Kamal900
02-01-2015, 04:03 PM
Journal of Human Genetics (2015) 60, 41–49; doi:10.1038/jhg.2014.99; published online 4 December 2014
History
In historical times, because of its location on the main maritime roads of the Mediterranean, Tunisia has been settled successively by many diversed populations including Phoenicians, Romans, Vandals and Byzantines. By the end of the seventh century, Muslim armies from the Arabian Peninsula invaded North Africa and reached the region known today as Tunisia. In the late tenth century, Tunisia also experience an important movement of Arab populations, mostly Bedouin.6, 7 Therefore, it is likely that migrations and admixture processes might have played a pivotal role in shaping the peopling of Tunisia, particularly in coastal cities. In addition, because of its numerous small, isolated indigenous populations, Tunisia represents an interesting region to explore inter population relationships. Indeed, European, Near Eastern and sub-Saharan contributions to contemporary Tunisian populations during prehistory and historic times have been diverse.
Today, Tunisia has a population of about 11 millions represented by Berbers, Arabs, Andalusians, Jews, Europeans and people of sub-Saharan origins. Tunisian cosmopolitan populations are situated on coastal locations. One of such city is Sousse, founded in the eleventh century B.C. as Hadrumetum by the Phoenicians it developed into an important center within the Carthaginian dominion. Sousse soon became the most important trading post on the North African coastline. Through history Hadrumetum came under the control of a number major cultures including the Vandals after the fall of the Roman Empire in the sixth century and later by the Byzantines that renamed it Hunerikopolis and Justinianopolis, respectively. The city became one of the most important Byzantine bases in North Africa. In the seventh century, the Arabs conquered the city renaming it Susa and introducing the Islamic religion and Arabic language.8 The city became a prosperous seaport during the Islamic Aghlabid Dynasty, which occupied and controlled Northern Africa for several centuries.
Subsequently, Sousse was invaded by the Normans of Sicily in the twelveth century9 followed by the Spanish. During the sixteenth century, Sousse received additional, but limited, contributions from the Ottoman Turks. Later, the city came under the control of the French, who once again renamed it to its current name of Sousse.10 Considering this complex history, the expectation is that the genetic landscape of Sousse has been shaped by varying degrees of influences from the above listed invaders who occupied the region in different periods of its history. In addition, Sousse is the most ancient settlement in Tunisia with uninterrupted habitation since its foundation by the Phoenicians.11 Towns such as Carthage and Utique, also established by the Phoenicians,12, 13 were destroyed and their population dispersed. Berber groups, on the other hand, have been rather isolated, since their towns and villages were not located on the coast.14 Studies on Tunisian cosmopolitan populations often examine Tunis which was founded later than Sousse and does not provide a prolong continuous antiquity. Hence, the case of the Sousse population represents an unique case study in population genetics. Despite its historical importance and strategic location, only one molecular genetics study has been performed on this anthropological interesting population.
Y-chromosome lineage diversity
The partitioning of paternal lineages and their frequencies are displayed in a hierarchical phylogeny in Figure 1. The 220 Sousse Y-chromosomes represent 24 different haplogroups, the majority of them belonging to haplogroups E and J that account for 90% of our dataset (E; 56% and J; 34%) (Supplementary Table S3). The predominant E sublineage, also commonly found in other North African populations,18, 19, 20, 21, 22 is E-M81. All E-M81 derived chromosome are in subhaplogroup E-M183 (44.55%). Besides the common E-M81 lineage, traces of other lineages within the major E-M215 haplogroup were detected including E-M35, E-M78 and E-M123. These lineages are also found at various frequencies throughout North and East Africa. Haplogroup E-M78 which has a wide distribution, including Europe, the Near East and North Africa,20 is mostly represented by subhaplogroup E-V65 (4.09%), with the exception of two individuals that belong to subhaplogroups E-V13 and E-V22 (0.45% each). Lineage E-M123, on the other hand, is detected at low frequency (1.82%). It is interesting that the E-M2 clade which is particularly frequent in sub-Saharan Africa33, 34 and present in some North African populations most likely as a result of sub-Saharan migration18, 19, 35, is not detected in the Sousse samples.
