Ocampo Daza, D. | Search bioRxiv

bioRxiv2019

Chitin is present within the Ampullae of Lorenzini of chondrichthyan fishes

ABSTRACTChitin is synthesized by a variety of organisms using enzymes called chitin synthases and was recently discovered in a number of aquatic vertebrates. In our ongoing investigations into the presence of vertebrate chitin, we unexpectedly found evidence of the polysaccharide within the electrosensory organs, known as Ampullae of Lorenzini, of diverse chondrichthyan fishes. Experiments with histochemical reagents, chemical analyses, and enzymatic digestions suggested that chitin is a component of the hydrogel filling the structures. Further, in situ hybridization with a sequence from the little skate (Leucoraja erinacea) revealed that chitin synthase expression is localized to cells inside the organs. Collectively, these findings suggest that chondrichthyan fishes endogenously synthesize chitin and beg further investigation into the function of chitin in the electrosensory system.Competing Interest StatementThe authors have declared no competing interest.View Full Text

molecular biology↗

bioRxiv2019

Reconstruction of the carbohydrate 6-O sulfotransferase gene family evolution in vertebrates reveals novel member, CHST16, lost in amniotes

Glycosaminoglycans are sulfated polysaccharide molecules, essential for many biological processes. The 6-O sulfation of glycosaminoglycans is carried out by carbohydrate 6-O sulfotransferases (C6OST), previously named Gal/GalNAc/GlcNAc 6-O sulfotransferases. Here for the first time we present a detailed phylogenetic reconstruction, analysis of gene synteny conservation and propose an evolutionary scenario for the C6OST family in major vertebrate groups, including mammals, birds, non-avian reptiles, amphibians, lobe-finned fishes, ray-finned fishes, cartilaginous fishes and jawless vertebrates. The C6OST gene expansion likely occurred in the chordate lineage, after the divergence of tunicates and before the emergence of extant vertebrate lineages.\n\nThe two rounds of whole genome duplication in early vertebrate evolution (1R/2R) only contributed two additional C6OST subtype genes, increasing the vertebrate repertoire from four genes to six, divided into two branches. The first branch includes CHST1 and CHST3 as well as a previously unrecognized subtype, CHST16, that was lost in amniotes. The second branch includes CHST2, CHST7 and CHST5. Subsequently, local duplications of CHST5 gave rise to CHST4 in the ancestor of tetrapods, and to CHST6 in the ancestor of primates.\n\nThe teleost specific gene duplicates were identified for CHST1, CHST2 and CHST3 and are result of whole genome duplication (3R) in the teleost lineage. We could also detect multiple, more recent lineage-specific duplicates. Thus, the repertoire of C6OST genes in vertebrate species has been shaped by different events at several stages during vertebrate evolution, with implications for the evolution of the skeleton, nervous system and cell-cell interactions.

genomics↗