Visceral and subcutaneous fat have different origins and evidence supports a mesothelial source

International audience: Fuelled by the obesity epidemic, there is considerable interest in the developmental origins of white adipose tissue (WAT) and the stem and progenitor cells from which it arises. Whereas increased visceral fat mass is associated with metabolic dysfunction, increased subcutaneous WAT is protective. There are six visceral fat depots: perirenal, gonadal, epicardial, retroperitoneal, omental and mesenteric, and it is a subject of much debate whether these have a common developmental origin and whether this differs from that for subcutaneous WAT. Here we show that all six visceral WAT depots receive a significant contribution from cells expressing Wt1 late in gestation. Conversely, no subcutaneous WAT or brown adipose tissue arises from Wt1-expressing cells. Postnatally, a subset of visceral WAT continues to arise from Wt1-expressing cells, consistent with the finding that Wt1 marks a proportion of cell populations enriched in WAT progenitors. We show that all visceral fat depots have a mesothelial layer like the visceral organs with which they are associated, and provide several lines of evidence that Wt1-expressing mesothelium can produce adipocytes. These results reveal a major ontogenetic difference between visceral and subcutaneous WAT, and pinpoint the lateral plate mesoderm as a major source of visceral WAT. They also support the notion that visceral WAT progenitors are heterogeneous, and suggest that mesothelium is a source of adipocytes

Imaging features and treatment of an intradural lumbar cystic schwannoma Achados imagenológicos e tratamento de um schwannoma cístico intradural lombar

Spinal schwannomas are frequently observed among patients treated in a reference neurosurgery center. Cystic spinal schwannomas, however, are very scantly found. Due to its indolent behavior and benign course, the diagnosis of schwannomas may pose a challenge to the care giver, and the imaging findings can be misleading. In this article, we illustrate an example of a pauci-symptomatic 55 year-old male patient whose complaint was solely a non specific lumbar pain. Investigation revealed a large cystic lesion comprising the lower lumbar intradural space. He was then treated with microneurosurgical technique involving complete removal of the tumor and reconstruction of the duramater. Histological and immunohystochemical diagnosis were consistent with cystic schwannoma. The patient presented with complete recovery of his symptom. In this article we aim to emphasize the clinical presentation and treatment of lumbar spine schwannomas, and to illustrate the imaging findings within this uncommon case.<br>O schwannoma cístico intra-espinal é tumor muito raro e poucos casos estão descritos na literatura: são usualmente assintomáticos e somente diagnosticados quando atingem grande tamanho causando compressão radicular. Com o intuito de ilustrar as armadilhas existentes referentes ao diagnóstico e tratamento desse tipo de tumor, nós relatamos um caso raro, focando nos passos da investigação e terapêutica. É descrito o caso de um paciente de 55 anos que apresentava apenas queixas de dor lombar. A investigação revelou uma lesão cística extensa na região intradural lombar inferior. O tumor foi totalmente ressecado por técnica microneurocirúrgica, sendo a dura-máter reconstruída. O diagnóstico patológico e imuno-histoquímico evidenciou tratar-se de um schwannoma cístico. Neste artigo, nós procuramos enfatizar as características clínicas e tratamento de schwannomas lombares, ilustrando os achados imagenológicos desse caso incomum

Arteries are formed by vein-derived endothelial tip cells

Tissue vascularization entails the formation of a blood vessel plexus, which remodels into arteries and veins. Here we show, by using time-lapse imaging of zebrafish fin regeneration and genetic lineage tracing of endothelial cells in the mouse retina, that vein-derived endothelial tip cells contribute to emerging arteries. Our movies uncover that arterial-fated tip cells change migration direction and migrate backwards within the expanding vascular plexus. This behaviour critically depends on chemokine receptor cxcr4a function. We show that the relevant Cxcr4a ligand Cxcl12a selectively accumulates in newly forming bone tissue even when ubiquitously overexpressed, pointing towards a tissue-intrinsic mode of chemokine gradient formation. Furthermore, we find that cxcr4a mutant cells can contribute to developing arteries when in association with wild-type cells, suggesting collective migration of endothelial cells. Together, our findings reveal specific cell migratory behaviours in the developing blood vessel plexus and uncover a conserved mode of artery formation

Transcription coactivators p300 and CBP are necessary for photoreceptor-specific chromatin organization and gene expression.

Rod and cone photoreceptor neurons in the mammalian retina possess specialized cellular architecture and functional features for converting light to a neuronal signal. Establishing and maintaining these characteristics requires appropriate expression of a specific set of genes, which is tightly regulated by a network of photoreceptor transcription factors centered on the cone-rod homeobox protein CRX. CRX recruits transcription coactivators p300 and CBP to acetylate promoter-bound histones and activate transcription of target genes. To further elucidate the role of these two coactivators, we conditionally knocked out Ep300 and/or CrebBP in differentiating rods or cones, using opsin-driven Cre recombinase. Knockout of either factor alone exerted minimal effects, but loss of both factors severely disrupted target cell morphology and function: the unique nuclear chromatin organization seen in mouse rods was reversed, accompanied by redistribution of nuclear territories associated with repressive and active histone marks. Transcription of many genes including CRX targets was severely impaired, correlating with reduced histone H3/H4 acetylation (the products of p300/CBP) on target gene promoters. Interestingly, the presence of a single wild-type allele of either coactivator prevented many of these defects, with Ep300 more effective than Cbp. These results suggest that p300 and CBP play essential roles in maintaining photoreceptor-specific structure, function and gene expression