Single cell transcriptome analysis reveals similarities and differences in gene expression of adult and embryonic neural stem cells
Creators: name: Patel, Nirali
Publisher: name: No Publisher Supplied
Year: 2018

description: Adult and embryonic stem cells both harbor advantages and disadvantages for use in cell therapy. Embryonic stem cells are pluripotent and have a greater potential for differentiation than adult stem cells. Adult stem cells, although considered less plastic, have less risk of immune rejection. However, specific differences between adult and embryonic stem cells are not clear. Using single cell transcriptome analysis, adult and embryonic neural stem cells (NSCs) were examined for differences in gene expression patterns, the top 60 highest expressed genes, and cell homogeneity. When examining the top 60 expressed genes, only 19 genes were similar in terms of expression levels amongst adult and embryonic NSCs, indicating more differences in the genes that were highest expressed than similarities. In both adult and embryonic NSCs, genes encoding for cell growth and differentiation, neurogenesis, and tumor suppression were present, however, genes for each function were expressed at different levels within the two cells types. Within adult NSCs, Meg3 was highly expressed for tumor suppression, however in embryonic NSCs, the Sparc gene was highly expressed for the same function. In terms of genes coding for neurogenesis, adult NSCs expressed Ptprs and Gpm6a while embryonic NSCs highly expressed Npm1, Tubb3, Enc1, and Sox11. Differences in genes coding for the same function such as differentiation can potentially lead to differences in differentiation efficiency, or the time it takes for cells to differentiate. By clustering cells into different groups, differences in gene expression patterns were observed. Embryonic NSCS failed to cluster with adult NSCs in two out of three studies implying differences in gene expression patterns across the two cell types. Upregulated genes in adult NSCs were downregulated in embryonic NSCs, e.g., Kctd16, Kcnh 3, Kcnh1 and Rab26 were amongst genes that were upregulated for most adult NSCs, however they were downregulated across all embryonic NSCs. Kcnh1, in particular, is a gene specific to the brain and regulates myoblast differentiation, neurotransmitter release, and neuronal excitability.  Overexpression of this gene may be important in embryogenesis or lead to cancer cell formation, however, this gene was found to be downregulated amongst all embryonic NSCs, while being upregulated in many adult NSCs. It is possible that this gene is not upregulated in embryonic NSCs as they are considered more pluripotent than adult stem cells. Genes that were distinct to only adult NSCs function in ionotropic glutamate receptor signaling pathway, excitatory postsynaptic potential, central nervous system development, and associative learning such as: memory, cognition, and behavior.  The highest regulated genes in embryonic stem cells function, instead, in telomerase holoenzyme complex assembly and the regulation of cell size. Genes that were common to both adult and embryonic NSCs were mainly involved in protein folding and cell cycle regulation. Together, single cell transcriptome analysis reveals that differences in gene expression patterns amongst adult and embryonic NSCs are evident and these molecular differences are the basis for the different properties of the two types of NSCs.