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The bone marrow contains peripheral nerves that promote haematopoietic regeneration after irradiation or chemotherapy (myeloablation), but little is known about how this is regulated. Here we found that nerve growth factor (NGF) produced by leptin receptor-expressing (LepR + ) stromal cells is required to maintain nerve fibres in adult bone marrow. In nerveless bone marrow, steady-state haematopoiesis was normal but haematopoietic and vascular regeneration were impaired after myeloablation. LepR + cells, and the adipocytes they gave rise to, increased NGF production after myeloablation, promoting nerve sprouting in the bone marrow and haematopoietic and vascular regeneration. Nerves promoted regeneration by activating β2 and β3 adrenergic receptor signalling in LepR + cells, and potentially in adipocytes, increasing their production of multiple haematopoietic and vascular regeneration growth factors. Peripheral nerves and LepR + cells thus promote bone marrow regeneration through a reciprocal relationship in which LepR + cells sustain nerves by synthesizing NGF and nerves increase regeneration by promoting the production of growth factors by LepR + cells. Gao et al. report that leptin receptor + stromal cells sustain nerves in the bone marrow by producing nerve growth factor. After myeloablation, nerves promote marrow regeneration by increasing the production of multiple growth factors by leptin receptor + cells.

Inhibition of DOT1L, the H3K79 histone methyltransferase, increases cell reprogramming and substituted for KLF4 and c-Myc, showing that chromatin-modifying enzymes act not only as facilitators but also as barriers to reprogramming. Chromatin in iPS-cell formation A study of the role of chromatin-modifying enzymes in the reprogramming of human fibroblasts to induced pluripotent stem (iPS) cells suggests that such enzymes can act as facilitators — but also as barriers — to epigenetic remodelling. By knocking down 22 selected genes involved in DNA and histone methylation pathways, George Daley and colleagues identified both positive and negative regulators of iPS-cell generation. In particular, inhibition of DOT1L, the H3K79 histone methyltransferase, increased reprogramming and substituted for KLF4 and c-Myc, two of the factors needed in the reprogramming cocktail. The effect of DOT1L inhibition seems to be associated with increase in the reprogramming factors NANOG and LIN28. This work demonstrates that specific chromatin modifiers can be modulated to generate iPS cells more efficiently and with fewer exogenously introduced transcription factors. Generation of induced pluripotent stem cells (iPSCs) by somatic cell reprogramming involves global epigenetic remodelling 1 . Whereas several proteins are known to regulate chromatin marks associated with the distinct epigenetic states of cells before and after reprogramming 2 , 3 , the role of specific chromatin-modifying enzymes in reprogramming remains to be determined. To address how chromatin-modifying proteins influence reprogramming, we used short hairpin RNAs (shRNAs) to target genes in DNA and histone methylation pathways, and identified positive and negative modulators of iPSC generation. Whereas inhibition of the core components of the polycomb repressive complex 1 and 2, including the histone 3 lysine 27 methyltransferase EZH2, reduced reprogramming efficiency, suppression of SUV39H1, YY1 and DOT1L enhanced reprogramming. Specifically, inhibition of the H3K79 histone methyltransferase DOT1L by shRNA or a small molecule accelerated reprogramming, significantly increased the yield of iPSC colonies, and substituted for KLF4 and c-Myc (also known as MYC). Inhibition of DOT1L early in the reprogramming process is associated with a marked increase in two alternative factors, NANOG and LIN28, which play essential functional roles in the enhancement of reprogramming. Genome-wide analysis of H3K79me2 distribution revealed that fibroblast-specific genes associated with the epithelial to mesenchymal transition lose H3K79me2 in the initial phases of reprogramming. DOT1L inhibition facilitates the loss of this mark from genes that are fated to be repressed in the pluripotent state. These findings implicate specific chromatin-modifying enzymes as barriers to or facilitators of reprogramming, and demonstrate how modulation of chromatin-modifying enzymes can be exploited to more efficiently generate iPSCs with fewer exogenous transcription factors.

