Innate immunity and the new forward genetics

Abstract

As it is a hard-wired system for responses to microbes, innate immunity is particularly susceptible to classical genetic analysis. Mutations led the way to the discovery of many of the molecular elements of innate immune sensing and signaling pathways. In turn, the need for a faster way to find the molecular causes of mutation-induced phenotypes triggered a huge transformation in forward genetics. During the 1980s and 1990s, many heritable phenotypes were ascribed to mutations through positional cloning. In mice, this required three steps. First, a genetic mapping step was used to show that a given phenotype emanated from a circumscribed region of the genome. Second, a physical mapping step was undertaken, in which all of the region was cloned and its gene content determined. Finally, a concerted search for the mutation was performed. Such projects usually lasted for several years, but could produce breakthroughs in our understanding of biological processes. Publication of the annotated mouse genome sequence in 2002 made physical mapping unnecessary. More recently we devised a new technology for automated genetic mapping, which eliminated both genetic mapping and the search for mutations among candidate genes. The cause of phenotype can now be determined instantaneously. We have created more than 100,000 coding/splicing mutations. And by screening for defects of innate and adaptive immunity we have discovered many “new” proteins needed for innate immune function.

KDM5A mutations identified in autism spectrum disorder using forward genetics

“…Forward genetics has long been recognized as an unbiased genome-wide method to identify genes underlying many biological processes ( Beutler, 2016 ). By screening ENU mutagenized mice for ASD-like behaviors, we identified Kdm5a as a candidate ASD gene that regulates vocalization and nesting.…”

The dual role of innate immunity during influenza

“…Moreover, the receptors are strategically located in various subcellular compartments, such as the cell membrane, the endosomal system, the cytosol and mitochondria. Such an arrangement enables the host to mount defences that are tailored to the invading pathogen and take into account its tissue tropism, intracellular life style and reproductive strategy [10] . Thus, in the case of influenza and other infections, innate responses can be conveniently divided into modules, each involving different cell types, receptors, effector molecules and intracellular compartments [11] .…”

Rel-Dependent Immune and Central Nervous System Mechanisms Control Viral Replication and Inflammation during Mouse Herpes Simplex Encephalitis

“…N-Ethyl-N-nitrosourea (ENU), a potent mutagen that randomly induces point mutations in the germline of a male mouse, is often used in mouse forward genetic screens for genes that affect resistance or susceptibility to pathogens (30)(31)(32). We applied an ENU mutagenesis screen for HSV-1 susceptibility and have previously uncovered the Ptprc gene (CD45) as a cause of HSE in mice that implicates a protective T cell response in the peripheral control of viral replication (25).…”