FDP: “Forensic DNA Phenotyping” Aplicaciones de marcadores genéticos en la inferencia de características visibles externas y origen ancestral con fines forenses

En la actualidad, el estudio de la genética forense abarca nuevos marcadores moleculares que son de utilidad para un cierto número de casos en donde los polimorfismos convencionales suelen presentar limitaciones, por ejemplo, cuando no existen perfiles disponibles para comprar ni correspondencia con las bases de datos disponibles, o cuando se analizan muestras en estado de degradación. Esta implementación de nuevos marcadores moleculares, ha permitido una variedad de aplicaciones al estudio del ADN humano con fines forenses. Entre los nuevos polimorfismos empleados, destacan los SNPs (Single Nucleotide Polimorphisms) los cuales han sido considerados como potenciales marcadores genéticos en este campo por varias razones, entre las que destacan: la corta longitud de los fragmentos de amplificación que permite obtener información a partir de material genético degradado, el poder de automatización que permite adaptar estos marcadores a diversas plataformas de genotipado, su poder para la definición de grupos ancestrales biogeográficos así como de linajes en comparación con otros marcadores y finalmente, la asociación que poseen estos marcadores en la inferencia de rasgos físicos o características visibles externas (EVC). Por ello, estos polimorfismos ofrecen una alternativa de valor aportando información adicional que permite reconstruir al menos en parte, la apariencia física de un individuo en cuestión a partir del ADN, de tal forma que sea posible reducir el universo de sospechosos presentes en la población. El objetivo en el presente trabajo de investigación, se basa en la inferencia de características físicas en un contexto forense a través del análisis SNPs presentes en el ADN, análisis conocido como Forensic DNA Phenotyping (FDP). Este término reúne la información obtenida tanto del grupo ancestral biogeográfico como de los EVCs de un individuo. El análisis de FDP tiene aplicaciones también en el estudio de restos antiguos y en la identificación de víctimas en desastres naturales, adicionalmente, su empleo puede contribuir a evitar errores en la identificación de sospechosos dado que a consecuencia del trauma, un alto porcentaje de víctimas de un delito pueden equivocarse en las ruedas de reconocimiento, o presentar testimonios confusos, mientras que el valor en la predicción de características físicas con marcadores genéticos poseerá en todo caso un respaldo estadístico

Development of a Panel of Genome-Wide Ancestry Informative Markers to Study Admixture Throughout the Americas

Most individuals throughout the Americas are admixed descendants of Native American, European, and African ancestors. Complex historical factors have resulted in varying proportions of ancestral contributions between individuals within and among ethnic groups. We developed a panel of 446 ancestry informative markers (AIMs) optimized to estimate ancestral proportions in individuals and populations throughout Latin America. We used genome-wide data from 953 individuals from diverse African, European, and Native American populations to select AIMs optimized for each of the three main continental populations that form the basis of modern Latin American populations. We selected markers on the basis of locus-specific branch length to be informative, well distributed throughout the genome, capable of being genotyped on widely available commercial platforms, and applicable throughout the Americas by minimizing within-continent heterogeneity. We then validated the panel in samples from four admixed populations by comparing ancestry estimates based on the AIMs panel to estimates based on genome-wide association study (GWAS) data. The panel provided balanced discriminatory power among the three ancestral populations and accurate estimates of individual ancestry proportions (R2>0.9 for ancestral components with significant between-subject variance). Finally, we genotyped samples from 18 populations from Latin America using the AIMs panel and estimated variability in ancestry within and between these populations. This panel and its reference genotype information will be useful resources to explore population history of admixture in Latin America and to correct for the potential effects of population stratification in admixed samples in the region

Development of a panel of genome-wide ancestry informative markers to study admixture throughout the Americas.

Most individuals throughout the Americas are admixed descendants of Native American, European, and African ancestors. Complex historical factors have resulted in varying proportions of ancestral contributions between individuals within and among ethnic groups. We developed a panel of 446 ancestry informative markers (AIMs) optimized to estimate ancestral proportions in individuals and populations throughout Latin America. We used genome-wide data from 953 individuals from diverse African, European, and Native American populations to select AIMs optimized for each of the three main continental populations that form the basis of modern Latin American populations. We selected markers on the basis of locus-specific branch length to be informative, well distributed throughout the genome, capable of being genotyped on widely available commercial platforms, and applicable throughout the Americas by minimizing within-continent heterogeneity. We then validated the panel in samples from four admixed populations by comparing ancestry estimates based on the AIMs panel to estimates based on genome-wide association study (GWAS) data. The panel provided balanced discriminatory power among the three ancestral populations and accurate estimates of individual ancestry proportions (R² > 0.9 for ancestral components with significant between-subject variance). Finally, we genotyped samples from 18 populations from Latin America using the AIMs panel and estimated variability in ancestry within and between these populations. This panel and its reference genotype information will be useful resources to explore population history of admixture in Latin America and to correct for the potential effects of population stratification in admixed samples in the region

Development of a panel of genome-wide ancestry informative markers to study admixture throughout the Americas

Most individuals throughout the Americas are admixed descendants of Native American, European, and African ancestors. Complex historical factors have resulted in varying proportions of ancestral contributions between individuals within and among ethnic groups. We developed a panel of 446 ancestry informative markers (AIMs) optimized to estimate ancestral proportions in individuals and populations throughout Latin America. We used genome-wide data from 953 individuals from diverse African, European, and Native American populations to select AIMs optimized for each of the three main continental populations that form the basis of modern Latin American populations. We selected markers on the basis of locus-specific branch length to be informative, well distributed throughout the genome, capable of being genotyped on widely available commercial platforms, and applicable throughout the Americas by minimizing within-continent heterogeneity. We then validated the panel in samples from four admixed populations by comparing ancestry estimates based on the AIMs panel to estimates based on genome-wide association study (GWAS) data. The panel provided balanced discriminatory power among the three ancestral populations and accurate estimates of individual ancestry proportions (R2>0.9 for ancestral components with significant between-subject variance). Finally, we genotyped samples from 18 populations from Latin America using the AIMs panel and estimated variability in ancestry within and between these populations. This panel and its reference genotype information will be useful resources to explore population history of admixture in Latin America and to correct for the potential effects of population stratification in admixed samples in the region

Validation of the AIMs panel compared to ancestry estimates using GWAS data.

<p>Validation of the AIMs panel compared to ancestry estimates using GWAS data.</p

Performance of nested subsets of AIMs.

<p>Performance of nested subsets of AIMs.</p

Time since admixture for Mestizo and African descendent populations.

<p>Time since admixture for Mestizo and African descendent populations.</p

Ancestry of Latin American populations.

<p>Ancestries are given in median and 25^th:75^th percentiles.</p