Kazak mitochondrial genomes provide insights into the human population history of Central Eurasia

High prevalence of m.1555A > G in patients with hearing loss in the Baikal Lake region of Russia as a result of founder effect

Mitochondrial forms account approximately 1-2% of all nonsyndromic cases of hearing loss (HL). One of the most common causative variants of mtDNA is the m.1555A > G variant of the MT-RNR1 gene (OMIM 561000). Currently the detection of the m.1555A > G variant of the MT-RNR1 gene is not included in all research protocols. In this study this variant was screened among 165 patients with HL from the Republic of Buryatia, located in the Baikal Lake region of Russia. In our study, the total contribution of the m.1555A > G variant to the etiology of HL was 12.7% (21/165), while the update global prevalence of this variant is 1.8% (863/47,328). The m.1555A > G variant was notably more prevalent in Buryat (20.2%) than in Russian patients (1.3%). Mitogenome analysis in 14 unrelated Buryat families carrying the m.1555A > G variant revealed a predominant lineage: in 13 families, a cluster affiliated with sub-haplogroup A5b (92.9%) was identified, while one family had the D5a2a1 lineage (7.1%). In a Russian family with the m.1555A > G variant the lineage affiliated with sub-haplogroup F1a1d was found. Considering that more than 90% of Buryat families with the m.1555A > G variant belong to the single maternal lineage cluster we conclude that high prevalence of this variant in patients with HL in the Baikal Lake region can be attributed to a founder effect.

Diversity of HLA-A, -B, -C, -DRB1, and -DQB1 alleles and haplotypes in Kazakhstani Tatar population and genetic relatedness to other populations

BACKGROUND

Kazakhstan is a transcontinental former Soviet Union republic whose present-day population comprises more than 100 ethnic groups. Insofar as Human Leukocyte Antigen (HLA) genotyping is useful for anthropological studies, data on the HLA profile of Kazakhstani Tatars are lacking.

OBJECTIVE

We extend our earlier findings on the unique HLA profile of distinct Kazakhstani populations by examining HLA class I and class II loci in Kazakhstani (Volga) Tatar minority population and its relatedness to those of bordering and worldwide communities.

METHODS

HLA class I and class II genotypes of the Kazakhstan Tatar minority were analyzed by PCR-SSP and were compared to neighboring populations using Neighbor-Joining (NJ) trees and standard genetic distances (SGD) analysis.

RESULTS

In total, 132 HLA alleles were identified in a sample of 103 Kazakhstani Tatars, of which HLA-A*02:01 (20.1 %), -B*07:02 (12.1 %), -C*07:02 (12.7 %), -DRB1*07:01 (18.1 %), and -DQB1*02:01 (19.6 %) were the most frequent. The most frequent two-locus haplotypes were B*07:02 ∼ C*07:02 (10.6 %) B*07:02 ∼ DRB1*15:01 (06.1 %), B*07:02 ∼ DQB1*06:02 (07.1 %), and DRB1*15:01 ∼ DQB1*06:02 (11.6 %).

CONCLUSIONS

Considering historical data, the close relatedness of Kazakhstani Tatars to European Russians (including Russian Tatars) suggests that Kazakhstani Tatars may be Russian Tatars, who originated from the Volga region, following their massive migrations to central Asia.

Refining the Global Phylogeny of Mitochondrial N1a, X, and HV2 Haplogroups Based on Rare Mitogenomes from Croatian Isolates

Mitochondrial DNA (mtDNA) has been used for decades as a predominant tool in population genetics and as a valuable addition to forensic genetic research, owing to its unique maternal inheritance pattern that enables the tracing of individuals along the maternal lineage across numerous generations. The dynamic interplay between evolutionary forces, primarily genetic drift, bottlenecks, and the founder effect, can exert significant influence on genetic profiles. Consequently, the Adriatic islands have accumulated a subset of lineages that exhibits remarkable absence or rarity within other European populations. This distinctive genetic composition underscores the islands' potential as a significant resource in phylogenetic research, with implications reaching beyond regional boundaries to contribute to a global understanding. In the initial attempt to expand the mitochondrial forensic database of the Croatian population with haplotypes from small isolated communities, we sequenced mitogenomes of rare haplogroups from different Croatian island and mainland populations using next-generation sequencing (NGS). In the next step and based on the obtained results, we refined the global phylogeny of haplogroup N1a, HV2, and X by analyzing rare haplotypes, which are absent from the current phylogenetic tree. The trees were based on 16 novel and 52 previously published samples, revealing completely novel branches in the X and HV2 haplogroups and a new European cluster in the ancestral N1a variant, previously believed to be an exclusively African-Asian haplogroup. The research emphasizes the importance of investigating geographically isolated populations and their unique characteristics within a global context.