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Hickman M.A.,University of Minnesota | Hickman M.A.,Emory University | Paulson C.,University of Minnesota | Dudley A.,Pacific Northwest Diabetes Research Institute | And 2 more authors.
Genetics | Year: 2015

The opportunistic pathogen Candida albicans has a large repertoire of mechanisms to generate genetic and phenotypic diversity despite the lack of meiosis in its life cycle. Its parasexual cycle enables shifts in ploidy, which in turn facilitate recombination, aneuploidy, and homozygosis of whole chromosomes to fuel rapid adaptation. Here we show that the tetraploid state potentiates ploidy variation and drives population heterogeneity. In tetraploids, the rate of losing a single heterozygous marker [loss of heterozygosity (LOH)] is elevated ∼30-fold higher than the rate in diploid cells. Furthermore, isolates recovered after selection for LOH of one, two, or three markers were highly aneuploid, with a broad range of karyotypes including strains with a combination of di-, tri-, and tetrasomic chromosomes. We followed the ploidy trajectories for these tetraploid- and aneuploid-derived isolates, using a combination of flow cytometry and double-digestion restriction-site-associated DNA analyzed with next-generation sequencing. Isolates derived from either tetraploid or aneuploid isolates predominately resolved to a stable euploid state. The majority of isolates reduced to the conventional diploid state; however, stable triploid and tetraploid states were observed in ∼30% of the isolates. Notably, aneuploid isolates were more transient than tetraploid isolates, resolving to a euploid state within a few passages. Furthermore, the likelihood that a particular isolate will resolve to the same ploidy state in replicate evolution experiments is only ∼50%, supporting the idea that the chromosome loss process of the parasexual cycle is random and does not follow trajectories involving specific combinations of chromosomes. Together, our results indicate that tetraploid progenitors can produce populations of progeny cells with a high degree of genomic diversity, from altered ploidy to homozygosis, providing an excellent source of genetic variation upon which selection can act. © 2015 by the Genetics Society of America.

Ortiz D.,University of Washington | Bryan J.,Pacific Northwest Diabetes Research Institute
Frontiers in Endocrinology | Year: 2015

ATP-sensitive K+ (KATP) channels composed of potassium inward-rectifier type 6.2 and sulfonylurea receptor type 1 subunits (Kir6.2/SUR1)4 are expressed in various cells in the brain and endocrine pancreas where they couple metabolic status to membrane potential. In β-cells, increases in cytosolic [ATP/ADP]c inhibit KATP channel activity, leading to membrane depolarization and exocytosis of insulin granules. Mutations in ABCC8 (SUR1) or KCNJ11 (Kir6.2) can result in gain or loss of channel activity and cause neonatal diabetes (ND) or congenital hyperinsulinism (CHI), respectively. SUR1 is reported to be a Mg2+-dependent ATPase. A prevailing model posits that ATP hydrolysis at SUR1 is required to stimulate openings of the pore. However, recent work shows nucleotide binding, without hydrolysis, is sufficient to switch SUR1 to stimulatory conformations. The actions of nucleotides, ATP and ADP, on ND (SUR1E1506D) and CHI (SUR1E1506K) mutants, without Kir6.2, were compared to assess both models. Both substitutions significantly impair hydrolysis in SUR1 homologues. SUR1E1506D has greater affinity for MgATP than wildtype; SUR1E1506K has reduced affinity. Without Mg2+, SUR1E1506K has a greater affinity for ATP4- consistent with electrostatic attraction between ATP4-, unshielded by Mg2+, and the basic lysine. Further analysis of ND and CHI ABCC8 mutants in the second transmembrane and nucleotide binding domains (TMD2 & NBD2), found a relation between their affinities for ATP (± Mg2+) and their clinical phenotype. Increased affinity for ATP is associated with ND; decreased affinity with CHI. In contrast, MgADP showed a weaker relationship. Diazoxide, known to reduce insulin release in some CHI cases, potentiates switching of CHI mutants from non-stimulatory to stimulatory states consistent with diazoxide stabilizing a nucleotide-bound conformation. The results emphasize the greater importance of nucleotide binding vs hydrolysis in the regulation of KATP channels in vivo. © 2015 Bryan and Ortiz.

Nadeau J.H.,Pacific Northwest Diabetes Research Institute
Genome Biology | Year: 2015

Not so fast. The Iqbal et. al. study and the associated Whitelaw commentary highlight the appropriately high standards of study design and interpretation needed to obtain good evidence for or against epigenetic inheritance. Please see related article: www.dx.doi.org/10.1186/s13059-015-0714-1. © 2015 Nadeau.

Vallerie S.N.,Harvard University | Vallerie S.N.,Pacific Northwest Diabetes Research Institute | Hotamisligil G.S.,Harvard University
Science Translational Medicine | Year: 2010

The stress-activated c-Jun amino-terminal kinase (JNK) plays a pivotal role in metabolic conditions such as obesity, insulin resistance, and type 2 diabetes. Intricate tissue-specific tweaking of JNK activity in preclinical models of metabolic diseases reveals a complex interplay among local and systemic effects on carbohydrate and lipid metabolism. Synthesis of these entangled effects illustrates that for JNK inhibitors to have therapeutic impact, they must function in multiple cell types to modulate JNK activity.

News Article | March 28, 2016
Site: www.techtimes.com

Do you find Swiss and Belgian chocolates tastier than your country's own chocolate? If so, you might thank the yeast present in your chocolate for giving that distinctive taste. Diverse yeast population may give the difference in taste of chocolates and coffee that can be seen from different parts of the world, researchers said. The authors sought to know which human activity have influenced the yeasts in the coffee and cacaos fermentation came from. According to the study, wine production differs from the production of chocolate and coffee in a few vital aspects. Initially, the production of wine uses vessels in its fermentation like oak barrels, are exported to new areas where their yeast are native from its origin. As compared to chocolates and coffee, wherein the fermentation style used might have a population of yeast which is different from the area of origin. "Humans have transported and cultivated the plants, but at least for one important species, their associated microbes have arisen from transport and mingling in events that are independent of the transport of the plants themselves," said Aimee Dudley of Pacific Northwest Diabetes Research Institute in Seattle, U.S.A. The researchers fermented the cacao beans' surrounding pulp through a microbe-driven process. The microbe-driven process used lactic acid bacteria and acetic acid bacteria to digest the surrounding pectinaceous pulp of the beans. The process has a vital role in the different characteristics of the beans such as flavor and color. On the other hand, researchers found that the microbiota of coffee beans showed little yeasts in its fermentation. As compared to the natural way of fermenting the coffee through the digestion of its cherry pulp by coffee growers, the researchers attempted to culture live yeasts through unroasted coffee and cacao beans derived from different geographical and ecological niches. Researchers said that the yeast strains seen from the chocolate and coffee making shows greater diversity than those yeast associated in making wines. The findings published in the journal Current Biology, showed that the coffee and cocoa strains have multiple origins and the approach used in it can also isolate other microorganisms. Coffee trees and cacao beans are now commonly grown across the "bean belt" which surrounds the equator but originally cultivated in Ethiopia and Amazon rain forest.

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