Nuclease activities and DNA fragmentation during programmed cell death of megagametophyte cells of white spruce (Picea glauca) seeds

The haploid megagametophyte of white spruce (Picea glauca) seeds undergoes programmed cell death (PCD) during post-germinative seedling growth. Death of the megagametophyte storage parenchyma cells was preceded by reserve mobilization and vacuolation. TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling)-positive nuclei indicated that the first megagametophyte cells to die were those closest to the radicle at the micropylar end of the seed as well as those that comprised the most peripheral and innermost layers at the chalazal end of the seed. The death process was accompanied by nuclear fragmentation and internucleosomal DNA cleavage and the sequential activation of several nucleases. The latter comprised at least two groups: those induced relatively early during post-germinative seedling growth, that had pH optima in the neutral range (33, 31, 17 and 15 kDa), and those induced later that had pH optima in the acidic range (73, 62, 48, 43 and 29 kDa). Activities of all of the nucleases were stimulated by Ca²⁺, Mg²⁺ and Mn²⁺; only the nucleases active at neutral pH were inhibited by Zn²⁺. The temporal pattern of induction of the neutral and acidic nucleases may suggest that the latter function after tonoplast rupture.     

Molecular classification of cancer types from microarray data using the combination of genetic algorithms and support vector machines

Simultaneous multiclass classification of tumor types is essential for future clinical implementations of microarray-based cancer diagnosis. In this study, we have combined genetic algorithms (GAs) and all paired support vector machines (SVMs) for multiclass cancer identification. The predictive features have been selected through iterative SVMs/GAs, and recursive feature elimination post-processing steps, leading to a very compact cancer-related predictive gene set. Leave-one-out cross-validations yielded accuracies of 87.93% for the eight-class and 85.19% for the fourteen-class cancer classifications, outperforming the results derived from previously published methods.     

A novel human hydroxysteroid dehydrogenase like 1 gene (HSDL1) is highly expressed in reproductive tissuesa

We report the cloning and characterization of a novel human hydroxysteroid dehydrogenase like gene (HSDL1) located on human chromosome 16q24.2. The HSDL1 cDNA is 3407 base pair in length, encoding a 309 amino acid polypeptide related to human 17-HSD3. Northern blot reveals that the HSDL1 is highly expressed in testis and ovary. In situ hybridization indicates that the expression of HSDL1 is predominantly increased in the prostate cancer tissue compared with the normal prostate tissue, which suggests that the gene expression is important to the arising of prostate cancer.     

The role of CD154 in organ transplant rejection and acceptance

CD154 plays a critical role in determining the outcome of a transplanted organ. This simple statement is amply supported by experimental evidence demonstrating that anti-CD154 antibodies are potent inhibitors of allograft rejection in many rigorous transplant models. Unfortunately, despite intensive investigation over the past ten years, the precise mechanisms by which antibodies against CD154 exert their anti-rejection effects have remained less obvious. Though originally classified with reference to B-cell function, CD154-CD40 interactions have also been shown to be important in T cell-antigen-presenting cell interactions. Accordingly, CD154 has been classified as a T-cell co-stimulatory molecule. However, mounting data suggest that treatment with anti-CD154 antibodies does not simply block costimulatory signals, but rather that the antibodies appear to induce signalling in receptor-bearing T cells. Other data suggest that anti-CD154 effects may be mediated by endothelial cells and possibly even platelets. In fact, the current literature suggests that CD154 can either stimulate or attenuate an immune response, depending upon the model system under study. CD154 has secured a fundamental place in transplant biology and general immunology that will no doubt be the source of considerable investigation and therapeutic manipulation in the coming decade.     

Polylink: to support two-point linkage analysis in autotetraploids

SUMMARY: Polylink runs under Microsoft Windows (95 or later). It performs various calculations that are useful for investigating two-point linkage analysis for autopolyploids, based on the random chromosome pairing model. These include calculation of offspring phenotypic probabilities as functions of the recombination fraction, calculation of theoretical standard errors for the maximum likelihood estimator of and numerical computation of maximum likelihood estimates. It also includes simulation facilities. AVAILABILITY: Polylink is free and available from Xiangming Xu via email     

SNT-1/FRS2alpha physically interacts with Laloo and mediates mesoderm induction by fibroblast growth factor.

Members of the fibroblast growth factor (FGF) ligand family play a critical role in mesoderm formation in the frog Xenopus laevis. While many components of the signaling cascade triggered by FGF receptor activation have been identified, links between these intracellular factors and the receptor itself have been difficult to establish. We report here the characterization of Xenopus SNT-1 (FRS2alpha), a scaffolding protein previously identified as a mediator of FGF activity in other biological contexts. SNT-1 is widely expressed during early Xenopus development, consistent with a role for this protein in mesoderm formation. Ectopic SNT-1 induces mesoderm in Xenopus ectodermal explants, synergizes with low levels of FGF, and is blocked by inhibition of Ras activity, suggesting that SNT-1 functions to transmit signals from the FGF receptor during mesoderm formation. Furthermore, dominant-inhibitory SNT-1 mutants inhibit mesoderm induction by FGF, suggesting that SNT-1 is required for this process. Expression of dominant-negative SNT-1 in intact embryos blocks mesoderm formation and dramatically disrupts trunk and tail development, indicating a requirement for SNT-1, or a related factor inhibited by the mutant construct, during axis formation in vivo. Finally, we demonstrate that SNT-1 physically associates with the Src-like kinase Laloo, and that SNT-1 activity is required for mesoderm induction by Laloo, suggesting that SNT-1 and Laloo function as components of a signaling complex during mesoderm formation in the vertebrate.     

Activity identification of chimeric anti-caspase-3 mRNA hammerhead ribozyme in vitro and in vivo

To study the expression activity of various vectors containing anti-caspase-3 ribozyme cassettesin vivo, and to further study the role of caspas-3 in the apoptotic pathway, we constructed anti-caspase-3 hammerhead ribozyme embedded into the human snRNA U6, and detected the activity of the ribozymein vitro andin vivo. Meanwhile we compared it with the self-cleaving hammerhead ribozymes that we previously studied, and with the general ribozyme, cloned into RNA polymerase II expression systems. The results showed that the three ribozymes, p1.5RZ107, pRZ107 and pU6RZ107 had the correct structure, and that they could cleave caspase-3 mRNA exactly to produce two fragments: 143nt/553nt. p1.5RZ107 has the highest cleavage efficiencyin vitro, almost 80%. However, the U6 chimeric ribozyme, pU6RZ107, has the highest cleavage activityin vivo, almost to 65%, though it has lower cleavage activityin vitro. The cleavage results demonstrated that the pU6RZ107, the U6 chimeric ribozyme, could more efficiently express and downregulate the level of caspase-3in vivo, and the ribozyme could provide an alternative approach to the research into the mechanism of apoptosis and human gene therapy also.