BPAG1n4 is essential for retrograde axonal transport in sensory neurons

Disruption of the BPAG1 (bullous pemphigoid antigen 1) gene results in progressive deterioration in motor function and devastating sensory neurodegeneration in the null mice. We have previously demonstrated that BPAG1n1 and BPAG1n3 play important roles in organizing cytoskeletal networks in vivo. Here, we characterize functions of a novel BPAG1 neuronal isoform, BPAG1n4. Results obtained from yeast two-hybrid screening, blot overlay binding assays, and coimmunoprecipitations demonstrate that BPAG1n4 interacts directly with dynactin p150Glued through its unique ezrin/radixin/moesin domain. Studies using double immunofluorescent microscopy and ultrastructural analysis reveal physiological colocalization of BPAG1n4 with dynactin/dynein. Disruption of the interaction between BPAG1n4 and dynactin results in severe defects in retrograde axonal transport. We conclude that BPAG1n4 plays an essential role in retrograde axonal transport in sensory neurons. These findings might advance our understanding of pathogenesis of axonal degeneration and neuronal death.     

A nonparametric bootstrap method for testing close linkage vs. pleiotropy of coincident quantitative trait loci.

A novel method using the nonparametric bootstrap is proposed for testing whether a quantitative trait locus (QTL) at one chromosomal position could explain effects on two separate traits. If the single-QTL hypothesis is accepted, pleiotropy could explain the effect on two traits. If it is rejected, then the effects on two traits are due to linked QTLs. The method can be used in conjunction with several QTL mapping methods as long as they provide a straightforward estimate of the number of QTLs detectable from the data set. A selection step was introduced in the bootstrap procedure to reduce the conservativeness of the test of close linkage vs. pleiotropy, so that the erroneous rejection of the null hypothesis of pleiotropy only happens at a frequency equal to the nominal type I error risk specified by the user. The approach was assessed using computer simulations and proved to be relatively unbiased and robust over the range of genetic situations tested. An example of its application on a real data set from a saline stress experiment performed on a recombinant population of wheat (Triticum aestivum L. ) doubled haploid lines is also provided.     

Generation time: a reliable metric to measure life-history variation among mammalian populations

Oli and Dobson proposed that the ratio between the magnitude and the onset of reproduction (F/ alpha ratio) allows one to predict the relative importance of vital rates on population growth rate in mammalian populations and provides a reliable measure of the ranking of mammalian species on the slow-fast continuum of life-history tactics. We show that the choice of the ratio F/ alpha is arbitrary and is not grounded in demographic theory. We estimate the position on the slow-fast continuum using the first axis of a principal components analysis of all life-history variables studied by Oli and Dobson and show that most individual vital rates perform as well as the F/ alpha ratio. Finally, we find, in agreement with previous studies, that the age of first reproduction is a reliable predictor of the ranking of mammalian populations along the slow-fast continuum and that both body mass and phylogeny markedly influence the generation time of mammalian species. We conclude that arbitrary ratios such as F/ alpha correlate with life-history types in mammals simply because life-history variables are highly correlated in response to allometric, phylogenetic, and environmental influences. We suggest that generation time is a reliable metric to measure life-history variation among mammalian populations and should be preferred to any arbitrary combination between vital rates.     

Synthesis of 3'-O2-(azaheterocycle)-thymidines

The synthesis of 3'-O2-(azaheterocycle)-thymidines is presented from 1-thia-3-aza- 1,3-butadiene precursors (N-thioacylamidines). A variety of heterocycles is accessible using the dienic, the electrophilic or the nucleophilic reactivity of these thia-azabutadiene systems. 3'-O2-(azaheterocycle)-thymidine analogues are regarded as potential substrates to interfere with the DNA-polymerization process.     

Stereoselectivity of the demethylation of nicotine piperidine homologues by Nicotiana plumbaginifolia cell suspension cultures

The metabolism of (R,S)-N-methylanabasine and (R,S)-N-methylanatabine has been studied in a cell suspension culture of Nicotiana plumbaginifolia. Both substrates are effectively demethylated, anabasine or anatabine, respectively, accumulating in the medium. Similarly, there is strong stereoselectivity for the (R)-isomers of both substrates. The kinetics of metabolism of (R,S)-N-methylanabasine differ significantly from those of nicotine in that no further degradation of the initial demethylation product occurs. (R,S)-N-Methylanatabine, however, shows kinetics closer to those of nicotine, with loss of alkaloid from the system. Further more, (R,S)-N-methylanabasine does not diminish (S)-nicotine demethylation, indicating a lack of competition. However, the metabolism of (S)-nicotine is affected by the presence of (R,S)-N-methylanabasine. Hence, the demethylation of the piperidine homologues of nicotine is seen to be similar but not identical to that of the pyridine analogues. The implications of these different metabolic profiles in relation to the demethylation activity are discussed.     

Simultaneous monitoring of two fungal genotypes on plant roots by single nucleotide polymorphism quantification with an innovative KASPar quantitative PCR

An innovative quantitative PCR-based method derived from the Kompetitive Allele Specific PCR Assay Reagent (KASPar) system was developed to quantify the genomic DNA from two coexisting genotypes on the same tissues of a host-plant. For this purpose, the classical end-point KASPar method was evolved to a real-time method thanks to the addition of an adapted measurement step after each PCR cycle. It was applied to the quantification of the two genotypes G1 and G2 of the Gaeumannomyces graminis var. tritici (Ggt) soilborne fungus, pathogenic on wheat roots. Specific primers targeting a single nucleotide polymorphism from the ITS sequence were used allowing simultaneous quantification of both genotypes in the same reaction. The assays were applied to quantify fungal DNA of each genotype, aside or mixed together, after DNA extraction from fungal pure cultures and from single or co-inoculated roots in artificial medium or in soil. The detection and quantification lower limits for the two genotypes were 1.25 pg and 5 pg for DNA from fungal pure cultures, and 1.8 pg and 7 pg for DNA from fungal inoculated roots. The advantages of this cost-effective method are the high levels of specificity, sensitivity and reproducibility. Moreover, the accuracy of the method is independent of the copy numbers of the target sequences. The method is the first one to adapt the non-quantitative genotyping KASPar system to a quantitative application of two known genotypes of a species simultaneously and is suitable for simultaneous genotype-specific quantification of any other organisms (fungi, bacteria, plants).