Development of a small panel of SNPs to infer ancestry in Chileans that distinguishes Aymara and Mapuche components

BACKGROUND: Current South American populations trace their origins mainly to three continental ancestries, i.e. European, Amerindian and African. Individual variation in relative proportions of each of these ancestries may be confounded with socio-economic factors due to population stratification. Therefore, ancestry is a potential confounder variable that should be considered in epidemiologic studies and in public health plans. However, there are few studies that have assessed the ancestry of the current admixed Chilean population. This is partly due to the high cost of genome-scale technologies commonly used to estimate ancestry. In this study we have designed a small panel of SNPs to accurately assess ancestry in the largest sampling to date of the Chilean mestizo population (n = 3349) from eight cities. Our panel is also able to distinguish between the two main Amerindian components of Chileans: Aymara from the north and Mapuche from the south. RESULTS: A panel of 150 ancestry-informative markers (AIMs) of SNP type was selected to maximize ancestry informativeness and genome coverage. Of these, 147 were successfully genotyped by KASPar assays in 2843 samples, with an average missing rate of 0.012, and a 0.95 concordance with microarray data. The ancestries estimated with the panel of AIMs had relative high correlations (0.88 for European, 0.91 for Amerindian, 0.70 for Aymara, and 0.68 for Mapuche components) with those obtained with AXIOM LAT1 array. The country's average ancestry was 0.53 ± 0.14 European, 0.04 ± 0.04 African, and 0.42 ± 0.14 Amerindian, disaggregated into 0.18 ± 0.15 Aymara and 0.25 ± 0.13 Mapuche. However, Mapuche ancestry was highest in the south (40.03%) and Aymara in the north (35.61%) as expected from the historical location of these ethnic groups. We make our results available through an online app and demonstrate how it can be used to adjust for ancestry when testing association between incidence of a disease and nongenetic risk factors. CONCLUSIONS: We have conducted the most extensive sampling, across many different cities, of current Chilean population. Ancestry varied significantly by latitude and human development. The panel of AIMs is available to the community for estimating ancestry at low cost in Chileans and other populations with similar ancestry.

Esquizofrenia resistente: Definiciones e Implicancias del concepto de Esquizofrenia Resistente a tratamiento / Treatment resistant schizophrenia: definitions and implications of the Treatment Resistant Schizophrenia concept

Resumen La esquizofrenia (EQZ) es una entidad clínica altamente heterogénea. Determina un severo impacto en la calidad de vida de los pacientes y un alto costo para la sociedad. Los antipsicóticos son la primera línea de tratamiento, sin embargo, hasta un tercio de los pacientes presentaran una esquizofrenia resistente a tratamiento (ERT). Se ha propuesto que la ERT podría corresponder a un grupo neurobiológicamente distinto de la enfermedad con una arquitectura genética particular y no solo al extremo del espectro de severidad de la misma. A pesar de ello, actualmente no existe consenso en la literatura en torno a la definición de ERT. En este trabajo presentamos una revisión de diferentes definiciones de ERT centrándonos principalmente en las guías clínicas publicadas. Además se discuten las alternativas terapéuticas en ERT y, finalmente, se proponen perspectivas futuras en torno a la necesidad de desarrollar predictores de respuesta a antipsicóticos de primera y segunda línea, así como también la posibilidad de comprender la neurobiología de la ERT.

Schizophrenia (SZ) is a highly heterogeneous clinical entity. It causes a severe disruption in quality of life, and it imposes a significant burden to society. Antipsychotics are the first line treatment, however up to a 30% of the patients will present resistance to treatment. Treatment resistant schizophrenia (TRS) could be a neurobiologically distinct disorder and not merely an extremely severe form of SZ. However, there is no consensus in the literature as to the definition of TRS. In the present work we review different definitions of TRS, mainly from clinical guidelines. Furthermore, we discuss therapeutic alternatives for TRS and suggest future perspectives regarding the identification of response predictors and understanding the neurobiology of TRS.