Determining the mechanism of gene function is greatly enhanced using conditional mutagenesis. However, generating engineered conditional alleles is inefficient and has only been widely used in mice. Importantly, multiplex conditional mutagenesis requires extensive breeding. Here we demonstrate a system for one-generation multiplex conditional mutagenesis in zebrafish (Danio rerio) using transgenic expression of both cas9 and multiple single guide RNAs (sgRNAs). We describe five distinct zebrafish U6 promoters for sgRNA expression and demonstrate efficient multiplex biallelic inactivation of tyrosinase and insulin receptor a and b, resulting in defects in pigmentation and glucose homeostasis. Furthermore, we demonstrate temporal and tissue-specific mutagenesis using transgenic expression of Cas9. Heat-shock-inducible expression of cas9 allows temporal control of tyr mutagenesis. Liver-specific expression of cas9 disrupts insulin receptor a and b, causing fasting hypoglycemia and postprandial hyperglycemia. We also show that delivery of sgRNAs targeting ascl1a into the eye leads to impaired damage-induced photoreceptor regeneration. Our findings suggest that CRISPR/Cas9-based conditional mutagenesis in zebrafish is not only feasible but rapid and straightforward.

Stromal cells in adult bone marrow that express leptin receptor (LEPR) are a critical source of growth factors, including stem cell factor (SCF), for the maintenance of haematopoietic stem cells and early restricted progenitors 1 – 6 . LEPR + cells are heterogeneous, including skeletal stem cells and osteogenic and adipogenic progenitors 7 – 12 , although few markers have been available to distinguish these subsets or to compare their functions. Here we show that expression of an osteogenic growth factor, osteolectin 13 , 14 , distinguishes peri-arteriolar LEPR + cells poised to undergo osteogenesis from peri-sinusoidal LEPR + cells poised to undergo adipogenesis (but retaining osteogenic potential). Peri-arteriolar LEPR + osteolectin + cells are rapidly dividing, short-lived osteogenic progenitors that increase in number after fracture and are depleted during ageing. Deletion of Scf from adult osteolectin + cells did not affect the maintenance of haematopoietic stem cells or most restricted progenitors but depleted common lymphoid progenitors, impairing lymphopoiesis, bacterial clearance, and survival after acute bacterial infection. Peri-arteriolar osteolectin + cell maintenance required mechanical stimulation. Voluntary running increased, whereas hindlimb unloading decreased, the frequencies of peri-arteriolar osteolectin + cells and common lymphoid progenitors. Deletion of the mechanosensitive ion channel PIEZO1 from osteolectin + cells depleted osteolectin + cells and common lymphoid progenitors. These results show that a peri-arteriolar niche for osteogenesis and lymphopoiesis in bone marrow is maintained by mechanical stimulation and depleted during ageing. A peri-arteriolar niche in the bone marrow for osteogenesis and lymphopoiesis is maintained by mechanical stimulation and is depleted during ageing.

MicroRNA (miRNAs) are evolutionarily conserved, small non-coding RNAs that post-transcriptionally regulate gene expression. They were initially identified in forward genetic screens in C. elegans as regulators of developmental timing (Lee et al., 1993; Wightman et al., 1993). Later, they were also discovered in plants, flies and vertebrates, involved in nearly all developmental and pathological processes (Ambros, 2003; Chen et al., 2005; Lagos-Quintana et al., 2003; Pasquinelli et al., 2000). As of March 2018, the miRNA registry (http://www.mirbase.org/) contained 38,589 miRNAs in vertebrates and invertebrates, with 2588 annotated miRNAs in the human genome; although biological functions of most of these miRNAs remain to be discovered (Griffiths-Jones et al., 2006). miRNA-mediated gene silencing involves two main components, miRNAs baseparing with their target mRNAs in complex with Argonaute (AGO) proteins thereby recruiting factors that initiate translational repression as well as mRNA deadenylation and decay (Huntzinger and Izaurralde, 2011). miRNA binding sites are generally located in the 3’ untranslated region (UTR) of mRNAs and referred as miRNA recognition elements (MREs) (Bartel, 2009). For target recognition, the crucial region on the miRNA is located from nucleotides 2 to 7 and termed as the ‘miRNA seed’. Meanwhile, the nucleotides downstream of the seed sequence are involved in additional imperfect basepairing of the miRNA with the target mRNA. In the human genome, more than 60% of protein-coding genes carry at least one conserved MRE. When non-conserved MREs are also taken into consideration, most protein-coding genes are thought to be regulated by miRNAs (Friedman et al., 2009). While miRNAs can bind to many target mRNAs, multiple miRNA can also target the same mRNAs. This characteristic makes miRNAs unique potent regulators of gene expression. Thus, the biogenesis and function of miRNAs themselves are tightly regulated as well. Due to gene duplication in the genomes of many species, there are multiple related miRNA loci with related sequences. miRNAs with identical seed sequences are generally referred as ‘miRNA families’ (Bartel, 2009). One example is the let-7 family which consists of 14 paralogous loci in the human genome. miRNA family members generally have redundant functions, although some distinct roles have been reported as well (Ha and Kim, 2014). Some miRNAs may share common evolutionarily origins, but nevertheless diverge in their seed sequences. One such example is miR-141 and miR- 200c miRNAs that derived from miR-200 superfamily but their seed sequences vary by 1 nucleotide. It has been shown that targets of miR-141 and miR-200c do not overlap; therefore each miRNA has distinct functions (Kim et al., 2013). (Shortened by ProQuest.)

