Genetic heritage of Croatians in the Southeastern European gene pool-Y chromosome analysis of the Croatian continental and Island population

Y Chromosome Story-Ancient Genetic Data as a Supplementary Tool for the Analysis of Modern Croatian Genetic Pool

Due to its turbulent demographic history, marked by extensive settlement and gene flow from diverse regions of Eurasia, Southeastern Europe (SEE) has consistently served as a genetic crossroads between East and West and a junction for the migrations that reshaped Europe's population. SEE, including modern Croatian territory, was a crucial passage from the Near East and even more distant regions and human populations in this region, as almost any other European population represents a remarkable genetic mixture. Modern humans have continuously occupied this region since the Upper Paleolithic era, and different (pre)historical events have left a distinctive genetic signature on the historical narrative of this region. Our views of its history have been mostly renewed in the last few decades by extraordinary data obtained from Y-chromosome studies. In recent times, the international research community, bringing together geneticists and archaeologists, has steadily released a growing number of ancient genomes from this region, shedding more light on its complex past population dynamics and shaping the genetic pool in Croatia and this part of Europe.

The genetic history of the Southern Arc: A bridge between West Asia and Europe

By sequencing 727 ancient individuals from the Southern Arc (Anatolia and its neighbors in Southeastern Europe and West Asia) over 10,000 years, we contextualize its Chalcolithic period and Bronze Age (about 5000 to 1000 BCE), when extensive gene flow entangled it with the Eurasian steppe. Two streams of migration transmitted Caucasus and Anatolian/Levantine ancestry northward, and the Yamnaya pastoralists, formed on the steppe, then spread southward into the Balkans and across the Caucasus into Armenia, where they left numerous patrilineal descendants. Anatolia was transformed by intra-West Asian gene flow, with negligible impact of the later Yamnaya migrations. This contrasts with all other regions where Indo-European languages were spoken, suggesting that the homeland of the Indo-Anatolian language family was in West Asia, with only secondary dispersals of non-Anatolian Indo-Europeans from the steppe.

Croatian genetic heritage: an updated Y-chromosome story

AIM

To analyze an additional set of ˝Y-chromosome genetic markers to acquire a more detailed insight into the diversity of the Croatian population.

METHODS

A total of 518 Yfiler Plus profiles were genotyped. Allele frequencies, haplotype frequencies, and haplotype diversity were calculated by using the STRAF software v. 2.0.4. Genetic distances were quantified by Rst with AMOVA online tool from the YHRD. The evolutionary history was inferred with the neighbor-joining method of phylogenetic tree construction in the MEGAX software. Whit Athey's Haplogroup Predictor v. 5 was used for additional comparison with regional and other European populations.

RESULTS

A total of 507 haplotypes were used for genetic STR analysis. An interpopulation study on 17 Y-STR markers showed the lowest genetic diversity between the Croatian and Bosnian-Herzegovinian populations and the highest between the Croatian and Irish populations. Additional interpopulation comparison with the original 27 Y-STR markers (for the population with available data) was also performed. A total of 518 haplotypes were used in the determination of haplogroup diversity. Haplogroup I with its sublineage I2a expressed the highest prevalence. The second most prevalent haplogroup was R, with its major sublineage R1a, except for the subpopulation of Hvar, where E1b1b was the second most prevalent haplogroup. Rare haplogroups also confirmed in this study were L, T, and Q. G1 was detected for the first time in the Croatian population.

CONCLUSION

We obtained a new insight into the differences between examined subpopulations of Croatia and their possible (dis)similarities with neighboring and distant populations.

Mapping the Mountains of Giants: Anthropometric Data from the Western Balkans Reveal a Nucleus of Extraordinary Physical Stature in Europe

The inhabitants of the Dinaric Alps (former Yugoslavia and Albania) have long been known as people of impressive body height, but after World War II, there was a critical lack of data related to this phenomenon. This anthropological synthesis includes the measurements of 47,158 individuals (24,642 males and 22,516 females) from the period 2010−2018 and describes detailed regional differences in male stature in the Western Balkans. According to these data, young men from Montenegro (182.9 cm) are currently the tallest 18-year-olds in the world, surpassing their Dutch peers (182.4 cm), and 18-year-old boys from Dalmatia are even taller (183.7 cm) at a regional level. A continuous belt of extraordinary height means (>184 cm) stretches from the Adriatic coast of Dalmatia through Herzegovina to the central part of Montenegro. This article summarizes all the key socio-economic, nutritional, and genetic data, and offers possible explanations for this anthropological phenomenon. Since the remarkable height of the Dinaric populations cannot be connected with any commonly known environmental factor, the most probable hypothesis is genetic and links these physical characteristics with the local founder effect of Y haplogroup I-M170. Furthermore, given that both the level of socio-economic development and dietary protein quality are still sub-optimal, the local upward trend in body height has the potential to continue in the future.

