Towards the genetic architecture of seed lipid biosynthesis and accumulation in Arabidopsis thaliana

We report the quantitative genetic analysis of seed oil quality and quantity in six Arabidopsis thaliana recombinant inbred populations, in which the parent accessions were from diverse geographical origins, and were selected on the basis of variation for seed oil content and lipid composition. Although most of the biochemical steps involved in lipid biosynthesis are known and the key genes have been identified, the regulation of the processes that results in the final oil composition and total amount is not understood. By using physically anchored markers it was possible to compare results across populations. A total of 219 quantitative trait loci (QTLs) were identified, of which 81 were significant at P<0.001. Some of these colocalise with QTLs identified previously, but many novel QTLs were also identified. The results highlight the importance of studying traits in multiple populations, which will lead to a better understanding of the contribution that natural variation makes to the genetic architecture of a phenotype.     

Metallothionein-1 and nitric oxide expression are inversely correlated in a murine model of Chagas disease

Chagas disease, caused by Trypanosoma cruzi, represents an endemic among Latin America countries. The participation of free radicals, especially nitric oxide (NO), has been demonstrated in the pathophysiology of seropositive individuals with T. cruzi. In Chagas disease, increased NO contributes to the development of cardiomyopathy and megacolon. Metallothioneins (MTs) are efficient free radicals scavengers of NO in vitro and in vivo. Here, we developed a murine model of the chronic phase of Chagas disease using endemic T. cruzi RyCH1 in BALB/c mice, which were divided into four groups: infected non-treated (Inf), infected N-monomethyl-L-arginine treated (Inf L-NAME), non-infected L-NAME treated and non-infected vehicle-treated. We determined blood parasitaemia and NO levels, the extent of parasite nests in tissues and liver MT-I expression levels. It was observed that NO levels were increasing in Inf mice in a time-dependent manner. Inf L-NAME mice had fewer T. cruzi nests in cardiac and skeletal muscle with decreased blood NO levels at day 135 post infection. This affect was negatively correlated with an increase of MT-I expression (r = -0.8462, p < 0.0001). In conclusion, we determined that in Chagas disease, an unknown inhibitory mechanism reduces MT-I expression, allowing augmented NO levels.     

Single-step detection of mutant huntingtin in animal and human tissues: A bioassay for Huntington’s disease

The genetic mutation causing Huntington’s disease is a polyglutamine expansion in the huntingtin protein where more than 37 glutamines cause disease by formation of toxic intracellular fragments, aggregates, and cell death. Despite a clear pathogenic role for mutant huntingtin, understanding huntingtin expression during the presymptomatic phase of the disease or during disease progression has remained obscure. Central to clarifying the role in the pathomechanism of disease is the ability to easily and accurately measure mutant huntingtin in accessible human tissue samples as well as cell and animal models. Here we describe a highly sensitive time-resolved Förster resonance energy transfer (FRET) assay for quantification of soluble mutant huntingtin in brain, plasma, and cerebrospinal fluid. Surprisingly, in mice, soluble huntingtin levels decrease during disease progression, inversely correlating with brain aggregate load. Mutant huntingtin is easily detected in human brain and blood-derived fractions, providing a utility to assess mutant huntingtin expression during disease course as well as a pharmacodynamic marker for disease-modifying therapeutics targeting expression, cleavage, or degradation of mutant huntingtin. The design of the homogeneous one-step method for huntingtin detection is such that it can be easily applied to measure other proteins of interest.     

Multilevel selection and human altruism

Views on the evolution of altruism based upon multilevel selection on structured populations pay little attention to the difference between fortuitous and deliberate processes leading to assortative grouping. Altruism may evolve when assortative grouping is fortuitously produced by forces external to the organism. But when it is deliberately produced by the same proximate mechanism that controls altruistic responses, as in humans, exploitation of altruists by selfish individuals is unlikely and altruism evolves as an individually advantageous trait. Groups formed with altruists of this sort are special, because they are not affected by subversion from within. A synergistic process where altruism is selected both at the individual and at the group level can take place.     

