A Novel Pale-Yellow Coat Color of Rabbits Generated via MC1R Mutation With CRISPR/Cas9 System

Revolutionizing cattle breeding: Gene editing advancements for enhancing economic traits

Beef and dairy products are rich in protein and amino acids, making them highly nutritious for human consumption. The increasing use of gene editing technology in agriculture has paved the way for genetic improvement in cattle breeding via the development of the CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR-associated protein) system. Gene sequences are artificially altered and employed in the pursuit of improving bovine breeding research through targeted knockout, knock-in, substitution, and mutation methods. This review offers a comprehensive analysis of the advancements in gene editing technology and its diverse applications in enhancing both quantitative and qualitative traits across livestock. These applications encompass areas such as meat quality, milk quality, fertility, disease resistance, environmental adaptability, sex control, horn development, and coat colour. Furthermore, the review considers prospective ideas and insights that may be employed to refine breeding traits, enhance editing efficiency, and navigate the ethical considerations associated with these advancements. The review's focus on improving the quality of beef and milk is intended to enhance the economic viability of these products. Furthermore, it constitutes a valuable resource for scholars and researchers engaged in the fields of cattle genetic improvement and breeding.

Animal Transgenesis and Cloning: Combined Development and Future Perspectives

The revolution in animal transgenesis began in 1981 and continues to become more efficient, cheaper, and faster to perform. New genome editing technologies, especially CRISPR-Cas9, are leading to a new era of genetically modified or edited organisms. Some researchers advocate this new era as the time of synthetic biology or re-engineering. Nonetheless, we are witnessing advances in high-throughput sequencing, artificial DNA synthesis, and design of artificial genomes at a fast pace. These advances in symbiosis with animal cloning by somatic cell nuclear transfer (SCNT) allow the development of improved livestock, animal models of human disease, and heterologous production of bioproducts for medical applications. In the context of genetic engineering, SCNT remains a useful technology to generate animals from genetically modified cells. This chapter addresses these fast-developing technologies driving this biotechnological revolution and their association with animal cloning technology.

Genetically Modified Rabbits for Cardiovascular Research

Rabbits are one of the most used experimental animals for investigating the mechanisms of human cardiovascular disease and lipid metabolism because they are phylogenetically closer to human than rodents (mice and rats). Cholesterol-fed wild-type rabbits were first used to study human atherosclerosis more than 100 years ago and are still playing an important role in cardiovascular research. Furthermore, transgenic rabbits generated by pronuclear microinjection provided another means to investigate many gene functions associated with human disease. Because of the lack of both rabbit embryonic stem cells and the genome information, for a long time, it has been a dream for scientists to obtain knockout rabbits generated by homologous recombination-based genomic manipulation as in mice. This obstacle has greatly hampered using genetically modified rabbits to disclose the molecular mechanisms of many human diseases. The advent of genome editing technologies has dramatically extended the applications of experimental animals including rabbits. In this review, we will update genetically modified rabbits, including transgenic, knock-out, and knock-in rabbits during the past decades regarding their use in cardiovascular research and point out the perspectives in future.

Analysis of MC1R, MITF, TYR, TYRP1, and MLPH Genes Polymorphism in Four Rabbit Breeds with Different Coat Colors

Simple Summary

Coat color is an important breed characteristic and economic trait for rabbits, and it is regulated by a few genes. In this study, the gene frequencies of some pigmentation genes were investigated in four Chinese native rabbit breeds with different coat colors. A total of 14 genetic variants were detected in the gene fragments of MC1R, MITF, TYR, TYRP1, and MLPH genes, and there was low-to-moderate polymorphism in the populations. The gene frequency showed significant differences among the four rabbit populations. The above results suggest that these genetic variations play an important role in regulating the coat color of rabbits. This study will provide potential molecular markers for the breeding of coat color traits in rabbits.

Abstract

Pigmentation genes such as MC1R, MITF, TYR, TYRP1, and MLPH play a major role in rabbit coat color. To understand the genotypic profile underlying coat color in indigenous Chinese rabbit breeds, portions of the above-mentioned genes were amplified and variations in them were analyzed by DNA sequencing. Based on the analysis of 24 Tianfu black rabbits, 24 Sichuan white rabbits, 24 Sichuan gray rabbits, and 24 Fujian yellow rabbits, two indels in MC1R, three SNPs in MITF, five SNPs (single nucleotide polymorphisms) in TYR, one SNP in TYRP1, and three SNPs in MLPH were discovered. These variations have low-to-moderate polymorphism, and there are significant differences in their distribution among the different breeds (p < 0.05). These results provide more information regarding the genetic background of these native rabbit breeds and reveal their high-quality genetic resources.

Mouse Hair Significantly Lightened Through Replacement of the Cysteine Residue in the N-Terminal Domain of Mc1r Using the CRISPR/Cas9 System

A loss-of-function mutation in the melanocortin 1 receptor gene (MC1R), which switches off the eumelanin production, causes yellowish coat color variants in mammals. In a wild population of sables (Martes zibellina) in Hokkaido, Japan, the mutation responsible for a bright yellow coat color variant was inferred to be a cysteine replacement at codon 35 of the N-terminal extracellular domain of the Mc1r receptor. In the present study, we validated these findings by applying genome editing on Mc1r in mouse strains C3H/HeJ and C57BL/6N, altering the codon for cysteine (Cys33Phe). The resulting single amino acid substitution (Cys33Phe) and unintentionally generated frameshift mutations yielded a color variant exhibiting substantially brighter body color, indicating that the Cys35 replacement produced sufficient MC1R loss of function to confirm that this mutation is responsible for producing the Hokkaido sable yellow color variant. Notably, the yellowish mutant mouse phenotype exhibited brown coloration in subapical hair on the dorsal side in both the C3H/HeJ and C57BL/6N strains, despite the inability of the latter to produce the agouti signaling protein (Asip). This darker hair and body coloration was not apparent in the Hokkaido sable variant, implying the presence of an additional genetic system shaping yellowish hair variability.

Rabbits - their domestication and molecular genetics of hair coat development and quality

The European rabbit (Oryctolagus cuniculus) is the only representative of its genus living in present-day Europe and North Africa, and all domestic rabbits are descendants of this one species, which is native to the Iberian Peninsula. There are over 300 breeds of rabbits that differ in size, coat color, length of ears and type of fur. Rabbits are bred for various reasons, such as for laboratory animals and a source of meat, wool and fur, as well as for pets and exhibition animals. The hair coat is a important economic trait of rabbits. Its development and quality are influenced by various factors, both environmental and genetic. The genetic mechanisms underlying its development have not been thoroughly researched. The aim of this review is to discuss the domestication of rabbits and the different aspects of rabbit genetics. A brief review of the properties of rabbit hair coat, hair coat development and hair cycle will be provided, followed by discussion of the factors regulating hair coat development, molecular control of hair coat development and the role of non-coding RNAs in the regulation of gene expression in the hair follicles of rabbits. Information about genetic regulation of pathways could provide useful tools for improving hair coat quality and be of practical use in rabbit breeding.