Agglutination of plasma, hemocyanin, and separated hemocyanin from the hemolymph of the freshwater prawn Macrobrachium rosenbergii (De Man, 1879) (Decapoda: Caridea: Palaemonidae)

Hemocyanin, the predominant protein in the hemolymph of crustaceans, was isolated from the plasma of the giant freshwater prawn Macrobrachium rosenbergii (De Man, 1879) and investigated, with its separated proteins MrHc1, 2, 3, and 4 (60, 114, 50, and 325 kDa, respectively) for hemagglutination (HA) activity. Hemocyanin against erythrocytes from human A, B, and O blood groups, mouse, rat sheep, water buffalo, and rabbit showed HA titer values higher than plasma. Of the four proteins isolated from hemocyanin, MrHc1 alone appeared to agglutinate the tested erythrocytes. Evaluated specific hemagglutination activity was higher for hemocyanin when compared to plasma. Sugar binding ability with N-acetylated sugars observed for plasma was restricted to N-acetyl neuraminic acid for hemocyanin and MrHc1. Inhibition of hemagglutination (HAI) by bovine submaxillary mucin (BSM) further defined the agglutination ability of hemocyanin and MrHc1. The hemocyanin protein MrHc1 on matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI–TOF/MS) and search in MASCOT database showed homology to hypothetical protein of Branchiostoma floridae Hubbs, 1922 (Cephalochordata). The results clearly indicated that the structure of the hemocyanin had evolved binding sites for sugar or sugar-linkages independently lacking homology with other hemocyanin or lectin-like proteins. The immunogenicity of this hemocyanin probably has biomedical applications as carrier adjuvants, which needs further investigation.

Single cell chromatin accessibility of the developmental cephalochordate

The phylum chordata are composed of three groups: vertebrata, tunicate and cephalochordata. Single cell developmental atlas for typical species in vertebrata (mouse, zebrafish, western frog, worm) and tunicate (sea squirts) has been constructed recently. However, the single cell resolution atlas for lancelet, a living proxy of vertebrate ancestors, has not been achieved yet. Here, we profiled more than 57 thousand cells during the development of florida lancelet (Branchiostoma floridae), covering important processes including embryogenesis, organogenesis and metamorphosis. We identified stage and cluster specific regulatory elements. Additionally, we revealed the regulatory codes underlying functional specification and lineage commitment. Based on epigenetic features, we constructed the developmental trajectory for lancelet, elucidating how cell fates were established progressively. Overall, our study provides, by far, the first single cell regulatory landscape of amphioxus, which could help us to understand the heterogeneity and complexity of lancet development at single cell resolution and throw light upon the great transition from simple chordate ancestor to modern vertebrates with amazing diversity and endless forms.