Fibroblast growth factor receptor 1 (FGFR1) variants and craniofacial variation in Amerindians and related populations

OBJECTIVES: The polymorphic site rs4647905 of the FGFR1 gene was previously associated with a decrease in cephalic index (CI). Here, we evaluate the relationships between genotypes and cephalometric measurements and indices in one Mexican Native and two mestizo Mexican populations using two haplotype-tag SNPs (rs4647905 and rs3213849) that represent >85% of the FGFR1 variability, plus three other SNPs (rs2293971, rs2304000, and rs930828) situated nearby. In addition, we genotyped five South American natives, two European, one African, and one Siberian populations to evaluate their intra and intercontinental population diversity. METHODS: The five SNPs were tested and the craniofacial measurements and indices were collected using standardized procedures. Principal Component Analysis was used to verify individual/population comparisons. Associations were performed through the generalized linear model (GLM), coefficient of determination R(2) and linear regression tests. RESULTS: We found a tendency for a decrease in CI in individuals homozygous for allele rs4647905C, regardless of the population to which they belong, though the effect is more pronounced in mestizo. When the GLM analyses were performed using the absolute/linear cephalometric measurements, a statistically significant association was found between four SNPs and head length in the mestizo population. CONCLUSIONS: FGFR1 polymorphisms, especially rs4647905, can have an important role in the normal human skull variation, primarily due to their influence in head length, which would affect other cephalometric absolute/linear measures as well as indices like CI as a result of the pervasive nature of the morphological integration that characterizes the human skull.

Brief communication: 5-HTTLPR genetic diversity and mode of subsistence in Native Americans

The relationship between the "individualism-collectivism" and the serotonin transporter functional polymorphism (5-HTTLPR), suggested in the previous reports, was tested in Native South Amerindian populations. A total of 170 individuals from 21 populations were genotyped for the 5-HTTLPR alleles. For comparative purposes, these populations were classified as individualistic (recent history of hunter-gathering) or collectivistic (agriculturalists). These two groups showed an almost identical S allele frequency (75 and 76%, respectively). The analysis of molecular variance showed no structural differences between them. Behavioral typologies like those suggested by JY Chiao and KD Blizinsky (Proc R Soc B 277 () 529-537) are always a simplification of complex phenomena and should be regarded with caution. In addition, classification of a whole nation in the individualist/collectivist dichotomy is controversial. The focus on modes of subsistence in preindustrial societies, as was tested here, may be a good alternative although the postulated association between the 5-HTTLPR S allele and the collectivist societies was not confirmed.

Reconstructing Native American population history

The peopling of the Americas has been the subject of extensive genetic, archaeological and linguistic research; however, central questions remain unresolved. One contentious issue is whether the settlement occurred by means of a single migration or multiple streams of migration from Siberia. The pattern of dispersals within the Americas is also poorly understood. To address these questions at a higher resolution than was previously possible, we assembled data from 52 Native American and 17 Siberian groups genotyped at 364,470 single nucleotide polymorphisms. Here we show that Native Americans descend from at least three streams of Asian gene flow. Most descend entirely from a single ancestral population that we call 'First American'. However, speakers of Eskimo-Aleut languages from the Arctic inherit almost half their ancestry from a second stream of Asian gene flow, and the Na-Dene-speaking Chipewyan from Canada inherit roughly one-tenth of their ancestry from a third stream. We show that the initial peopling followed a southward expansion facilitated by the coast, with sequential population splits and little gene flow after divergence, especially in South America. A major exception is in Chibchan speakers on both sides of the Panama isthmus, who have ancestry from both North and South America.