Treating messenger RNA transcript abundances as quantitative traits and mapping gene expression quantitative trait loci for these traits has been pursued in gene-specific ways. Transcript abundances often serve as a surrogate for classical quantitative traits in that the levels of expression are significantly correlated with the classical traits across members of a segregating population. The correlation structure between transcript abundances and classical traits has been used to identify susceptibility loci for complex diseases such as diabetes and allergic asthma. One study recently completed the first comprehensive dissection of transcriptional regulation in budding yeast, giving a detailed glimpse of a genome-wide survey of the genetics of gene expression. Unlike classical quantitative traits, which often represent gross clinical measurements that may be far removed from the biological processes giving rise to them, the genetic linkages associated with transcript abundance affords a closer look at cellular biochemical processes. Here we describe comprehensive genetic screens of mouse, plant and human transcriptomes by considering gene expression values as quantitative traits. We identify a gene expression pattern strongly associated with obesity in a murine cross, and observe two distinct obesity subtypes. Furthermore, we find that these obesity subtypes are under the control of different loci.

Genetics of gene expression surveyed in maize, mouse and man

Abstract Owing to advances in microanalytical techniques over the last 15 years, there is a growing database on the volatile contents of subduction-related magmas as recorded in melt (glass) inclusions trapped in phenocrysts in volcanic rocks. Basaltic magmas from subduction zones show a wide range of water contents, ranging from as high as 6–8 to 3000 ppm, suggesting that no melt inclusions sample undegassed arc magmas. The Cl and S contents of arc basaltic magmas are greater than midocean ridge basalts, indicating that these volatiles are also recycled from subducted sediment and altered oceanic crust back into the mantle wedge. Comparison of the fluxes of volatiles subducted back into the mantle along subduction zones and returned from the mantle to the surface reservoir (crust, ocean, and atmosphere) via magmatism suggests that there is an approximate balance for structurally bound H2O and Cl. In contrast, ∼50% of subducted C appears to be returned to the deep mantle by subduction, but uncertainties are relatively large. For S, the amount returned to the surface reservoir by subduction zone magmatism is only ∼15–30% of the total amount being subducted. Dacitic and rhyolitic magmas in arcs contain 1–6 wt.% H2O, a range that overlaps considerably with the values for basaltic magmas. Either basaltic parents for these differentiated magmas are relatively H2O-poor, or intermediate to silicic arc magmas form through open-system processes involving variable amounts of crustal melting, mixing with basalt and basaltic differentiates, and fluxing of CO2-rich vapor from mafic magma recharged into silicic magma bodies. Consideration of H2O–CO2 relations and gaseous SO2 emissions for intermediate to silicic arc magmas shows that such magmas are typically vapor-saturated during crystallization in the middle to upper crust. Gas emissions thus reflect migration and accumulation of volatiles within complex open magmatic systems.

Volatiles in subduction zone magmas : concentration and fluxes based on melt inclusion and volcanic gas data

http://www.geo.mtu.edu/EHaz/ConvergentPlatesClass/wallace/Wallace_2005_SOTA.pdf

Volatiles in subduction zone magmas: concentrations and fluxes based on melt inclusion and volcanic gas data

http://www.yskw.ac.cn/UploadFile/HZQ68.pdf

Contribution of syncollisional felsic magmatism to continental crust growth: A case study of the Paleogene Linzizong volcanic Succession in southern Tibet

The dynamic history of the Trans-Mexican Volcanic Belt and the Mexico subduction zone

Igneous petrogenesis of the Trans-Mexican Volcanic Belt

Formation of hybrid arc andesites beneath thick continental crust

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a microanalytical tool especially suitable for providing fast and precise U-Pb geochronological results on zircon grains. A new 193 nm excimer laser adapted to a micromachining workstation, equipped with a newly designed two-volume ablation cell and coupled with a quadrupole ICP-MS, is presented here. The system was tuned routinely to achieve sensitivities in the range of 3000 cps/μg g−1 for 238U (< 2% RSD), with a 34 μm spot size, at 5 Hz and ∼ 8 J cm−2, while ablating the NIST SRM 612 glass reference material. The system was capable of providing fast (< 1.5 minutes each analysis) and precise (generally < 1.5% 1s errors) 206Pb/238U zircon ages. The ages of widely used reference material zircons (Plesovice, 337 Ma; Temora, 416 Ma; R33, 418 Ma; Sri Lanka, 564 Ma; 91500, 1065 Ma) could be precisely matched, with an accuracy on isotopic ratios that ranged from ∼ 2 to ∼ 6%, depending on the homogeneity of the natural reference materials.