Reconciling emergences: An information-theoretic approach to identify causal emergence in multivariate data

The broad concept of emergence is instrumental in various of the most challenging open scientific questions—yet, few quantitative theories of what constitutes emergent phenomena have been proposed. This article introduces a formal theory of causal emergence in multivariate systems, which studies the relationship between the dynamics of parts of a system and macroscopic features of interest. Our theory provides a quantitative definition of downward causation, and introduces a complementary modality of emergent behaviour—which we refer to as causal decoupling. Moreover, the theory allows practical criteria that can be efficiently calculated in large systems, making our framework applicable in a range of scenarios of practical interest. We illustrate our findings in a number of case studies, including Conway’s Game of Life, Reynolds’ flocking model, and neural activity as measured by electrocorticography.     

The epidemiology of coccidioidomycosis in Mexico

Coccidioidomycosis, also known as San Joaquin Valley Fever, is an endemic mycosis restricted to the American deserts, caused by the ascomycete Coccidioides spp. In 2000 it was estimated that more than 100,000 cases of the disease took place in the United States, and that these numbers have been rising over time. The current impact of this disease in Mexico is unknown, but the available data suggest that an increase of the incidence of this mycosis in California and Arizona might have the same impact in Mexican nearby States. These two USA States both have a bioclimatic pattern similar to the nearby Mexican States endemic for coccidioidomycosis. The main objective of this study was to collect the available information on the historical and epidemiological research done in Mexico to assess the impact of the disease and to evaluate whether the disease have a tendency to increase in the endemic areas and if this grow could represent a problem of public health in Mexico. We have conducted an extensive search on this topic in Health institutions and Academic facilities of California, Arizona and Mexico. After analyzing the scarce Mexican records we found that: 1) the main studies conducted in Mexico are limited to the northern desert areas of the country, mainly in the states of Sonora, Coahuila, Nuevo Leon and the Baja California peninsula; 2) until 1994 an increase of coccidioidomycosis in Mexico was noted; and 3) we found that Mexico shares a similar epidemiological data as that reported in the United States. For instance, the most affected groups in Mexico were children under 5 years-old and adults over 45 years-old. The collective information suggests the need to implement joined organized efforts and multi-institutional collaboration to clarify the current situation of this important endemic disease of North America to administer a viable early detection plan of this mycosis in Mexico.     

Plastid DNA diversity is higher in the island endemic Guadalupe cypress than in the continental Tecate cypress

Background

Callitropsis guadalupensis (Guadalupe cypress) is endemic to Guadalupe Island, Mexico, where it is the dominant species of the only forest. The species has suffered declining numbers following the introduction of goats to the island over 150 years ago. Callitropsis guadalupensis is closely related to Callitropsis forbesii (Tecate cypress), distributed in small isolated populations in mainland Baja California and southern California. The objective of the present study was to compare the genetic diversity of the island endemic to the continental species.

Methodology/Principal Findings

We measured genetic diversity in Callitropsis guadalupensis (n = 54) from Guadalupe Island and in Callitropsis forbesii (n = 100) from five populations in mainland Baja California. The plastid DNA trnS-trnG spacer and the trnL-trnF region were chosen for characterization. Thirty-four haplotypes were observed, of which six were shared between both species. One of these haplotypes was also shared with three other species, Callitropsis lusitanica, Callitropsis montana, and Callitropsis stephensonii. Haplotype diversity (h) and nucleotide diversity (π) were significantly higher for Callitropsis guadalupensis (h = 0.698, π = 0.00071) than for Callitropsis forbesii (h = 0.337, π = 0.00024).

Conclusions/Significance

Callitropsis guadalupensis shows no evidence of a founder effect or of a genetic bottleneck, and can be added to a growing list of insular species with higher genetic diversity than their mainland relatives.     

Facial ontogeny in Neanderthals and modern humans

One hundred and fifty years after the discovery of Neanderthals, it is held that this morphologically and genetically distinct human species does not differ from modern Homo sapiens in its craniofacial ontogenetic trajectory after the early post-natal period. This is striking given the evident morphological differences between these species, since it implies that all of the major differences are established by the early post-natal period and carried into adulthood through identical trajectories, despite the extent to which mechanical and spatial factors are thought to influence craniofacial ontogeny. Here, we present statistical and morphological analyses demonstrating that the spatio-temporal processes responsible for craniofacial ontogenetic transformations differ. The findings emphasize that pre-natal as well as post-natal ontogeny are both important in establishing the cranial morphological differences between adult Neanderthals and modern humans.