Self-awareness in Transient Global Amnesia: distinguishing the effects of transient memory disorder vs. pre-existing vulnerability factors.

Numerous evidences suggest the existence of relationships between the impairment of episodic memory, acute stress exposure and variations in self-awareness (SA). Here, we examined 27 patients presenting transient global amnesia (TGA), a clinical condition which combines episodic amnesia and high anxiety, thanks to state and trait questionnaires of SA. We observed variation of SA depending on the stage of TGA (acute, recovery and follow-up). We also found preexisting differences in patient's awareness of their own image when the precipitating event was physical, encouraging us to give more consideration to the social determinants of stress in physiological cascade of TGA.

Patterns of genetic variation within and between Gibbon species.

Gibbons are small, arboreal, highly endangered apes that are understudied compared with other hominoids. At present, there are four recognized genera and approximately 17 species, all likely to have diverged from each other within the last 5-6 My. Although the gibbon phylogeny has been investigated using various approaches (i.e., vocalization, morphology, mitochondrial DNA, karyotype, etc.), the precise taxonomic relationships are still highly debated. Here, we present the first survey of nuclear sequence variation within and between gibbon species with the goal of estimating basic population genetic parameters. We gathered ~60 kb of sequence data from a panel of 19 gibbons representing nine species and all four genera. We observe high levels of nucleotide diversity within species, indicative of large historical population sizes. In addition, we find low levels of genetic differentiation between species within a genus comparable to what has been estimated for human populations. This is likely due to ongoing or episodic gene flow between species, and we estimate a migration rate between Nomascus leucogenys and N. gabriellae of roughly one migrant every two generations. Together, our findings suggest that gibbons have had a complex demographic history involving hybridization or mixing between diverged populations.

Episodic Autobiographical Memory Impairment and Differences in Pronoun Use: Study of Self-Awareness in Functional Amnesia and Transient Global Amnesia.

The subjective experience associated to memory processing is the core of the definition of episodic autobiographical memory (EAM). However, while it is widely known that amnesia affects the content of memories, few studies focused on the consequences of an impairment of EAM on the subjective self, also called the I-self. In the present study, we explored the I-self in two puzzling disorders that affect EAM: functional amnesia, which has an impact on autobiographical memory, and transient global amnesia (TGA), which only affects episodic memory. I-self was assessed through an original measure of self-integration in autobiographical narratives, namely the use of general or personal pronouns. Results showed that patients with functional amnesia tended to use general pronouns, whereas patients with TGA preferentially used the first person. The link between I-self and depersonalization-derealisation tendencies was also explored, showing dissociative tendencies in patients with functional amnesia but not in patients with TGA. We discuss these results from a combined neuropsychological and psychopathological perspective, with a view to proposing an explanatory model of the links between self-awareness and the episodic component of autobiographical memory.

Genetic structure of chimpanzee populations.

Little is known about the history and population structure of our closest living relatives, the chimpanzees, in part because of an extremely poor fossil record. To address this, we report the largest genetic study of the chimpanzees to date, examining 310 microsatellites in 84 common chimpanzees and bonobos. We infer three common chimpanzee populations, which correspond to the previously defined labels of "western," "central," and "eastern," and find little evidence of gene flow between them. There is tentative evidence for structure within western chimpanzees, but we do not detect distinct additional populations. The data also provide historical insights, demonstrating that the western chimpanzee population diverged first, and that the eastern and central populations are more closely related in time.

Learning about modes of speciation by computational approaches.

How often do the early stages of speciation occur in the presence of gene flow? To address this enduring question, a number of recent papers have used computational approaches, estimating parameters of simple divergence models from multilocus polymorphism data collected in closely related species. Applications to a variety of species have yielded extensive evidence for migration, with the results interpreted as supporting the widespread occurrence of parapatric speciation. Here, we conduct a simulation study to assess the reliability of such inferences, using a program that we recently developed MCMC estimation of the isolation-migration model allowing for recombination (MIMAR) as well as the program isolation-migration (IM) of Hey and Nielsen (2004). We find that when one of many assumptions of the isolation-migration model is violated, the methods tend to yield biased estimates of the parameters, potentially lending spurious support for allopatric or parapatric divergence. More generally, our results highlight the difficulty in drawing inferences about modes of speciation from the existing computational approaches alone.

Complete resequencing of 40 genomes reveals domestication events and genes in silkworm (Bombyx).

