Abstract
The genetic modification of the mouse genome using the cre-lox system has been an invaluable tool in deciphering gene and protein function in a temporal and/or spatial manner. However, it has its pitfalls, as researchers have shown that the unregulated expression of cre recombinase can cause DNA damage, the consequences of which can be very detrimental to mouse health. Previously published literature on the most utilized cardiac-specific cre, αMHC-cre, mouse model exhibited a nonlethal hypertrophic cardiomyopathy (HCM) with aging. However, using the same αMHC-cre mice, we observed a cardiac pathology, resulting in complete lethality by 11 months of age. Echocardiography and histology revealed that the αMHC-cre mice were displaying symptoms of dilated cardiomyopathy (DCM) by seven months of age, which ultimately led to their demise in the absence of any HCM at any age. Molecular analysis showed that this phenotype was associated with the DNA damage response through the downregulation of activated p38 and increased expression of JNK, p53, and Bax, known inducers of myocyte death resulting in fibrosis. Our data urges strong caution when interpreting the phenotypic impact of gene responses using αMHC-cre mice, since a lethal DCM was induced by the cre driver in an age-dependent manner in this commonly utilized model system.
Highlights
Genetic manipulations in model organisms are the crux of biological and medical research in terms of ascribing physiological or pathological roles for the gene of interest [1]
The genotype of these animals was determined through PCR to differentiate wild-type (Wt) littermates and establish the α-myosin heavy chain (αMHC)-cre only (Cre+) experimental animals
We observed a 50% loss of Cre+ mice by approximately 8 months of age, with the remainder dying before 11 months of age (Figure 1B)
Summary
Genetic manipulations in model organisms are the crux of biological and medical research in terms of ascribing physiological or pathological roles for the gene of interest [1]. Genetic modifications of the mouse take place through the manipulation of mouse embryonic stem cells by taking advantage of the stem cells’ natural inclination toward homologous recombination to selectively replace the endogenous target gene sequence with modified exogenous DNA [4]. Significant strides in genetic engineering have allowed us to utilize many models and systems for modifying the genome, such as the cre-lox system [5]. The cre-lox system is a site-specific recombination system used to modify DNA through manipulation derived from the P1 bacteriophage [6]. It is a two-part system where the recombinase, cre, binds to a specific 34-base pair sequence known as a loxP site [7].
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