Beyond knockouts: cre resources for conditional mutagenesis

Lentiviruses allow widespread and conditional manipulation of gene expression in the developing mouse brain

Generation of transgenic mice, in utero electroporation and viral injection are common approaches to manipulate gene expression during embryonic development of the mammalian brain. While very powerful in many contexts, these approaches are each characterized by their own limitations: namely, that generation of transgenic mice is time-consuming and electroporation only allows the targeting of a small area of the brain. Similarly, viral injection has been predominantly characterized by using retroviruses or adenoviruses that are limited by a relatively low infectivity or lack of integration, respectively. Here we report the use of integrating lentiviral vectors as a system to achieve widespread and efficient infection of the whole brain after in utero injection in the telencephalic ventricle of mouse embryos. In addition, we explored the use of Cre-mediated recombination of loxP-containing lentiviral vectors to achieve spatial and temporal control of gene expression of virtually any transgene without the need for generation of additional mouse lines. Our work provides a system to overcome the limitations of retroviruses and adenoviruses by achieving widespread and high efficiency of transduction. The combination of lentiviral injection and site-specific recombination offers a fast and efficient alternative to complement and diversify the current methodologies to acutely manipulate gene expression in developing mammalian embryos.

Molecular anatomy of the gut-brain axis revealed with transgenic technologies: implications in metabolic research

Neurons residing in the gut-brain axis remain understudied despite their important role in coordinating metabolic functions. This lack of knowledge is observed, in part, because labeling gut-brain axis neurons and their connections using conventional neuroanatomical methods is inherently challenging. This article summarizes genetic approaches that enable the labeling of distinct populations of gut-brain axis neurons in living laboratory rodents. In particular, we review the respective strengths and limitations of currently available genetic and viral approaches that permit the marking of gut-brain axis neurons without the need for antibodies or conventional neurotropic tracers. Finally, we discuss how these methodological advances are progressively transforming the study of the healthy and diseased gut-brain axis in the context of its role in chronic metabolic diseases, including diabetes and obesity.

Tracking cells in their native habitat: lineage tracing in epithelial neoplasia

For tumours to develop, mutations must disrupt tissue homeostasis in favour of deregulated proliferation. Genetic lineage tracing has uncovered the behaviour of proliferating cells that underpins the maintenance of epithelial tissues and the barriers that are broken in neoplastic transformation. In this Review, we focus on new insights revealed by quantifying the behaviour of normal, preneoplastic and tumour cells in epithelia in transgenic mice and consider their potential importance in humans.