Genetics; CRISPR; Mutation; Tyrosinase; Ciona intestinalis
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Genetic manipulation has come a long way in the past ten years alone. Scientists have had access to gene editing techniques for decades, but until recently these methods have proven to be expensive and unpredictable. However, thanks to the development of a new, more efficient genome editing strategy called CRISPR/Cas9, more aggressive progress can now be made in genetics research.
CRISPR is not a machine or a physical tool, but rather it is a system that involves introducing a protein into a cell, along with a DNA segment that will attract the protein to a desired location on the DNA. The Cas9 protein then induces a double stranded break at the location, silencing whichever gene is located there.
The major goal of my project was to demonstrate the successful implementation of CRISPR using embryos spawned from the model chordate Ciona intestinalis, also known as the sea squirt. We will use the system to inactivate the gene in Ciona embryos which encodes for the tyrosinase enzyme responsible for producing the pigment seen in the dark eye spots of Ciona embryos during the late tailbud stage. In mutated embryos, the tyrosinase gene becomes inactivated by the CRISPR system, causing the entire larvae to appear white under the microscope with no visible eye spots.
This experiment provides a proof of concept for the use of CRISPR/Cas9 in the Irvine lab. Ongoing experiments utilizing CRISPR aim to silence other genes involved in temperature response pathways. These tests will further our understanding of how projected increases in ocean temperatures will impact reproduction in Ciona populations, and potentially in other aquatic species as well.