Expression Changes And Characteristics Of Small RNAs During Spermatogenesis In Rabbits

Rabbits are very close to both humans and mice in evolution.They belong to the euarchonta.The rabbit is a typical representative of lagomorpha.Through the study of rabbits,it is helpful to find out the similarities and differences between rabbits and humans,and to provide the basis for future use of rabbits as a model for reproductive disease.Now it is unclear about the expression of small RNA in rabbits spermatogenesis.In this study,we studied the small RNAs in the testis of rabbits at different developmental stages to increase our understanding of the expression of small RNAs in rabbit spermiogenesis.In rabbit spermatogenesis,the regulation of small RNA has a great influence on spermatogenesis.We first annotated the small RNAs during rabbit spermiogenesis using bioinformatics methods,and predicted 707 new miRNAs and a large number of piRNA clusters.Many of these miRNAs and piRNA clusters are conserved in human and mouse.Then we analyzed the expression characteristics of small RNAs during rabbit spermiogenesis.Our study found that in rabbit spermatogenesis,there are two types of small RNAs that are highly expressed,namely miRNA and piRNA.These two types of small RNA have a dynamic expression process in rabbit spermatogenesis.In the process of spermatogenesis in rabbits,miRNAs are mainly expressed from day 1 to day 90,and piRNAs are mainly expressed from day100 to day 180.The miRNAs from the X chromosome are consistent with the MSCI phenomenon,which is very similar to mice.Moreover,the X chromosome-derived miRNA has two very conserved miRNA clusters.We analyzed its function and found that it may be related to sperm morphology.The piRNA sequence had obvious bias of1A10 U from day 10 to day 90,and strong 1U bias from day 100 to day 180.The alignment of piRNA sequences to the rabbit genome revealed that most of the 10 to 90-day piRNAs(more than 80%)had multiple alignment sites,and most of the day 100 to180-day piRNAs(about 75%)had only one alignment location.Analysis of the genomic annotation of piRNAs showed that piRNAs mainly originate from the repetitive regions and intergenic regions in 10 to 90 days,and mainly from the intergenic regions in 100 to 180 days.The piRNAs that from 10 days to 100 days originating from the repetitive regions are predominantly L1,and L1 and ERV2 are predominant from 110 days to 180 days.We found that the piRNAs from L1 and ERV had very obvious ping-pong signals,indicating that the piRNAs in rabbits also have ping-pong cycling.The piRNA biased sense strands in L1 and ERV,the LTR and SINE major positive strands,and the LTR transitions in the chain direction when the pre-pachyteen and pachyteen transition.The piRNAs derived from genes are mainly distributed on 3UTR and CDS.In addition,we also conducted a conservative analysis of piRNA clusters and found that piRNA clusters in mammalian spermatogenesis are conserved with humans and mice.This study mainly annotated the small RNAs in rabbits spermatogenesis,and analyzed the expression changes and characteristics of miRNAs and piRNAs,laying the foundation for us to understand the spermatogenesis of rabbits from the small RNA level.