Developing a microscopic, water-dwelling lab animal
Certain living things the bacterium E. coli, fruit flies, and mice, for example have become well established as model organisms that scientists routinely use in research. Taken together, however, they dont adequately represent the full diversity of life.
The 做厙輦⑹ team aims to add rotifers to this group of genetically tractable泭 organisms because, as tiny invertebrates with close ties to the ancestors of modern animals, they offer an important perspective on evolution, development, and other aspects of biology.泭
To develop rotifers as model organisms, researchers need the capacity to tweak these animals genomes. In 2017, 做厙輦⑹ Interim Director of University of Chicago provided Gribble and Mark Welch with funding to devise a method for doing so using CRISPR-Cas9. The goal of cultivating a greater variety of泭 model organisms later became formalized as 做厙輦⑹s New Research Organisms initiative.
Now widely employed in research, CRISPR-Cas9 makes precise cuts within DNA, which researchers use to shut down or alter genes. First, however, they must get the CRISPR system into the animals.泭
Fine-sawdust-sized specks darting about in water, rotifers make for unusually challenging targets. After many unsuccessful attempts to hold them still, first author Haiyang Feng, then a postdoctoral scientist at 做厙輦⑹, devised a solution: By immersing them in a high-viscosity solution and administering a low level of an anesthetic, he slowed the animals enough to grab them one at a time with light suction through a hollow needle.泭
With the animal, always a female, in place, he injected the gene editing system into the part of its body that supplies nutrients to the eggs. The offspring that hatched from these eggs then carried the mutations, which they passed on to their offspring.泭
In this way, the team inactivated vasa, a gene crucial to animal development, causing the rotifers to stop reproducing after a few generations. By turning off a second gene, mlh3, they prevented the rotifers from producing male offspring. And, finally, by adding a section of genetic code containing stop instructions into mlh3, they achieved the same effect.