Kinetochore fiber formation in animal somatic cells : dueling mechanisms come to a draw

Author Posting. © The Author, 2005. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Chromosoma 114 (2005): 310-318, doi:10.1007/s00412-005-0028-2.The attachment to and movement of a chromosome on the mitotic spindle is mediated by the formation of a bundle of microtubules (MTs) that tethers the kinetochore on the chromosome to a spindle pole. The origin of these “kinetochore fibers” (K-fibers) has been investigated for over 125 years. As noted in 1944 by Schrader, there are only three possible ways to form a K-fiber: either it a) grows from the pole until it contacts the kinetochore; b) grows directly from the kinetochore; or c) it forms as a result of an interaction between the pole and the chromosome. Since Schrader’s time it has been firmly established that K-fibers in centrosome-containing animal somatic cells form as kinetochores capture MTs growing from the spindle pole (route a). It is now similarly clear that in cells lacking centrosomes, including plants and many animal oocytes, K-fibers “self-assemble” from MTs generated by the chromosomes (route b). Can animal somatic cells form K-fibers in the absence of centrosomes by the “self-assembly” pathway? In 2000 the answer to this question was shown to be a resounding “yes”. With this result, the next question became whether the presence of a centrosome normally suppresses K-fiber self-assembly, or if this route works concurrently with centrosome-mediated K-fiber formation. This question, too, has recently been answered: observations on untreated live animal cells expressing GFP-tagged tubulin clearly show that kinetochores can nucleate the formation of their associated MTs in the presence of functional centrosomes. The concurrent operation of these two “dueling” routes for forming K-fibers in animals helps explain why the attachment of kinetochores and the maturation of K-fibers occur as quickly as it does on all chromosomes within a cell.The work is sponsored by NIH grant GMS 40198

Persistence of DNA threads in human anaphase cells suggests late completion of sister chromatid decatenation

PICH (Plk1-interacting checkpoint helicase) was recently identified as an essential component of the spindle assembly checkpoint and shown to localize to kinetochores, inner centromeres, and thin threads connecting separating chromosomes even during anaphase. In this paper, we have used immuno-fiber fluorescence in situ hybridization and chromatin-immunoprecipitation to demonstrate that PICH associates with centromeric chromatin during anaphase. Furthermore, by careful analysis of PICH-positive anaphase threads through FISH as well as bromo-deoxyurdine and CREST labeling, we strengthen the evidence that these threads comprise mainly alphoid centromere deoxyribonucleic acid. Finally, by timing the addition of ICRF-193 (a specific inhibitor of topoisomerase-II alpha) to cells synchronized in anaphase, we demonstrate that topoisomerase activity is required specifically to resolve PICH-positive threads during anaphase (as opposed to being required to prevent the formation of such threads during earlier cell cycle stages). These data indicate that PICH associates with centromeres during anaphase and that most PICH-positive threads evolve from inner centromeres as these stretch in response to tension. Moreover, they show that topoisomerase activity is required during anaphase for the resolution of PICH-positive threads, implying that the complete separation of sister chromatids occurs later than previously assumed

Chronic Exposure to the Herbicide, Atrazine, Causes Mitochondrial Dysfunction and Insulin Resistance

There is an apparent overlap between areas in the USA where the herbicide, atrazine (ATZ), is heavily used and obesity-prevalence maps of people with a BMI over 30. Given that herbicides act on photosystem II of the thylakoid membrane of chloroplasts, which have a functional structure similar to mitochondria, we investigated whether chronic exposure to low concentrations of ATZ might cause obesity or insulin resistance by damaging mitochondrial function. Sprague-Dawley rats (n = 48) were treated for 5 months with low concentrations (30 or 300 µg kg−1 day−1) of ATZ provided in drinking water. One group of animals was fed a regular diet for the entire period, and another group of animals was fed a high-fat diet (40% fat) for 2 months after 3 months of regular diet. Various parameters of insulin resistance were measured. Morphology and functional activities of mitochondria were evaluated in tissues of ATZ-exposed animals and in isolated mitochondria. Chronic administration of ATZ decreased basal metabolic rate, and increased body weight, intra-abdominal fat and insulin resistance without changing food intake or physical activity level. A high-fat diet further exacerbated insulin resistance and obesity. Mitochondria in skeletal muscle and liver of ATZ-treated rats were swollen with disrupted cristae. ATZ blocked the activities of oxidative phosphorylation complexes I and III, resulting in decreased oxygen consumption. It also suppressed the insulin-mediated phosphorylation of Akt. These results suggest that long-term exposure to the herbicide ATZ might contribute to the development of insulin resistance and obesity, particularly where a high-fat diet is prevalent

Transfer and transition practices in 96 European adult congenital heart disease centres.

