If one or more of the patientвЂ™s symptoms are observed in the zebrafish knock-out or knock-in model, the zebrafish can be used for further studies to help determine why the mutation in that gene causes the disease. Although it is much more difficult to do, the exact mutation that the patient has can be introduced into zebrafish as well-this is called a вЂњknock-inвЂќ. To determine if loss of function of that gene could cause the symptoms seen in the patient, the same gene is mutated or вЂњknocked-outвЂќ in zebrafish, and then the fish are examined for similar symptoms. Often a patientвЂ™s DNA is sequenced in order to find a mutation in a gene that could potentially cause his or her disease symptoms. How exactly do you use zebrafish to investigate human diseases? Additionally, zebrafish are not useful models for human diseases that mainly take place in a tissue type or body part that zebrafish do not have (e.g., prostate, mammary glands, lungs). Human diseases caused by genes that do not exist in zebrafish require a different animal model. However, there is a limit on what types of diseases can be studied in zebrafish. Mouse embryos are not clear and develop inside the mother, so the observation of live embryo development like that in zebrafish is not possible. Their transparency also enables the visualization of fluorescently labeled tissues in transgenic zebrafish embryos. Zebrafish larva, the stage of development from between three and thirty days post-fertilization, grow in length from approximately 3.5 to 8 millimeters.ДЇurthermore, zebrafish embryos are clear, which allows scientists to watch the fertilized eggs grow into fully formed baby fish under a microscope. To keep the embryos alive after fertilizing or injecting them, they would need to be transplanted into another female mouse, as well. Mouse embryos develop inside the mother, and to access and manipulate them the mother would have to be sacrificed. Working with mice in this way is much more complicated. The one-cell-stage fertilized eggs can be easily injected with DNA or RNA to permanently modify their genetic makeup in order to generate transgenic or knock-out zebrafish lines. In vitro fertilization can be performed if necessary. Zebrafish embryos are also laid and fertilized externally, which allows them to be easily manipulated in a variety of ways. Scientific experiments are generally repeated multiple times in order to prove that the results are accurate, so having an animal that can produce a large number of offspring over and over is helpful. This is quite different from mice as they generally produce litters of one to 10 pups and can only bear approximately three litters in their lifetime. The NIH Zebrafish Core houses hundreds of thousands of zebrafish in a state-of-the-art facility.ДЄnother advantage is that adult zebrafish breed readily (approximately every 10 days) and can produce as many as 50 to 300 eggs at a time.

As a result, they require much less space and are cheaper to maintain than mice. One important advantage of zebrafish is that the adults are small and prefer to be housed in large groups, or вЂњshoalsвЂќ. While mice are evolutionarily more similar to humans because they are mammals, zebrafish have several advantages over their furry competitors. Why use zebrafish when you could use mice?

Thus, any type of disease that causes changes in these body parts in humans could theoretically be modeled in zebrafish. Many of the genes and critical pathways that are required to grow these features are highly conserved between humans and zebrafish. Moreover, zebrafish have two eyes, a mouth, brain, spinal cord, intestine, pancreas, liver, bile ducts, kidney, esophagus, heart, ear, nose, muscle, blood, bone, cartilage, and teeth. In fact, 70% of human genes are found in zebrafish. How can you model a human disease in fish?ДЄlthough humans may appear to be extremely different than zebrafish, we are actually much more similar to them than you might think. Zebrafish, so named due to their stripes, prefer to live in large groups called shoals. The name вЂњzebrafishвЂќ comes from the horizontal blue stripes on each side of their bodies. In the wild, they are found in rivers and ponds of India, however they are now often available in pet shops. Zebrafish are tropical fresh-water fish in the minnow family. While mice and rats have been common choices for modeling human diseases in the past, the use of zebrafish is rapidly gaining popularity. Research often utilizes patientsвЂ™ cells or tissue samples, but to determine if a mutation in a specific gene can cause a patientвЂ™s symptoms, we often need experimental animal models. Scientists use a variety of laboratory techniques to investigate the genetic cause of human diseases.

Humans have stripes