# Whole-Transcriptome Sequencing and Differential Expression Analysis of the Epididymis in Junggar Bactrian Camels Before and After Sexual Maturity

## TL;DR

This study identifies genetic changes in the epididymis of Bactrian camels during sexual maturity, offering insights into reproduction and potential improvements in breeding.

## Contribution

The study provides the first comprehensive transcriptome analysis of epididymal development in Bactrian camels, revealing novel genes and pathways.

## Key findings

- Identified 683 differentially expressed mRNAs, including genes like TPM2 and FASN, involved in sperm transport and hormone signaling.
- Discovered 260 differentially expressed long non-coding RNAs and 11 microRNAs linked to epididymal development.
- Key pathways include Cell Adhesion Molecules and Phospholipase D signaling, impacting reproductive function.

## Abstract

This study explored the genetic changes that occur in the epididymis of Bactrian camels as they mature sexually. By comparing camels before (3 years old) and after (5 years old) puberty, researchers discovered thousands of differences in gene activity, including, mRNA, protein-coding genes, long non-coding RNAs (LncRNAs), and microRNAs (miRNAs)—many of which were previously unknown. These genes play an important role in sperm storage, sperm transport, and hormone signaling. The key pathways involved in epididymal development were also identified, such as cell recognition, cell activation and signal transduction, cell proliferation and differentiation, cell stretching and movement, and other key signaling pathways. The findings provide new insights into camel reproduction and may help improve breeding programs for this economically important species.

The Junggar Bactrian camel, a primitive indigenous breed in China, exhibits low reproductive efficiency under natural grazing conditions. This is partly attributed to the development of the epididymis and the quality of semen, both of which directly affect reproductive performance. The epididymis is a key male reproductive organ responsible for sperm storage and transport. However, the gene expression profile of camel epididymal tissue remains poorly understood. In this study, we conducted whole-transcriptome sequencing of epididymal tissues from Junggar Bactrian camels before and after sexual maturity. A total of 683 differentially expressed mRNAs (DEmRNAs) were identified, including TPM2, ITGA5, FASN, and ACP5, of which 415 were upregulated and 268 were downregulated. Additionally, 260 differentially expressed long non-coding RNAs (DELncRNAs), including LOC123611838, LOC105083505, and LOC123614702, were identified, with 113 upregulated and 147 downregulated. An additional 11 differentially expressed microRNAs (DEmiRNAs), including eca-miR-206 and eca-miR-216a, were also detected. Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses revealed that key differentially expressed genes (DEGs), including TPM2, ITGA5, DDIT4, FASN, and ACP5, were mainly involved in pathways such as Cell Adhesion Molecules, Phospholipase D signaling, Cytokine–Cytokine Receptor Interaction, and Olfactory Transduction. This study presents a comprehensive whole-transcriptome analysis of the epididymis in Junggar Bactrian camels before and after sexual maturity, identifying key genes and regulatory pathways associated with epididymal development and reproductive function. These findings provide a theoretical foundation and valuable data for future research on reproductive performance and epididymal biology in Bactrian camels.