How Octopi Can Edit Their Own RNA to Rapidly Respond to Environmental Changes

 Organisms have multiple ways that they change their gene expression in response to stimuli. For example, an octopus thats suddenly put into frigid water can slow their enzyme activity. Some organisms can control their genetic responses to stimuli in another way, RNA editing. RNA editing involves the insertion and deletion of nucleotides in the RNA and has been visualized in mRNAs, tRNAs, rRNAs. It has not been yet visualized in prokaryotes. RNA editing is divided into two categories. One categories being insertion and deletion of nucleotides that changes the length of the target DNA. The second category is editing by base modification that changes a nucleotide into a different nucleotide, without changing the length of the RNA. The article describes how cephalapods, octopi, squid, and cuttlefish can change their mRNA in ways that can alter enzymes. Since the edits are in RNA and not DNA, they can go away quickly. The nucleotide adenine in the mRNA is replaced with inosine, a nucleoside that acts similar to guanine. This RNA edit can be known as "A-to-I RNA editing" and if it occurs in a protein, it alters its function. Finding out what the cephalopods use this RNA editing for was the big question. Researchers tested this by using the California two-spot octopus, which cannot generate its own body temperature, and placed both captive and wild octopi in tanks of 13 degress celcius. In these tanks, the researchers observed an increase in 13,285 mRNAs where the edited genes altered the proteins functions. When placing the animals back into warmer water of 22 degrees celcius, the amount of mRNAs decreased to 550. These RNA edits affected their nervous system and the scientists could hypothesize that the octopi were using these gene edits to cope with the change in temperature. 

Temperature-induced RNA recoding in octopus

The difficulty in adjusting to the significant seasonal temperature fluctuations in the Pacific Ocean around the southern Californian coast is faced by Octopus bimaculoides. A research by Birk et al. published in Cell examined the effects of temperature on RNA recoding across the neural transcriptome of adult octopuses in order to comprehend the processes behind this acclimatization process. For two to three weeks, the scientists kept octopuses in temperature-controlled aquariums at 13 °C and 22 °C. They discovered that this acclimatization process was greatly aided by RNA editing via adenosine deamination. At 13 °C compared to 22 °C (cold-induced), almost 33% of the recoding locations in the stellate ganglia had greater editing levels. When the temperature changed, these alterations happened quickly within hours and stabilized after four days. Kinesin-1 and synaptotagmin, two brain proteins involved in axonal transport and synaptic transmission, respectively, underwent structural and functional reconfiguration as a result of the cold's induction of RNA editing. The kinetics of Ca2+-binding and these proteins' motility were changed. The study discovered comparable results in populations of wild octopuses collected in the winter and late summer, indicating that closely related species like O. bimaculoides and O. bimaculatus also exhibit cold-induced RNA editing.

This study shows that brain proteome reconfiguration in octopus adaptation to changing environmental circumstances is significantly mediated by temperature-dependent RNA recoding. The study showed that quick and adaptable RNA editing in response to temperature changes alters the structure and function of brain proteins. Further evidence for the evolutionary conservation of this mechanism comes from the discovery of comparable patterns in populations of wild octopuses. The results offer up new lines of inquiry for future studies to investigate if RNA editing can adapt to other environmental changes and what role it can play in the adaptation and survival of diverse creatures encountering comparable difficulties.

MicroRNAs discovered as direct relation to intelligence in octopus brain

Octopuses also referred to as soft bodied cephalopods are invertebrates with a very complex nervous system. In a recent study referred to in the article; MicroRNAs are deeply linked to the emergence of the complex octopus brain , elevated RNA editing in the nervous tissue was related to RNA regulation and the large role it plays in cognitive function and success among this species. More specifically the miRNA were expressed more frequently in the adult's neuronal tissues and during development suggesting that the miRNAs are in direct correlation with the evolution of complexity in animal's brains. 

In agreeance that microRNAs are a key contributor to complexity in brains is Michael Le Page in the article; Octopus brains may have become complex the same way human brains did. High intelligence in many species is being directly correlated with high numbers of microRNAs and their ability to generate different types of neurons. Although, these invertebrates evolved completely separately from invertebrates the microRNAs both became present in animals with complex brains. I find it important to recognize others species intelligence and brain complexity in order to understand how humans and other species evolved into todays present species. It is also important moving forward how it will increase complexity and in what species. 

 

Chromosomal Gene Analysis of Cephalopods Give Scientists a Sneak Peek Into the Their Evolution

 

A Cephalopods nervous system is about as weird as the creatures’ external features. The evolutionary pathway that led to this infinitely complex nervous system has long been cloudy and less understood than other aquatic species. Recently, chromosomal assemblies of three cephalopod species – two squids  know as Doryteuthis pealeii and Euprymna scolopes along with an octopus species known as Octopus bimaculoides – have allowed scientists to better recognize which specific genes are present and in what order. This newfound knowledge can allow geneticists to further study components within the genome that are driving the expression of these genes (Nature).

Cephalopod genomes are notably different than those found in humans. Genomes within the two species of squid were found to be about 1.5 times larger than that of humans. While the Octopus’ genes more closely resemble a humans at about 90% size. Furthermore, it is found that while humans evolved through meiosis, a process in which two rounds of genome duplication occurs, a cephalopods evolution does not involve whole genome duplication, but instead undergoes “immense genome rearrangements” according to a Science Daily article. Which makes sense given that cephalopods started evolving 300 million years before humans existed. Discovery of this difference in duplication is a foot forward in finding out how these complex and highly intelligent creatures have evolved and thrived.

A Genetic Oddity May Give Octopuses and Squids Their Smarts

Octopuses, cuttlefish and squid belong to the coleoid cephalopods family of invertebrates. Dr. Eisenberg, Dr. Rosenthal and Noa Liscovitch-Brauer, at Tel Aviv University, studied these intelligent species more in depth. They found out that they make their RNA useful unlike any other species. These coleoids were recoding their sites, where RNA editing results in a protein different from what was initially encoded by DNA. This discovery breaks the norm of enzymes used for recoding like ACGU, now these coleoids can add new riffs to its base genetic blueprint.

This is fascinating because it proves how brilliant these species are. Although it’s a slow process, its proves that the change is well worth it. It might be of great use to further study these coleoid and understand what features in the brain allow them to edit these sites.