Whole transcriptome sequencing reveals core genes related to spermatogenesis in Bactrian camels

Bactrian camels survive and reproduce better in extreme climatic conditions than other domestic animals can. However, the reproductive efficiency of camels under their natural pastoral conditions is low. Several factors affect mammalian reproductive performance, including testicular development, semen quality, libido, and mating ability. Testis is a main reproductive organ of the male and is responsible for producing spermatozoa and hormones. However, our understanding of the expression patterns of the genes in camel testis is minimal. Thus, we performed total RNA-sequencing to investigate the gene expression pattern. As a result, 1,538 differential expressed mRNAs (DEmRNAs), 702 differential expressed long non-coding RNAs (DElncRNAs), and 61 differential expressed microRNAs (DEmiRNAs) were identified between pubertal and adult Bactrian camel testes. Then the genomic features, length distribution, and other characteristics of the lncRNAs and mRNAs in the Bactrian camel testis were investigated. Target genes of the DEmiRNAs and DEmRNAs were further subjected to gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Genes, such as AMHR2, FGF1, ACTL7A, GATA4, WNT4, ID2, LAMA1, IGF1, INHBB, and TLR2, were mainly involved in the TGF-beta, PI3K-AKT, Wnt, GnRH, and Hippo signaling pathways which relate to spermatogenesis. Some of the DEmiRNAs were predicted to be associated with numerous DElncRNAs and DEmRNAs through competing endogenous RNA (ceRNA) regulatory network. At last, the candidate genes were validated by RT-qPCR, dual fluorescent reporter gene, and a fluorescence in situ hybridization (FISH) assay. This research provides high-throughput RNA sequencing data of the testes of Bactrian camels across different developmental stages. It lays the foundation for further investigations on lncRNAs, miRNAs, and mRNAs that involved in Bactrian camel spermatogenesis. The LOC105072226, miR-362-3p, INHBB, LOC116153108, miR-140-5p, and TLR2 were related to testicular development and spermatogenesis in Bactrian camels. Bactrian camel breeding has a long history and has played an extremely important role in desert and semi-desert management and grassland culture, economy, and ecological development. As a precious livestock resource, the Bactrian camel has developed into an important part of China's grassland livestock industry. However, due to their biological characteristics, camels have lower fertility than other livestock. Fertility is one of the most important factors affecting camel productivity. Maintaining a high level of fertility is essential to improve their performance and genetic improvement. Fertility is mainly related to testicular development and regulation of gene expression during spermatogenesis. Therefore, the study of genes related to testicular development and spermatogenesis and the elucidation of their molecular mechanisms are important for improving and protecting male fertility and preventing male reproductive disorders. This study provided a theoretical foundation for further research into the molecular mechanisms of testis development and spermatogenesis in Bactrian camels by constructing the lncRNA-miRNA-mRNA regulatory interactions network.