Genetic mapping of size-related quantitative trait loci (QTL) in the bay scallop (Argopecten irradians) using AFLP and microsatellite markers

We constructed genetic linkage maps for the bay scallop Argopecten irradians using AFLP and microsatellite markers and conducted composite interval mapping (CIM) of body-size-related traits. Three hundred seventeen AFLP and 10 microsatellite markers were used for map construction. The female parent map contained 120 markers in 15 linkage groups, spanning 479.6 cM with an average interval of 7.0 cM. The male parent map had 190 markers in 17 linkage groups, covering 883.8 cM at 7.2 cM per marker. The observed coverage was 70.4% for the female and 81.1% for the male map. Markers that were distorted toward the same direction were closely linked to each other on the genetic maps, suggesting the presence of genes important for survival. Six size-related traits, shell length, shell height, shell width, total weight, soft tissue weight, and shell weight, were measured for QTL mapping. The size data were significantly correlated with each other. We subjected the data, log transformed firstly, to a principle component analysis and use the first principle component for QTL mapping. CIM analysis revealed one significant QTL (LOD=2.69, 1000 permutation, P<0.05) in linkage group 3 on the female parent map. The mapping of size-related QTL in this study raises the possibility of improving the growth of bay scallops through marker-assisted selection. (c) 2007 Published by Elsevier B.V.

Identification and mapping of amplified fragment length polymorphism markers linked to shell color in bay scallop, Argopecten irradians irradians (Lamarck, 1819)

Amplified fragment length polymorphisms (AFLP) were used to study the inheritance of shell color in Argopecten irradians. Two scallops, one with orange and the other with white shells, were used as parents to produce four F-1 families by selfing and outcrossing. Eighty-eight progeny, 37 orange and 51 white, were randomly selected from one of the families for segregation and mapping analysis with AFLP and microsatellite markers. Twenty-five AFLP primer pairs were screened, yielding 1138 fragments, among which 148 (13.0%) were polymorphic in two parents and segregated in progeny. Six AFLP markers showed significant (P < 0.05) association with shell color. All six loci were mapped to one linkage group. One of the markers, F1f335, is completely linked to the gene for orange shell, which we designated as Orange1, without any recombination in the progeny we sampled. The marker was amplified in the orange parent and all orange progeny, but absent in the white parent and all the white progeny. The close linkage between F1f335 and Orange1 was validated using bulk segregation analysis in two natural populations, and all our data indicate that F1f335 is specific for the shell color gene, Orange1. The genomic mapping of a shell color gene in bay scallop improves our understanding of shell color inheritance and may contribute to the breeding of molluscs with desired shell colors.

Genetic variation and phylogeographic history of Picea likiangensis revealed by RAPD markers

Repeated cycles of retreat and recolonization during the Quaternary ice ages are thought to have greatly influenced current species distributions and their genetic diversity. It remains unclear how this climatic oscillation has affected the distribution of genetic diversity between populations of wind-pollinated conifers in the Qinghai-Tibetan region. In this study, we investigated the within-species genetic diversity and phylogenetic relationships of Picea likiangensis, a dominant forest species in this region using polymorphic DNA (RAPD) markers. Our results suggest that this species has high overall genetic diversity, with 85.42% of loci being polymorphic and an average expected heterozygosity (H (E)) of 0.239. However, there were relatively low levels of polymorphism at population levels and the differences between populations were not significant, with percentages of polymorphic bands (PPB) ranging from 46.88 to 69.76%, Nei's gene diversity (H (E)) from 0.179 to 0.289 and Shannon's indices (Hpop) from 0.267 to 0.421. In accordance with our proposed hypothesis, a high level of genetic differentiation among populations was detected based on Nei's genetic diversity (G (ST) = 0.256) and AMOVA analysis (Phi (st) = 0.236). Gene flow between populations was found to be limited (Nm = 1.4532) and far lower than reported for other conifer species with wide distribution ranges from other regions. No clusters corresponding to three morphological varieties found in the south, north and west, respectively, were detected in either UPGMA or PCO analyses. Our results suggest that this species may have had different refugia during the glacial stages in the southern region and that the northern variety may have multiple origins from these different refugia.

Genetic variation within and among populations of Rhodiola alsia (Crassulaceae) native to the Tibetan Plateau as detected by ISSR markers

Genetic variation of 10 Rhodiola alsia ( Crassulaceae) populations from the Qinghai - Tibet Plateau of China was investigated using intersimple sequence repeat (ISSR) markers. R. alsia is an endemic species of the Qinghai - Tibet Plateau. Of the 100 primers screened, 13 were highly polymorphic. Using these primers, 140 discernible DNA fragments were generated with 112 (80%) being polymorphic, indicating pronounced genetic variation at the species level. Also there were high levels of polymorphism at the population level with the percentage of polymorphic bands (PPB) ranging from 63.4 to 88.6%. Analysis of molecular variance (AMOVA) showed that the genetic variation was mainly found among populations (70.3%) and variance within populations was 29.7%. The main factors responsible for the high level of differentiation among populations are probably the isolation from other populations and clonal propagation of this species. Occasional sexual reproduction might occur in order to maintain high levels of variation within populations. Environmental conditions could also influence population genetic structure as they occur in severe habitats. The strong genetic differentiation among populations in our study indicates that the conservation of genetic variability in R. alsia requires maintenance of as many populations as possible.

Endothelial microparticles released in thrombotic thrombocytopenic purpura express von Willebrand factor and markers of endothelial activation

It has been suggested that endothelial apoptosis is a primary lesion in the pathogenesis of thrombotic thrombocytopenic purpura (TTP). We tested this hypothesis by examining the phenotypic signatures of endothelial microparticles (EMP) in TTP patients. In addition, the effect of TTP plasma on microvascular endothelial cells (MVEC) in culture was further delineated. EMP released by endothelial cells (EC) express markers of the parent EC; EMP released in activation carry predominantly CD54 and CD62E, while those in apoptosis CD31 and CD105. We investigated EMP release in vitro and in TTP patients. Following incubation of MVEC with TTP plasma, EMP and EC were analysed by flow cytometry for the expression of CD31, CD51, CD54, CD62E, CD105, CD106 and von Willebrand factor (VWF) antigen. EMP were also analysed in 12 TTP patients. In both EC and EMP, CD62E and CD54 expression were increased 3- to 10-fold and 8- to 10-fold respectively. However, CD31 and CD105 were reduced 40-60% in EC but increased twofold in EMP. VWF expression was found in 55 +/- 15% of CD62E(+) EMP. Markers of apoptosis were negative. In TTP patients, CD62E(+) and CD31(+)/CD42b(-) EMP were markedly elevated, and preceded and correlated well with a rise in platelet counts and a fall in lactate dehydrogenase. CD62E(+) EMP (60 +/- 20%) co-expressed VWF and CD62E. The ratio of CD31(+)/42b(-) to CD62E(+) EMP exhibited a pattern consistent with activation. In conclusion, our studies indicate endothelial activation in TTP. EMP that co-express VWF and CD62E could play a role in the pathogenesis of TTP.

Urinary nucleosides as biological markers for patients with colorectal cancer

AIM: Fourteen urinary nucleosides, primary degradation products of tRNA, were evaluated to know the potential as biological markers for patients with colorectal cancer.