SPARC as an essential regulator of fat body development and maintenance critical for Drosophila melanogaster larval progression

SPARC 作为脂肪体发育和维持的重要调节剂，对果蝇幼虫的发育至关重要

• 批准号: RGPIN-2015-03830
• 负责人: Ringuette, Maurice
• 金额: $ 2.19万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=629044
• 关键词: SPARC; essential; regulator; fat; body

The emergence of multicellular organisms was co-incident with the appearance of genes coding for extracellular matrix (ECM) molecules that gave rise to two distinct ECMs, interstitial matrices and basal laminae (BL)/basement membranes. BL, which are highly conserved in multicellular organisms, underlie epithelial and endothelial cells and envelop tissues and organs as well as nerves, muscle fibers and adipocytes. In addition to providing mechanical support and serving as an adhesive substrata for cell migration and survival, BL make critical contributions to the development of organisms via interactions with a diverse number of transmembrane receptors, growth factors and cytokines. The basic components of BLs include network-forming Collagen IV (ColIV), Laminin (LM), Perlecan, and Nidogen, which are assembled into sheet-like networks through complex and still poorly understood processes. The goal of the research program outlined in this application is to define key components that orchestrate BL assembly using Drosophila melanogaster as a model. We have shown that SPARC (Secreted Protein, Acidic, Rich in Cysteine), a Ca2+- and collagen-binding matricellular diffusible glycoprotein, is a major component of Drosophila embryonic BL. Our recent data indicate that SPARC deficiency leads to larval lethality associated with precocious remodelling of fat body BL. The embryonic and larval fat body is essential to fly development that functions nutrient storage and regulation of energy availability. The fat body is largely composed of adipocytes, individually enveloped within a BL, similar to adipocytes within vertebrates. Loss of SPARC results in rounded fat body adipocytes surrounded with an accumulation of improperly assembly BL components and precocious feeding behavior. Clonal analyses revealed that the accumulation of BL components was cell autonomous. Larval lethality was rescued with a genomic construct expressing SPARC under the control of the native SPARC promoter and driver lines restricting SPARC expression to the fat body. Based on these findings, we hypothesize that SPARC, via Ca2+-dependent interactions with CoIIV, promotes the proper sheet-like assembly of BL surrounding adipocytes. Loss of SPARC results in the aberrant formation and accumulation of BL, leading to remodeling of the fat body that results in larval lethality.

多细胞生物体的出现与编码细胞外基质（ECM）分子的基因的出现是一致的，所述ECM分子产生两种不同的ECM，间质基质和基底层（BL）/基底膜。BL在多细胞生物体中高度保守，位于上皮细胞和内皮细胞之下，并包裹组织和器官以及神经、肌纤维和脂肪细胞。除了提供机械支持和作为细胞迁移和存活的粘附基质外，BL还通过与多种跨膜受体、生长因子和细胞因子的相互作用对生物体的发育做出重要贡献。BL的基本组分包括网络形成胶原蛋白IV（ColIV）、层粘连蛋白（LM）、珍珠层蛋白聚糖和Nidogen，它们通过复杂且仍然知之甚少的过程组装成片状网络。在本申请中概述的研究计划的目标是使用果蝇作为模型来定义编排BL组装的关键组件。我们已经证明，分泌蛋白，酸性，富含半胱氨酸（分泌蛋白，酸性，富含半胱氨酸），钙和胶原结合的基质细胞扩散糖蛋白，是果蝇胚胎BL的主要组成部分。我们最近的数据表明，脂肪体BL的过早重塑，导致幼虫的死亡率与缺乏。胚胎和幼虫的脂肪体对苍蝇的发育至关重要，它具有储存营养和调节能量的功能。脂肪体主要由脂肪细胞组成，单独包裹在BL内，类似于脊椎动物中的脂肪细胞。脂肪体缺失导致圆形脂肪体脂肪细胞周围聚集不正确组装的BL组分和早熟的进食行为。克隆分析表明，BL组分的积累是细胞自主的。幼虫致死率是用在天然的p2p启动子和将p2p表达限制于脂肪体的驱动系的控制下表达p2p的基因组构建体拯救的。基于这些发现，我们假设，通过Ca 2+依赖的相互作用与CoIIV，促进适当的片状组装BL周围的脂肪细胞。脂肪酶的缺失导致BL的异常形成和积累，导致脂肪体的重塑，从而导致幼虫死亡。