Genomic Insights Into the Genetic Structure and Natural Selection of Mongolians

Genetic history and biological adaptive landscape of the Tujia people inferred from shared haplotypes and alleles

BACKGROUND

High-quality genomic datasets from under-representative populations are essential for population genetic analysis and medical relevance. Although the Tujia are the most populous ethnic minority in southwestern China, previous genetic studies have been fragmented and only partially reveal their genetic diversity landscape. The understanding of their fine-scale genetic structure and potentially differentiated biological adaptive features remains nascent.

OBJECTIVES

This study aims to explore the demographic history and genetic architecture related to the natural selection of the Tujia people, focusing on a meta-Tujia population from the central regions of the Yangtze River Basin.

RESULTS

Population genetic analyses conducted on the meta-Tujia people indicate that they occupy an intermediate position in the East Asian North-South genetic cline. A close genetic affinity was identified between the Tujia people and neighboring Sinitic-speaking populations. Admixture models suggest that the Tujia can be modeled as a mixture of northern and southern ancestries. Estimates of f3/f4 statistics confirmed the presence of ancestral links to ancient Yellow River Basin millet farmers and the BaBanQinCen-related groups. Furthermore, population-specific natural selection signatures were explored, revealing highly differentiated functional variants between the Tujia and southern indigenous populations, including genes associated with hair morphology (e.g., EDAR) and skin pigmentation (e.g., SLC24A5). Additionally, both shared and unique selection signatures were identified among ethnically diverse but geographically adjacent populations, highlighting their extensive admixture and the biological adaptations introduced by this admixture.

CONCLUSIONS

The study unveils significant population movements and genetic admixture among the Tujia and other ethno-linguistically diverse East Asian groups, elucidating the differentiated adaptation processes across geographically diverse populations from the current genetic landscape.

Genetic and cultural adaptations underlie the establishment of dairy pastoralism in the Tibetan Plateau

BACKGROUND

Domestication and introduction of dairy animals facilitated the permanent human occupation of the Tibetan Plateau. Yet the history of dairy pastoralism in the Tibetan Plateau remains poorly understood. Little is known how Tibetans adapted to milk and dairy products.

RESULTS

We integrated archeological evidence and genetic analysis to show the picture that the dairy ruminants, together with dogs, were introduced from West Eurasia into the Tibetan Plateau since ~ 3600 years ago. The genetic admixture between the exotic and indigenous dogs enriched the candidate lactase persistence (LP) allele 10974A > G of West Eurasian origin in Tibetan dogs. In vitro experiments demonstrate that - 13838G > A functions as a LP allele in Tibetans. Unlike multiple LP alleles presenting selective signatures in West Eurasians and South Asians, the de novo origin of Tibetan-specific LP allele - 13838G > A with low frequency (~ 6-7%) and absence of selection corresponds - 13910C > T in pastoralists across eastern Eurasia steppe.

CONCLUSIONS

Results depict a novel scenario of genetic and cultural adaptations to diet and expand current understanding of the establishment of dairy pastoralism in the Tibetan Plateau.

Inferring the population history of Kyrgyz in Xinjiang, Northwest China from genome-wide array genotyping

OBJECTIVES

Xinjiang plays a vital role in the trans-Eurasian population migration, language diffusion, and culture and technology exchange. However, the underrepresentation of Xinjiang's genomes has hindered a more comprehensive understanding of Xinjiang's genetic structure and population history.

MATERIALS AND METHODS

We collected and genotyped 70 southern Xinjiang's Kyrgyz (SXJK) individuals and combined the data with modern and ancient Eurasians published. We used allele-frequency methods, including PCA, ADMIXTURE, f-statistics, qpWave/qpAdm, ALDER, Treemix, and haplotype-shared methods including shared-IBD segments, fineSTRUCTURE, and GLOBETROTTER to unveil the fine-scale population structure and reconstruct admixture history.

RESULTS

We identified genetic substructure within the SXJK population with subgroups showing different genetic affinities to West and East Eurasians. All SXJK subgroups were suggested to have close genetic relationships with surrounding Turkic-speaking groups that is, Uyghur, Kyrgyz from north Xinjiang and Tajikistan, and Chinese Kazakh, suggesting a shared ancestry among those populations. Outgroup-f3 and symmetrical f4 statistics showed a high genetic affinity of SXJK to present-day Tungusic, Mongolic-speaking populations and Ancient Northeast Asian (ANA) related groups. Allele sharing and haplotype sharing profiles revealed the east-west admixture pattern of SXJK. The qpAdm-based admixture models showed that SXJK derived ancestry from East Eurasian (ANA and East Asian, 42.7%-83.3%) and West Eurasian (Western Steppe herders and Central Asian, 16.7%-57.3%), the recent east-west admixture event could be traced to 1000 years ago based on ALDER and GLOBETROTTER analysis.

DISCUSSION

The high genetic affinity of SXJK to present-day Tungusic and Mongolic-speaking populations and short-shared IBD segments indicated their shared common ancestry. SXJK harbored a close genetic affinity to ANA-related populations, indicating the Northeast Asian origin of SXJK. The West and East Eurasian admixture models observed in SXJK further provided evidence of the dynamic admixture history in Xinjiang. The east-west admixture pattern and the identified ancestral makeup of SXJK suggested a genetic continuity from some Iron Age Xinjiang populations to present-day SXJK.

Case report of a pediatric Chinese cystic fibrosis patient with the c.1521_1523delCTT/c.3874-4522A>G genotype

This report describes a case of an 11-year-old Chinese boy with cystic fibrosis (CF) bearing the c.1521_1523delCTT/c.3874-4522A>G genotype, an extremely rare CF genotype in the Chinese population. Notably, the deep intron mutation c.3874-4522A>G, which has mainly been reported in patients with phenotypically mild CF, is identified here for the first time in a Chinese patient with severe CF. In the case discussed here, the c.3874-4522A>G mutation was associated with severe pulmonary disease with early symptoms onset, progressive bronchiectasis, recurrent airway infection with both Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus, rapid decline of lung function and poor weight gain. Despite intensive hospital-based pulmonary care and optimized therapy, the child died of cardiopulmonary failure 3 months after discharge.

Genomic insights into the genetic structure and population history of Mongolians in Liaoning Province

The Mongolian population exceeds six million and is the largest population among the Mongolic speakers in China. However, the genetic structure and admixture history of the Mongolians are still unclear due to the limited number of samples and lower coverage of single-nucleotide polymorphism (SNP). In this study, we genotyped genome-wide data of over 700,000 SNPs in 38 Mongolian individuals from Fuxin in Liaoning Province to explore the genetic structure and population history based on typical and advanced population genetic analysis methods [principal component analysis (PCA), admixture, F_ST, f₃-statistics, f₄-statistics, qpAdm/qpWave, qpGraph, ALDER, and TreeMix]. We found that Fuxin Mongolians had a close genetic relationship with Han people, northern Mongolians, other Mongolic speakers, and Tungusic speakers in East Asia. Also, we found that Neolithic millet farmers in the Yellow River Basin and West Liao River Basin and Neolithic hunter–gatherers in the Mongolian Plateau and Amur River Basin were the dominant ancestral sources, and there were additional gene flows related to Eurasian Steppe pastoralists and Neolithic Iranian farmers in the gene pool of Fuxin Mongolians. These results shed light on dynamic demographic history, complex population admixture, and multiple sources of genetic diversity in Fuxin Mongolians.