title: High differentiation among eight villages in a secluded area of Sardinia revealed by genome-wide high density SNPs analysis.
abstract: To better design association studies for complex traits in isolated populations it's important to understand how history and isolation moulded the genetic features of different communities. Population isolates should not "a priori" be considered homogeneous, even if the communities are not distant and part of a small region. We studied a particular area of Sardinia called Ogliastra, characterized by the presence of several distinct villages that display different history, immigration events and population size. Cultural and geographic isolation characterized the history of these communities. We determined LD parameters in 8 villages and defined population structure through high density SNPs (about 360 K) on 360 unrelated people (45 selected samples from each village). These isolates showed differences in LD values and LD map length. Five of these villages show high LD values probably due to their reduced population size and extreme isolation. High genetic differentiation among villages was detected. Moreover population structure analysis revealed a high correlation between genetic and geographic distances. Our study indicates that history, geography and biodemography have influenced the genetic features of Ogliastra communities producing differences in LD and population structure. All these data demonstrate that we can consider each village an isolate with specific characteristics. We suggest that, in order to optimize the study design of complex traits, a thorough characterization of genetic features is useful to identify the presence of sub-populations and stratification within genetic isolates.
authors.affiliation: Istituto di Genetica delle Popolazioni, CNR, Alghero, Sassari, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Pistis
authors.forename: Ignazio
authors.initials: I
authors.lastname: Piras
authors.forename: Nicola
authors.initials: N
authors.lastname: Pirastu
authors.forename: Ivana
authors.initials: I
authors.lastname: Persico
authors.forename: Alessandro
authors.initials: A
authors.lastname: Sassu
authors.forename: Andrea
authors.initials: A
authors.lastname: Picciau
authors.forename: Dionigio
authors.initials: D
authors.lastname: Prodi
authors.forename: Cristina
authors.initials: C
authors.lastname: Fraumene
authors.forename: Evelina
authors.initials: E
authors.lastname: Mocci
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Manias
authors.forename: Rossano
authors.initials: R
authors.lastname: Atzeni
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Cosso
authors.forename: Mario
authors.initials: M
authors.lastname: Pirastu
authors.forename: Andrea
authors.initials: A
authors.lastname: Angius
mesh_terms: D005828:Genetics, Population; D015894:Genome, Human; D006801:Humans; D007558:Italy; D015810:Linkage Disequilibrium; D020641:Polymorphism, Single Nucleotide; D012424:Rural Population