Expression of m⁶A methylation enzymes METTL3 and WTAP in tissues and adipocytes of yak

The aim of this study was to investigate the expression pattern of the m⁶A RNA methylesterases, METTL3 and WTAP, in different tissues, and yak (Bos grunniens) preadipocyte proliferation and differentiation, as well as the level of mRNA m⁶A during preadipocyte differentiation. In this study, qRT-PCR was used to detect mRNA expression levels of METTL3 and WTAP in the subcutaneous fat, muscle, heart, liver, spleen, lung, kidney, and subcutaneous adipose tissue of yaks at 18 and 30 months of age. The type I collagenase digestion method was used to obtain yak preadipocytes, Oil Red O staining was used to identify lipid-containing cells, and adipogenesis marker genes were detected to establish a differentiation model of yak preadipocytes. qRT-PCR was used to detect the mRNA expression levels of METTL3 and WTAP in the proliferation and differentiation stages of preadipocytes. The results showed that METTL3 expression was the highest in the liver tissue (P < 0.05) and the lowest in the subcutaneous adipose tissue (P < 0.05). WTAP expression was most abundant in the subcutaneous adipose tissue and lowest in the spleen (P < 0.05). The expression of METTL3 and WTAP was higher in subcutaneous adipose tissue at 30 months than at 18 months of age. After 12 days of preadipocyte-induced differentiation, multiple and dense lipid rings appeared in the cells, and the expression of the adipocyte differentiation-specific marker genes, FABP4, C/EBPα, and PPARγ, was significantly higher on day 12 than on day 0 (P < 0.05). Expression of METTL3 and WTAP at the cell proliferation stage (24, 48, and 72 h) showed a decreasing trend (P < 0.05). At the differentiation stage of yak preadipocytes (0, 4, 8, and 12 d), METTL3 expression showed a rising-declining-rising trend, and WTAP showed a rising-declining trend. The mRNA m⁶A level showed a gradual increase at the differentiation stage, and the highest intracellular mRNA m⁶A abundance was observed after 12 days of differentiation (P < 0.05). Our results show the changes in METTL3 and WTAP in different tissues and yak preadipocytes and the changes in mRNA m⁶A levels during preadipocyte differentiation and revealed that WTAP and METTL3 have important regulatory roles in yak lipid metabolism.