RESUMEN
Objective: Low HDL-C (high-density lipoprotein cholesterol) is the most frequent dyslipidemia in Mexicans, but few studies have examined the underlying genetic basis. Our purpose was to identify genetic variants associated with HDL-C levels and cardiovascular risk in the Mexican population. Approach and Results: A genome-wide association studies for HDL-C levels in 2335 Mexicans, identified four loci associated with genome-wide significance: CETP, ABCA1, LIPC, and SIDT2. The SIDT2 missense Val636Ile variant was associated with HDL-C levels and was replicated in 3 independent cohorts (P=5.9×10−18 in the conjoint analysis). The SIDT2/Val636Ile variant is more frequent in Native American and derived populations than in other ethnic groups. This variant was also associated with increased ApoA1 and glycerophospholipid serum levels, decreased LDL-C (low-density lipoprotein cholesterol) and ApoB levels, and a lower risk of premature CAD. Because SIDT2 was previously identified as a protein involved in sterol transport, we tested whether the SIDT2/Ile636 protein affected this function using an in vitro site-directed mutagenesis approach. The SIDT2/Ile636 protein showed increased uptake of the cholesterol analog dehydroergosterol, suggesting this variant affects function. Finally, liver transcriptome data from humans and the Hybrid Mouse Diversity Panel are consistent with the involvement of SIDT2 in lipid and lipoprotein metabolism. Conclusions: This is the first genome-wide association study for HDL-C levels seeking associations with coronary artery disease in the Mexican population. Our findings provide new insight into the genetic architecture of HDL-C and highlight SIDT2 as a new player in cholesterol and lipoprotein metabolism in humans.
Asunto(s)
HDL-Colesterol/sangre , Enfermedad de la Arteria Coronaria/genética , Hiperlipoproteinemia Tipo II/genética , Proteínas de Transporte de Nucleótidos/genética , Polimorfismo de Nucleótido Simple , Adulto , Edad de Inicio , Animales , Biomarcadores/sangre , Estudios de Casos y Controles , Niño , Enfermedad de la Arteria Coronaria/sangre , Enfermedad de la Arteria Coronaria/diagnóstico , Enfermedad de la Arteria Coronaria/epidemiología , Modelos Animales de Enfermedad , Femenino , Predisposición Genética a la Enfermedad , Estudio de Asociación del Genoma Completo , Células HEK293 , Factores de Riesgo de Enfermedad Cardiaca , Humanos , Hiperlipoproteinemia Tipo II/sangre , Hiperlipoproteinemia Tipo II/diagnóstico , Hiperlipoproteinemia Tipo II/epidemiología , Masculino , Análisis de la Aleatorización Mendeliana , México/epidemiología , Ratones , Persona de Mediana Edad , Proteínas de Transporte de Nucleótidos/metabolismo , Fenotipo , Medición de RiesgoRESUMEN
Understanding the genetic structure of Native American populations is important to clarify their diversity, demographic history, and to identify genetic factors relevant for biomedical traits. Here, we show a demographic history reconstruction from 12 Native American whole genomes belonging to six distinct ethnic groups representing the three main described genetic clusters of Mexico (Northern, Southern, and Maya). Effective population size estimates of all Native American groups remained below 2,000 individuals for up to 10,000 years ago. The proportion of missense variants predicted as damaging is higher for undescribed (~ 30%) than for previously reported variants (~ 15%). Several variants previously associated with biological traits are highly frequent in the Native American genomes. These findings suggest that the demographic and adaptive processes that occurred in these groups shaped their genetic architecture and could have implications in biological processes of the Native Americans and Mestizos of today.
Asunto(s)
Etnicidad/genética , Variación Genética , Genética de Población/métodos , Genoma Humano/genética , Frecuencia de los Genes , Genotipo , Migración Humana , Humanos , México , Modelos Genéticos , Factores de TiempoRESUMEN
Mexico harbors great cultural and ethnic diversity, yet fine-scale patterns of human genome-wide variation from this region remain largely uncharacterized. We studied genomic variation within Mexico from over 1000 individuals representing 20 indigenous and 11 mestizo populations. We found striking genetic stratification among indigenous populations within Mexico at varying degrees of geographic isolation. Some groups were as differentiated as Europeans are from East Asians. Pre-Columbian genetic substructure is recapitulated in the indigenous ancestry of admixed mestizo individuals across the country. Furthermore, two independently phenotyped cohorts of Mexicans and Mexican Americans showed a significant association between subcontinental ancestry and lung function. Thus, accounting for fine-scale ancestry patterns is critical for medical and population genetic studies within Mexico, in Mexican-descent populations, and likely in many other populations worldwide.