Y chromosome genetic data defined by 23 short tandem repeats in a Serbian population on the Balkan Peninsula

BACKGROUND

Serbs mainly live in the territory of the recently re-established state of Serbia. However, the turbulent history in the Balkan Peninsula has led to settlement of Serbs not only within present day Serbia, but also in different parts of neighbouring countries.

AIM

To define polymorphisms of 23 Y-chromosomal short tandem repeat (STR) loci in a modern Serbian population from the central part of the Balkan Peninsula.

SUBJECTS AND METHODS

The reference sample consisted of 303 men declared as Serbs over three generations. Localities of the collected materials include the territories of Serbia, Bosnia and Herzegovina, Croatia and Montenegro. DNA samples were typed using the PowerPlex^®Y23 amplification kit.

RESULTS

The highest locus diversity was observed for DYS385 and DYS481. In this study the most abundant haplogroups were I2a, E1b1b, R1a and I1. The largest genetic distances between the Serbs and other close Southern Slavs were for the Macedonians and Slovenians.

CONCLUSION

This study is the first one to define STR polymorphism of Serbian people not only from Serbia but also from other parts of the Balkan Peninsula. The presented genetic data may be useful in further examinations of the genesis and genetic structuring of the present-day Serbian gene pool.

The coast of giants: an anthropometric survey of high schoolers on the Adriatic coast of Croatia

The aim of this anthropometric survey was to map regional differences in height and body proportions in eight counties adjacent to the Adriatic coast of Croatia. Body height was measured in 1,803 males and 782 females aged 17-20 years at 66 schools in 23 towns. When corrected for population size in regions, mean male height is 182.6 cm in all eight counties, 182.8 cm in seven counties of Adriatic Croatia, and 183.7 cm in four counties of Dalmatia proper. Regional variation is considerable: from 180.6 cm in the county of Karlovac to 184.1 cm in the county of Split-Dalmacija. The mean height of females is based on more limited data (168.0 cm in seven counties). These results show that young men from Dalmatia are currently the tallest in the world in the age category of 18 years, and the north-to-south gradient of increasing stature on the Adriatic coast largely mirrors that in neighbouring Bosnia and Herzegovina (BiH). The extraordinary values of height in Croatia and BiH can most likely be explained by unique genetic predispositions that are shared by the local populations of the Dinaric Alps.

Recombination hotspots in an extended human pseudoautosomal domain predicted from double-strand break maps and characterized by sperm-based crossover analysis

The human X and Y chromosomes are heteromorphic but share a region of homology at the tips of their short arms, pseudoautosomal region 1 (PAR1), that supports obligate crossover in male meiosis. Although the boundary between pseudoautosomal and sex-specific DNA has traditionally been regarded as conserved among primates, it was recently discovered that the boundary position varies among human males, due to a translocation of ~110 kb from the X to the Y chromosome that creates an extended PAR1 (ePAR). This event has occurred at least twice in human evolution. So far, only limited evidence has been presented to suggest this extension is recombinationally active. Here, we sought direct proof by examining thousands of gametes from each of two ePAR-carrying men, for two subregions chosen on the basis of previously published male X-chromosomal meiotic double-strand break (DSB) maps. Crossover activity comparable to that seen at autosomal hotspots was observed between the X and the ePAR borne on the Y chromosome both at a distal and a proximal site within the 110-kb extension. Other hallmarks of classic recombination hotspots included evidence of transmission distortion and GC-biased gene conversion. We observed good correspondence between the male DSB clusters and historical recombination activity of this region in the X chromosomes of females, as ascertained from linkage disequilibrium analysis; this suggests that this region is similarly primed for crossover in both male and female germlines, although sex-specific differences may also exist. Extensive resequencing and inference of ePAR haplotypes, placed in the framework of the Y phylogeny as ascertained by both Y microsatellites and single nucleotide polymorphisms, allowed us to estimate a minimum rate of crossover over the entire ePAR region of 6-fold greater than genome average, comparable with pedigree estimates of PAR1 activity generally. We conclude ePAR very likely contributes to the critical crossover function of PAR1.

