Pacific oyster (Crassostrea gigas) is one of the most widely cultivated shellfish species in the world. Because of its economic value and complex life cycle involving drastic changes from a free-swimming larva to a sessile juvenile, C. gigas has been used as a model for developmental, environmental, and aquaculture research. However, due to the lack of genetic tools for functional analysis, gene functions associated with biological or economic traits cannot be easily determined. Here, we reported a successful application of CRISPR/Cas9 technology for knockout of myosin essential light chain gene (CgMELC) in C. gigas. C. gigas embryos injected with sgRNAs/Cas9 contained extensive indel mutations at the target sites. The mutant larvae showed defective musculature and reduced motility. In addition, knockout of CgMELC disrupted the expression and patterning of myosin heavy chain positive myofibers in larvae. Together, these data indicate that CgMELC is involved in larval muscle contraction and myogenesis in oyster larvae.

太平洋牡蛎（Crassostrea gigas）是世界上养殖最广泛的贝类物种之一。由于其经济价值和复杂的生命周期，涉及从自由游动的幼虫到无柄幼虫的剧烈变化，C. gigas已被用作发育、环境和水产养殖研究的模型。然而，由于缺乏用于功能分析的遗传工具，与生物或经济性状相关的基因功能无法轻易确定。在这里，我们报道了 CRISPR/Cas9 技术在C. gigas 中成功应用肌球蛋白必需轻链基因 (CgMELC) 的敲除。C. gigas注射了 sgRNAs/Cas9 的胚胎在目标位点含有大量的 indel 突变。突变幼虫表现出有缺陷的肌肉组织和运动能力降低。此外，CgMELC 的敲除破坏了幼虫中肌球蛋白重链阳性肌纤维的表达和模式。总之，这些数据表明 CgMELC 参与牡蛎幼虫的幼虫肌肉收缩和肌生成。