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A comparison of Y-chromosome variation in Sardinia and Anatolia is more consistent with cultural rather than demic diffusion of agriculture.

ABSTRACT: Two alternative models have been proposed to explain the spread of agriculture in Europe during the Neolithic period. The demic diffusion model postulates the spreading of farmers from the Middle East along a Southeast to Northeast axis. Conversely, the cultural diffusion model assumes transmission of agricultural techniques without substantial movements of people. Support for the demic model derives largely from the observation of frequency gradients among some genetic variants, in particular haplogroups defined by single nucleotide polymorphisms (SNPs) in the Y-chromosome. A recent network analysis of the R-M269 Y chromosome lineage has purportedly corroborated Neolithic expansion from Anatolia, the site of diffusion of agriculture. However, the data are still controversial and the analyses so far performed are prone to a number of biases. In the present study we show that the addition of a single marker, DYSA7.2, dramatically changes the shape of the R-M269 network into a topology showing a clear Western-Eastern dichotomy not consistent with a radial diffusion of people from the Middle East. We have also assessed other Y-chromosome haplogroups proposed to be markers of the Neolithic diffusion of farmers and compared their intra-lineage variation--defined by short tandem repeats (STRs)--in Anatolia and in Sardinia, the only Western population where these lineages are present at appreciable frequencies and where there is substantial archaeological and genetic evidence of pre-Neolithic human occupation. The data indicate that Sardinia does not contain a subset of the variability present in Anatolia and that the shared variability between these populations is best explained by an earlier, pre-Neolithic dispersal of haplogroups from a common ancestral gene pool. Overall, these results are consistent with the cultural diffusion and do not support the demic model of agriculture diffusion.

SUBMITTER: Morelli L

PROVIDER: S-EPMC2861676 | biostudies-literature | 2010 Apr

REPOSITORIES: biostudies-literature

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A comparison of Y-chromosome variation in Sardinia and Anatolia is more consistent with cultural rather than demic diffusion of agriculture.

Morelli Laura L Contu Daniela D Santoni Federico F Whalen Michael B MB Francalacci Paolo P Cucca Francesco F

PloS one 20100429 4

Two alternative models have been proposed to explain the spread of agriculture in Europe during the Neolithic period. The demic diffusion model postulates the spreading of farmers from the Middle East along a Southeast to Northeast axis. Conversely, the cultural diffusion model assumes transmission of agricultural techniques without substantial movements of people. Support for the demic model derives largely from the observation of frequency gradients among some genetic variants, in particular h ...[more]

PMID: 20454687

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Project description:Many studies estimate that chromosomal mosaicism within the cleavage stage human embryo is high. However, comparison of two unique methods of aneuploidy screening of blastomeres within the same embryo has not been conducted and may indicate whether mosaicism is overestimated due to technical inconsistency rather than biological phenomena. The present study investigates the prevalence of chromosomal abnormality and mosaicism found with two different single cell aneuploidy screening techniques.Thirteen arrested cleavage stage embryos were studied. Each was biopsied into individual cells (n=160). The cells from each embryo were randomized into two groups. Those destined for FISH based aneuploidy screening (n=75) were fixed, 1 cell per slide. Cells for SNP microarray based aneuploidy screening (n=85) were put into individual tubes. Microarray was significantly more reliable (96%) than FISH (83%) for providing an interpretable result (P=0.004). Markedly different results were obtained when comparing microarray and FISH results from individual embryos. Mosaicism was significantly less commonly observed by microarray (4 of 13 embryos; 31%) than by FISH (13 of 13 embryos; 100%)(P=0.0005). Although FISH evaluated fewer chromosomes per cell and fewer cells per embryo, FISH still displayed significantly more unique genetic diagnoses per embryo (3.2+0.2) than microarray (1.3+0.2)(P<0.0001). This is the first prospective, randomized, blinded, and paired comparison between microarray and FISH based aneuploidy screening. Aneuploidy and mosaicism were less common with microarray. While evaluating a smaller number of chromosomes with a proportionally smaller opportunity for finding mosaicism, FISH still had a dramatically higher level of inter-cell variation in diagnosis. SNP microarray based 24 chromosome aneuploidy screening provides more complete and consistent results than FISH. Affymetrix SNP arrays were processed according to the manufacturer's directions on DNA extracted from 13 arrested cleavage stage embryos and biopsied into individual blastomere cells. Individual blastomeres were randomized and blinded for SNP microarray analysis (n = 85). Afflymetrix SNP array analysis was successfully completed on 82 blastomeres.

Dataset Information

A comparison of Y-chromosome variation in Sardinia and Anatolia is more consistent with cultural rather than demic diffusion of agriculture.

Publications

A comparison of Y-chromosome variation in Sardinia and Anatolia is more consistent with cultural rather than demic diffusion of agriculture.

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