Transcriptome Comparison of Chorion-Attached and Non-chorion-attached Endometrium in Mid-gestation of Rabbit.

Background: The chorion from the placenta is directly attached to the endometrium (CA) after embryo implantation while some parts of the endometrium are not chorion-attached (NCA). The differences in gene expression between the CA and NCA endometrium mid-gestation are unknown. Our objective was to compare the gene expression profiles of the CA and NCA endometrium of rabbit, to identify the differentially expressed genes (DEGs), and correlate the differences with the physiological state of the endometrium at mid-gestation of rabbit. Methods: We used transcriptome sequencing to reveal the differences in gene expression between CA and NCA endometrium (n = 3), and then determined the concentration of inflammatory cytokines in CA and NCA tissue and serum by ELISA. Results: Six Hundred and Forty-Six DEGs were identified between the CA and NCA endometrium [p < 0.05, |log2 (fold change) |≥ 2], The expression levels of 590 DEGs were higher in the NCA endometrium than in the CA endometrium, while the expression level of only 56 DEGs were higher in CA than in NCA. The DEGs were enriched in gene ontology (GO) terms and pathways related to immune regulation and cellular adhesions. Six hub-genes related to inflammatory mediator regulation of transient receptor potential (TRP) channels and chemokine signaling pathways had a lower expression level in the CA endometrium compared to the NCA endometrium, and the expression levels of genes related to focal adhesion and extracellular matrix (ECM)-receptors were significantly higher in NCA endometrium than in CA endometrium. The level of pro-inflammatory cytokines accumulated in the CA endometrium, and high abundance of integrin-ß and THBS1 were localized in the luminal epithelium of the NCA endometrium, but not in the CA endometrium. Conclusions: Our study reveals differences in gene expression between the CA and NCA endometrium at mid-gestation of rabbit, and suggests implications for endometrial physiological function. The CA endometrium showed relative low-level gene expression compared to the NCA endometrium, while the NCA endometrium performed physiological functions related to focal adhesion and ECM-receptor interaction.

Circular RNA, microRNA and Protein Profiles of the Longissimus Dorsi of Germany ZIKA and Sichuan White Rabbits.

Due to the dietetic properties and remarkable nutritive value of rabbit meat, its industry is increasing rapidly. However, the association between circular RNAs, microRNAs, and proteins and muscle fiber type, and meat quality of rabbit is still unknown. Here, using deep sequencing and iTRAQ proteomics technologies we first identified 3159 circRNAs, 356 miRNAs, and 755 proteins in the longissimus dorsi tissues from Sichuan white (SCWrabs) and Germany great line ZIKA rabbits (ZIKArabs). Next, we identified 267 circRNAs, 3 miRNAs, and 29 proteins differentially expressed in the muscle tissues of SCWrabs and ZIKArabs. Interaction network analysis revealed some key regulation relationships between noncoding RNAs and proteins that might be associated with the muscle fiber type and meat quality of rabbit. Further, miRNA isoforms and gene variants identified in SCWrabs and ZIKArabs revealed some pathways and biological processes related to the muscle development. This is the first study of noncoding RNA and protein profiles for the two rabbit breeds. It provides a valuable resource for future studies in rabbits and will improve our understanding of the molecular regulation mechanisms in the muscle development of livestock. More importantly, the output of our study will benefit the researchers and producers in the rabbit breeding program.

[Progress on breeding for best-hybridized crossing of meat rabbits].

Best-hybridized crossing should ideally result in optimal exploitation of heterosis of lines and capitalize on expressed heterosis. Rabbit breeding is heading in the direction of breeding for best-hybridized crossing of meat rabbits. Most special sire lines are selected for post-weaning average daily gain and marketing weight. Post-weaning growth has a negative and favorable genetic correlation with the feed conversion ratio, which is used in indirect selection for feed conversion ratio. The most common selection criteria for special maternal lines are related to litter size at birth or at weaning. Since the heritability of most reproductive traits is low, we must collect as many individual and relative records as possible in the genetic evaluation of rabbits. The BLUP procedure under an animal repeatability model is the most common procedure used for evaluation of animals in selection programs for special lines of meat rabbits. Direct selection for litter size is less efficient than selection for post-weaning growth, but the estimation of heterosis is generally higher for litter size than that for the post-weaning growth. Evaluation of heterosis could be performed by estimating crossbreeding parameters in the cross or comparing contemporary productivity among purebreds and crossbreds. Here, we reviewed breeding of special lines, exploitation of heterosis of crossbreds, and establishment of crossbreeding system of hybrid meat rabbits and summarized the methodologies of breeding special lines, criteria in selection programs, and the result of heterosis estimates.