Y-Chromosomal DNA Variation in Pakistan
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Am. J. Hum. Genet. 70:1107–1124, 2002 Y-Chromosomal DNA Variation in Pakistan Raheel Qamar,1,2 Qasim Ayub,1,2 Aisha Mohyuddin,1,2 Agnar Helgason,3 Kehkashan Mazhar,1 Atika Mansoor,1 Tatiana Zerjal,2 Chris Tyler-Smith,2 and S. Qasim Mehdi1 1Biomedical and Genetic Engineering Division, Dr. A. Q. Khan Research Laboratories, Islamabad; 2Cancer Research Campaign, Chromosome Molecular Biology Group, Department of Biochemistry, and 3Institute of Biological Anthropology, University of Oxford, Oxford, United Kingdom; and deCODE Genetics, Reykjavik Eighteen binary polymorphisms and 16 multiallelic, short-tandem-repeat (STR) loci from the nonrecombining portion of the human Y chromosome were typed in 718 male subjects belonging to 12 ethnic groups of Pakistan. These identified 11 stable haplogroups and 503 combination binary marker/STR haplotypes. Haplogroup fre- quencies were generally similar to those in neighboring geographical areas, and the Pakistani populations speaking a language isolate (the Burushos), a Dravidian language (the Brahui), or a Sino-Tibetan language (the Balti) resembled the Indo-European–speaking majority. Nevertheless, median-joining networks of haplotypes revealed considerable substructuring of Y variation within Pakistan, with many populations showing distinct clusters of haplotypes. These patterns can be accounted for by a common pool of Y lineages, with substantial isolation between populations and drift in the smaller ones. Few comparative genetic or historical data are available for most pop- ulations, but the results can be compared with oral traditions about origins. The Y data support the well-established origin of the Parsis in Iran, the suggested descent of the Hazaras from Genghis Khan’s army, and the origin of the Negroid Makrani in Africa, but do not support traditions of Tibetan, Syrian, Greek, or Jewish origins for other populations. Introduction the 3d and 2d millennia B.C. (Dales 1991). Around 1500 B.C., the Indo-European–speaking nomadic pastoral tribes The earliest evidence of Paleolithic human presence in the from further north—often called the Aryans—crossed the Indo-Pakistani subcontinent consists of stone implements Hindu Kush Mountains into the subcontinent. Subse- found scattered around the Soan River Valley in northern quent historical events include the invasion of Alexander Pakistan (Hussain 1997). Despite the lack of fossil evi- the Great (327–325 B.C.) and the Arab and Muslim con- dence, these tools appear to indicate the presence of hom- quest from 711 A.D. onwards (Wolpert 2000). inids in the subcontinent as early as 200,000–400,000 The present population of Pakistan consists of 1150 years ago (Wolpert 2000) and thus are likely to have been million individuals (according to current WHO figures) associated with archaic Homo species. Pakistan lies on who belong to at least 18 ethnic groups and speak 160 the postulated southern coastal route followed by ana- languages (Grimes 1992). Most of these languages are tomically modern H. sapiens out of Africa, and so may Indo-European, but they also include an isolate, Bu- have been inhabited by modern humans as early as rushaski; a Dravidian language, Brahui; and a Sino- 60,000–70,000 years ago. There is evidence of cave dwell- Tibetan language, Balti. Punjabi-speaking individuals ers in Pakistan’s northwest frontier, but fossil evidence form the majority population of Pakistan, but they rep- from the Paleolithic has been fragmentary (Hussain resent a complex admixture of ethnic castes and groups 1997). Evidence has been uncovered at Mehrghar, in (Ibbetson 1883) and are not analyzed here; 12 ethnic southwestern Pakistan, indicating Neolithic settlements groups are included in the present survey. The infor- mation available about them is summarized in table 1, from as long ago as 7,000 B.C. (Jarrige 1991), which were followed by the Indus Valley civilizations (including the together with hypotheses about their origins (Mehdi et cities of Harappa and Mohenjodaro) that flourished in al. 1999). Although some of these hypotheses are well- supported (e.g., the origin of the Parsis in Iran), most are based on oral traditions and have not been tested Received Novermber 27, 2001; accepted for publication January 24, 2002; electronically published March 15, 2002. against other sources of evidence. Address for correspondence and reprints: Dr. Chris Tyler-Smith, Scanty genetic data are available for these Pakistani Cancer Research Campaign Chromosome Molecular Biology Group, ethnic groups. Early studies of the ABO blood groups Department of Biochemistry, University of Oxford, South Parks Road, and classical protein markers did not include all groups Oxford OX1 3QU, United Kingdom. E-mail: [email protected] ᭧ 2002 by The American Society of Human Genetics. All rights reserved. and mostly classified them according to their place of 0002-9297/2002/7005-0005$15.00 residence. A population tree based on 54 classical en- 1107 1108 Am. J. Hum. Genet. 