Biochemische und strukturelle Rekonstitution des äußeren Kinetochores von Drosophila melanogaster

Eine genaue Chromosomensegregation während der Mitose und der Meiose ist entscheidend für die zelluläre und organisatorische Lebensfähigkeit. Kinetochore verbinden Chromosomen mit Spindel-Mikrotubuli und sind für die Chromosomensegregation essentiell. Diese großen Proteingerüste entstehen aus dem Zentromer, einer spezialisierten Region des Chromosoms, angereichert mit der Histon-H3-Variante CENP-A. In den meisten Eukaryoten besteht der Kinetochore-Kern aus dem Zentromer-proximalen konstitutiven Zentromer-assoziierten Netzwerk (CCAN), das CENP-A bindet und 16 Untereinheiten enthält, und des Zentromer-distalen Knl1/Zwint, Mis12C, Ndc80-Komplexnetzwerk (KMN). Das KMN-Komplexnetzwerk bindet Mikrotubuli und setzt sich aus 10 Untereinheiten zusammen. In der Fruchtfliege Drosophila melanogaster erlebte die Kinetochore bemerkenswerte Vereinfachungen. Alle CCAN-Untereinheiten, mit Ausnahme von Zentromer-Protein C (CENP-C) und zwei KMN-Untereinheiten, Dsn1 und Zwint, können in diesem Organismus nicht identifiziert werden. Zusätzlich sind zwei paralogs der KMN-Untereinheit Nnf1 (Nnf1a und Nnf1b) vorhanden. Schließlich erlebte die Spc105R-Untereinheit, homolog zu humanem Knl1/CASC5, im Vergleich zu anderen Organismen erhebliche Sequenzänderungen. Wir kombinierten die biochemische Rekonstitution mit biophysikalischen und strukturellen Methoden, um zu untersuchen, wie sich diese Veränderungen auf die Organisation des Drosophila KMN Netzwerks auswirken. Wir zeigen, dass die Nnf1a- und Nnf1b-Paralogs Untereinheiten unterschiedlicher Komplexe sind, die beide direkt mit Spc105 und mit CENP-C wechselwirken, wobei letztere eine Bindungsstelle an der Mis12-Untereinheit identifizieren. Unsere Studien beleuchten die strukturelle und funktionelle Organisation eines stark divergierenden Kinetochore-Teilchens.Dividing cells go through a series of events, named the cell cycle, to generate two new cells that are genetically equal. Faithful sister chromatid separation to the arising daughter cells is a crucial step in the cell cycle. To achieve that, kinetochores, multi-protein complexes that assemble on centromeric chromatin, act as a bridge between microtubules and chromatids. In human and yeast, kinetochores consist of two major parts: the constitutive centromere-associated network (CCAN, the inner kinetochore) and the Knl1 complex, Mis12 complex, Ndc80 complex (KMN) network. The CCAN contains 16 subunits and links the kinetochore to CENP-A. The KMN network contains 10 subunits and is responsible for the binding of microtubules and the recruitment of spindle assembly checkpoint (SAC) components. The popular model organisms Drosophila melanogaster and related organisms have a significantly simplified kinetochore: they lost all CCAN components with the exception of CENP-C and lost two outer kinetochore subunits (one Mis12 complex (Mis12C) subunit and one Knl1 complex subunit, Zwint). In addition, there are two homologues of the Mis12C subunit Nnf1 (Nnf1a and Nnf1b). The simplified Drosophila kinetochore thus forms an ideal model to study conserved structural and functional properties of kinetochores. During my doctoral work, I studied the Drosophila KMN network using an in vitro biochemical reconstitution approach. My reconstitution experiments indicate that there are two distinct three-subunit Mis12 complexes in Drosophila, DmMis12a and DmMis12b complexes. Despite the absent subunit, negative stain electron microscopy shows that the DmMis12C has an extended polarized structures, comparable to its human and yeast counterparts. Biochemical studies combined with cross-linking-mass spectrometry (XL-MS) proved that Mis12 and Nnf1 form the backbone of Mis12C in both DmMis12a and DmMis12b. Using deletion experiments, I proved that both the C-terminal of Knl1 and the N-terminal of CENP-C bind to DmMis12C. Furthermore, I identified the motifs responsible for the binding between CENP-C and Mis12C in Drosophila: the conserved 3 phenylalanine residues at the N-terminal of Mis12 (F12, F13 and F15) and the 27 amino acids at the N-terminal end of CENP-C (residues 9 to 35). In cooperation with Dr. Arsen Petrovic and Dr. Jenny Keller, we solved the high-resolution structure of the tetrameric human Mis12C in complex with the N-terminal segment of CENP-C. We provided a model for how Aurora B controls Mis12C assembling to kinetochore. We demonstrated that the Dsn1 subunit is an important substrate of Aurora B in the human Mis12C. Together with a structure-based in silico analysis, this led us to hypothesize that the lost subunit in Drosophila Mis12 complex could be Nsl1, and not Dsn1 as previously suggested. In summary, my studies provided new insights on the structural and functional properties of outer kinetochores in humans and Drosophila

Combining remote sensing and ground census data to develop new maps of the distribution of rice agriculture in China

