Transcriptome Sequencing and Differential Analysis of Testes in One- and Two-Year-Old Kazakh Horses.

Overview

• This research investigated the developmental changes and gene expression differences in the testes of one- and two-year-old Kazakh horses to understand the molecular mechanisms regulating sexual maturation.

Background and Objectives

• The testis undergoes significant changes during sexual maturation, a critical period for reproductive capability.
• Kazakh horses, an important local breed, lack detailed characterization of testicular development at the molecular level.
• The study aimed to combine histological examination and transcriptome sequencing to systematically explore the cellular and molecular changes in testicular tissues between one- and two-year-old horses.

Methods

• Histological Observation:
  • Testicular tissue samples were collected from one-year-old and two-year-old Kazakh horses.
  • Microscopic examination focused on the presence and development of testicular lumen and cell types such as supporting cells, spermatogonia, spermatocytes, and spermatozoa.
• Transcriptome Sequencing (RNA-Seq):
  • RNA was extracted from testicular tissues to perform high-throughput sequencing.
  • Differential gene expression analysis was conducted to identify genes with altered expression between the two age groups.
• Bioinformatics Analysis:
  • Gene Ontology (GO) annotations were used to classify the biological processes, molecular functions, and cellular components associated with differentially expressed genes (DEGs).
  • Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis identified key signaling and metabolic pathways related to testicular maturation.
  • Protein-protein interaction (PPI) networks were constructed to pinpoint core regulatory genes involved in testicular development.
• Validation:
  • Real-time quantitative PCR (RT-qPCR) was performed on select genes to confirm the accuracy and reliability of RNA-Seq results.

Key Findings

• Histological Differences:
  • In one-year-old horse testes, no obvious tubular lumen was observed; cells inside primarily comprised supporting cells and spermatogonia located on the basement membrane.
  • In testes of two-year-old horses, the seminiferous tubule lumen was well-formed and contained spermatogonia, spermatocytes, and mature spermatozoa, indicating near-complete spermatogenic maturation.
• Differential Gene Expression:
  • A total of 979 DEGs were found between the two age groups.
  • Of these, 209 genes were up-regulated in the two-year-old testes, while 770 genes were down-regulated.
  • The study abstract did not specify all named genes but indicated important regulatory genes were highlighted.
• Functional Enrichment:
  • GO enrichment showed DEGs were primarily involved in multicellular organism development, cell membrane structure, and ion binding functions.
  • KEGG pathway analysis revealed significant enrichment in:
    • Calcium signaling pathway — important for cell signaling and spermatogenesis regulation.
    • Cell adhesion molecules — critical for cellular interactions and structural formation in the testis.
    • Neuroactive ligand-receptor interaction — indicating roles in cellular communication relevant to testicular function.
• Protein-Protein Interaction Network:
  • Core genes within the PPI network were identified as central to regulatory processes in testis development and function.
  • Although specific core genes were not named in the abstract, these genes represent key targets for future research and genetic improvement efforts.
• Validation with RT-qPCR:
  • The RNA-Seq data results were validated for accuracy by confirming gene expression patterns with RT-qPCR.
  • This step supports the reliability of the transcriptomic findings made in the study.

Implications and Conclusions

• The study provides a clear molecular and cellular developmental profile of testis maturation in Kazakh horses from ages one to two years.
• The identification of key genes and pathways offers a theoretical basis for understanding the regulation of spermatogenesis in this breed.
• These findings can guide selective breeding and genetic improvement programs aiming to enhance reproductive traits in Kazakh horses.
• The combination of histological, transcriptomic, and bioinformatics analyses presents a comprehensive approach for investigating reproductive development in livestock species.