ARPP19 phosphorylation site evolution and the switch in cAMP control of oocyte maturation in vertebrates.

cAMP-PKA signaling initiates the crucial process of oocyte meiotic maturation in many animals, but inhibits it in vertebrates. To address this 'cAMP paradox', we exchanged the key PKA substrate ARPP19 between representative species, the vertebrate Xenopus and the cnidarian Clytia, comparing its phosphorylation and function. We found that, as in Xenopus, Clytia maturing oocytes undergo ARPP19 phosphorylation on a highly conserved Gwl site, which inhibits PP2A and promotes M-phase entry.

Conserved meiotic mechanisms in the cnidarian revealed by knockout.

During meiosis, DNA recombination allows the shuffling of genetic information between the maternal and paternal chromosomes. Recombination is initiated by double-strand breaks (DSBs) catalyzed by the conserved enzyme Spo11. How this crucial event is connected to other meiotic processes is unexpectedly variable depending on the species.

Past, present and future of Clytia hemisphaerica as a laboratory jellyfish.

The hydrozoan species Clytia hemisphaerica was selected in the mid-2000s to address the cellular and molecular basis of body axis specification in a cnidarian, providing a reliable daily source of gametes and building on a rich foundation of experimental embryology. The many practical advantages of this species include genetic uniformity of laboratory jellyfish, derived clonally from easily-propagated polyp colonies. Phylogenetic distance from other laboratory models adds value in providing an evolutionary perspective on many biological questions.

Whole-animal multiplexed single-cell RNA-seq reveals transcriptional shifts across medusa cell types.

We present an organism-wide, transcriptomic cell atlas of the hydrozoan medusa and describe how its component cell types respond to perturbation. Using multiplexed single-cell RNA sequencing, in which individual animals were indexed and pooled from control and perturbation conditions into a single sequencing run, we avoid artifacts from batch effects and are able to discern shifts in cell state in response to organismal perturbations. This work serves as a foundation for future studies of development, function, and regeneration in a genetically tractable jellyfish species.

An improved whole life cycle culture protocol for the hydrozoan genetic model .

The jellyfish species (Cnidaria, Hydrozoa) has emerged as a new experimental model animal in the last decade. Favorable characteristics include a fully transparent body suitable for microscopy, daily gamete production and a relatively short life cycle. Furthermore, whole genome sequence assembly and efficient gene editing techniques using CRISPR/Cas9 have opened new possibilities for genetic studies.