Genomic diversity and demographic history of the Dromiciops genus (Marsupialia: Microbiotheriidae).

Three orders represent the South American fauna of marsupials. Of these, Microbiotheria was until recently known as a monotypic genus with the only surviving species Dromiciops gliroides (monito del monte). The recent proposal of a new Dromiciops species (Dromiciops bozinovici), together with new information on the origin and diversification of living microbioterians has changed the prevailing paradigm around the evolutionary history of these emblematic marsupials. Here, we used a RADseq approach to test for evidence of admixture and past or current gene flow among both species of Dromiciops and evaluate the genetic structure within D. gliroides. We analyzed 127 samples of Dromiciops distributed across the known distribution range of both species. We also inferred the joint demographic history of these lineages, thus corroborating the status of D. bozinovici as a distinct species. Demographic history reconstruction indicated that D. bozinovici diverged from D. gliroides around 4my ago and has remained isolated and demographically stable ever since. In contrast, D. gliroides is subdivided into three subclades that experienced recent expansions and moderate gene flow among them (mostly from north to south). Furthermore, genetic distances among populations within D. gliroides were significantly correlated with geographic distances. These results suggest that some of the D. gliroides populations would have survived in glacial refuges, with posterior expansions after ice retreat. Our results have important implications for the systematics of the genus and have profound conservation consequences for the new species, especially considering the fragmentation level of the temperate rainforest.

The biogeography of Dromiciops in southern South America: Middle Miocene transgressions, speciation and associations with Nothofagus.

The current distribution of the flora and fauna of southern South America is the result of drastic geological events that occurred during the last 20 million years, including marine transgressions, glaciations and active vulcanism. All these have been associated with fragmentation, isolation and subsequent expansion of the biota, south of 35°S, such as the temperate rainforest. This forest is mostly dominated by Nothofagus trees and is the habitat of the relict marsupial monito del monte, genus Dromiciops, sole survivor of the order Microbiotheria. Preliminary analyses using mtDNA proposed the existence of three main Dromiciops lineages, distributed latitudinally, whose divergence was initially attributed to recent Pleistocene glaciations. Using fossil-calibrated dating on nuclear and mitochondrial genes, here we reevaluate this hypothesis and report an older (Miocene) biogeographic history for the genus. We performed phylogenetic reconstructions using sequences from two mitochondrial DNA and four nuclear DNA genes in 159 specimens from 31 sites across Chile and Argentina. Our phylogenetic analysis resolved three main clades with discrete geographic distributions. The oldest and most differentiated clade corresponds to that of the northern distribution (35.2°S to 39.3°S), which should be considered a distinct species (D. bozinovici, sensu D'Elía et al. 2016). According to our estimations, this species shared a common ancestor with D. gliroides (southern clades) about ~13 million years ago. Divergence time estimates for the southern clades (39.6°S to 42.0°S) ranged from 9.57 to 6.5 Mya. A strong genetic structure was also detected within and between clades. Demographic analyses suggest population size stability for the northern clade (D. bozinovici), and recent demographic expansions for the central and southern clades. All together, our results suggest that the diversification of Dromiciops were initiated by the Middle Miocene transgression (MMT), the massive marine flooding that covered several lowlands of the western face of Los Andes between 37 and 48°S. The MMT resulted from an increase in global sea levels at the Miocene climatic optimum, which shaped the biogeographic origin of several species, including Nothofagus forests, the habitat of Dromiciops.

Evaluation of clopidogrel response variability and identification of the CYP2C19 polymorphism in Mexican patients / Evaluación de la variabilidad en la respuesta a clopidogrel e identificación del polimorfismo CYP2C19 en pacientes mexicanos

