The variability of human mitochondrial DNA (mtDNA) has been the subject of countless studies that have allowed to expand the genetic and phylogeographic knowledge on the European populations. In Western Europe, Italy with its peculiar geophysical characteristics has been a crossroads for human migration and, over time, has become the perfect environment for the complex dynamics of internal populations. The high genomic variability of its populations, compared to other European regions, is the result of numerous inputs that have shaped the gene pool of its populations, starting from the Upper Paleolithic, and created its genetic structure. While macro-geographical analyses have been numerous, micro-geographical realities have not been thoroughly investigated. In this context, the Trentino region can be considered a valuable source of information. Its complex territory, 60% of which is located at an altitude above 1000m above the sea level, may have affected the mobility of populations, leading to geographical isolation, which would explain the considerable linguistic diversity. However, the numerous valleys have also provided excellent communication routes, facilitating movements and interactions. In particular, archaeological findings and historical records testify for a complex history of migrations that took place in the Rendena Valley (Trentino) and might be reflected in the genetic makeup of the current inhabitants of the valley. The aim of this thesis project was to investigate, for the first time, the mitochondrial variability of the current population of Rendena Valley. We started by collecting the biological sample of 121 volunteers currently living in the valley, asking them to compile a family tree in order to obtain information about the place of birth of ancestors. For this thesis, only individuals with at least two generations of maternal ancestors from the valley were selected. We then extracted their DNA and sequenced the mitochondrial control region. The samples were carefully analysed for mitochondrial variability, showing an extensive variation with 43 haplogroups and sub-haplogroups identified in the valley. Among the identified mitochondrial lines, U5a, J1c and T2 were the most frequent. Due to the high diversity found in the Rendena Valley, we have extended our analysis to the entire mitogenome. The analysis of 111 complete sequences of mitochondrial DNA allowed us to confirm the results obtained with the analysis of the control region and to build the first mitochondrial phylogenetic tree of the Rendena Valley. In particular, the high frequency (18%) of the haplogroup U5a, so far never identified in Italy, has pushed us to deepen the study of this particular haplogroup. The haplogroup U5a derives from the U5 branch of the human mitochondrial phylogenetic tree and probably originated between Eastern Europe and western Asia. U5a is further subdivided in two major branches, U5a1 and U5a2. Both were represented in the Rendena Valley, and were also differentiated into several sub-branches. Age estimates confirm an origin of U5a around 20 thousand years ago (kya) during the Last Glacial Maximum, while the two sub-haplogroups diverged at different times, thus pointing to separated sources and migrations. Intriguingly, the evolution of two major subclades, U5a1a1 and U5a2c, might suggest the possibility Indo-European migrations into the Valley during the Bronze Age (~2300-900 BCE).
La storia genetica della Val Rendena: uno studio micro-geografico basato sul DNA mitocondriale. La variabilità del DNA mitocondriale umano (mtDNA) è stata oggetto di innumerevoli studi che hanno permesso di ampliare le conoscenze genetiche e filogeografiche sulle popolazioni Europee. Nell'Europa occidentale, l'Italia con le sue peculiari caratteristiche geofisiche è stata crocevia di migrazioni umane e, nel tempo, ha rappresentato l’ambiente perfetto per le complesse dinamiche delle popolazioni interne. L’elevata variabilità genomica delle sue popolazioni, paragonata ad altre regioni europee, è il risultato di numerosi input che hanno modellato il pool genico delle sue popolazioni, a partire dal Paleolitico superiore, e creato la sua struttura genetica. Se da un lato le analisi macro-geografiche sono state numerose e approfondite, le realtà micro-geografiche non sono state accuratamente indagate. In questo contesto, la regione Trentino può essere considerata una preziosa fonte di informazioni. Il suo complesso territorio, il cui 60% è situato ad un’altitudine superiore ai 1000m sopra il livello del mare, potrebbe aver influenzato la mobilità delle popolazioni, portando ad un isolamento geografico che a sua volta spiegherebbe, almeno in parte, la notevole diversificazione linguistica. Tuttavia, le numerose valli hanno anche fornito ottime vie di comunicazione, agevolando movimenti e interazioni. In particolare, reperti archeologici e testimonianze storiche testimoniano una complessa storia di migrazioni che hanno avuto luogo nella Val Rendena (Trentino) e che potrebbero riflettersi sulla variabilità genetica degli attuali abitanti della valle. Lo scopo di questo progetto di tesi è stato proprio quello d’indagare, per la prima volta, la variabilità mitocondriale dell’attuale popolazione della Val Rendena. Siamo partiti raccogliendo il campione biologico di 121 volontari attualmente residenti nella valle, chiedendo loro di compilare anche un albero genealogico