La technique de spectrometrie de masse couplee a un plasma inductif et associee a un systeme d'ablation laser (LA-ICP-MS) est un outil micro analytique particulierement adapte pour acquerir rapidement et precisement des donnees geochronologiques U-Pb sur zircons. Un systeme comportant un nouveau laser “excimer 193 nm” adapte a une micro station de travail, equipee d'une cellule d'ablation a deux volumes de conception nouvelle et couplee a une ICP-MS quadripolaire est presente. Le systeme a ete mis au point pour atteindre en routine, lorsque le verre de reference NIST SRM 612 est ablate, des sensibilites de 3000 cps/μg g−1 pour 238U (< 2% RSD), en utilisant un spot de 34 μm de diametre a 5 Hz et ∼ 8 J cm−2. Le systeme a ete capable de fournir rapidement (temps d'analyse < 1.5 minutes) des âges 206Pb/238U precis (generalement ecart type de mesure < 1.5%). Les âges de zircons de reference largement utilises dans la litterature (Plesovice, 337 Ma; Temora, 416 Ma; R33, 418 Ma; Sri Lanka, 564 Ma; 91500, 1065 Ma) ont pu etre retrouves, avec une precision sur les rapports isotopiques variant de ∼ 2 a ∼ 6%, en fonction de l'homogeneite des materiaux de reference naturelle.

U‐Pb Zircon Geochronology with an Integrated LA‐ICP‐MS Microanalytical Workstation: Achievements in Precision and Accuracy

Geochemical studies of Plio-Quaternary volcanic rocks from theValle de Bravo^Zita¤ cuaro volcanic field (VBZ) in central Mexico indicate that slab melting plays a key role in the petrogenesis of theTransMexican Volcanic Belt. Rocks from the VBZ are typical arc-related high-Mg andesites, but two different rock suites with distinct trace element patterns and isotopic compositions erupted concurrently in the area, with a trace element character that is also distinct from that of other Mexican volcanoes. The geochemical differences between the VBZ suites cannot be explained by simple crystal fractionation and/or crustal assimilation of a common primitive magma, but can be reconciled by the participation of different proportions of melts derived from the subducted basalt and sediments interacting with the mantle wedge. Sr/Yand Sr/Pb ratios of theVBZ rocks correlate inversely with Pb and Sr isotopic compositions, indicating that the Sr and Pb budgets are strongly controlled by melt additions from the subducted slab. In contrast, an inverse correlation between Pb(Th)/Nd and Nd/Nd ratios, which extend to lower isotopic values than those for Pacific mid-ocean ridge basalts, indicates the participation of an enriched mantle wedge that is similar to the source of Mexican intraplate basalts. In addition, a systematic decrease in middle and heavy rare earth concentrations and Nb/Ta ratios with increasing SiO2 contents in theVBZ rocks is best explained if these elements are mobilized to some extent in the subduction flux, and suggests that slab partial fusion occurred under garnet amphibolite-facies conditions.

/pdf/geochemical-evidence-for-slab-melting-in-the-trans-mexican-4bnvuzdgj9.pdf

Arturo Gómez-Tuena

Papers

Igneous petrogenesis of the Trans-Mexican Volcanic Belt

Formation of hybrid arc andesites beneath thick continental crust

U‐Pb Zircon Geochronology with an Integrated LA‐ICP‐MS Microanalytical Workstation: Achievements in Precision and Accuracy

Geochemical Evidence for Slab Melting in the Trans-Mexican Volcanic Belt

Effects of prolonged flat subduction on the Miocene magmatic record of the central Trans-Mexican Volcanic Belt