70:1107–1124, 2002 Table 1 Pakistani Ethnic Groups Studied Ethnic Group Locationa Language Family Census Sizeb Suggested Origin(s) Baluch Baluchistan Indo-European 4,000,000 Syria: Aleppo (Quddus 1990) Balti Eastern Baltistan Sino-Tibetan 300,000 Tibet (Backstrom 1992) Brahui Baluchistan: Kalat Dravidian 1,500,000 West Asia (Hughes-Buller 1991) State, Sarawan and Jhalawan regions Burusho Karakorum Moun- Language isolate 50,000–60,000 Alexander’s army (Biddulph 1977) tains: Hunza, Nagar, and Yasin Hazara Southern Baluchistan: Indo-European NA Genghis Khan’s soldiers (Bellew 1979) Quetta and NWFP: Parachinar Kalash NWFP: Hindu Kush Indo-European 3,000–6,000 Greeks (Robertson 1896) or Mountains: Bum- “Tsyam,” possibly Syria (Decker buret, Rambur, and 1992) Birir valleys Kashmiri Kashmir Valley Indo-European NA Jewish (Ahmad 1952) Makrani Baluch Makran coast Indo-European NA West Asia (Hughes-Buller 1991) Negroid Makrani Makran coast Indo-European NA Rajput (Quddus 1990); Africa? Parsi Karachi Indo-European A few thousand Iran, via India (Nanavutty 1997) Pathan NWFP and Baluchistan Indo-European 17,000,000 Jewish (Ahmad 1952), Greek or Raj- put (Bellew 1998; Caroe 1958) Sindhi Sindh Indo-European 15,300,000 Mixed (Burton 1851) a NWFP p North West Frontier Province. b NA p not available. zyme markers places the Hazara and Pathans in the shed on the origins and genetic history of the subgroups West Asian cluster containing the northern Caucasoids that make up the Pakistani population. (Cavalli-Sforza et al. 1994). In another population tree, based on 47 classical protein polymorphisms, the Pak- Material and Methods istani samples form a small subcluster within the Indo- European speakers from India (Cavalli-Sforza et al. Samples 1994). The Y chromosomes of 718 unrelated male subjects, The Y chromosome provides a unique source of genetic belonging to 12 ethnic groups of Pakistan, were analyzed evidence (Tyler-Smith 1999; Jobling and Tyler-Smith (tables 1 and 2; fig. 1). Informed consent was obtained 2000). It carries the largest nonrecombining segment in from all participants in this study. An Epstein Barr vi- the genome and contains numerous stable binary mark- rus–transformed lymphoblastoid cell line was estab- ers, including base substitutions (see, e.g., Underhill et lished from each individual, and DNA was extracted al. 1997) and retroposon insertions (Hammer 1994; San- from these cell lines for analysis. tos et al. 2000), which can be used in combination with more-rapidly evolving markers, such as microsatellites Binary Polymorphism Typing (see, e.g., Ayub et al. 2000). Consequently, very detailed Y phylogenies can be constructed that allow male-specific We typed 15 SNPs, an Alu insertion (Hammer 1994; aspects of genetic history to be investigated. These are Hammer and Horai 1995), a LINE1 insertion (Santos strongly influenced by the small effective population size et al. 2000), and the 12f2 deletion (Casanova et al. of the Y chromosome, leading to rapid genetic drift, and 1985). The base substitutions were: 92R7 CrT (Mathias by the practice of patrilocality in many societies, leading et al. 1994); M9 CrG (Underhill et al. 1997); SRY-2627 to high levels of geographical differentiation of Y hap- CrT (Bianchi et al. 1997); SRY-1532 ArGrA (Whit- lotypes. Notwithstanding the work of Qamar et al. field et al. 1995; Kwok et al. 1996; Santos et al. 1999b); (1999) on the analysis of YAPϩ chromosomes (com- sY81 (DYS271) ArG (Seielstad et al. 1994); SRY-8299 prising ∼2.6% of the total) and analyses of STR variation GrA (Santos et al. 1999a); Apt GrA (Pandya et al. (Ayub et al. 2000; Mohyuddin et al. 2001), little work 1998); SRY ϩ465 CrT (Shinka et al. 1999); LLY22g has been carried out on Pakistani Y chromosomes. There- CrA and Tat TrC transition (Zerjal et al. 1997). In fore, we have now performed an extensive analysis of addition, the M17 marker (Underhill et al. 1997) was Pakistani Y lineages, to determine what light they can typed, by use of the primers GTGGTTGCTGGTTGTT- Qamar et al.: Y-Chromosomal DNA Variation in Pakistan 1109 Table 2 Diversity, Sample Size (n), and Number of Individuals Belonging to Each Y Haplogroup in 12 Pakistani Ethnic Groups NO. OF INDIVIDUALS IN HAPLOGROUP POPULATION DIVERSITY n 1 2 3 8 9 10 12 13 21 26 28 Baluch .7908 59 11 0 17 1 7 0 0 0 5 1 17 Balti .7692 13 2 1 6 0 2 0 0 0 0 0 2 Brahui .7516 110 9 11 43 3 31 2 1 1 0 1 8 Burusho .8065 94 26 7 26 0 7 8 0 0 0 4 16 Hazara .5573 23 14 1 0 0 1 7 0 0 0 0 0 Kalash .7558 44 4 17 8 0 4 0 0 0 0 0 11 Kashmiri .6212 12 3 0 7 0 2 0 0 0 0 0 0 Makrani Baluch .8100 25 6 0 7 1 6 0 0 0 1 0 4 Makrani Negroid .8352 33 6 4 10 3 6 0 0 0 1 0 3 Parsi .7441 90 24 3 7 0 35 0 0 0 5 0 16 Pathan .7539 93 10 15 42 0 6 0 0 0 2 6 12 Sindhi .6937 122 15 11 60 0 25 0 0 0 3 0 8 Overall .8011 718 130 70 233 8 132 17 1 1 17 12 97 ACGT and AGCTGACCACAAACTGATGTAGA fol- DYS389b, DYS390, DYS391, DYS393, DYS434, lowed by AflIII digestion of the PCR product; the an- DYS435, DYS437, and DYS439) and one pentanucleo- cestral allele was not digested.