Why Zebrafish is my favorite model ?
Drosophila melanogaster, yeah they are ‘Geneticist’s best friend’. They have indeed been the first model of choice ages ago and still remains as a valuable model to solve the conundrums in developmental biology. The fly people who revolutionized and updated our understandings of embryonic development caught an eye over the works of George Streisinger. So who is Streisinger? Don’t know? Keep reading then… He once moved some of the teleosts from the pet stores and natural reservoirs to the ‘Laboratory’(Oops! Are these teleosts happy here?). These teleosts gradually shed light on the developing field of developmental biology by bridging the gaps between mammalian and invertebrate models. Today zebrafish (Danio rerio) has taken its position as a favorite animal model of choice for researchers globally and this can be clearly seen from the rapid growth of research publications and the awarded grants of NIH- R01*. So, would you like to take a quick look about the Danios? Keep reading then…
So, why fishes?
Size: The embryos are 0.7mm and the hatched ones are 3.5mm. Nice to look under microscope ! Adults are between 2-3 cm when grown in captives. (Who is an adult Danio? Those elegant and beautifully stripped, active and healthy Danios from 3 months of age)
Fecundity: A pair of well-fed healthy adult can produce a clutch of embryos every 3-4 days. On a routine base in laboratory condition, approximately two-weeks interval is given between each breeding cycle to generate about 500 embryos. Is the fecundity rate same as murine models? Fortunately not!
Fertilization: External fertilization is a pretty much advantage for visualization of growth and transplantation experiments.
Optical transparency: This is an add-on strength to observe development and growth of the organism externally under a microscope. The embryos are safely packed inside a transparent chorion and the embryos when placed in a glass dish appear like a little crystal clear creatures. The number of reporter lines gives the possinilty of fluorescence, time-lapse, 3D and tomographic imaging.
Rapid development: A complete body plan is established within 2 days’ post-fertilization. A functional heart with major blood vessels can be seen when the embryos are 1-day old. The rapid development of organs is a helpful feature found in zebrafish as we can see other vertebrate models lacking this speedy development. So if you are in a super hurry to study organ development in vertebrates, these teleosts are waiting!
Maintainance: Google says, ‘’Zebrafish housing and maintenance is easier and cheaper than the traditional rodent models’’. Yup, partially true ! However dedicated care to raise the larvae, look after the health of adults, and the precious transgenics/mutant, maintain the facility are needed. Got to be grateful to those fish room technicians!
Sounds easy and cool thinking of zebrafish eh? Hold on now… We all know that each model organism has its own pros and cons. Some of the same potential strengths of zebrafish are more likely to give the model its limitations too. For instance, the small size of the embryos may not produce enough tissue. There lacks cell line models and specific antibodies for this model. High rate fecundity may not mean 100% of the embryos can be raised to healthy adults. In the hands of a well-skilled personnel and under good maintenance condition, on an average about 60% of the embryos are raised into adults. ‘’Optically-transparent’’ only during the first 24 hours of age. After which pigmentation starts to spread all over the embryos. Anyway, there are reagents to inhibit melanization, and mutants like ‘casper’, ‘crystal’ have been generated. Looking through the external fertilization and development, it absolutely does not mirror the in-utero condition of a mammalian model. Though the pattern of organ development is conserved in vertebrates, the respiratory and reproductive organs are different in teleosts. Finally, the fact that a duration of 3 months is sufficient to raise them into adults may not be reliable when creating a homozygous mutants or transgenics. Hence designing an ideal stratergy for the same might be necessary to speed up the generation time. Despite these limitations, zebrafish adults as well as the embryos, have positioned themesevels stably in the midst of other mammalian models that are routinely used for research. In the near future, this model would untangle the puzzling questions for the geneticists.
* A look at trends in NIH’s Model Organism Research Support, Posted on July 14, 2016 by Mike Lauerhttp://www.geneticengg.com/2018/04/10/why-zebrafish-is-my-favorite-model/http://www.geneticengg.com/wp-content/uploads/2016/06/zebrafish_Novartis_edit1.jpghttp://www.geneticengg.com/wp-content/uploads/2016/06/zebrafish_Novartis_edit1-150x150.jpgGeneticszebrafishanimal model,developmental biology,drosophila,fertilization,zebrafishDrosophila melanogaster, yeah they are ‘Geneticist’s best friend’. They have indeed been the first model of choice ages ago and still remains as a valuable model to solve the conundrums in developmental biology. The fly people who revolutionized and updated our understandings of embryonic development caught an eye over...Preethi KrishnarajPreethi Krishnarajsudharsan@cambrionics.comEditorGeneticEngg.com