Beş yüzyıl boyunca Balkanları yöneten Türkler 19. yüzyılın sonlarından itibaren Osmanlı Devleti'nin dağılmasıyla Balkanlar’da büyük baskı ve sorunlarla karşılaşmıştır. Yaşanmış olan bu sorunlar sonucunda Türkler özellikle Balkanlardan Anadolu’ya doğru göç etmeye başlamıştır. Bulgaristan Türkleri ise 1900lerin başından itibaren önce faşist yönetim ardından da komünist yönetimin uyguladığı asimilasyon politikası sonucunda ülkelerini terk etmeye başlamışlardır. Bulgar komünist yönetimi kurulduğu ilk zamanlarda Türklere ayrıcalık ve hak tanıyacaklarını belirterek onların güvenini kazanmıştır. Ancak rejimin bu söylemleri rejimin başlangıcından hemen sonra ortadan kalkmıştır. Uzun yıllar devam edecek olan büyük baskıcı bir dönem başlamıştır. Bu da hem göç etmeyip Bulgaristan’da kalanlar hem de baskılara dayanamayıp göç edenler için beraberinde eğitim sorunlarını gündeme getirmiştir. Baskıcı rejim Türklerin özellikle dillerini ve dinlerini değiştirdiklerinde onların kendi emirlerini yerine getireceklerini düşünmüştür. Büyük 1989 göçü öncesinde ve sonrasında Bulgaristan’da kalanlar tarafından anadilde eğitim konusunda büyük çabalar sarf edilmiştir. Yaşanmış olan sorunların içinde özellikle Türkçe konusundaki uygulamaları bölgede bulunan Türkleri oldukça etkilemiştir. Türklerin isimleri değiştirilmiş, zorla göç ettirilmiş, mallarına el konulmuştur. Ancak baskıcı rejimin sona ermesi ile bazı bölgelerde Türkçe eğitim konusunda izinler verilmeye başlanmıştır. Yaşanılan göç olayları sonrası göç eden Türkler de bazı problemlerle karşılaşmışlardır. Gelen Türklerin çoğu uzun yıllar boyunca baskı altında yaşadıkları için her ne kadar anavatanları da olsa alışmada büyük güçlükler yaşamışlardır. Göç edenlerin penceresinden bakacak olursak onların da Türkiye’de başta eğitim olmak üzere çalışma hayatı ve sosyal hayatta adaptasyon problemleri yaşadıkları görülmüştür. Bu tezimizde Bulgaristan Türkeri’nin özellikle Türkiye’ye göç ettikten sonra yaşadıkları eğitim sorunları başta olmak üzere Bulgaristan’dan göç etmeyip kalanlar için de yıllara göre yaşadıkları sorunlar rakamsal verilerle ve bizzat göçü yaşayan kişilerle söyleşiler yapılarak irdelenecek ve yorumlanacaktır.

IntroductionThe identification of diastolic heart failure (DHF) is important for determining the prognosis of congestive heart failure patients. This study attempted to determine the accuracy of emergency physicians who performed bedside echocardiography (BECH) in patients with diastolic dysfunction.MethodsThree attending emergency physicians underwent 3 h of didactic and 3 h of hands-on training taught by a cardiology specialist for the echocardiographic diagnostic criteria of DHF. Between February and April 2010, the emergency physicians performed BECH for patients presenting with dyspnoea, and echocardiographic views were recorded. Our gold standard for the diagnosis of diastolic dysfunction was the cardiologists' echocardiography report. Results were compared with χ2 testing.ResultsOf the 69 enrolled patients, 51 were diagnosed as having diastolic dysfunction by emergency physicians. The sensitivity of BECH was 89% (77–95) and specificity was 80% (51–95) with 95% CI. The accuracy of the emergency physicians' echocardiographic diagnosis was 87%.ConclusionBECH performed by emergency physicians may serve as an objective, rapid, non-invasive tool in the assessment of patients presenting with dyspnoea in ED.