What similarity at the cellular level between the human brain and rodents?
Wednesday, 23 de October de 2019
As we know, rodents like rats and mice are still considered the main and most used animal models in the scientific world, especially when we are talking about basic research. This is justified by the fact that rodents are easy laboratory animals, and has, in the case of mice for example, about 80% of their genes in common with that of the human species, and have the same basic human needs that allow the continuity of the species, making the brain mechanism that drives these behaviors similar. This all enables a greater ability to employ scientific and specific studies and better suited to the study of human diseases. However, we know that rodent brains have certain limitations and structural constraints, such as cognitive development of their cortex and volume (as we can see in the video below). But at the cellular level, how similar are the brains of these species?
To answer this question, research published in the journal Nature this year 2019 performed an analysis of single-core RNA sequencing for molecular identification of human cortical human tissue in areas of the primary visual cortex and premotor cortex, or even Given that there is not much work, as this technique requires fresh tissue, human samples of this nature are difficult to obtain.
Transcribed data from nearly 16,000 nuclei were analyzed and similarities and differences in gene expression were used to group or exclude, respectively, each nuclear transcriptome into "clusters". Using databases from other single nucleotide RNA sequencing analysis work in mice, a comparison was made between the cell types and the genetic expression of this species and the human species. For cell types, a similarity of approximately 32 neuronal cell types, including excitatory neurons, hormone inhibitors and inhibitors, and 5 non-neuronal cell subclasses, such as some olingodentrocyte subtypes, were observed. Despite these types of homologous cells existing between species, in terms of gene expression and morphology of each cell type, it varied widely between humans and mice for the same cell types, making their cell different. This expression difference is shown in the graph below, where for each gene (equivalent to each cell type) you can see a larger difference (indicated in black color), a moderate difference (gray) or low difference (white) between species. This can be explained by the observation of differences in neurotransmitter receptors, ion channels, elements of the extracellular matrix of cellular connecting molecules between the same cell types.
But what is the importance of knowing this kind of information? Identifying the different cell types in the cortex and how they are organized can be important in understanding how to increase cognition. In addition, the data provided show the need for work with non-human primate expression profiles to better understand their cellular functions, as these species are closely related to various aspects of human brain structure and function. The resolution offered by these molecular technologies also shows great promise to accelerate our mechanistic understanding of evolution and brain disease.
Reference:
Hodge, Rebecca D., et al. "Conserved cell types with divergent features in human versus mouse cortex." Nature 573.7772 (2019): 61-68.
Khan, Aziz, and Xuegong Zhang. "dbSUPER: a database of super-enhancers in mouse and human genome." Nucleic acids research 44.D1 (2015): D164-D171.
Glasser, M. F. et al. A multi-modal parcellation of human cerebral cortex. Nature 536, 171–178 (2016).
The content published here is the exclusive responsibility of the authors.