Abstract：MicroRNA(miRNA) is a class of small RNA, it is involved in the intracellular complicated and precise regulatory networks. In order to study the effect of castration on the expression of miR-122 and miR-378 and the regulation effect of miR-122 and miR-378 on androstenone and skatole metabolism, we detected the skatole content in subcutaneous fat of boars and barrows with the help of high performance liquid chromatography (HPLC) and the expression of miR-122 and miR-378 in various growth stages in liver of Jinhua Pig (Sus scrofa) by quantitative Real-time PCR (qRT-PCR) and analysed the expression variation between boars and barrows. The results showed that the skatole content in adipose tissue was higher (P<0.01) in boars (mean 87.21 μg/kg, n=9) than that in barrows (79.87 μg/kg, n=9), and there was a significance change of the expression of miR-122 and miR-378 between embryonic and growth period. In the embryonic period the expression of miR-122 increased firstly and lasted to the 80th day, and then decreased. In the growth period the expression of miR-122 was decreased gradually. With the development of embryonic liver the expression of miR-378 continued to increase, while in the growth period miR-378 increased firstly and then decreased, and at 60 d reached the maximum. After 60 d the expression of both miR-122 and miR-378 of boars and barrows decreased significantly (P<0.01) with the increase of day age. At 60 and 120 d the expression of miR-122 of barrows were significantly decreased (P<0.01) by comparison to boars, and at 90th day it was also decreased significantly (P<0.05). After castration, the expression of miR-378 was decreased significantly (P<0.01) at 60, 90 and 120 d. We also predicted the transcription factors which may affect the transcription of pre-miR-122 and pre-miR-378, and the target genes which may affect the androstenone and skatole metabolism. We found that miR-122 and miR-378 had target relationship with androstenone and skatole metabolism genes SULT1A1(sulfotransferase family, cytosolic, 1A, phenol-preferring, member 1), SULT2A1(sulfotransferase family, cytosolic, 2A, dehydroepiandrosterone (DHEA)-preferring, member 1) and CYP2E1(cytochrome P450, family 2, subfamily E, polupeptide 1). We forecasted that the upstream sequence of 5.2~4.9 kb of pre-miR-122 and the upstream sequence of 2.2~1.8 kb of pre-miR-378 were the promoter region, and there were related transcription factor binding sites. In the upstream sequence of pre-miR-378, there was a CpG island close to the promoter region, which indicated that the transcription of pre-miR-378 might be affected by methylation. In conclusion, we suggested that the changes of hormone level after castration may affect the expression of microRNA through the relevant transcription factors, and then affect the boar taint by regulating the androstenone and skatole metabolism directly or indirectly. And microRNAs may play an important role in the regulatory networks.All in all ,we provide a new idea for further research on boar taint.
