Dissecting a human isolate: Novel sampling criteria for analysis of the genetic structure of the Val di Scalve (Italian Pre-Alps)

BACKGROUND: The choice of criteria for correct DNA sampling in isolated populations is often affected by ambiguities, despite its importance in medical and anthropological genetics. AIM: We propose a novel biodemographic approach to the study of isolates based on surname analysis and migration matrices, and we apply it to a candidate isolated population: the Val di Scalve (Italian Pre-Alps). METHODS: Kinship matrices and self-organizing maps (SOMs) were applied to information extracted from 2870 marriage records relative to the years 1866-1935. RESULTS: The Val di Scalve shows the typical genetic trademarks of an isolate at least up to the first half of the 20th century. Furthermore, the area was characterized by differential mobility patterns between males and females, consistent with the virilocal migration model. These data suggest reliable criteria for an efficient DNA sampling design by (a) detecting the units of analysis to be investigated (internal population subdivisions); (b) maximizing the number of paternal lineages in the sample for Y-chromosome studies (surnames); and (c) calculating the most convenient sample size. CONCLUSION: The surname-based sampling procedure can be exported and applied to larger and non-isolated populations.