Epidermal cell fusion promotes the transition from an embryonic to a larval transcriptome in C. elegans

Cell fusion is a fundamental process in the development of multicellular organisms, but its precise influence on gene regulation during critical developmental stages remains largely unknown. The Caenorhabditis elegans epidermis, a powerful model for studying cell fusion, forms 8–10 syncytial cells. The largest of these, hyp7, integrates 139 individual nuclei via cell–cell fusion mediated by the fusogenic protein EFF-1. To explore the effects of cell fusion on developmental progression and associated gene expression changes, we conducted transcriptomic analyses of eff-1 knockout and fusion-deficient C. elegans mutants. Our RNAseq findings showed widespread transcriptomic changes including enrichment for epidermal genes and key molecular pathways involved in epidermal function during larval development. Subsequent single-molecule fluorescence in situ hybridization validated the altered expression of mRNA transcripts, confirming quantifiable changes in gene expression in the absence of embryonic epidermal fusion. These results underscore the significance of cell–cell fusion in shaping transcriptional programs during development and raise questions regarding the precise identities and specialized functions of different subclasses of nuclei within developing syncytial cells and tissues. Overall design: RNAseq of L1 wildtype and mutant larva

细胞融合是多细胞生物发育过程中的核心生物学过程，但其在关键发育阶段对基因调控的精准影响仍尚未明确。

作为研究细胞融合的经典模型，秀丽隐杆线虫（Caenorhabditis elegans）表皮可形成8~10个合胞体细胞。其中最大的合胞体hyp7可通过由融合蛋白EFF-1介导的细胞间融合过程，整合139个独立细胞核。

为探究细胞融合对发育进程及相关基因表达变化的影响，本研究对eff-1基因敲除及融合缺陷型秀丽隐杆线虫突变体开展了转录组分析。本研究的RNA测序（RNA-seq）结果显示，转录组存在广泛变化，包括幼虫发育阶段表皮基因及参与表皮功能的关键分子通路的富集。

后续通过单分子荧光原位杂交（single-molecule fluorescence in situ hybridization）验证了mRNA转录本的表达变化，证实了胚胎表皮融合缺失时基因表达的可量化改变。

上述结果凸显了细胞间融合在塑造发育过程中转录程序的重要意义，并提出了新的科学问题：发育中的合胞体细胞与组织内不同细胞核亚群的精准身份及其特化功能究竟为何。

整体实验设计：第一龄幼虫（L1期）野生型与突变体线虫的RNA测序分析。