Linguistic isolates in Portugal: insights from the mitochondrial DNA pattern.

Miranda do Douro, located in the northeastern region of Portugal, has notable characteristics not only from a geographic or naturalistic point of view, but also from a cultural perspective. A remarkable one is the coexistence of two different languages: Portuguese and Mirandese, the second being an Astur-Leonese dialect. The current persistence of the Astur-Leonese dialect in this population falls on the singularity of the region: relative isolation, implying difficulties to communicate with other Portuguese regions, while the same location facilitated the establishment of social and commercial relationships with adjacent Spanish territories, origin of the Astur-Leonese language. The objective of this study was to characterize the population from Miranda through the analysis of maternal lineages in order to evaluate whether its mitochondrial DNA diversity fitted the patterns previously reported for other populations from the Iberian Peninsula. Viewing that, the entire control region of mitochondrial DNA from 121 individuals was examined. Miranda showed a haplogroup composition usual for a Western European population, in the sense that as high as 63.6% of sequences belonged to macro-haplogroup R0. Lineages ascribed to have an African (L2a and L1b) origin, were detected, but reaching an amount commonly found in Portugal. Miranda also presented a few haplogroups typically found in Jewish populations, while rarely observed in other Iberian populations. The finding can be explained by gene flow with crypto-Jew communities that since long are known to be established in the region where Miranda is located. In Miranda, both genetic and nucleotide diversities presented low values (0.9292 ± 0.0180 and 0.01101 ± 0.00614 respectively) when compared to populations from its micro-geographical framework, which constitute a sign of population isolation that certainly provided conditions for the survival of the Astur-Leonese dialect in the region.

Nuclear insertions of mitochondrial origin: Database updating and usefulness in cancer studies.

Nuclear insertions of mitochondrial origin (NUMTs) can be useful tools in evolution and population studies. However, due to their similarity to mitochondrial DNA (mtDNA), NUMTs may also be a source of contamination in mtDNA studies. The main goal of this work is to present a database of NUMTs, based on the latest version of the human genome-GRCh37 draft. A total of 755 insertions were identified. There are 33 paralogous sequences with over 80% sequence similarity and of a greater length than 500bp. The non-identical positions between paralogous sequences are listed for the first time. As an application example, the described database is used to evaluate the impact of NUMT contamination in cancer studies. The evaluation reveals that 220 positions from 256 with zero hits in the current mtDNA phylogeny could in fact be traced to one or more nuclear insertions of mtDNA. This is due to they are located in non-identical positions between mtDNA and nuclear DNA (nDNA). After in silico primer validation of each revised cancer study, risk of co-amplification between mtDNA and nDNA was detected in some cases, whereas in others no risk of amplification was identified. This approach to cancer studies clearly proves the potential of our NUMT database as a valuable new tool to validate mtDNA mutations described in different contexts. Moreover, due to the amount of information provided for each nuclear insertion, this database should play an important role in designing evolutionary, phylogenetic and epidemiological studies.