Extreme Exfoliation

Spiny Mouse

An Eastern Spiny Mouse (Acomys dimidiatus). A relative of the species in this study.Photo by Marcel Burkhard.

There may be more than one way to skin a cat, but before you go all Cruella de Vil on the local felines take a minute to consider an easier prospect:  African Spiny Mice. These particular rodents have an intriguing adaptation. If one of these mice is attacked by a predator its skin breaks away easily, giving the mouse precious seconds before the predator realises it has only come away with an appetiser, while the main course is still running for cover. The process of dropping body parts to evade predation is known as autotomy and it is very rare in mammals relative to other classes. Most observed cases in mammals relate to caudal autotomy (detachment of the tail) in rodents, a feat that African Spiny Mice are also capable of. The example of a lizard “dropping” its tail is perhaps the best known example of autotomy in nature, but many other species display autotomy as a defensive behaviour.

While skin autotomy is in itself a fascinating phenomenon, what’s even more remarkable is that the mice can quickly close the wound and regenerate the lost skin complete with sebaceous glands and follicles. This amazing restorative capacity even extends to damaged ear tissue.

Seifert et al. Ear regeneration

Tissue Regeneration in A. kempii, progressing from Day 0 (a) to Day 40 (c). Photo from Seifert et al. 2012.

So why should we be getting excited about this? After all we’ve observed more extreme feats of regeneration elsewhere in the animal kingdom. Surely a mouse growing its skin back is less impressive than a salamander regrowing a fully functional limb following amputationAshley Seifert of the University of Florida explains the significance “… these animals could become a new model for understanding mechanisms that regulate regeneration in mammals. Like rabbits, their ability to regenerate new hair follicles and ear tissue, including cartilage, means they have “unlocked”, for lack of a better term, their regenerative ability. In general, mammals are poor regenerators. There are plenty of hypotheses about why this is, but it’s been difficult to test. These animals provide a tool to do that.”

It is because they are mammals, like us, that these mice are of such special interest. Due to our mammalian commonalities, they may prove to be useful model organisms in the field of Regenerative Medicine. The possibilities are enticing, but there is still much to learn from these fascinating creatures. Whatever secrets these mice keep, Seifert seems determined to unveil them ,  “At the end of the day, I wonder about things, and as a scientist, there is nothing better than being able to act on that wonder to find out why something happens the way it does. Of course, this always creates more questions, but that’s part of science. Its our choice to determine just how far down the rabbit hole we want to go. I for one plan to follow these guys as far as they will take me.”

 So how do the mice shed their skin with such apparent ease? For starters, African Spiny Mice (Acomys percivali and Acomys kempi) have skin that is about 20 times weaker than that of lab mice (Mus musculus). Seifert’s research, published in Nature, found that while Mus skin displayed a certain amount of elasticity before tearing, the skin of Acomys was brittle and tore almost immediately when subjected to tension. However, despite this obvious difference in toughness, the skin of both species is structurally quite similar. The difference between the species may be attributed to the size of their follicles and the associated glands. Acomys species have much larger follicles and as a result less of the dermis is occupied by connective tissue, potentially accounting for the observed brittleness.

As for the method of regeneration? It appears that it follows a similar course to that observed in some amphibians. Following limb loss, salamanders first heal the wound via epithelial cells migrating to cover the exposed tissue. Shortly afterwards a blastema (a mass of progenitor cells) is formed at the distal portion of the wound stump. These cells then differentiate forming the necessary tissues to reconstruct the lost limb. This process is very similar to the way limbs develop during embryogenesis.

So there you have it. If you’re still hell bent on making a fur coat, put down the cat and lose the razor. Just grab yourself a few spiny mice and start pinching. Personally I don’t find the idea of a mouse-fur coat to be particularly appealing, but if you want to flaunt your verminous ensemble all over town like some kind of demented Disney villain then go nuts. It’s no skin off my back.

Sources:

Seifert, Ashley W., et al. “Skin shedding and tissue regeneration in African spiny mice (Acomys).” Nature 489.7417 (2012): 561-565.

Photos:

Eastern Spiny Mouse Marcel Burkhard alias cele4

Tissue Regeneration: Seifert et al. 2012 supplementary material.

Many thanks to Ashley Seifert for his contribution to this post.

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