# Comparative Transcriptomic Analysis Between High- and Low-Growth-Rate Meat-Type Rabbits Reveals Key Pathways Associated with Muscle Development

## TL;DR

This study compares muscle development in fast- and slow-growing rabbits to identify key genes and pathways that influence meat production.

## Contribution

This is the first comparative transcriptomic study of muscle development in high- and low-growth-rate meat-type rabbits.

## Key findings

- Ju rabbits showed higher body weight than Ma rabbits after 3 weeks, but Ma rabbits had larger muscle fiber areas at 56 days.
- Differentially expressed genes were enriched in pathways related to muscle cell migration, glycolysis, and HIF-1 signaling.
- Energy metabolism differences may explain the interbreed disparities in muscle development.

## Abstract

Rabbit meat represents a nutrient-dense, protein-rich food source experiencing increasing demand in the Asia-Pacific region. To investigate muscle growth differences between Sichuan linen (Ma) and Checkered Giant (Ju) rabbits, this study examined muscle fiber development in thigh and longissimus dorsi muscles at 28, 56, and 84 days post-natal. Significant differences in the muscle fiber area were observed between Ma and Ju rabbit at 56 days. Gene expression profiles of 56-day-old muscles were identified, followed by analysis of differentially expressed genes (DEGs) associated with muscle growth development. Functional analyses revealed critical biological pathways including glycolysis and HIF-1 signaling, as well as cellular processes such as muscle cell migration and programmed cell death. As the first comparative investigation of muscle development and transcriptional profiles between high- and low-growth-rate meat-type rabbits, this study elucidates molecular mechanisms underlying muscle growth, while offering a foundation for genetic enhancements aimed at optimizing meat production traits.

Rabbit meat constitutes a high-protein, low-fat nutritional resource demonstrating rising consumption, particularly within the Asia-Pacific region. Consequently, muscle growth and developmental pattern in meat rabbits represent critical economic considerations. To elucidate the primary signaling pathways governing muscle development, we first performed comparative body weight analyses between two rabbit breeds exhibiting divergent growth rates: the fast-growing Checkered Giant (Ju) and slow-growing Sichuan Ma rabbit. Subsequent, post-natal qualities of thigh and longissimus dorsi muscle fiber were quantified across three developmental phases (28, 56, and 84 days post-natal). The results showed the body weight of Ju rabbit was significantly higher than that of Ma rabbit beyond 3 weeks post-natal (p < 0.05), while Ma rabbit exhibited larger muscle fiber areas in both tissues at 56 days (p < 0.05). The transcriptome analysis showed that 284 and 305 differentially expressed genes (DEGs) (|log2FC| > 1, padj < 0.05) were identified in thigh muscle and longissimus dorsi muscle, respectively. GO (Gene Ontology) analysis of DEGs indicated DEGs in the thigh muscle were enriched in these terms related to biological processes of muscle cell migration and smooth muscle cell migration, cellular components of sarcomere, myofibril, and actin filament bundle, while DEGs in longissimus dorsi muscle were enriched in these terms associated with biological processes of muscle cell migration, smooth muscle cell migration and muscle structure development, cellular component of actin cytoskeleton, contractile fiber, myofibril, myosin complex and molecular function of actin filament binding. Integrated GO, KEGG and PPI analyses of co-expressive DEGs implicated the HIF-1 signaling pathway and Glycolysis/Gluconeogenesis in muscular development. Different expression of energy metabolism hub-genes might be the primary reason for interbreed muscle developmental disparities.