Abstract Objective Drug inhibition of platelet P2Y12 adenosine diphosphate receptor has reduced the incidence of adverse cardiovascular events after percutaneous coronary interventions. The analysis of the phosphorylation status of vasodilator-stimulated phosphoprotein by flow cytometry has shown a predictive value for adverse events and stent thrombosis. Polymorphisms of CYP2C19 in high risk patients may also relate to adverse cardiovascular events. Methods Ninety patients were enrolled. Patients received a 600 mg clopidogrel loading dose. Blood samples were obtained at the time of the procedure and 24 h later, platelet reactivity was assessed by vasodilator-stimulated phosphoprotein phosphorylation measurement using flow cytometry. Low response to clopidogrel was defined as a platelet reactivity index ≥ 50%. The presence of CYP2C19*2 was identified with the restriction enzyme Smal. Results Mean platelet reactivity index: 53.45 ± 22.48% in the baseline sample and 57.14 ± 23.08% at 24 h (p = 0.183); 40% of patients behaved as good responders, the rest behaved as non-responders with 38% of patients showing platelet reactivity indexes between 50-70% and 22% showing indexes above 70%. The CYP2C19*2 polymorphism was found in 17% of patients, with a 3.9% AA homozygous genotype carriers. Conclusion Response to the clopidogrel loading dose showed a wide variability among patients with 40% responding to the drug according to previously established cut-off values. Our results showed that 3.9% of patients show the AA genotype. To our knowledge, this is the first study involving clopidogrel response by flow citometry and genotype typification in Mexican Mestizo population.

Resumen Objetivo La inhibición del receptor plaquetario P2Y12 se ha asociado con reducción en incidencia de eventos cardiovasculares mayores en pacientes sometidos a intervenciones coronarias percutáneas. El estudio de la fosfoproteína estimulada por vasodilatadores mediante citometría de flujo tiene valor predictivo para desarrollo de eventos adversos y trombosis del stent. Los polimorfismos del CYP2C19 en pacientes de alto riesgo pueden también asociarse con eventos adversos. Método 90 pacientes, dosis de carga de clopidogrel: 600 mg. Se obtuvieron muestras de sangre basales y post-24 horas. La reactividad plaquetaria se estudió mediante medición de fosfoproteína estimulada por vasodiatadores por citometría de flujo. Se consideró baja respuesta al clopidogrel un índice de reactividad plaquetaria ≥50%. La presencia del CYP2C19*2 se identificó con enzima de restricción Smal. Resultados La media del índice de reactividad plaquetaria fue: 53.45 ± 22.48% en muestras basales y 57.14 ± 23.08% a 24 h (p = 0.183); 40% de los pacientes repondieron a clopidogrel, el resto de comportó como no-respondedores, un 38%, mostró índices de reactividad plaquetaria entre 50 -70% y 22%, índices > 70%. El polimorfismo CYP2C19*2 se encontró en 17% pacientes, con un 3.9% portadores de genotipo homozigótico AA. Conclusiones La respuesta a clopidogrel mostró amplia variabilidad entre pacientes, el 40% presentó respuesta de acuerdo con puntos de corte pre establecidos. Un 3.9% de los pacientes presentó genotipo AA. Consideramos que este es el primer estudio realizado en población mestizo-mexicana utilizado citometría de flujo para evaluar la respuesta a clopidogrel así como la tipificación genética de los pacientes.

Evaluation of clopidogrel response variability and identification of the CYP2C19 polymorphism in Mexican patients.

OBJECTIVE: Drug inhibition of platelet P2Y12 adenosine diphosphate receptor has reduced the incidence of adverse cardiovascular events after percutaneous coronary interventions. The analysis of the phosphorylation status of vasodilator-stimulated phosphoprotein by flow cytometry has shown a predictive value for adverse events and stent thrombosis. Polymorphisms of CYP2C19 in high risk patients may also relate to adverse cardiovascular events. METHODS: Ninety patients were enrolled. Patients received a 600mg clopidogrel loading dose. Blood samples were obtained at the time of the procedure and 24h later, platelet reactivity was assessed by vasodilator-stimulated phosphoprotein phosphorylation measurement using flow cytometry. Low response to clopidogrel was defined as a platelet reactivity index≥50%. The presence of CYP2C19*2 was identified with the restriction enzyme SmaI. RESULTS: Mean platelet reactivity index: 53.45±22.48% in the baseline sample and 57.14±23.08% at 24h (p=0.183); 40% of patients behaved as good responders, the rest behaved as non-responders with 38% of patients showing platelet reactivity indexes between 50-70% and 22% showing indexes above 70%. The CYP2C19*2 polymorphism was found in 17% of patients, with a 3.9% AA homozygous genotype carriers. CONCLUSION: Response to the clopidogrel loading dose showed a wide variability among patients with 40% responding to the drug according to previously established cut-off values. Our results showed that 3.9% of patients show the AA genotype. To our knowledge, this is the first study involving clopidogrel response by flow citometry and genotype typification in Mexican Mestizo population.