Evolution of Excitation-Contraction Coupling

Epithelial Tissues as Active Solids: From Nonlinear Contraction Pulses to Rupture Resistance

“…The study of T. adhaerens and other early-divergent animals brings tissue-mechanics to the context of evolution of multicellularity. Alongside the fundamental ability of cells to stay cohesive as tissues, it may shed light on the origin of the excitation-contraction coupling and the nervous-muscular system [18]. We suggest to further investigate dynamics in early-epithelia not only in the context of "active cohesion", but also as possible embodied calculations yielding "behavior" and supporting physiological needs (e.g.…”

“…Hence, it is likely that the spontaneous contractions involve calcium as well. However, it is unclear how one contraction triggers the other during a contraction pulse in an early animal that lacks synapses or gap junctions [18]. Diffusion of neuro-peptides in the surrounding water was suggested to coordinate ciliary beating in the ventral tissue of this animal [19], but chemical diffusion is not likely to govern the contraction pulses in the dorsal epithelium, due to the nature of their propagation (uniaxial propagation, front split, pulses annihilation etc).…”

Phylogenetic and biochemical analysis of calsequestrin structure and association of its variants with cardiac disorders

“…We also discovered that the Chondrichthye and Avian taxa lost casq1 but retained the casq2. Arthropoda do not have the calsequestrin gene, although they have transversely striated muscle similar to the vertebrate skeletal muscle 56 with well-developed transverse tubules associated SR cisternae 57,58 . Considering that Arthropoda move by means of their segmental appendages, they may not require high capacity Ca 2+ stores.…”

“…Comparison between the evolutionary distribution of calsequestrin and the RyR proteins 58 provides insight into the evolution of the excitation-contraction coupling system in metazoan muscles. While we were unable to identify calsequestrin homologues, RyR homologues have been found in the genomes of holozoans such as 1.…”

“…[ www.nature.com/scientificreports/ Capsaspora and choanoflagellates, suggesting that the RyR protein evolved first. The pairing of the calsequestrin and ryanodine receptors seems not to have been established as essential in non-vertebrate animals, given the lack of calsequestrin in sponges but presence in cniderians and ctenophores and the opposite for the RyRs 58 . The presence of the preduplicated RyR but absence of calsequestrin in insects suggests lack of essentiality of the paired regulation as well.…”