The genetics of Mexico recapitulates Native American substructure and affects biomedical traits
Mexico, hosted many cultures such as the Olmec, the Toltec, the Maya and the Aztec, conquered and colonized by the Spanish Empire in 1521. The country harbors a large source of pre-Columbian diversity and their genetic contributions to today’s population.

In a recent paper, Moreno-Estrada et al. 2014 performed a detailed genetic study of Mexican genetic diversity. The results showed the genetic stratification among indigenous populations and an association between subcontinental ancestry and lung function.

In the first part of the study, to estimate the genetic diversity, researchers examined autosomal single-nucleotide polymorphisms for more than 500 Native Mexican individuals from all around Mexico. Statistical analysis of genomic data showed that some populations within Mexico are more differentiated than European and East Asian populations. This extreme differentiation thought to be a result of isolation followed by a bottleneck and small effective population sizes.

The data was analyzed in various ways (ROH and IBD analysis, PCA etc.) and revealed the population substructure of Mexico. In all of the analysis, the results confirmed that Seri (northernmost) and Lacandon (southernmost) have the highest level of differentiation. Also, the differentiation between Seri and Lacandon was greater than average differentiation between human populations. The relationships between other populations were accordance with geography, migration and language history. When African and European genetic data were included in the analysis of native Mexicans, it had been shown that most individuals have the genetic composition of Native and European ancestry. Further analysis indicated the ancient Native American substructure was recapitulated even after postcolonial admixture.

In the second part of the study, Moreno-Estrada et al. 2014 investigated the potential biomedical applications of genetic substructure information. Previous studies indicated the relationship between forced expiratory volume in 1 second (FEV1) could be an indicative of pulmonary disease and another study suggested that the proportion of European ancestry was associated with FEV1 in Mexicans. Researchers measured the lung function in Mexican and Mexican-American children with asthma and correlated these findings with native ancestry. Results showed 7.3% change in FEV1 moving from Sonora to Yucatan and researchers proposed that native ancestry could alone have effects on lung function in admixed individuals within Mexico.

Personal Comments

This paper provides novel insights to Mexican genetic diversity and proposes the biomedical applications of genetic data. The sampling locations cover most of the country and the analysis of the data in various methods gives confidence to reader. The paper is easy to follow and the figures are quite helpful.

However, I think there is a critical point that needs to be discussed from a medical point of view. As far as I know, asthma is a complex disease and thought to be caused by both genetic and environmental factors. In this study, I could not find any information about the developmental and medical history of patients. I think this is a critical point because of heterogeneous geography of the county. Where were they raised – in volcano towns, Pacific shores, Sumidero Canyon, Laguna Salada (-10m) or piedmont plains of Pico de Orizaba (5636m)? Did their mothers smoke during pregnancy? Were they born in Mexico City – the city named as “the most polluted city on the planet” by United Nations in 1992? I hope the researchers have already checked for this type information and found them unnecessary to include.

Nevertheless, this is an interesting paper and shows the genetic history of Mexico – before and after 16th century. I recommend reading this paper and discussing with a medical doctor 😉

Moreno-Estrada, A., Gignoux, C., Fernandez-Lopez, J., Zakharia, F., Sikora, M., Contreras, A., Acuna-Alonzo, V., Sandoval, K., Eng, C., Romero-Hidalgo, S., Ortiz-Tello, P., Robles, V., Kenny, E., Nuno-Arana, I., Barquera-Lozano, R., Macin-Perez, G., Granados-Arriola, J., Huntsman, S., Galanter, J., Via, M., Ford, J., Chapela, R., Rodriguez-Cintron, W., Rodriguez-Santana, J., Romieu, I., Sienra-Monge, J., Navarro, B., London, S., Ruiz-Linares, A., Garcia-Herrera, R., Estrada, K., Hidalgo-Miranda, A., Jimenez-Sanchez, G., Carnevale, A., Soberon, X., Canizales-Quinteros, S., Rangel-Villalobos, H., Silva-Zolezzi, I., Burchard, E., & Bustamante, C. (2014). The genetics of Mexico recapitulates Native American substructure and affects biomedical traits Science, 344 (6189), 1280-1285 DOI: 10.1126/science.1251688

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