State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing 400715, China.
Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City & Southwest University, Chongqing 400715, China.
Int J Mol Sci. 2023 Feb 9;24(4):3468. doi: 10.3390/ijms24043468.
DNA N6-methyladenine (6mA) has recently been found to play regulatory roles in gene expression that links to various biological processes in eukaryotic species. The functional identification of 6mA methyltransferase will be important for understanding the underlying molecular mechanism of epigenetic 6mA methylation. It has been reported that the methyltransferase METTL4 can catalyze the methylation of 6mA; however, the function of METTL4 remains largely unknown. In this study, we aim to investigate the role of the homolog METTL4 (BmMETTL4) in silkworm, a lepidopteran model insect. By using CRISPR-Cas9 system, we somatically mutated BmMETTL4 in silkworm individuates and found that disruption of BmMETTL4 caused the developmental defect of late silkworm embryo and subsequent lethality. We performed RNA-Seq and identified that there were 3192 differentially expressed genes in BmMETTL4 mutant including 1743 up-regulated and 1449 down-regulated. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses showed that genes involved in molecular structure, chitin binding, and serine hydrolase activity were significantly affected by BmMETTL4 mutation. We further found that the expression of cuticular protein genes and collagens were clearly decreased while collagenases were highly increased, which had great contributions to the abnormal embryo and decreased hatchability of silkworm. Taken together, these results demonstrated a critical role of 6mA methyltransferase BmMETTL4 in regulating embryonic development of silkworm.
DNA N6-甲基腺嘌呤（6mA）最近被发现可在真核生物中发挥调节基因表达的作用，这种调节作用与多种生物学过程有关。6mA 甲基转移酶的功能鉴定对于理解表观遗传 6mA 甲基化的潜在分子机制将是重要的。据报道，甲基转移酶 METTL4 可以催化 6mA 的甲基化；然而，METTL4 的功能在很大程度上仍然未知。在本研究中，我们旨在研究 6mA 甲基转移酶的同源物 METTL4（BmMETTL4）在鳞翅目模式昆虫家蚕中的作用。通过使用 CRISPR-Cas9 系统，我们在家蚕个体中体细胞突变 BmMETTL4，并发现 BmMETTL4 的破坏导致后期家蚕胚胎发育缺陷和随后的致死性。我们进行了 RNA-Seq 并鉴定出 BmMETTL4 突变体中有 3192 个差异表达基因，包括 1743 个上调基因和 1449 个下调基因。基因本体论和京都基因与基因组百科全书分析表明，参与分子结构、几丁质结合和丝氨酸水解酶活性的基因受到 BmMETTL4 突变的显著影响。我们进一步发现，表皮蛋白基因和胶原的表达明显降低，而胶原酶的表达明显升高，这对家蚕胚胎异常和孵化率降低有很大贡献。总之，这些结果表明 6mA 甲基转移酶 BmMETTL4 在调控家蚕胚胎发育中起着关键作用。