BACKGROUND: Irrespective of initial treatment for congenital heart disease (CHD) in childhood, CHD is a lifelong condition, leaving patients at risk for complications. To support uninterrupted, age- and development-based care for young persons with CHD, guidelines and consensus papers emphasise the need for formal transition programmes, including transfer to adult CHD (ACHD) clinics. Here, we surveyed existing transfer and transition programmes in European ACHD centres. Our aims were to provide a contemporary view of transitional care for patients with CHD and to evaluate progress over the last decade. METHODS: We conducted a descriptive, cross-sectional survey in 96 ACHD centres in Europe. A specific survey form was developed that sampled the practices of transfer and/or transition. We used a transfer-transition index to quantify adherence to quality indicators of successful transfer and transition. RESULTS: Of the 96 ACHD centres, 40 (41.7%) offered a formal transition, and 85 (88.5%) had structured transfer from paediatric to ACHD care. Although 31% of the centres performed at a 'good' level on the transfer-transition index, only 4 (4.2%) satisfied all criteria. Most centres with a transition programme offered education and support through a dedicated transition specialist, who was a master's-prepared nurse in most centres. A minority of the ACHD centres offered a flexible transition process, starting at least two years before transfer. CONCLUSIONS: Nearly half of the included ACHD centres offered a formal transition programme, and almost 90% offered structured transfer. Despite some improvements since 2009, most of the programmes lacked an age- and development-based approach.status: Published onlin

Staffing, activities, and infrastructure in 96 specialised adult congenital heart disease clinics in Europe.

BACKGROUND Clinical guidelines emphasise the need for specialised adult congenital heart disease (ACHD) programmes. In 2014, the working group on Grown-up Congenital Heart Disease of the European Society of Cardiology (ESC) published recommendations on the organisation of specialised care for ACHD. To appraise the extent to which these recommendations were being implemented throughout Europe, we assessed the number of patients in active follow-up and available staff resources in European ACHD programmes. METHODS We conducted a descriptive, cross-sectional, paper-based survey of specialised ACHD centres in Europe in late 2017 concerning their centre status in 2016. Data from 96 ACHD centres were analysed. We categorised ACHD programmes into seven different centre types based on their staff resources and composition of interdisciplinary teams. RESULTS Only four centres fulfilled all medical and non-medical staffing requirements of the ESC recommendations. Although 60% of the centres offered all forms of medical care, they had incomplete non-medical resources (i.e., specialised nurses, social workers, or psychologists). The participating centres had 226,506 ACHD patients in active follow-up, with a median of 1500 patients per centre (IQR: 800-3400). Six per cent of the patients were followed up in a centre that lacked a CHD surgeon or congenital interventional cardiologist. CONCLUSIONS A minority of European ACHD centres have the full recommended staff resources available. This suggests that as of 2016 either ACHD care in Europe was still not optimally organised, or that the latest ESC recommendations were not fully implemented in clinical practice

Transfer and transition practices in 96 European adult congenital heart disease centres.

BACKGROUND Irrespective of initial treatment for congenital heart disease (CHD) in childhood, CHD is a lifelong condition, leaving patients at risk for complications. To support uninterrupted, age- and development-based care for young persons with CHD, guidelines and consensus papers emphasise the need for formal transition programmes, including transfer to adult CHD (ACHD) clinics. Here, we surveyed existing transfer and transition programmes in European ACHD centres. Our aims were to provide a contemporary view of transitional care for patients with CHD and to evaluate progress over the last decade. METHODS We conducted a descriptive, cross-sectional survey in 96 ACHD centres in Europe. A specific survey form was developed that sampled the practices of transfer and/or transition. We used a transfer-transition index to quantify adherence to quality indicators of successful transfer and transition. RESULTS Of the 96 ACHD centres, 40 (41.7%) offered a formal transition, and 85 (88.5%) had structured transfer from paediatric to ACHD care. Although 31% of the centres performed at a 'good' level on the transfer-transition index, only 4 (4.2%) satisfied all criteria. Most centres with a transition programme offered education and support through a dedicated transition specialist, who was a master's-prepared nurse in most centres. A minority of the ACHD centres offered a flexible transition process, starting at least two years before transfer. CONCLUSIONS Nearly half of the included ACHD centres offered a formal transition programme, and almost 90% offered structured transfer. Despite some improvements since 2009, most of the programmes lacked an age- and development-based approach