View Full Version : Origin and spread of mtDna U7

10-04-17, 16:59
Hovhannes Sahakyan (http://www.nature.com/articles/srep46044/email/correspondent/c1/new) et al


"Hg U is subdivided into U1, U5, U6, and a fourth subclade, which further divides into U2, U3, U4′9, U7, and U8 (including hg K). Many of these U subclades display region-specific frequency patterns in present-day populations: hgs U1 and U3 are largely restricted to the Near East14 (http://www.nature.com/articles/srep46044#ref14),15 (http://www.nature.com/articles/srep46044#ref15),16 (http://www.nature.com/articles/srep46044#ref16), U4 and U5 to Europe7 (http://www.nature.com/articles/srep46044#ref7),9 (http://www.nature.com/articles/srep46044#ref9),17 (http://www.nature.com/articles/srep46044#ref17),18 (http://www.nature.com/articles/srep46044#ref18), U6 to the circum-Mediterranean region, with a frequency peak in North Africa19 (http://www.nature.com/articles/srep46044#ref19),20 (http://www.nature.com/articles/srep46044#ref20),21 (http://www.nature.com/articles/srep46044#ref21), while U8 is more prevalent in the Near East and Europe7 (http://www.nature.com/articles/srep46044#ref7),22 (http://www.nature.com/articles/srep46044#ref22),23 (http://www.nature.com/articles/srep46044#ref23),24 (http://www.nature.com/articles/srep46044#ref24),25 (http://www.nature.com/articles/srep46044#ref25) and U9 is rare with only sporadic occurrences in Arabia, Ethiopia and India26 (http://www.nature.com/articles/srep46044#ref26),27 (http://www.nature.com/articles/srep46044#ref27). Hg U2 harbours frequency and diversity peaks in South Asia, whereas its subclades U2d and U2e are confined to the Near East and Europe25 (http://www.nature.com/articles/srep46044#ref25),28 (http://www.nature.com/articles/srep46044#ref28),29 (http://www.nature.com/articles/srep46044#ref29),30 (http://www.nature.com/articles/srep46044#ref30)."

"Compared to other subclades of hg U, both the phylogenetic structure and the ancestral origin of hg U7 are rather obscure. This haplogroup is characterized by generally low population frequencies and limited sequence diversity, despite a geographic distribution ranging from Europe to India14 (http://www.nature.com/articles/srep46044#ref14),16 (http://www.nature.com/articles/srep46044#ref16),25 (http://www.nature.com/articles/srep46044#ref25),27 (http://www.nature.com/articles/srep46044#ref27),30 (http://www.nature.com/articles/srep46044#ref30),31 (http://www.nature.com/articles/srep46044#ref31),32 (http://www.nature.com/articles/srep46044#ref32),33 (http://www.nature.com/articles/srep46044#ref33). Recently, it has been detected in skeletal remains from Southwest Iran dated ~six thousand years ago (kya)34 (http://www.nature.com/articles/srep46044#ref34) as well as in remains from the Tarim Basin in Northwest China (3.5–4.0 kya)35 (http://www.nature.com/articles/srep46044#ref35)."

"The maximum-parsimony reconstruction of 367 sequences of hg U7 yielded a tree with a basal hard polytomy that cannot be resolved (to a dichotomous one) at the level of whole-mtDNA sequence data: we identified eight independent branches that coalesce at the root of U7 (Fig. 1A (http://www.nature.com/articles/srep46044#f1) and Supplementary Figure S1 (http://www.nature.com/articles/srep46044#s2)). Consistent with previous studies, we found that three major branches, U7a–c, capture most (96%) of the U7 mitogenomes. Besides these three previously known branches, we identified three additional clades, hereby designated as U7d, U7e, and U7f (Table 1 (http://www.nature.com/articles/srep46044#t1)). These were exclusively seen in Iran and the Caucasus. Finally, two mitogenomes – also from Iran and the Caucasus – did not cluster with any of hgs U7a–f and remained as unlabelled single lineages."

"In agreement with previous observations16 (http://www.nature.com/articles/srep46044#ref16), U7c appears to be restricted to South Asia (Fig. 1A (http://www.nature.com/articles/srep46044#f1) and Supplementary Figure S1 (http://www.nature.com/articles/srep46044#s2)). In contrast, U7a is the dominant branch of U7 throughout the Near East and South Asia with subclades specific to Central Asia (U7a12–15), Mediterranean and Southeast Europe (U7a17 and U7a19; Figs 1B (http://www.nature.com/articles/srep46044#f1) and 2B (http://www.nature.com/articles/srep46044#f2), Supplementary Figure S1 (http://www.nature.com/articles/srep46044#s2)). U7b exhibits a higher frequency than U7a in Europe with elevated levels of diversity in the Mediterranean and southeastern regions (Figs 1C (http://www.nature.com/articles/srep46044#f1) and 2C (http://www.nature.com/articles/srep46044#f2) and Supplementary Figure S1 (http://www.nature.com/articles/srep46044#s2)). It is distributed also in the Near East, South and Central Asia."