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. 2019 Sep 24;15(9):e1008385.
doi: 10.1371/journal.pgen.1008385. eCollection 2019 Sep.

Distinct genetic variation and heterogeneity of the Iranian population

Zohreh Mehrjoo  1 , Zohreh Fattahi  1 , Maryam Beheshtian  1 , Marzieh Mohseni  1 , Hossein Poustchi  2 , Fariba Ardalani  1 , Khadijeh Jalalvand  1 , Sanaz Arzhangi  1 , Zahra Mohammadi  2 , Shahrouz Khoshbakht  1 , Farid Najafi  3 , Pooneh Nikuei  4 , Mohammad Haddadi  5 , Elham Zohrehvand  1 , Morteza Oladnabi  6   7 , Akbar Mohammadzadeh  1 , Mandana Hadi Jafari  1 , Tara Akhtarkhavari  1 , Ehsan Shamsi Gooshki  8   9 , Aliakbar Haghdoost  10   11 , Reza Najafipour  12 , Lisa-Marie Niestroj  13 , Barbara Helwing  14 , Yasmina Gossmann  15 , Mohammad Reza Toliat  13 , Reza Malekzadeh  2   15 , Peter Nürnberg  13   16 , Kimia Kahrizi  1 , Hossein Najmabadi  1 , Michael Nothnagel  13   16
Affiliations

Distinct genetic variation and heterogeneity of the Iranian population

Zohreh Mehrjoo et al. PLoS Genet. .

Abstract

Iran, despite its size, geographic location and past cultural influence, has largely been a blind spot for human population genetic studies. With only sparse genetic information on the Iranian population available, we pursued its genome-wide and geographic characterization based on 1021 samples from eleven ethnic groups. We show that Iranians, while close to neighboring populations, present distinct genetic variation consistent with long-standing genetic continuity, harbor high heterogeneity and different levels of consanguinity, fall apart into a cluster of similar groups and several admixed ones and have experienced numerous language adoption events in the past. Our findings render Iran an important source for human genetic variation in Western and Central Asia, will guide adequate study sampling and assist the interpretation of putative disease-implicated genetic variation. Given Iran's internal genetic heterogeneity, future studies will have to consider ethnic affiliations and possible admixture.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Internal Iranian population structure.
Relative sample locations with respect to the first two MDS components. (A) Relative sample locations of the Iranian ethnic groups from this study, including 90% density limits; (B) zoomed view into the subset of the seven groups belonging to the Central Iranian Cluster (CIC).
Fig 2
Fig 2. Iranian ethnic groups in a global context.
Relative sample locations with respect to the first two MDS components. Iranian ethnic groups in a global context (subset of “Old World” populations from the global 1000G data set); inlet zoomed view of the CIC and adjacent European populations.
Fig 3
Fig 3. Iranian ethnic groups in a regional context.
Relative sample locations with respect to the first two MDS components. Iranian ethnic groups (solid points) in a local context of samples from [2, 6, 44] (open symbols, triangles and 90% density limits).
Fig 4
Fig 4. ADMIXTURE inference of Iranian ethnic groups.
(A) Inference in Iranian data set. Inferred mixture proportions for 1021 Iranian samples from this study for k = 4 ancestral populations, yielding a minimal cross-validation (CV) error of 0.544; (B) Inference in global data set. Additional inclusion of the global 1000G data set (k = 13; CV = 0.499). (C) Inference in local data set. Additional inclusion of the local data set (k = 8; CV = 0.575).
Fig 5
Fig 5. Ancient DNA samples from 45,000 (Upper Palaeolithic)–3350 BCE in the context of extant Iranian ethnic groups.
Time-period specific ancient DNA samples (S3 Table) projected onto extant human variation (S18 Fig). The geographic origin of the ancient samples is coded by color.
Fig 6
Fig 6. Ancient DNA samples from 3350–1200 BCE in the context of extant Iranian ethnic groups.
Time-period specific ancient DNA samples (S3 Table) projected onto extant human variation (S18 Fig). The geographic origin of the ancient samples is coded by color. Previous time strata are indicated by 95% density limits (refer to Fig 5).
Fig 7
Fig 7. Ancient DNA samples from 1200 BCE–1460 CE in the context of extant Iranian ethnic groups.
Time-period specific ancient DNA samples (S3 Table) projected onto extant human variation (S18 Fig). The geographic origin of the ancient samples is coded by color. Previous time strata are indicated by 95% density limits (refer to Figs 5 and 6).
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Grants and funding

This work was supported by Deputy of Research, University of Social Welfare and Rehabilitation Sciences (grant number: 95/801/T/32058) to H.N., Iran National Science Foundation (grant number: 950022) to H.N., (grant number: 92035782) to K.K. We also thank Iran’s National Elites Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.