engleski

Macroevolutionary reconstruction of glycosylation from the perspective of homo sapiens genome

Glycosylation is present in all living organisms, ranging from bacteria and archaea all the way to humans. Glycan structures attached to lipids and proteins are not coded into genome but are precisely added by enzymes involved in glycosylation process. Observed increase in glycan structure complexity through the evolution suggests that the glycosylation processes are under continuous evolutionary change. To reconstruct the evolutionary origin of the genes involved in glycosylation and their target proteins in H. sapiens we applied phylostratigraphic approach. Results showed that homologs of most human genes involved in glycosylation could be traced back to the last universal common ancestor (LUCA) suggesting that the protein glycosylation is an essential to all cellular life. By focusing on the evolutionary origin of genes involved in N-glycosylation pathway, we observed significant enrichment in the last eukaryotic common ancestor (LECA), probably linked to the emergence of endomembrane system which plays important role in eukaryotic glycosylation. Similarly, in the last common ancestor of all eumetazoans we found enrichment of genes related to glycosaminoglycans (GAGs) suggesting importance of GAGs for development of true tissues in the eumetazoan clade. Comparable to genes involved in glycosylation we found that significant number of glycoproteins, genes which are glycosylated, could be traced back to LUCA. The phylostrata (phylogenetic internodes) that mark origins of metazoans, eumetazoans, deuterostomes and vertebrates are also periods loaded with glycoproteins. Functional enrichment analyses on the organ level revealed that high proportion of genes related to immune, nervous and circulatory system processes were coding for glycoproteins. On the cellular level, cell-cell signaling, cell differentiation and cell maturation are functions enriched in glycoproteins. These results suggest the ancient origin of the glycosylation machinery, but also point to its fine tuning in metazoans and vertebrates.

Glycobiology ; Evolution ; Genomic Phylostratigraphy

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