Large-scale assessments of the potential for food production and its impact on biogeochemical cycling require the best possible information on the distribution of cropland. This information can come from ground-based agricultural census data sets and/or spaceborne remote sensing products, both with strengths and weaknesses. Official cropland statistics for China contain much information on the distribution of crop types, but are known to significantly underestimate total cropland areas and are generally at coarse spatial resolution. Remote sensing products can provide moderate to fine spatial resolution estimates of cropland location and extent, but supply little information on crop type or management. We combined county-scale agricultural census statistics on total cropland area and sown area of 17 major crops in 1990 with a fine-resolution land-cover map derived from 1995–1996 optical remote sensing (Landsat) data to generate 0.5° resolution maps of the distribution of rice agriculture in mainland China. Agricultural census data were used to determine the fraction of crop area in each 0.5° grid cell that was in single rice and each of 10 different multicrop paddy rice rotations (e.g., winter wheat/rice), while the remote sensing land-cover product was used to determine the spatial distribution and extent of total cropland in China. We estimate that there were 0.30 million km2 of paddy rice cropland; 75% of this paddy land was multicropped, and 56% had two rice plantings per year. Total sown area for paddy rice was 0.47 million km2. Paddy rice agriculture occurred on 23% of all cultivated land in China

The Performances Optimization of Finger Seal Based on Fuzzy Game Theory

AbstractLeakage and abrasion are two key performances of finger seals (FS). They not only contradict each other in FS design but also relate to many design parameters. Moreover, in the multi-objective optimization progress, the problems of optimizing results decision and preference requirement for optimization objectives are still challenge to researcher. So far, they are still important influence factors for advanced FS design. Therefore, the current work presents a new multi-objective optimization method by introducing game theory and fuzzy comprehensive evaluation theory. The optimizing results are compared to that of the general optimization method and finite element method (FEM). The study show that the FS, which is obtained by presented optimization method, has good performances. Compared respectively with the general optimization method and FEM, the computational results indicate that the presented method can effectively reflect the different response requirements of optimization objectives. Furthermore, the decision-making difficulty for multi-objective optimization of FS performances is significantly reduced

Abdominal Multiple Splenosis Mimicking Liver and Colon Tumors: A Case Report and Review of the Literature

Splenosis is not an uncommon disease. However, it is often misdiagnosed as malignant tumors, and then the patients underwent unnecessary operations. Unfortunately, it is very difficult to diagnose it prior to operation. We report a rare case of a 49-year-old female patient with liver and colon splenosis, misdiagnosed as liver and colon tumors, and summarize experience how to diagnose it preoperatively according to literatures. We come to conclusion that in patients who ever underwent splenectomy especially owning to trauma, and were found mass in abdomen, clinicians must consider the existence of splenosis, and take some measures, such as scintigraphy with (99m) Tc labelled heat-denatured erythrocyte rather than biopsy, to diagnose it correctly to prevent unnecessary operations

Gamified Live-streaming: Is Avatar Better than Human Being?

Live-streaming has emerged as a popular direct selling channel to foster synchronous interaction between streamers and consumers, with the avatar streamer largely underexplored. Using the data from a fashion retailer, we adopt the Generalized Synthetic Control (GSC) method to examine the effect of gamified and human live-streaming on product sales and return rate. We find that (1) the gamified live-streaming reduces product sales and the return rate simultaneously; (2) human live-streaming boosts product sales but increases the return rate, and (3) the dual-type live-streaming can increase product sales and decrease return rates. Furthermore, we proposed that the reason for the differentiated effects between gamified and human live-streaming could be driven by the impulse-buying behavior of viewers only in human live-streaming. Our findings contribute to the growing literature on the business value of AI technology and gamification in live-streaming and shed light on practical decisions made by online retailers

Hem-o-lok Clip Found in Common Bile Duct after Laparoscopic Cholecystectomy and Common Bile Duct Exploration: A Clinical Analysis Of 8 Cases

Currently laparoscopic cholecystectomy (LC) and common bile duct exploration (LCBDE) has become the standard surgical procedure for cholecystolithiasis and choledocholithiasis. During the operation cystic duct and vessels are usually controlled by Hem-o-lok clips. However, recently we found clips dropping into CBD in 8 patients during fiberoptic choledochoscope 2-3 months after operation. Therefore, there is risk that clip can migrate during postoperative period, which probably lead to hemorrhage and bile leakage after LC if this occurs within postoperative few days, or even cause recurrent stone in CBD. So, using of Hem-o-lok clips may be not a safe method to control vessels and cystic duct during LC. To our knowledge, this condition has not previously been reported. In our view, other more effective and safe method ligating cystic duct and gallbladder vessels, such as effective and convenient thread knotting method, should be investigated

Quasi-Closeness: A Toolkit for Social Network Applications Involving Indirect Connections

We come up with a punishment in the form of exponential decay for the number of vertices that a path passes through, which is able to reconcile the contradictory effects of geodesic length and edge weights. This core thought is the key to handling three typical applications; that is, given an information demander, he may be faced with the following problems: choosing optimal route to contact the single supplier, picking out the best supplier between multiple candidates, and calculating his point centrality, which involves indirect connections. Accordingly, three concrete solutions in one logic thread are proposed. Firstly, by adding a constraint to Dijkstra algorithm, we limit our candidates for optimal route to the sample space of geodesics. Secondly, we come up with a unified standard for the comparison between adjacent and nonadjacent vertices. Through punishment in the form of exponential decay, the attenuation effect caused by the number of vertices that a path passes through has been offset. Then the adjacent vertices and punished nonadjacent vertices can be compared directly. At last, an unprecedented centrality index, quasi-closeness, is ready to come out, with direct and indirect connections being summed up