Responses in isolated cells due to external influences may give us an indication of how the entire organism would respond in such cases. NIFES has established cultures of embryonic stem cells isolated from turbot, halibut and cod, in order to study such alterations.
All living organisms have stem cells. These cells are unspecialised cells which can divide several times and turn into more specialised cells which then adopt specific functions in the body. There are several types of stem cells. One type is embryonic stem cells which are only found in fertilised eggs until it reaches a specific stage during development. Embryonic stem cells have the inherent ability to become any cell/tissue in the organism, including blood, muscle and neurons.
Why study stem cell cultures?
Embryonic stem cells cultured in petri dishes are in an isolated system where responses to single alteration
can be carefully monitored. Such cultures can for example be used to examine the specialisation process into other cells, such as pigment cells, due to an external influence like the addition of a single nutrient. Monitoring alteration of gene expression and protein levels in such cases may provide insight into why certain nutrients seem to affect pigmentation during farming of halibut and turbot. Experiments on cell cultures allow us to test several substances over a shorter period of time and at a lower cost than feeding trials, which is the alternative. The results from cell cultures allow for more tailored feeding trials to take place in order to test hypothesis arisen from the cell culture work.
Embryonic stem cell cultures from turbot,halibut and cod
Previously, NIFES has established cultures of embryonic stem cell from turbot and halibut and in 2006 embryonic stem cells from cod were generated at the institute. Such cultures are a useful tool to study underlying cellular mechanisms in fish. The cultures will be used to study how stem cells are affected during exposure to fatty acids and vitamins, and examine the mechanisms related to larval malformation which can occur during development.
A genetic marker for embryonic stem cells
Until recently, it has been difficult to separate specialised from unspecialised cells in embryonic stem cell cultures. NIFES has now identified two genetic markers that aid the identification of embryonic stem cells in cod cell cultures and in fertilised eggs. One of the genes (ac-pou2) is only present in embryonic stem cells. When the specialisation process starts the expression of this gene is turned of. At the same time another gene (ac-sox2) is turned on. By detecting the expression of these genes it is possible to identify when the cultured cells are stem cells and when they loose their stem cell status. Previous studies have shown a similar gene expression pattern in embryonic stem cells from mouse.
All cells in cod embryos are embryonic stem cells until
approximately 35 hours after fertilisation.
The specialisation process starts around
35 hours after fertilisation.
The fish larvae just before hatching.
Yolk sac larvaes.