A transgenic animal is a genetically modified species in which researchers have modified an existing gene or genes by genetic engineering techniques. Genetic modification involves the mutation, insertion, or deletion of genes. Mouse is the most widely used mammalian species for creating transgenic lines. There are two types of transgenic animals: (i) gene deleted (“knock-out”) and (ii) gene overexpressed (“knock-in”). The loss or gain of gene activity often causes changes in a mouse's phenotype, which includes appearance, behavior and other observable characteristics. Knockout mice are key animal models for studying the role of genes which have been sequenced but whose functions have not been determined. They include constitutive knockouts (gene deleted since birth) and conditional knockout (gene turned off later after birth). The first knockout mouse was created in 1989 by Mario Capecchi, Martin Evans, and Oliver Smithies, for which they were awarded the 2007 Nobel Prize in Physiology or Medicine. Transgenic mouse models have revolutionized the biomedical research and provided a power tool for understanding health and disease. Transgenic animals have been created for bulk production of biotechnology and pharmaceutical products. In 2009, the FDA approved the first human biological drug ATryn, an anticoagulant extracted from the transgenic goat's milk. The recently discovered CRISPER gene editing technology is providing new frontiers in correcting abnormal genes and hopefully provide cures for genetic diseases in the future.
Loss of mGluR5 in D1 Receptor-Expressing Neurons Improves Stress Coping