To scrutinize the male ancestry of extant Native American populations, we examined eight biallelic and six microsatellite polymorphisms from the nonrecombining portion of the Y chromosome, in 438 individuals from 24 Native American populations (1 Na Dené and 23 South Amerinds) and in 404 Mongolians. One of the biallelic markers typed is a recently identified mutation (M242) characterizing a novel founder Native American haplogroup. The distribution, relatedness, and diversity of Y lineages in Native Americans indicate a differentiated male ancestry for populations from North and South America, strongly supporting a diverse demographic history for populations from these areas. These data are consistent with the occurrence of two major male migrations from southern/central Siberia to the Americas (with the second migration being restricted to North America) and a shared ancestry in central Asia for some of the initial migrants to Europe and the Americas. The microsatellite diversity and distribution of a Y lineage specific to South America (Q-M19) indicates that certain Amerind populations have been isolated since the initial colonization of the region, suggesting an early onset for tribalization of Native Americans. Age estimates based on Y-chromosome microsatellite diversity place the initial settlement of the American continent at approximately 14,000 years ago, in relative agreement with the age of well-established archaeological evidence.

We examined the mtDNA RFLP diversity of 17 Native American populations from Colombia. Five of the populations studied were found to have variable frequencies of a mtDNA type lacking the characteristic changes of haplogroups A-D. Sequencing of mtDNA HVS-I and II showed that this "null" RFLP type carries all the substitutions characteristic of Native American founder lineage C. A back mutation has therefore recreated the +13,259 HincII/-13,262 AluI restriction sites that tipify RFLP haplogroup C. This revertant C lineage is further characterized by three changes in HVS-II sequence: C/T transitions at positions 115 and 152, and the deletion of an A residue at position 116. This lineage is observed at high frequency mostly in populations from Greenberg's Equatorial-Tucano linguistic family. Genetic structure analyses are consistent with the reversion mutation occurring at an early stage during the tribalization process.

Co-expression networks may provide insights into the patterns of molecular interactions that underlie cellular processes. To obtain a better understanding of miRNA expression patterns in gastric adenocarcinoma and to provide markers that can be associated with histopathological findings, we performed weighted gene correlation network analysis (WGCNA) and compare it with a supervised analysis. Integrative analysis of target predictions and miRNA expression profiles in gastric cancer samples was also performed. WGCNA identified a module of co-expressed miRNAs that were associated with histological traits and tumor condition. Hub genes were identified based on statistical analysis and network centrality. The miRNAs 100, let-7c, 125b and 99a stood out for their association with the diffuse histological subtype. The 181 miRNA family and miRNA 21 highlighted for their association with the tumoral phenotype. The integrated analysis of miRNA and gene expression profiles showed the let-7 miRNA family playing a central role in the regulatory relationships.

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