The dysregulation of microRNA (miRNA) is implicated in cancer, inflammation, cardiovascular disorders, drug resistance, and aging. While most researchers study miRNA’s role as a biomarker, for example, to distinguish between various sub-forms or stages of a given disease of interest, research is also ongoing to utilize these small nucleic acids as therapeutics. An example of a common pleiotropic disease that could benefit from miRNA-based therapeutics is inflammatory bowel disease (IBD), which is characterized by chronic inflammation of the small and large intestines. Due to complex interactions between multiple factors in the etiology of IBD, development of therapies that effectively maintain remission for this disease is a significant challenge. In this review, we discuss the role of dysregulated miRNA expression in the context of clinical ulcerative colitis (UC) and Crohn’s disease (CD)—the two main forms of IBD—and the various preclinical mouse models of IBD utilized to validate the therapeutic potential of targeting these miRNA. Additionally, we highlight advances in the development of genetically engineered animal models that recapitulate clinical miRNA expression and provide powerful preclinical models to assess the diagnostic and therapeutic promise of miRNA in IBD.

Background: Gene disruption in mouse embryonic stem cells or zygotes is a conventional genetics approach to identify gene function in vivo. However, because different gene disruption strategies use different mechanisms to disrupt genes, the strategies can result in diverse phenotypes in the resulting mouse model. To determine whether different gene disruption strategies affect the phenotype of resulting mutant mice, we characterizedRhbdf1mouse mutant strains generated by three commonly used strategies—definitive-null, targeted knockout (KO)-first, and CRISPR/Cas9.Results: We find thatRhbdf1responds differently to distinct KO strategies, for example, by skipping exons and reinitiating translation to potentially yield gain-of-function alleles rather than the expected null or severe hypomorphic alleles. Our analysis also revealed that at least 4% of mice generated using the KO-first strategy show conflicting phenotypes.Conclusions: Exon skipping is a widespread phenomenon occurring across the genome. These findings have significant implications for the application of genome editing in both basic research and clinical practice.

The epidermal growth factor (EGF)‐receptor ligand amphiregulin (AREG) is a potent growth factor implicated in proliferative skin diseases and in primary and metastatic epithelial cancers. AREG, synthesized as a propeptide, requires conversion to an active peptide by metalloproteases by a process known as ectodomain shedding. Although (ADAM17) a disintegrin and metalloprotease 17 is a key sheddase of AREG, ADAM8‐, ADAM15‐, and batimastat (broad metalloprotease inhibitor)‐sensitive metalloproteases have also been implicated in AREG shedding. In the present study, using a curly bare (Rhbdf2^cub) mouse model that shows loss‐of‐hair, enlarged sebaceous gland, and rapid cutaneous wound‐healing phenotypes mediated by enhanced Areg mRNA and protein levels, we sought to identify the principal ectodomain sheddase of AREG. To this end, we generated Rhbdf2^cub mice lacking ADAM17 specifically in the skin and examined the above phenotypes of Rhbdf2^cub mice. We find that ADAM17 deficiency in the skin of Rhbdf2^cub mice restores a full hair coat, prevents sebaceous gland enlargement, and impairs the rapid wound‐healing phenotype observed in Rhbdf2^cub mice. Furthermore, in vitro, stimulated shedding of AREG is abolished in Rhbdf2^cub mouse embryonic keratinocytes lacking ADAM17. Thus, our data support previous findings demonstrating that ADAM17 is the major ectodomain sheddase of AREG.

The Cre-Lox system is a powerful tool in mouse genetics, enabling precise spatiotemporal control of gene expression and conditional knockout models. Since its development, it has transformed genome editing by facilitating targeted deletions, translocations, inversions, and complex modifications—double-floxed inverse orientation. Its utility extends beyond mice to rats, pigs, and zebrafish. However, challenges such as high costs, lengthy timelines, and unpredictable recombination remain, highlighting the need for ongoing improvements to enhance efficiency, reliability, and applicability across genetic models. In this study, we perform a systematic analysis of Cre-mediated recombination in mice, creating 11 new strains with conditional alleles at the Rosa26 locus, using the C57BL/6J background. Factors influencing recombination efficiency include inter-loxP distance, mutant loxP sites, zygosity, chromosomal location, and breeder age. Our results demonstrate that the choice of Cre-driver strain plays a significant role in recombination efficiency. Optimal recombination is achieved when loxP sites are spaced by less than 4 kb and mutant loxP sites by 3 kb. Complete recombination fails with wildtype loxP sites spaced ≥ 15 kb or mutant lox71/66 sites spaced ≥ 7 kb. The best recombination efficiency is observed in breeders aged 8–20 weeks and when using heterozygous floxed alleles. The Cre-Lox system remains indispensable for genetic engineering, offering flexibility beyond standalone applications by integrating with CRISPR-based methods to expand its utility. Despite challenges, our findings provide a framework for optimizing Cre-mediated recombination. By refining Cre-Lox strategies, this knowledge enhances experimental precision, improves reproducibility, and ultimately reduces the time and cost of genome modification.

In humans, gain-of-function (GOF) mutations in RHBDF2 cause the skin disease tylosis. We generated a mouse model of human tylosis and show that GOF mutations in RHBDF2 cause tylosis by enhancing the amount of AREG secretion. Furthermore, we show that genetic disruption of AREG ameliorates skin pathology in mice carrying the human tylosis disease mutation. Collectively, our data suggest that RHBDF2 plays a critical role in regulating EGFR signaling and its downstream events, including development of tylosis, by facilitating enhanced secretion of AREG. Thus, targeting AREG could have therapeutic benefit in the treatment of tylosis.