Female Ambystoma Salamanders are Gene Thieves

It has been known for about a decade that an all-female species of Ambystoma salamanders were genetic thieves— mating with multiple males under the Ambystoma species and stealing copies of their genomes. The all-female lineage is suspected to be a mutation that occurred 5 to 6 million years ago when a pair of salamanders mated; with the mutation still persisting to this day. It has been recently discovered, however, that the female salamander does not just go around stealing genomes. They use the genetic material collected from males and incorporates all three genomes equally to pass down to her offspring, as well as "discarding" genes she does not need to use. This process is dubbed kleptogenesis (theft of genetic material), and the all-female Ambystoma species is the only animal on the planet performing this act.

Researchers from the University of Iowa were curious about how the female salamander chooses which genes to keep and which ones to throw away. The research team analyzed more than 3,000 genes from a single unisexual Ambystoma female that had three genomes (triploid) from different male Ambystoma species. About 72% of the male genes analyzed were equally expressed, meaning the female chose to use around the same number of genes from each male salamander species. Although the process of how the female salamander picks certain genes is still unknown, lead author Kyle McElroy theorizes that the genes are like a sports team. The sports team has equally competent players with no particular star athlete standing out. If someone gets injured, the competent team won't be affected by it because they are all on the same level. It is suspected that the female salamander doesn't decide which genes to keep individually, but has a balanced ratio of genes from the three different male species that work for her to create a successful hybrid.

I find this species of salamander to be very unique, especially since they are the only female species on the planet to take genes from several different male Ambystoma species. Normally offspring receive chromosomes from one female parent and one male parent, but the offspring for these female salamanders receive genetic traits from the mother and many different fathers. It is very interesting to see how the all-female Ambystoma species adapted to a mutation that happened millions of years ago and that they are still using kleptogenesis to this day.

Links:
https://www.sciencedaily.com/releases/2017/06/170612115339.htm
https://www.livescience.com/59639-salamanders-steal-genes.html

Axolotl Genome Sequenced: Unlocking Regeneration

Mexican axolotl salamanders are amphibians that spend their whole lives underwater. Credit: Jamie Catto

The axolotl (Ambystoma mexicanum) is an endangered salamander that can be found in the waters of Mexico. These salamanders spend their entire lives under water, so they are already different from the salamanders we are used to here in New Jersey. But there are other qualities to this fantastic creature that are pretty unexpected. The axolotl can regrow any severed limb with fully functioning bone, muscle, and nerves. But that's not all - they can even repair a broken spinal cord to the point where it functions like it was never damaged. The genome of these natural wonders was unsequenced and a mystery, until January 2018 when The axolotl genome and the evolution of key tissue formation regulators was published in Nature. 

The study was finally able to sequence the genome of the axolotl, revealing that it has a sequence of 32 billion base pairs - that's a bit more than 10x the amount of base pairs in the human genome. The scientists working on this project even had to develop a new gene assembler called MARVEL for the project! The findings from this genome indicated that some genes that are responsible for limb regeneration may be restricted by species, and that intron size may play a key role in the genes used during development. Further, the study found that the axolotl "does not contain the essential developmental gene Pax3" (Nowoshilo et. al. 2018), but they do have a paralogue, Pax7, which could lead to further understandings of the developmental genes of the axolotl. The ultimate goal for understanding the axolotl genome is to understand how their genes are able to make changes in RNA and proteins in order to transform adult cells to stem cells that facilitate regeneration. 

I think that the potential in understanding the axolotl genome is incredible. The ability for the axolotl to regenerate it's limbs and spinal cord functions after damage is incredible on it's own, and the potential for understanding stem cell production could be a huge step for human medical research. I'm looking forward to seeing how further research into the axolotl genome pans out, and how we are able to relate their wealth of genetic information to the human genome and development.