Divergent selection for total fleece weight in Angora rabbits: Correlated responses in wool characteristics

Altered hair root gene expression profiles highlight calcium signaling and lipid metabolism pathways to be associated with curly hair initiation and maintenance in Mangalitza pigs

Hair types have been under strong targeted selection in domestic animals for their impact on skin protection, thermoregulation and exterior morphology, and subsequent economic importance. In pigs, a very special hair phenotype was observed in Mangalitza, who expresses a thick coat of curly bristles and downy hair. Two breed-specific missense variants in TRPM2 and CYP4F3 were suggested to be associated with the Mangalitza pig's hair shape due to their role in hair follicle morphogenesis reported for human and mice. However, the mechanism behind this expression of a curly hair type is still unclear and needs to be explored. In our study, hair shafts were measured and investigated for the curvature of the hair in Mangalitza and crossbreeds in comparison to straight-coated pigs. For molecular studies, hair roots underwent RNA sequencing for a differential gene expression analysis using DESeq2. The output matrix of normalized counts was then used to construct weighted gene co-expression networks. The resulting hair root gene expression profiles highlighted 454 genes to be significantly differentially expressed for initiation of curly hair phenotype in newborn Mangalitza piglets versus post-initiation in later development. Furthermore, 2,554 genes showed a significant differential gene expression in curly hair in comparison to straight hair. Neither TRPM2 nor CYP4F3 were identified as differentially expressed. Incidence of the genes in weighted co-expression networks associated with TRPM2 and CYP4F3, and prominent interactions of subsequent proteins with lipids and calcium-related pathways suggested calcium signaling and/or lipid metabolism as essential players in the induction of the curly hair as well as an ionic calcium-dependency to be a prominent factor for the maintenance of this phenotype. Subsequently, our study highlights the complex interrelations and dependencies of mutant genes TRPM2 and CYP4F3 and associated gene expression patterns, allowing the initiation of curly hair type during the development of a piglet as well as the maintenance in adult individuals.

Analysis of histology and long noncoding RNAs involved in the rabbit hair follicle density using RNA sequencing

BACKGROUND

Hair follicle density influences wool fibre production, which is one of the most important traits of the Wan Strain Angora rabbit. However, molecular mechanisms regulating hair follicle density have remained elusive.

RESULTS

In this study, hair follicle density at different body sites of Wan Strain Angora rabbits with high and low wool production (HWP and LWP) was investigated by histological analysis. Haematoxylin-eosin staining showed a higher hair follicle density in the skin of the HWP rabbits. The long noncoding RNA (lncRNA) profile was investigated by RNA sequencing, and 50 and 38 differentially expressed (DE) lncRNAs and genes, respectively, were screened between the HWP and LWP groups. A gene ontology analysis revealed that phospholipid, lipid metabolic, apoptotic, lipid biosynthetic, and lipid and fatty acid transport processes were significantly enriched. Potential functional lncRNAs that regulate lipid metabolism, amino acid synthesis, as well as the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) and hedgehog signalling pathways, were identified. Consequently, five lncRNAs (LNC_002171, LNC_000797, LNC_005567, LNC_013595, and LNC_020367) were considered to be potential regulators of hair follicle density and development. Three DE lncRNAs and genes were validated by quantitative real-time polymerase chain reaction (q-PCR).

CONCLUSIONS

LncRNA profiles provide information on lncRNA expression to improve the understanding of molecular mechanisms involved in the regulation of hair follicle density.

Genetic description of a divergent selection experiment in Angora rabbits with overlapping generations

The chief aims of this paper were the following: (i) to describe the demography and genetic structure in two divergent selected lines for total fleece weight (TFW) of French Angora rabbits with overlapping generations; (ii) to describe the effects of inbreeding during an experiment of divergent selection. A study of longevity with the survival kit showed that there was no significant difference in the risk of death or culling between the low line (LL) and high line (HL). A significant effect of inbreeding (p < 0.05) was observed with a 30% higher risk factor in the highest class of inbreeding coefficient compared with the other classes. The means of generation interval were 562 and 601 days in LL and HL, respectively. The numbers of generations for LL and HL were 3.90 and 3.64, respectively. Generation intervals decreased significantly from 1995 to 2000 (p < 0.05). The number of daughters in HL was very variable. The number of animals per generation was higher in HL than in LL. Each buck left nearly three daughters to the next generation (2.52 in LL, 3.24 in HL). In both lines, the effective number of ancestor genomes still present in the genetic pool of the generation was around eight from the reference population of 1995 to that of 2001. Inbreeding in HL was always higher than in LL. The effect of inbreeding was also significant (p < 0.05) on TFW and live weight. The animals with the lowest inbreeding category produced a higher TFW (p < 0.05) than the others. The observed selection differentials were lower than that expected owing to the breeding animal management rules in order to control inbreeding increase.