95% of our genome is contained in 22 pairs of chromosomes shared by all humans. However, women and men differ in their sex chromosomes: while women have two X chromosomes, men have an X and a smaller, sex-determining Y chromosome. To ensure correct partition of X and Y into sperm, genetic exchange (crossover) must occur between these very different chromosomes in a short, shared region. The location of the boundary of this region was thought to have been conserved since before the divergence from old world monkeys at least 27 million years ago, but recently it has been shown that some human males carry an extended version on their Y chromosomes, thanks to the transposition of a piece of DNA from the X chromosome. Here, we asked if genetic exchange occurs in this newly extended region. To do this, we used previously published information that signposted the positions within the X chromosome segment which exhibit the hallmarks of crossover initiation. We then sought direct evidence of crossover in the sperm of men carrying the extension. This work showed that the signposts were accurate, pointing to frequent crossover in this novel shared sex-chromosomal domain.

A glance of genetic relations in the Balkan populations utilizing network analysis based on in silico assigned Y-DNA haplogroups

The aim of this study is to provide an insight into Balkan populations’ genetic relations utilizing in silico analysis of Y-STR haplotypes and performing haplogroup predictions together with network analysis of the same haplotypes for visualization of the relations between chosen haplotypes and Balkan populations in general. The population dataset used in this study was obtained using 23, 17, 12, 9 and 7 Y-STR loci for 13 populations. The 13 populations include: Bosnia and Herzegovina (B&H), Croatia, Macedonia, Slovenia, Greece, Romany (Hungary), Hungary, Serbia, Montenegro, Albania, Kosovo, Romania and Bulgaria. The overall dataset contains a total of 2179 samples with 1878 different haplotypes. I2a was detected as the major haplogroup in four out of thirteen analysed Balkan populations. The four populations (B&H, Croatia, Montenegro and Serbia) which had I2a as the most prevalent haplogroup were all from the former Yugoslavian republic. The remaining two major populations from former Yugoslavia, Macedonia and Slovenia, had E1b1b and R1a haplogroups as the most prevalent, respectively. The populations with E1b1b haplogroup as the most prevalent one are Macedonian, Romanian, as well as Albanian populations from Kosovo and Albania. The I2a haplogroup cluster is more compact when compared to E1b1b and R1b haplogroup clusters, indicating a larger degree of homogeneity within the haplotypes that belong to the I2a haplogroup. Our study demonstrates that a combination of haplogroup prediction and network analysis represents an effective approach to utilize publicly available Y-STR datasets for population genetics.

The mountains of giants: an anthropometric survey of male youths in Bosnia and Herzegovina

The aim of this anthropometric survey, conducted between 2015 and 2016 in Bosnia and Herzegovina (BiH), was to map local geographical differences in male stature and some other anthropometric characteristics (sitting height, arm span). In addition, to investigate the main environmental factors influencing physical growth, the documented values of height would be compared with available nutritional and socioeconomic statistics. Anthropometric data were collected in 3192 boys aged approximately 18.3 years (17-20 years), from 97 schools in 37 towns. When corrected for population size in the examined regions, the average height of young males in BiH is 181.2 cm (181.4 cm in the Bosniak-Croat Federation, 180.9 cm in Republika Srpska). The regional variation is considerable-from 179.7 cm in the region of Doboj to 184.5 cm in the region of Trebinje. These results fill a long-term gap in the anthropological research of the Western Balkans and confirm older reports that the population of the Dinaric Alps is distinguished by extraordinary physical stature. Together with the Dutch, Montenegrins and Dalmatians, men from Herzegovina (183.4 cm) can be regarded as the tallest in the world. Because both nutritional standards and socioeconomic conditions are still deeply suboptimal, the most likely explanation of this exceptional height lies in specific genetic factors associated with the spread of Y haplogroup I-M170. The genetic potential for height in this region could then be the greatest in the world. Future studies should further elucidate the roots of this intriguing phenomenon, which touches an important aspect of human biodiversity.