Animal Molecular Breeding 2024, Vol.14, No.2, 178-186 http://animalscipublisher.com/index.php/amb 180 compared to other genome editing technologies like TALENs and ZFNs, making it more accessible for widespread use (Borrelli et al., 2018; Eş et al., 2019). Additionally, the decreasing cost of CRISPR-Cas9 technology over time makes it a cost-effective option for genetic improvement programs (Islam et al., 2020; Martínez et al., 2020). Finally, the ability to create transgene-free animals through CRISPR-Cas9-mediated gene editing addresses some of the public and regulatory concerns associated with genetically modified organisms (GMOs) (Langner et al., 2018; Ahmad et al., 2020). 3 Disease Resistance in Cattle: Key Targets for Gene Editing 3.1 Common infectious diseases in cattle Cattle are susceptible to a variety of infectious diseases that can significantly impact their health and productivity. Some of the most common infectious diseases include bovine respiratory disease (BRD), bovine viral diarrhea (BVD), and Mastitis. These diseases not only affect the well-being of the animals but also lead to substantial economic losses in the dairy and beef industries. Effective management and prevention strategies are crucial to mitigate these impacts. 3.2 Identification of genetic markers associated with disease resistance The identification of genetic markers associated with disease resistance in cattle is a critical step towards enhancing their resilience through gene editing. Advances in genome sequencing and bioinformatics have enabled the discovery of specific genes and genetic variants that confer resistance to various pathogens. For instance, the eIF4E gene has been identified as a key player in plant virus resistance and could serve as a model for similar studies in cattle (Chandrasekaran et al., 2016). Additionally, the use of high-fidelity CRISPR-Cas9 variants, such as SpCas9-HF1 and eSpCas9(1.1), has improved the precision of genome editing, reducing off-target effects and increasing the reliability of genetic modifications (Chen et al., 2017). 3.3 CRISPR-Cas9 targets for enhancing resistance to specific diseases CRISPR-Cas9 technology offers a powerful tool for enhancing disease resistance in cattle by enabling precise modifications of target genes (Mushtaq et al., 2019). For example, the CRISPR-Cas9 system has been successfully used to develop virus-resistant cucumber plants by targeting the eIF4E gene, which could be adapted for similar applications in cattle (Chandrasekaran et al., 2016; Memi et al., 2018). Moreover, the development of new CRISPR-Cas9 variants with enhanced specificity and reduced off-target activity, such as HypaCas9, provides a more accurate approach to gene editing in livestock (Chen et al., 2017). By targeting specific genetic markers associated with disease resistance, CRISPR-Cas9 can be used to create cattle that are more resilient to infectious diseases, thereby improving animal health and productivity. 4 Case Study: CRISPR-Cas9 Mediated Resistance to Bovine Tuberculosis 4.1 Background on bovine tuberculosis Bovine tuberculosis (bTB) is a chronic infectious disease caused by Mycobacterium bovis, which affects cattle and other animals, including humans. It poses significant economic and public health challenges due to its impact on livestock productivity and its zoonotic potential. Traditional control measures, such as test-and-slaughter policies and vaccination, have limitations, necessitating the exploration of advanced genetic approaches to enhance disease resistance in cattle. 4.2 Identification of resistant genes The identification of genes associated with resistance to bTB is crucial for developing genetically resistant cattle. Recent advances in immunogenomics have facilitated the identification of candidate genes that play a role in the host immune response to M. bovis infection (Figure 2). One such gene is NRAMP1 (natural resistance-associated macrophage protein 1), which has been implicated in the resistance to various intracellular pathogens, including Mycobacterium species (Islam et al., 2020). 4.3 Application of CRISPR-Cas9 in developing tuberculosis-resistant cattle The CRISPR-Cas9 system has emerged as a powerful tool for precise genome editing, enabling the targeted modification of genes associated with disease resistance. In the context of bTB, CRISPR-Cas9 has been employed
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