The frequency of haplogroup E-M81 (Figure 2a), for example, is much higher in northwestern Africa particularly in Tunisian and moderate in the Near East and Europe. On the other hand, the frequencies of haplogroups E-M78 and E-M123 are much higher in northeast Africa exhibiting a focal point of extreme frequencies in Egypt-Palestine (Figures 2b and c, respectively). The J-M267 lineage is prevalent in all North African and Levantine groups (Figure 2d). In North Africa, J-M267 exhibits the highest frequency in Andalusians from Zaghouan. It is also found at relatively high frequency in the Levantine samples.
http://www.nature.com/jhg/journal/v60/n1/images/jhg201499f2.jpg
Genetic structure
To explore the genetic relationships among the populations of Sousse, Tunisia as a whole and the 23 other geographically targeted populations obtained from the literature (Supplementary Table S1), we performed a PCA based on haplogroup frequencies (Supplementary Table S2). The first two components of the PCA account for 55.18% of the variation and reveal distinct geographical partitioning (Figure 4a). The North African populations form a cluster located in the upper-left portion of the plot, except for the Egyptians that lie closest to Palestinians to the lower right. This cluster of North African populations is defined by the predominance of haplogroup E-M81. In contrast, Egyptians are characterized by high frequency of the E-M78 haplogroup and the absence of the E-M81 lineage.
Within the North Africa cluster, the Sousse sample is close to the Cosmopolitans and Andalusians Tunisian groups and the general populations from neighboring states, namely Libya, Algeria and Morocco. The Tunisian Berber collections form a tide conglomerate isolated in the upper-left corner of the graph. The sub-Saharan Africans which possess higher frequencies of haplogroups B-M96, A-M91, E-M2 and E*-M96 lie close to each other in the lower left of the plot. The PCA also illustrate the genetic affinity of Levantine populations to Europeans especially Italians. In fact, both groups present relatively high frequencies of J-M172 and share some other lineages in particular I-M170 and T-M70.
http://www.nature.com/jhg/journal/v60/n1/images/jhg201499f4.jpg
The populations were also contrasted using Rst estimates (Supplementary Table S4) computed from the 10 loci Y-STR haplotypes and plotted using multidimensional scaling (MDS) (Figure 4b). The MDS illustrate similar general features as the PCA, including the North Africans cluster close to Near Easterners with the Sousse population partitioning similarly relative to the other groups as well as the Egyptians affinity to the Palestinians. Yet in the MDS the Near Easterners and Tuareg segregate towards sub-Saharan Africans which, like in the PCA graph, aggregate in the lower-left corner of the plot distant from all other populations.
Discussion
Our results indicate that the frequency of the E-M81 haplogroup in the region of Sousse is relatively lower than in Berber group; it reaches a value of 45%, comparable with the values detected in the Cosmopolitan population from Tunis and Andalusians.21 This frequency range of 36–45% of E-M81 in these Cosmopolitan and Andalusian Tunisian populations is consistent with a strong common Berber back-ground that gives the typical profile to North African populations that aggregate in the same clusters in the PC and MDS analyses. However, depending on the Berber or Cosmopolitan status, North African populations can be classified into subclusters. This observation is in agreement with the analyses of molecular variance analyses that indicate significant differences in molecular variance for both SNP and STR marker systems (17.65 Pless than or equal to0.05 and 1.64 Pless than or equal to0.05, respectively) between Cosmopolitans and Berbers. In all of these parameters, the Sousse population exhibits characteristics of a highly genetically diverse North African population.
The E-M81 lineage exhibits a star-like network structure (Figure 3a), which suggests an ancient evolution. This network exhibits apparent rapid expansion at some point that may be explained by loss of diversity due to genetic drift. Indeed, most of the STR haplotypes belonging to the E-M81 haplogroup are shared among various North African communities without obvious genetic structure relative to geography.
