Cytogenetic and molecular characterization of eight new reciprocal translocations in the pig species. Estimation of their incidence in French populations

Eight new cases of reciprocal translocation in the domestic pig are described. All the rearrangements were highlighted using GTG banding techniques. Chromosome painting experiments were also carried out to confirm the proposed hypotheses and to accurately locate the breakpoints. Three translocations, rcp(4;6)(q21;p14), rcp(2;6)(p17;q27) and rcp(5;17)(p12;q13) were found in boars siring small litters (8.3 and 7.4 piglets born alive per litter, on average, for translocations 2/6 and 5/17, respectively). The remaining five, rcp(5;8)(p12;q21), rcp(15;17)(q24;q21), rcp(7;8)(q24;p21), rcp(5;8)(p11;p23) and rcp(3;15)(q27;q13) were identified in young boars controlled before entering reproduction. A decrease in prolificacy of 22% was estimated for the 3/15 translocation after reproduction of the boar carrier. A parental origin by inheritance of the translocation was established for the (5;8)(p11;p23) translocation. The overall incidence of reciprocal translocations in the French pig populations over the 2000/2001 period was estimated (0.34%).     

在中国应用垂直波束雷达监测褐飞虱和其他水稻害虫迁飞的可行性

近年来,可用于昆虫迁飞研究且可自动运行的垂直波束雷达(vertical-looking radar,VLR)的发展使得对迁飞性害虫的周年长期自动监测成为可能。本文提供了我们对能否将这种雷达应用于中国的褐飞虱和其他水稻害虫的监测与预测体系以改善其综合治理的可行性研究结果。以往的研究已经表明,这些害虫一般在300—2000m高度迁飞;而我们根据褐飞虱的雷达和射有效截面的计算结果表明,目前使用的3．2cm波长的VLR对褐飞虱个体目标的最大可检测高度仅约240m;虽然建造一部8．8mm波长的VLR即可覆盖褐飞虱迁飞高度的绝大部分,但其造价和维护费用均过于昂贵。为此,一个更可行的解决方案是,以3．2cm波长的VLR作为包括大多数水稻害虫在内的个体较大的迁飞性害虫的监测工具。     

Regulation of embryonic and induced pluripotency by aurora kinase-p53 signaling

Many signals must be integrated to maintain self-renewal and pluripotency in embryonic stem cells (ESCs) and to enable induced pluripotent stem cell (iPSC) reprogramming. However, the exact molecular regulatory mechanisms remain elusive. To unravel the essential internal and external signals required for sustaining the ESC state, we conducted a short hairpin (sh) RNA screen of 104 ESC-associated phosphoregulators. Depletion of one such molecule, aurora kinase A?(Aurka), resulted in compromised self-renewal and consequent differentiation. By integrating global gene expression and computational analyses, we discovered that loss of Aurka leads to upregulated p53 activity?that triggers ESC differentiation. Specifically, Aurka regulates pluripotency through phosphorylation-mediated inhibition of p53-directed ectodermal and mesodermal gene expression. Phosphorylation of p53 not only impairs p53-induced ESC differentiation but also p53-mediated suppression of iPSC reprogramming. Our studies demonstrate an essential role for Aurka-p53 signaling in the regulation of self-renewal, differentiation, and somatic cell reprogramming.     

Characterization of ribonuclease P from the archaebacterium Sulfolobus solfataricus

Ribonuclease P is the endonuclease that removes the leader fragments from the 5'-ends of precursor tRNAs. The enzyme isolated from eubacteria contains a catalytic RNA subunit. RNAs also copurify with eukaryotic RNase P, although catalysis by those RNAs has not been demonstrated. This paper reports the isolation and characterization of ribonuclease P from the thermoacidophilic archaebacterium Sulfolobus solfataricus. Archaebacteria are a primary evolutionary lineage, distinct from both eukaryotes and eubacteria. Ribonuclease P of S. solfataricus has reaction component requirements and a Km for substrate tRNA (2.5 X 10(-7) M) that are roughly similar to those reported for eubacterial and eukaryotic ribonuclease P. The temperature optimum for the reaction is 77 degrees C, reflecting the thermophilic character of the organism. The enzyme activity is not affected by treatment with micrococcal nuclease, suggesting that there is no RNA subunit or that it is protected from nuclease action. The density of the enzyme in cesium sulfate equilibrium density gradients is 1.27 g/ml, which is similar to that of protein. However, several RNAs between 200 and 400 nucleotides in size copurify with the enzyme activity on the density gradients, and one of them remains after micrococcal nuclease treatment. These properties of the S. solfataricus enzyme are compared with those of ribonuclease P from eukaryotes and eubacteria.     

Codon bias and plasticity in immunoglobulins

Immunoglobulin genes experience Darwinian evolution twice. In addition to the germline evolution all genes experience, immunoglobulins are subjected, upon exposure to antigen, to somatic hypermutation. This is accompanied by selection for high affinity to the eliciting antigen and frequently results in a significant increase in the specificity of the responding population. The hypermutation mechanism displays a strong sequence specificity. Thus arises the opportunity to manipulate codon bias in a site-specific manner so as to direct hypermutation to those parts of the gene that encode the antigen-binding portions of the molecule and away from those that encode the structurally conserved regions. This segregation of mutability would clearly be advantageous; it would enhance the generation of potentially useful variants while keeping mutational loss to acceptably low levels. But it is not clear that the advantage gained would be large enough to produce a measurable effect within the background stochasticity of the evolutionary process. I have performed a pair of statistical tests to determine whether site- specific codon bias in human immunoglobulin genes is correlated with the sequence specificity of the somatic mutation mechanism. The sequence specificity of the mutator was determined by analysis of a database of published immunoglobulin intron sequences that had experienced somatic mutation but not selection. The site-specific codon bias was determined by analysis of published sequences of human germline immunoglobulin V genes. Both tests strongly suggest that evolution has acted to enhance the plasticity of immunoglobulin genes under somatic hypermutation.