2018-05-20 11:22:01
To determine exactly how many different types of cells an organism contains and how these have been derived from the primordial cell that originated it, the fertilized zygote, it would be necessary to find out what part of the genomic information each individual cell of said organism uses. . To do this, it is necessary to identify which genes each cell has functioning at each moment, which can only be done with precision by obtaining the sequence of letters not from its genome, but from its transcriptome.
The transcriptome of a cell is the sequence of “letters” of just the genes that are being transcribed. Transcribed genes are the genes that are being used to make a copy of the information they contain and make some piece of the cellular machinery out of it. This copy is not made to another molecule of ADNbut to another nucleic acid, called ARN delivery courier. Therefore, to obtain the transcriptome of a cell supposes to obtain the information of the sequence of “letters” of all the ARN messengers that are being produced in a cell from the information contained in the genome.
Using nucleic acid manipulation and sequencing technologies, two research groups, one German; the other, made up of American and British researchers, have addressed the study of the individual cell transcriptome of the organism Schmidtea mediterranean. This is a flatworm (of the planaria family) considered immortal. This little animal contains numerous stem cells, which continuously form daughter cells that repopulate and regenerate the organism.
In these studies, the Anglo-Saxon scientists obtain the sequence of the genes that have more than 50,000 individual cells of these organisms functioning, which makes their unequivocal identification possible. In this way they identify new cells never detected before. The German researchers go a little further and use a computer algorithm that identifies genes that function in common in different cell types, making it possible to establish a kind of genealogy between the cells of that organism. In this way, they not only discover new cell types, but also the relationship between them. In addition, the scientists gain insight into the cellular transformations that occur during planarian regeneration, finding specific cell types whose numbers significantly decrease during this process. This suggests that these cells are sacrificed as a source of energy for regeneration.
These studies, in addition to providing relevant new information on developmental biology in a model organism, indicate that the use of transcriptomics to analyze the evolution of individual cells in humans, for example, cells that form a tumor in response to a treatment can be a reality that will help to better understand and treat many diseases.
Referencias: Mireya Plass et al. Cell type atlas and lineage tree of a whole complex animal by single-cell transcriptomics. Science 10.1126/science.aaq1723 (2018). Christopher T. Fincher et al. Cell type transcriptome atlas for the planarian Schmidtea mediterranea. Science 10.1126/science.aaq1736 (2018).
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