Interplay between Structure-Specific Endonucleases for Crossover Control during Caenorhabditis elegans Meiosis

The number and distribution of crossover events are tightly regulated at prophase of meiosis I. The resolution of Holliday junctions by structure-specific endonucleases, including MUS-81, SLX-1, XPF-1 and GEN-1, is one of the main mechanisms proposed for crossover formation. However, how these nucleases coordinately resolve Holliday junctions is still unclear. Here we identify both the functional overlap and differences between these four nucleases regarding their roles in crossover formation and control in the Caenorhabditis elegans germline. We show that MUS-81, XPF-1 and SLX-1, but not GEN-1, can bind to HIM-18/SLX4, a key scaffold for nucleases. Analysis of synthetic mitotic defects revealed that MUS-81 and SLX-1, but not XPF-1 and GEN-1, have overlapping roles with the Bloom syndrome helicase ortholog, HIM-6, supporting their in vivo roles in processing recombination intermediates. Taking advantage of the ease of genetic analysis and high-resolution imaging afforded by C. elegans, we examined crossover designation, frequency, distribution and chromosomal morphology in single, double, triple and quadruple mutants of the structure-specific endonucleases. This revealed that XPF-1 functions redundantly with MUS-81 and SLX-1 in executing crossover formation during meiotic double-strand break repair. Analysis of crossover distribution revealed that SLX-1 is required for crossover suppression at the center region of the autosomes. Finally, analysis of chromosome morphology in oocytes at late meiosis I stages uncovered that SLX-1 and XPF-1 promote meiotic chromosomal stability by preventing formation of chromosomal abnormalities. We propose a model in which coordinate action between structure-specific nucleases at different chromosome domains, namely MUS-81, SLX-1 and XPF-1 at the arms and SLX-1 at the center region, exerts positive and negative regulatory roles, respectively, for crossover control during C. elegans meiosis

Invasive behavior of ulcerative colitis-associated carcinoma is related to reduced expression of CD44 extracellular domain: comparison with sporadic colon carcinoma

<p>Abstract</p> <p>Background</p> <p>To elucidate relations of invasion of ulcerative colitis (UC)-associated carcinoma with its prognosis, the characteristics of invasive fronts were analyzed in comparison with sporadic colonic carcinomas.</p> <p>Methods</p> <p>Prognoses of 15 cases of UC-associated colonic carcinoma were compared with those of sporadic colon carcinoma cases, after which 75 cases of sporadic invasive adenocarcinoma were collected. Tumor budding was examined histologically at invasive fronts using immunohistochemistry (IHC) of pancytokeratin. Expressions of beta-catenin with mutation analysis, CD44 extracellular domain, Zo-1, occludin, matrix matalloproteinase-7, laminin-5γ2, and sialyl Lewis X (Le^X) were immunohistochemically evaluated.</p> <p>Results</p> <p>UC-associated carcinoma showed worse prognosis than sporadic colon carcinoma in all the cases, and exhibited a tendency to become more poorly differentiated when carcinoma invaded the submucosa or deeper layers than sporadic carcinoma. When the lesions were compared with sporadic carcinomas considering differentiation grade, reduced expression of CD44 extracellular domain in UC-associated carcinoma was apparent. Laminin-5γ2 and sialyl-Le^Xexpression showed a lower tendency in UC-associated carcinomas than in their sporadic counterparts. There were no differences in the numbers of tumor budding foci between the two lesion types, with no apparent relation to nuclear beta-catenin levels in IHC.</p> <p>Conclusions</p> <p>UC-associated carcinoma showed poorer differentiation when the carcinoma invaded submucosa or deeper parts, which may influence the poorer prognosis. The invasive behavior of UC-associated carcinoma is more associated with CD44 cleavage than with basement membrane disruption or sialyl-Lewis-antigen alteration.</p

Caenorhabditis elegans HIM-18/SLX-4 Interacts with SLX-1 and XPF-1 and Maintains Genomic Integrity in the Germline by Processing Recombination Intermediates

Homologous recombination (HR) is essential for the repair of blocked or collapsed replication forks and for the production of crossovers between homologs that promote accurate meiotic chromosome segregation. Here, we identify HIM-18, an ortholog of MUS312/Slx4, as a critical player required in vivo for processing late HR intermediates in Caenorhabditis elegans. DNA damage sensitivity and an accumulation of HR intermediates (RAD-51 foci) during premeiotic entry suggest that HIM-18 is required for HR–mediated repair at stalled replication forks. A reduction in crossover recombination frequencies—accompanied by an increase in HR intermediates during meiosis, germ cell apoptosis, unstable bivalent attachments, and subsequent chromosome nondisjunction—support a role for HIM-18 in converting HR intermediates into crossover products. Such a role is suggested by physical interaction of HIM-18 with the nucleases SLX-1 and XPF-1 and by the synthetic lethality of him-18 with him-6, the C. elegans BLM homolog. We propose that HIM-18 facilitates processing of HR intermediates resulting from replication fork collapse and programmed meiotic DSBs in the C. elegans germline