A single-base pair resolution silkworm genetic variation map was constructed from 40 domesticated and wild silkworms, each sequenced to approximately threefold coverage, representing 99.88% of the genome. We identified ~16 million single-nucleotide polymorphisms, many indels, and structural variations. We find that the domesticated silkworms are clearly genetically differentiated from the wild ones, but they have maintained large levels of genetic variability, suggesting a short domestication event involving a large number of individuals. We also identified signals of selection at 354 candidate genes that may have been important during domestication, some of which have enriched expression in the silk gland, midgut, and testis. These data add to our understanding of the domestication processes and may have applications in devising pest control strategies and advancing the use of silkworms as efficient bioreactors.

A new approach to estimate parameters of speciation models with application to apes.

How populations diverge and give rise to distinct species remains a fundamental question in evolutionary biology, with important implications for a wide range of fields, from conservation genetics to human evolution. A promising approach is to estimate parameters of simple speciation models using polymorphism data from multiple loci. Existing methods, however, make a number of assumptions that severely limit their applicability, notably, no gene flow after the populations split and no intralocus recombination. To overcome these limitations, we developed a new Markov chain Monte Carlo method to estimate parameters of an isolation-migration model. The approach uses summaries of polymorphism data at multiple loci surveyed in a pair of diverging populations or closely related species and, importantly, allows for intralocus recombination. To illustrate its potential, we applied it to extensive polymorphism data from populations and species of apes, whose demographic histories are largely unknown. The isolation-migration model appears to provide a reasonable fit to the data. It suggests that the two chimpanzee species became reproductively isolated in allopatry approximately 850 Kya, while Western and Central chimpanzee populations split approximately 440 Kya but continued to exchange migrants. Similarly, Eastern and Western gorillas and Sumatran and Bornean orangutans appear to have experienced gene flow since their splits approximately 90 and over 250 Kya, respectively.

Sodium channel beta4 subunit: down-regulation and possible involvement in neuritic degeneration in Huntington's disease transgenic mice.

Sodium channel beta4 is a very recently identified auxiliary subunit of the voltage-gated sodium channels. To find the primarily affected gene in Huntington's disease (HD) pathogenesis, we profiled HD transgenic mice using a high-density oligonucleotide array and identified beta4 as an expressed sequence tag (EST) that was significantly down-regulated in the striatum of HD model mice and patients. Reduction in beta4 started at a presymptomatic stage in HD mice, whereas other voltage-gated ion channel subunits were decreased later. In contrast, spinal cord neurons, which generate only negligible levels of expanded polyglutamine aggregates, maintained normal levels of beta4 expression even at the symptomatic stage. Overexpression of beta4 induced neurite outgrowth in Neuro2a cells, and caused a thickening of dendrites and increased density of dendritic spines in hippocampal primary neurons, indicating that beta4 modulates neurite outgrowth activities. These results suggest that down-regulation of beta4 may lead to abnormalities of sodium channel and neurite degeneration in the striatum of HD transgenic mice and patients with HD.

Strong-association-rule mining for large-scale gene-expression data analysis: a case study on human SAGE data.

BACKGROUND: The association-rules discovery (ARD) technique has yet to be applied to gene-expression data analysis. Even in the absence of previous biological knowledge, it should identify sets of genes whose expression is correlated. The first association-rule miners appeared six years ago and proved efficient at dealing with sparse and weakly correlated data. A huge international research effort has led to new algorithms for tackling difficult contexts and these are particularly suited to analysis of large gene-expression matrices. To validate the ARD technique we have applied it to freely available human serial analysis of gene expression (SAGE) data. RESULTS: The approach described here enables us to designate sets of strong association rules. We normalized the SAGE data before applying our association rule miner. Depending on the discretization algorithm used, different properties of the data were highlighted. Both common and specific interpretations could be made from the extracted rules. In each and every case the extracted collections of rules indicated that a very strong co-regulation of mRNA encoding ribosomal proteins occurs in the dataset. Several rules associating proteins involved in signal transduction were obtained and analyzed, some pointing to yet-unexplored directions. Furthermore, by examining a subset of these rules, we were able both to reassign a wrongly labeled tag, and to propose a function for an expressed sequence tag encoding a protein of unknown function. CONCLUSIONS: We show that ARD is a promising technique that turns out to be complementary to existing gene-expression clustering techniques.