Morphological changes and functional circRNAs screening of rabbit skeletal muscle development

Background The temporal expression pattern of circular RNAs (circRNAs) across developmental stages is essential for skeletal muscle growth and functional analysis. However, there are few analyses on the potential functions of circRNAs in rabbit skeletal muscle development. Results Initially, the paraffin sections showed extremely significant differences in the diameter, number, area and density of skeletal muscle fibers of the fetus, child, adult rabbit hind legs (P < 0.01). Then, RNA-seq libraries of these three stages were constructed. A total of 481 differentially expressed circRNAs (DE-circRNAs) and 5,658 differentially expressed genes (DEGs) were identified. Subsequently, DE-circRNAs, whose host genes were DEGs or non-DEGs, were analyzed by GO respectively. In the fetus vs. child group, up-regulated DE-circRNAs (whose host genes were DEGs) were related to muscle fiber structure, and down-regulated ones were related to mitosis. The up-regulated DE-circRNAs (whose host genes were non-DEGs) were involved in enzyme activity, methylation and glycosylation, and the down-regulated ones were involved in mitosis and catabolism. In the fetus vs. adult group, the up-regulated DE-circRNAs (whose host genes were DEGs) were related to skeletal muscle basic structure, and the down-regulated ones were also associated with cell proliferation. But the up-regulated DE-circRNAs (whose host genes were non-DEGs) were connected with regulation of histone ubiquitination, chromatin and organelles. The down-regulated DE-circRNAs were connected with the catabolism processes. In addition, novel_circ_0022663 and novel_circ_0005489, which might have coding potential, and novel_circ_0004210 and novel_circ_0001669, which might have miRNA sponge capability, were screened out. Conclusions In this study, hind leg muscles of fetus, child and adult rabbits were collected for paraffin section and RNA-seq to observe the structural changes of skeletal muscle and obtain circRNA expression profiles at different stages. These data provided a catalog of circRNAs related to muscle development in New Zealand rabbits, allowing us to better understand the functional transitions in mammalian muscle development.

Automated summary

This study observed structural changes in skeletal muscle and obtained circRNA expression profiles at different stages in hind leg muscles of fetus, child, and adult rabbits. The study identified differentially expressed circRNAs and genes, and found circRNAs with potential coding or miRNA sponge capability. These findings provide insights into the functional transitions in mammalian muscle development.