How to Make Animals That Can Turn On CRISPR Gene Editing

This patent describes creating genetically modified non-human animals, like mice, where a key CRISPR gene-editing protein (Cas9) can be turned on only in specific cells or at specific times using a special genetic switch.

What it covers

The patent details a "non-human transgenic animal" (Claim 1), meaning an animal whose genes have been changed. This animal has a special genetic package, called an "exogenous conditional expression cassette," inserted into its own DNA, specifically "knocked into an endogenous genomic locus" (Claim 1), like the "Rosa26 locus" (Claim 3) in mice. This cassette contains the instructions for making a "Cas9 protein," which is a molecular scissor used in CRISPR gene editing. The clever part is that the Cas9 protein is only made when another enzyme, "Cre recombinase," is present (Claim 1). This allows scientists to control exactly when and where the Cas9 protein is active. The Cas9 protein itself is designed with two "nuclear localization signals" (NLS), one at each end (N-terminus and C-terminus), to help it get into the cell's nucleus where the DNA is (Claim 1). For example, a researcher could use this to study how turning on Cas9 in only certain brain cells affects a neurological disease.

What it doesn't cover

• —Does not cover genetically modifying human beings.
• —Does not cover Cas9 protein expression that is always on or not dependent on Cre recombinase.
• —Does not cover Cas9 proteins that lack two nuclear localization signals (NLS), one at the N-terminus and one at the C-terminus.
• —Does not cover gene editing systems that use different proteins instead of Cas9 (e.g., other CRISPR enzymes or TALENs).
• —Does not cover inserting the Cas9 cassette into just any random spot in the genome; it must be "knocked into an endogenous genomic locus."

The clever bit

The novelty lies in combining the precise, conditional activation of Cas9 using Cre recombinase with the specific design of the Cas9 protein itself (two NLS signals) within a "knocked-in" cassette in a living animal, enabling fine-tuned gene editing studies.

Why it matters

This technology allows scientists to create highly specific animal models for studying diseases. By controlling exactly when and where the Cas9 gene editor is active, researchers can precisely investigate the role of specific genes in particular cell types or developmental stages. This precision helps in understanding complex biological processes and testing potential gene therapies in a controlled living system, which is crucial for drug discovery and development.

Real-world examples

• 1.Transgenic mouse models for neurological disorders
• 2.Mouse models for cancer research
• 3.Rat models for cardiovascular studies
• 4.Rabbit models for eye disease research