Asunto(s)
Variación Genética , Indígenas Norteamericanos/genética , Americanos Mexicanos/genética , Población/genética , Población Negra/genética , Genoma Humano , Humanos , México , Población Blanca/genéticaRESUMEN
The patatin like phospholipase domain-containing (PNPLA3) I148M variant is the strongest genetic factor associated with elevated alanine transaminase (ALT) levels in different populations, particularly in Hispanics who have the highest 148M risk allele frequency reported to date. It has been suggested that Indigenous ancestry is associated with higher ALT levels in Mexicans. The aim of the present study was to assess the frequency of the PNPLA3 148M risk allele in Mexican indigenous and Mestizo individuals, and to examine its association with serum ALT levels. The study included a total of 1624 Mexican individuals: 919 Indigenous subjects from five different native groups and 705 Mexican Mestizo individuals (141 cases with ALT levels ≥ 40 U/L and 564 controls with ALT <40 U/L). The I148M polymorphism was genotyped by TaqMan assays. The frequency of elevated ALT levels in Indigenous populations was 18.7%, and varied according to obesity status: 14.4% in normal weight, 19.9% in overweight and 24.5% in obese individuals. The Mexican indigenous populations showed the highest reported frequency of the PNPLA3 148M risk allele (mean 0.73). The M148M genotype was significantly associated with elevated ALT levels in indigenous individuals (OR = 3.15, 95 % CI 1.91-5.20; P = 7.1 × 10(-6)) and this association was confirmed in Mexican Mestizos (OR = 2.24, 95% CI 1.50-3.33; P = 8.1 × 10(-5)). This is the first study reporting the association between M148M genotype and elevated ALT levels in Indigenous Mexican populations. The 148M allele risk may be considered an important risk factor for liver damage in Mexican indigenous and Mestizo populations.
Asunto(s)
Alanina Transaminasa/genética , Hígado Graso/genética , Lipasa/genética , Hígado/enzimología , Proteínas de la Membrana/genética , Obesidad/genética , Polimorfismo Genético , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Alanina Transaminasa/metabolismo , Alelos , Hígado Graso/complicaciones , Hígado Graso/enzimología , Hígado Graso/etnología , Femenino , Frecuencia de los Genes , Predisposición Genética a la Enfermedad , Humanos , Indígenas Sudamericanos , Lipasa/metabolismo , Hígado/patología , Masculino , Proteínas de la Membrana/metabolismo , México/epidemiología , Persona de Mediana Edad , Obesidad/complicaciones , Obesidad/enzimología , Obesidad/etnología , Grupos de PoblaciónRESUMEN
This review focuses on six transcendental aspects that affect transplant immunology in Mexico: in first place, several immune factors which may lead to graft loss are highlighted; then, some features of the biological variability present in Mexican populations are pointed out in the context of their adaptive and sociopolitical history, leading to the discussion on the genetic diversity within the major histocompatibility complex (MHC) and the importance of resolution in genotypic characterization of the human leukocyte antigen (HLA) and related systems on the basis of human intra-population variability. Critical points on the interpretation of serological reactivity of anti-HLA antibodies are discussed in function of allelic frequency as a probability of finding a variant in a finite population. Finally, evidence of influence of other genetic systems on the recipient-graft relationship is emphasized.
Asunto(s)
Genética de Población , Inmunología del Trasplante/genética , Anticuerpos , Variación Genética/inmunología , Técnicas de Genotipaje , Antígenos HLA/inmunología , Humanos , MéxicoRESUMEN
It has been suggested that the higher susceptibility of Hispanics to metabolic disease is related to their Native American heritage. A frequent cholesterol transporter ABCA1 (ATP-binding cassette transporter A1) gene variant (R230C, rs9282541) apparently exclusive to Native American individuals was associated with low high-density lipoprotein cholesterol (HDL-C) levels, obesity and type 2 diabetes in Mexican Mestizos. We performed a more extensive analysis of this variant in 4405 Native Americans and 863 individuals from other ethnic groups to investigate genetic evidence of positive selection, to assess its functional effect in vitro and to explore associations with HDL-C levels and other metabolic traits. The C230 allele was found in 29 of 36 Native American groups, but not in European, Asian or African individuals. C230 was observed on a single haplotype, and C230-bearing chromosomes showed longer relative haplotype extension compared with other haplotypes in the Americas. Additionally, single-nucleotide polymorphism data from the Human Genome Diversity Panel Native American populations were enriched in significant integrated haplotype score values in the region upstream of the ABCA1 gene. Cells expressing the C230 allele showed a 27% cholesterol efflux reduction (P< 0.001), confirming this variant has a functional effect in vitro. Moreover, the C230 allele was associated with lower HDL-C levels (P = 1.77 x 10(-11)) and with higher body mass index (P = 0.0001) in the combined analysis of Native American populations. This is the first report of a common functional variant exclusive to Native American and descent populations, which is a major determinant of HDL-C levels and may have contributed to the adaptive evolution of Native American populations.