Distinct roles for COMPASS core subunits Set1, Trx, and Trr in the epigenetic regulation of Drosophila heart development. Distinct roles for COMPASS core subunits Set1, Trx, and Trr in the epigenetic regulation of Drosophila heart development

This study investigated the role Complex of Proteins Associated with Set1 (COMPASS) in heart development. These are evolutionarily highly conserved multiprotein complexes required for H3K4 methylation. In Drosophila, their core subunits are Set1, Trx, and Trr. We studied flies deficient for either of these three subunits their hearts. These flies showed high lethality at eclosion (emergence of adult flies from their pupal case) and significantly shortened lifespans for the adults that did emerge. Furthermore, their hearts showed reduced H3K4 monomethylation (H3K4me1) and dimethylation (H3K4me2), and significantly altered gene expression patterns. The data revealed that each of the COMPASS core subunits (Set1, Trx, and Trr) control methylation of different sets of genes with distinct temporal activity: Set1 throughout, whereas Trr was active early and Trx at later stages of heart development. We found that many metabolic pathways were active early in development and throughout, while muscle and heart differentiation processes were methylated during later stages of development. Taken together, the findings demonstrate the importance of COMPASS complexes during heart development, therewith supporting their implication in congenital heart diseases. Overall design: To investigate the gene expression patterns regulated by Set1, Trx, and Trr. We employed the Drosophila UAS-Gal4 system combined with RNAi knockdown. We used twist (twi)-Gal4 to tissue knockdown Set1, trx, or trr specifically in the Drosophila heart. We then performed gene expression profiling analysis using data obtained from RNA-Seq of three different samples for each genotype. Comparative gene expression profiling analysis of RNA-Seq data for wildtype and its knock-down (RNAi) derivatives (Set1, trx, and trr).

本研究探究了Set1相关蛋白复合物（Complex of Proteins Associated with Set1, COMPASS）在心脏发育中的作用。该复合物为进化高度保守的多蛋白复合物，是介导H3K4甲基化修饰所必需的。在果蝇中，该复合物的核心亚基为Set1、Trx与Trr。我们针对这三个核心亚基中任一亚基缺陷的果蝇心脏组织开展了研究。结果显示，这类果蝇在羽化阶段（成虫从蛹壳中钻出的过程）呈现极高的致死率，成功羽化的成虫寿命也显著缩短。此外，其心脏组织中H3K4单甲基化（H3K4me1）与双甲基化（H3K4me2）水平均出现下调，且基因表达模式发生显著改变。测序数据分析表明，COMPASS的三个核心亚基（Set1、Trx与Trr）分别调控不同基因集的甲基化修饰，且具有独特的时序活性：Set1在整个心脏发育阶段均发挥功能，Trr仅在发育早期活跃，而Trx则在发育后期行使作用。我们发现，众多代谢通路在发育早期及全程均处于激活状态，而肌肉与心脏分化过程则在发育后期发生甲基化修饰。综上，本研究结果证实了COMPASS复合物在心脏发育过程中的关键作用，同时为其与先天性心脏病存在潜在关联提供了实验依据。整体实验设计：为探究Set1、Trx及Trr所调控的基因表达模式，我们采用果蝇UAS-Gal4系统结合RNA干扰（RNA interference, RNAi）敲低技术。借助twist（twi）-Gal4驱动因子，我们可在果蝇心脏组织中特异性敲低Set1、trx或trr基因。随后，我们针对每种基因型的三个生物学重复样本进行RNA测序（RNA-Seq），并基于所得数据开展基因表达谱分析。对野生型样本及其对应的敲低（RNAi）衍生样本（Set1、trx及trr）的RNA测序数据，我们进行了比较基因表达谱分析。