Skeletal muscle development plays an important role in muscle quality and yield, which decides the economic value of livestock. Long non-coding RNAs (lncRNAs) have been reported to be associated with skeletal muscle development. However, little is revealed about the function of lncRNAs in rabbits’ muscle development. LncRNAs and mRNAs in two rabbit breeds (ZIKA rabbits (ZKR) and Qixin rabbits (QXR)) with different growth rates at three developmental stages (0 day, 35 days, and 84 days after birth) were researched by transcriptome sequencing. Differentially expressed lncRNAs and mRNAs were identified for two rabbit breeds at the same stages by DESeq package. Co-expression correlation analysis of differentially expressed lncRNAs and mRNAs were performed to construct lncRNA–mRNA pairs. To explore the function of lncRNAs, Gene Ontology (GO) analysis of co-expression mRNAs in lncRNA–mRNA pairs were performed. In three comparisons, there were 128, 109, and 115 differentially expressed lncRNAs, respectively. LncRNAs TCONS_00013557 and XR_518424.2 differentially expressed in the two rabbit breeds might play important roles in skeletal muscle development, for their co-expressed mRNAs were significantly enriched in skeletal muscle development related GO terms. This study provides potentially functional lncRNAs in skeletal muscle development of two rabbit breeds and might be beneficial to the production of rabbits.

The domestic rabbit (Oryctolagus cuniculus f. domesticus) is a very important variety in biomedical research and agricultural animal breeding. Due to the different geographical areas in which rabbit breeds originated, and the long history of domestication/artificial breeding, rabbits have experienced strong selection pressure, which has shaped many traits of most rabbit varieties, such as color and weight. An efficient genome-wide single-nucleotide polymorphism (SNP) detection strategy is genotyping-by-sequencing (GBS), which has been widely used in many organisms. This study attempted to explore bi-allelic SNPs associated with fur color and weight-related traits using GBS in five rabbit breeds. The data consisted of a total 831,035 SNPs in 150 individuals from Californian rabbits (CF), German Zika rabbits (ZK), Qixing rabbits (QX), Sichuan grey rabbits (SG), and Sichuan white rabbits (SW). In addition, these five breeds of rabbits were obviously independent populations, with high genetic differentiation among breeds and low genetic diversity within breeds. A total of 32,144 SNP sites were identified by selective sweep among the different varieties. The genes that carried SNP loci in these selected regions were related to important traits (fur color and weight) and signal pathways, such as the MAPK/ERK signaling pathway and the Hippo signaling pathway. In addition, genes related to fur color and weight were identified, such as ASIPs, MITFs and KITs, ADCY3s, YAPs, FASs, and ACSL5s, and they had more SNP sites. The research offers the foundation for further exploration of molecular genetic markers of SNPs that are related to 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.

Rabbit meat is a high-protein, low-fat health food with increasing consumption especially in the Asia-Pacific region. Therefore, muscle growth and development of meat rabbits are important economic traits. In order to reveal the primary signal pathway related to muscle growth, We first compared the body weight between two rabbit breeds with distinct growth rates (fast-growing(Checkered Giant (Ju)) vs. slow-growing (Sichuan linen (Ma)), and then examined the diameter of muscle fiber on 28-day, 56-day and 84-day. The transcriptome of thigh and longissimus thoracis from 56-day-old and rabbits was performed. The results showed the body weight of Ju rabbit was significantly higher than that of Ma rabbit after 3-week age (p>0.05), and the diameter of thigh and the longissimus dorsi muscle fiber from Ma rabbit was significantly bigger than that from Ju rabbit (p>0.05) at 56-day of age. Transcriptomic analysis showed that 284 and 305 DEGs were screened in thigh muscle and longissimus dorsi muscle, respectively using |log2FC|>1 and padj< 0.05. GO analysis of DEGs Ma vs Ju was performed, and these DEGs in the thigh muscle were enriched in these terms related to muscle cell migration, smooth muscle cell migration, sarcomere, myofibril, actin filament bundle, and those in Longissimus dorsi muscle were enriched in these terms related to muscle cell migration, smooth muscle cell migration, muscle structure development, actin cytoskeleton, contractile fiber, myofibril, myosin complex and actin filament binding. Sequentially, GO, KEGG and PPI analysis of DEGs or co-expressive DEGs in thigh and longissimus dorsi muscle suggested that HIF-1 signaling pathway and Glycolysis/Gluconeogenesis is related to muscle development between Ma and Ju rabbit, and the expressive difference of hub-genes related to energy metabolism might is the primary reason for the difference in muscle development between Ma and Ju rabbit.