In our previous work performed on Tunisian populations, this haplogroup was dated to 7.4±5.5 kya in the Neolithic, comparable with the age estimated in this study (5.7±3.9 kya), and by Arredi and collaborators.19 However, considering the high level of genetic drift typically experienced by uniparental marker systems such as the Y-chromosome, it is possible that the E-M81 haplogroup had a more ancient genesis in North Africa.
Along with the high prevalence of E-M81 in Sousse, we observed the E-M78 mutation at low frequency (5%). In contrast to the above-mentioned E-M81 haplogroup, E-M78 has a wide geographic distribution with its highest frequency observed in the Egypto-Palestinian area. It is detected at lower frequencies in Northwest Africa and is particularly observed in Andalusians and Cosmopolitans rather than Berbers. This suggests an east to west gene flow with greater penetration into the Cosmopolitan populations of North Africa.
A more recent potential Middle Eastern genetic contribution to the North Africa gene pool may be associated with the expansion of the Ottoman Empire. Sousse also may have been specifically impacted by the Turkish occupation of North Africa. Yet, the unique presence of J-M172 in Sousse and its absence from other Tunisian regions that were under Ottoman influence argues for J-M172 in Sousse as a Phoenician signal. Further, Sousse exhibits another haplogroup, T-M184, that is not detected in any other North African population attesting again to the Phoenicians contribution to that population. Haplogroup T-M184 is more common today in East Africa and it is thought to signal the spread of agriculture from the Fertile Crescent. Indeed, the oldest subclades and the greatest diversity of T-M184 are found in the Middle East, especially within the Fertile Crescent. Yet, T-M184 could also have been dispersed throughout the Mediterranean basin by the Phoenicians (1200–800 before the common era).
In conclusion, the analysis of admixed populations represents an unique opportunity to examine the impact of multiple migrations into a region. Within a historical context, both population isolation and admixture have had a considerable impact on the Tunisian population structure. The wide range of paternal lineages present in our Sousse population indicates a diverse origin. Indeed the genetic structure observed of paternal lineages in Sousse is more diversified than any other studied Tunisian population and reflects largely the influence of successive migrations since its foundation by the Phoenician
More --> http://www.nature.com/jhg/journal/v60/n1/full/jhg201499a.html
What do you guys think?
History
In historical times, because of its location on the main maritime roads of the Mediterranean, Tunisia has been settled successively by many diversed populations including Phoenicians, Romans, Vandals and Byzantines. By the end of the seventh century, Muslim armies from the Arabian Peninsula invaded North Africa and reached the region known today as Tunisia. In the late tenth century, Tunisia also experience an important movement of Arab populations, mostly Bedouin.6, 7 Therefore, it is likely that migrations and admixture processes might have played a pivotal role in shaping the peopling of Tunisia, particularly in coastal cities. In addition, because of its numerous small, isolated indigenous populations, Tunisia represents an interesting region to explore inter population relationships. Indeed, European, Near Eastern and sub-Saharan contributions to contemporary Tunisian populations during prehistory and historic times have been diverse.
Today, Tunisia has a population of about 11 millions represented by Berbers, Arabs, Andalusians, Jews, Europeans and people of sub-Saharan origins. Tunisian cosmopolitan populations are situated on coastal locations. One of such city is Sousse, founded in the eleventh century B.C. as Hadrumetum by the Phoenicians it developed into an important center within the Carthaginian dominion. Sousse soon became the most important trading post on the North African coastline. Through history Hadrumetum came under the control of a number major cultures including the Vandals after the fall of the Roman Empire in the sixth century and later by the Byzantines that renamed it Hunerikopolis and Justinianopolis, respectively. The city became one of the most important Byzantine bases in North Africa. In the seventh century, the Arabs conquered the city renaming it Susa and introducing the Islamic religion and Arabic language.8 The city became a prosperous seaport during the Islamic Aghlabid Dynasty, which occupied and controlled Northern Africa for several centuries.