カンキョウ コントロール ニ ヨル セイトウギョ

脊椎動物の性は、主に遺伝的要因により決定されるが、魚類においては、水温やpHなどの生育環境に応じて性が決定されることが知られている。しかしながら、この分子機構は未だに明らかにされていない。　XX/XY型の性決定システムを持つヒラメの遺伝的雌(XX)は、性分化時期に18℃で飼育すると雌へ、27℃で飼育すると雄へとほぼ完全に分化誘導することが可能であるため、水温依存的な性決定の分子機構を解析するための大変優れた実験動物である。我々は、XX個体を18℃で飼育するとアロマターゼ(アンドロゲンをエストロゲンに変換する酵素) mRNAの発現量が上昇するが、高水温(27℃)で飼育することによりアロマターゼmRNAの発現が抑制されて雄へと性分化する事を明らかにした。このことは、ヒラメの高水温による雄化にアロマターゼ遺伝子の転写調節が深く関与している事を示している。ここでは、まず、温度コントロールによる性統御を行う上で、キーとなる遺伝子であるアロマターゼ遺伝子の転写調節機構について紹介する。次に、高水温による雄化とコルチゾル（ストレスホルモン）との関連性に言及し、さらにこれらの機構が他の魚種でも保存されているかどうかについて議論したい

Bilan préopératoire de l'hépatectomie majeure [Preoperative assessment for extended hepatic resection]

The number of major hepatectomy performed for the treatment of primary or secondary liver cancer has increased over the past two decades. By definition, a major hepatectomy includes the resection of at least three liversegments. Advances in anesthesiology, surgical and radiological techniques and perioperative management allowed a broad patient selection with increased security. Every case must be discussed in multidisciplinary tumor board, and preoperative assessment should include biological, volumetric and functional hepatic parameters. In case of preoperative insufficient liver volume, portal vein embolization allows increasing the size of liver remnant. This paper aims describing preoperative work-up

ZHP-3 foci in late pachytene and diplotene nuclei of the nuclease-deficient mutants.

<p>ZHP-3 foci in late pachytene and diplotene nuclei of the nuclease-deficient mutants.</p

The interaction network between structure-specific endonucleases.

<p>The yeast two-hybrid system was used to examine the protein interactions between HIM-18, SLX-1, MUS-81, EME-1, XPF-1, ERCC-1, GEN-1 and RAD-54. Proteins are fused to either the DNA binding domain (DB) or the activation domain (AD) of GAL4. (A) The diploid yeast strains containing plasmids pVV212 (GAL4 DNA binding domain (DB)+<i>TRP1</i>) and pVV213 (GAL4 activation domain (AD)+<i>LEU2</i>) can grow on SC-LEU-TRP plates. All pair-wise combinations of the interactions are assayed with vector alone as the negative control. Interactions were scored on selective medium lacking leucine, tryptophan and histidine (SC-LEU-TRP-HIS). (B) Schematic representation of the interaction network. Arrows indicate protein-protein interactions.</p

Roles for the structure-specific nucleases in regulating crossover frequency and distribution.

<p>(A) Chromosome domains. Left tip, left arm, center, right arm and right tip are indicated according to <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003586#pgen.1003586-Rockman1" target="_blank">[26]</a>. SNPs that alter the restriction length and are located closest to the boundary of each chromosome domain were chosen for chromosomes V and X. (B) Schematic representation of the strategy for obtaining the F2 progeny for snip-SNP analysis. Circles indicate hermaphrodites. Squares indicate males. White, Bristol. Black, Hawaiian. (C) The representative band pattern of PCR products at position “a” on the X chromosome. The restriction enzyme (<i>Bsp</i>HI) treatment was performed before loading. (D) Crossover frequencies and distributions observed in the entire a–d interval, left arm (a–b), center (b–c), and right arm (c–d) on chromosomes V and X. Highlighted cells indicate statistical difference compared to wild type (blue; P<0.05, grey; P<0.01, and yellow; P<0.001 by the Fisher's Exact Test and corrected by Sidak adjustment for multiple comparisons). Bold type indicates statistical significance (P<0.05) before Sidak correction.</p