (Carano and Sanchez, 1964). The reduction of the native population and the resulting shortage of labor necessitated the importation of large groups of Filipino laborers, most of whom remained on Guam and married Chamorro women. The intermarriage of the Chamorros with Filipinos and Spanish became so extensive that "had it not been for intermarriage between the Chamorros and non-natives, the Marianas might eventually have been depopulated" (Carano and Sanchez, 1964). Since the beginning of the nineteenth century, the population of Guam increased steadily, although the number of pure Chamorros continued to di- minish. By the end of the nineteenth century a new Chamorro population had been established, comprised of an admixture of the original Chamorros with the Filipinos, Spaniards, and Mexicans. This hybrid has remained stable 724 BLOOD GROUPS AND HAPTOGLOBIN ON GUAM 45000 40000 350 30000 25000 0 44 10000 5000- Smallpox 4W000 Spanish- Epidemic 3000 Chamorro wars, 2000 Typhoons Smallpox Epidemic 1000 _4 0R ~ 0 0 0 0 0 Y E A IR FiG. 2. Fluctuations of the population of Guam from 1668 to 1960. (Data compiled from various historical reports and official census records.) and for the most part free from immigration since the beginning of the twentieth century. Detailed census reports since 1910 indicate that the abrupt increase in population is primarily due to the high birth/death ratio. MATERIAL AND METHODS A total of 343 blood samples were drawn into sterile ampules containing dry EDTA anticoagulant. The specimens were collected from the following districts: Merizo, 70 samples; Umatac, 39; Talofofo, 44; Mangilao, 63; and De- dedo, 94. The remaining 33 samples were drawn from individuals of unspeci- fied residence. Since contingency chi-square tests gave no significant differences among the various subsamples, the data from all districts were pooled. The bloods were typed on Guam using commercial reagents. The anti-Al and anti-A2 were prepared in our laboratory from seeds of Dolichos biflorus PLATO AND CRUZ 725 TABLE 1. ABO BLOOD GROUP PHENOTYPES AND GENE FREQUENCIES AMONG THE CHAMORROS OF GUAM AND IN RELATED POPULATIONS PHENOTYPES GENE FREQUENCIES A1 A2 B 0 A B A B Total p(A) p1(A1) p2(A2) q(B) r(O) Chamorros 99 0 55 169 20 0 343 .183 .183 0 .107 .710 Related Studies Chamorros (Guam), Myrianthopoulos and Pieper (1959) 1497 .180 .119 .701 Chamorros (Saipan), Plato et al. (1966) 142 .139 .139 0 .126 .737 Chamorros (Saipan), Misaitsu (1939) * 132 .219 .124 .657 Chamorros (Saipan), Takasaki (1939) * 293 .198 .082 .720 Filipinos, Fraser et al. (1964) 403 .170 .150 .680 Filipinos, Simmons and Graydon (1945) 382 .152 .181 .671 Mexicans (Mixteco), Rodriquez et al. (1963) 129 .024 .016 .960 Spaniards, Guasch et al. (1952) * 400 .259 .202 .057 .072 .669 * Cited by Mourant et al. (1958). and Ulex europaeus, respectively, and were used exclusively on the A bloods for the A1 and A2 subgroup determinations. The anti-Dia serum kindly was supplied to us by Dr. Miguel Layrisse of Caracas, Venezuela. The hapto- globin determinations were also performed on Guam by starch gel electro- phoresis. The blood specimens were typed for the following systems: ABO (including Al and A2), MNS (M,N,S,s,Mg), Kell (K,k,Kpa,Kpb), Kidd (JKb), Duffy (Fya), P, Wra, Vw, and Dia. RESULTS AND DISCUSSION The phenotypes and the allele frequencies of the various blood groups are presented in Tables 1, 2, 3, and 4. The results of previous blood group studies on the Chamorros are also summarized in these tables together with the available data on the Filipinos, Mexicans, and Spaniards. The Mexicans cited in this report are the Mixtecos who resided in the southwestern part of Mexico near the port of Acapulco (Rodriquez et al., 1963), the origin of most of the trans-Pacific voyages between Mexico and the Philippines. The results of the present survey are in agreement with those of previous studies involving the Chamorros of Guam and Saipan. All samples tested were negative for A2, Kpa, Wra, Vw, and Mg. Two specimens were positive for Kell (K) and all tested positively for Kpb. Besides the absence of A2, other outstanding observations are the high frequency of Dia and the rarity of Rh-negative, with a chromosomal cde frequency of .087. The Du phenotype is also absent. The genes S and Fyb are also rare, with frequencies of .101 and .121, respectively. The high frequency of P2 reported previously among the Saipan Chamorros was substantiated by the present study. The haptoglobin types follow the same general trend found in the Western Pacific and South- east Asia, with a low HpI gene frequency of .37 (Table 5). As seen from Tables 1-5, the frequencies of most of the blood group systems as well as those of the haptoglobins among the Chamorros show an over-all similarity to those of the Filipinos. 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