A new model mouse for Duchenne muscular dystrophy produced by 2.4 Mb deletion of dystrophin gene using Cre-loxP recombination system

Mouse chromosome engineering for modeling human disease

Chromosomal rearrangements are frequently in humans and can be disease-associated or phenotypically neutral. Recent technological advances have led to the discovery of copy-number changes previously undetected by cytogenetic techniques. To understand the genetic consequences of such genomic changes, these mutations need to be modeled in experimentally tractable systems. The mouse is an excellent organism for this analysis because of its biological and genetic similarity to humans, and the ease with which its genome can be manipulated. Through chromosome engineering, defined rearrangements can be introduced into the mouse genome. The resulting mouse models are leading to a better understanding of the molecular and cellular basis of dosage alterations in human disease phenotypes, in turn opening new diagnostic and therapeutic opportunities.

[Site specific mutagenesis by homologous recombination in embryonic stem cells]

Twenty years ago, the production of mice whose genomes have been deliberatly modified revolutionised biology. Indeed, it is now possible to eliminate a gene's expression to various levels in desired locations, and also to broadcast these genetic modifications created in vitro to the progeny. The isolation and culture of embryonic stem cells (ES) and the discovery of the mechanism of homologous recombination between two sequences of DNA in the 80's, have contributed to the development of site-directed mutagenesis. Today, site specific mutagenesis by homologous recombination in embryonic stem cells is a powerful technique and is widely used throughout the world. In parallel, new techniques to invalidate targeted genes are emerging. These genetics tools, which we will introduce, allow for a better understanding of a gene's function both in fundamental and clinical research. It is now possible to create murine models of human genetic diseases including Lesch-Nhyan syndrome, Adenomatous Polyposis and Duchenne muscular dystrophy which we will discuss as examples.

Cre/loxP-mediated chromosome engineering of the mouse genome

Together with numerous other genome modifications, chromosome engineering offers a very powerful tool to accelerate the functional analysis of the mammalian genome. The technology, based on the Cre/loxP system, is used more and more in the scientific community in order to generate new chromosomes carrying deletions, duplications, inversions and translocations in targeted regions of interest. In this review, we will present the basic principle of the technique either in vivo or in vitro and we will briefly describe some applications to provide highly valuable genetic tools, to decipher the mammalian genome organisation and to analyze human diseases in the mouse.

Modeling chromosomes in mouse to explore the function of genes, genomic disorders, and chromosomal organization

One of the challenges of genomic research after the completion of the human genome project is to assign a function to all the genes and to understand their interactions and organizations. Among the various techniques, the emergence of chromosome engineering tools with the aim to manipulate large genomic regions in the mouse model offers a powerful way to accelerate the discovery of gene functions and provides more mouse models to study normal and pathological developmental processes associated with aneuploidy. The combination of gene targeting in ES cells, recombinase technology, and other techniques makes it possible to generate new chromosomes carrying specific and defined deletions, duplications, inversions, and translocations that are accelerating functional analysis. This review presents the current status of chromosome engineering techniques and discusses the different applications as well as the implication of these new techniques in future research to better understand the function of chromosomal organization and structures.