Subsequently, Sousse was invaded by the Normans of Sicily in the twelveth century9 followed by the Spanish. During the sixteenth century, Sousse received additional, but limited, contributions from the Ottoman Turks. Later, the city came under the control of the French, who once again renamed it to its current name of Sousse.10 Considering this complex history, the expectation is that the genetic landscape of Sousse has been shaped by varying degrees of influences from the above listed invaders who occupied the region in different periods of its history. In addition, Sousse is the most ancient settlement in Tunisia with uninterrupted habitation since its foundation by the Phoenicians.11 Towns such as Carthage and Utique, also established by the Phoenicians,12, 13 were destroyed and their population dispersed. Berber groups, on the other hand, have been rather isolated, since their towns and villages were not located on the coast.14 Studies on Tunisian cosmopolitan populations often examine Tunis which was founded later than Sousse and does not provide a prolong continuous antiquity. Hence, the case of the Sousse population represents an unique case study in population genetics. Despite its historical importance and strategic location, only one molecular genetics study has been performed on this anthropological interesting population.
Y-chromosome lineage diversity
The partitioning of paternal lineages and their frequencies are displayed in a hierarchical phylogeny in Figure 1. The 220 Sousse Y-chromosomes represent 24 different haplogroups, the majority of them belonging to haplogroups E and J that account for 90% of our dataset (E; 56% and J; 34%) (Supplementary Table S3). The predominant E sublineage, also commonly found in other North African populations,18, 19, 20, 21, 22 is E-M81. All E-M81 derived chromosome are in subhaplogroup E-M183 (44.55%). Besides the common E-M81 lineage, traces of other lineages within the major E-M215 haplogroup were detected including E-M35, E-M78 and E-M123. These lineages are also found at various frequencies throughout North and East Africa. Haplogroup E-M78 which has a wide distribution, including Europe, the Near East and North Africa,20 is mostly represented by subhaplogroup E-V65 (4.09%), with the exception of two individuals that belong to subhaplogroups E-V13 and E-V22 (0.45% each). Lineage E-M123, on the other hand, is detected at low frequency (1.82%). It is interesting that the E-M2 clade which is particularly frequent in sub-Saharan Africa33, 34 and present in some North African populations most likely as a result of sub-Saharan migration18, 19, 35, is not detected in the Sousse samples.
The frequency of haplogroup E-M81 (Figure 2a), for example, is much higher in northwestern Africa particularly in Tunisian and moderate in the Near East and Europe. On the other hand, the frequencies of haplogroups E-M78 and E-M123 are much higher in northeast Africa exhibiting a focal point of extreme frequencies in Egypt-Palestine (Figures 2b and c, respectively). The J-M267 lineage is prevalent in all North African and Levantine groups (Figure 2d). In North Africa, J-M267 exhibits the highest frequency in Andalusians from Zaghouan. It is also found at relatively high frequency in the Levantine samples.
http://www.nature.com/jhg/journal/v60/n1/images/jhg201499f2.jpg
Genetic structure
To explore the genetic relationships among the populations of Sousse, Tunisia as a whole and the 23 other geographically targeted populations obtained from the literature (Supplementary Table S1), we performed a PCA based on haplogroup frequencies (Supplementary Table S2). The first two components of the PCA account for 55.18% of the variation and reveal distinct geographical partitioning (Figure 4a). The North African populations form a cluster located in the upper-left portion of the plot, except for the Egyptians that lie closest to Palestinians to the lower right. This cluster of North African populations is defined by the predominance of haplogroup E-M81. In contrast, Egyptians are characterized by high frequency of the E-M78 haplogroup and the absence of the E-M81 lineage.
Within the North Africa cluster, the Sousse sample is close to the Cosmopolitans and Andalusians Tunisian groups and the general populations from neighboring states, namely Libya, Algeria and Morocco. The Tunisian Berber collections form a tide conglomerate isolated in the upper-left corner of the graph. The sub-Saharan Africans which possess higher frequencies of haplogroups B-M96, A-M91, E-M2 and E*-M96 lie close to each other in the lower left of the plot. The PCA also illustrate the genetic affinity of Levantine populations to Europeans especially Italians. In fact, both groups present relatively high frequencies of J-M172 and share some other lineages in particular I-M170 and T-M70.
http://www.nature.com/jhg/journal/v60/n1/images/jhg201499f4.jpg
The populations were also contrasted using Rst estimates (Supplementary Table S4) computed from the 10 loci Y-STR haplotypes and plotted using multidimensional scaling (MDS) (Figure 4b). The MDS illustrate similar general features as the PCA, including the North Africans cluster close to Near Easterners with the Sousse population partitioning similarly relative to the other groups as well as the Egyptians affinity to the Palestinians. Yet in the MDS the Near Easterners and Tuareg segregate towards sub-Saharan Africans which, like in the PCA graph, aggregate in the lower-left corner of the plot distant from all other populations.