al fine di ottenere informazioni sul grado di parentela e sul luogo di nascita degli antenati. Per questo lavoro di tesi, sono stati selezionati solo individui con almeno due generazioni di antenati materni provenienti dalla valle. Abbiamo quindi estratto il loro DNA e sequenziato la regione di controllo mitocondriale. Sui campioni è stata condotta un’accurata analisi della variabilità mitocondriale, che ha portato alla classificazione in 43 diversi aplogruppi e sotto-aplogruppi. Tra le linee mitocondriali identificate, U5a, J1c e T2 sono risultate le più frequenti. Data l’elevata diversità riscontrata nella Val Rendena, abbiamo esteso le nostre analisi all’intero mitogenoma. L’analisi di 111 sequenze complete di DNA mitocondriale, ci ha permesso di confermare i risultati ottenuti con l’analisi della regione di controllo e di costruire il primo albero filogenetico mitocondriale della Val Rendena. In particolare, l’elevata frequenza (18%), ad oggi mai identificata in Italia, dell’aplogruppo U5a, ci ha permesso di approfondire lo studio di questo particolare aplogruppo. L'aplogruppo U5a deriva dal ramo U5 dell'albero filogenetico mitocondriale e probabilmente ha avuto origine tra l'Europa orientale e l'Asia occidentale. L’U5a è ulteriormente suddiviso in due rami principali, U5a1 e U5a2. Entrambi sono rappresentati in Val Rendena, dove si differenziano ulteriormente in più sottorami. Le stime sull'età confermano un'origine di U5a intorno a 20 mila anni fa, durante l'ultimo massimo glaciale, mentre i due sottoaplogruppi si sono generati in tempi diversi, indicando possibili migrazioni separate. Molto interessante è l'evoluzione di due principali sotto-cladi principali, U5a1a1 e U5a2c, che potrebbe suggerire la possibilità di migrazioni Indo-Europee nella valle durante l'Età del Bronzo (~ 2300-900 a.C.).
The genetic history of Val Rendena: a microgeographic mtDNA analysis
BOZZARI, GIULIA
2022/2023
Abstract
The variability of human mitochondrial DNA (mtDNA) has been the subject of countless studies that have allowed to expand the genetic and phylogeographic knowledge on the European populations. In Western Europe, Italy with its peculiar geophysical characteristics has been a crossroads for human migration and, over time, has become the perfect environment for the complex dynamics of internal populations. The high genomic variability of its populations, compared to other European regions, is the result of numerous inputs that have shaped the gene pool of its populations, starting from the Upper Paleolithic, and created its genetic structure. While macro-geographical analyses have been numerous, micro-geographical realities have not been thoroughly investigated. In this context, the Trentino region can be considered a valuable source of information. Its complex territory, 60% of which is located at an altitude above 1000m above the sea level, may have affected the mobility of populations, leading to geographical isolation, which would explain the considerable linguistic diversity. However, the numerous valleys have also provided excellent communication routes, facilitating movements and interactions. In particular, archaeological findings and historical records testify for a complex history of migrations that took place in the Rendena Valley (Trentino) and might be reflected in the genetic makeup of the current inhabitants of the valley. The aim of this thesis project was to investigate, for the first time, the mitochondrial variability of the current population of Rendena Valley. We started by collecting the biological sample of 121 volunteers currently living in the valley, asking them to compile a family tree in order to obtain information about the place of birth of ancestors. For this thesis, only individuals with at least two generations of maternal ancestors from the valley were selected. We then extracted their DNA and sequenced the mitochondrial control region. The samples were carefully analysed for mitochondrial variability, showing an extensive variation with 43 haplogroups and sub-haplogroups identified in the valley. Among the identified mitochondrial lines, U5a, J1c and T2 were the most frequent. Due to the high diversity found in the Rendena Valley, we have extended our analysis to the entire mitogenome. The analysis of 111 complete sequences of mitochondrial DNA allowed us to confirm the results obtained with the analysis of the control region and to build the first mitochondrial phylogenetic tree of the Rendena Valley. In particular, the high frequency (18%) of the haplogroup U5a, so far never identified in Italy, has pushed us to deepen the study of this particular haplogroup. The haplogroup U5a derives from the U5 branch of the human mitochondrial phylogenetic tree and probably originated between Eastern Europe and western Asia. U5a is further subdivided in two major branches, U5a1 and U5a2. Both were represented in the Rendena Valley, and were also differentiated into several sub-branches. Age estimates confirm an origin of U5a around 20 thousand years ago (kya) during the Last Glacial Maximum, while the two sub-haplogroups diverged at different times, thus pointing to separated sources and migrations. Intriguingly, the evolution of two major subclades, U5a1a1 and U5a2c, might suggest the possibility Indo-European migrations into the Valley during the Bronze Age (~2300-900 BCE).È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/16304