Discussion
Our results indicate that the frequency of the E-M81 haplogroup in the region of Sousse is relatively lower than in Berber group; it reaches a value of 45%, comparable with the values detected in the Cosmopolitan population from Tunis and Andalusians.21 This frequency range of 36–45% of E-M81 in these Cosmopolitan and Andalusian Tunisian populations is consistent with a strong common Berber back-ground that gives the typical profile to North African populations that aggregate in the same clusters in the PC and MDS analyses. However, depending on the Berber or Cosmopolitan status, North African populations can be classified into subclusters. This observation is in agreement with the analyses of molecular variance analyses that indicate significant differences in molecular variance for both SNP and STR marker systems (17.65 Pless than or equal to0.05 and 1.64 Pless than or equal to0.05, respectively) between Cosmopolitans and Berbers. In all of these parameters, the Sousse population exhibits characteristics of a highly genetically diverse North African population.
The E-M81 lineage exhibits a star-like network structure (Figure 3a), which suggests an ancient evolution. This network exhibits apparent rapid expansion at some point that may be explained by loss of diversity due to genetic drift. Indeed, most of the STR haplotypes belonging to the E-M81 haplogroup are shared among various North African communities without obvious genetic structure relative to geography.
In our previous work performed on Tunisian populations, this haplogroup was dated to 7.4±5.5 kya in the Neolithic, comparable with the age estimated in this study (5.7±3.9 kya), and by Arredi and collaborators.19 However, considering the high level of genetic drift typically experienced by uniparental marker systems such as the Y-chromosome, it is possible that the E-M81 haplogroup had a more ancient genesis in North Africa.
Along with the high prevalence of E-M81 in Sousse, we observed the E-M78 mutation at low frequency (5%). In contrast to the above-mentioned E-M81 haplogroup, E-M78 has a wide geographic distribution with its highest frequency observed in the Egypto-Palestinian area. It is detected at lower frequencies in Northwest Africa and is particularly observed in Andalusians and Cosmopolitans rather than Berbers. This suggests an east to west gene flow with greater penetration into the Cosmopolitan populations of North Africa.
A more recent potential Middle Eastern genetic contribution to the North Africa gene pool may be associated with the expansion of the Ottoman Empire. Sousse also may have been specifically impacted by the Turkish occupation of North Africa. Yet, the unique presence of J-M172 in Sousse and its absence from other Tunisian regions that were under Ottoman influence argues for J-M172 in Sousse as a Phoenician signal. Further, Sousse exhibits another haplogroup, T-M184, that is not detected in any other North African population attesting again to the Phoenicians contribution to that population. Haplogroup T-M184 is more common today in East Africa and it is thought to signal the spread of agriculture from the Fertile Crescent. Indeed, the oldest subclades and the greatest diversity of T-M184 are found in the Middle East, especially within the Fertile Crescent. Yet, T-M184 could also have been dispersed throughout the Mediterranean basin by the Phoenicians (1200–800 before the common era).
In conclusion, the analysis of admixed populations represents an unique opportunity to examine the impact of multiple migrations into a region. Within a historical context, both population isolation and admixture have had a considerable impact on the Tunisian population structure. The wide range of paternal lineages present in our Sousse population indicates a diverse origin. Indeed the genetic structure observed of paternal lineages in Sousse is more diversified than any other studied Tunisian population and reflects largely the influence of successive migrations since its foundation by the Phoenician
More --> http://www.nature.com/jhg/journal/v60/n1/full/jhg201499a.html
What do you guys think?