Transgenic cheetahs

Great Debates
1

On a mailing list to which I subscribe, another person pointed out this site which mentions the (lack of) genetic diversity among cheetahs (N.B.: this page appears to me to be accurate in outline. but I can’t vouch for the specific numbers given).

Now, assuming adequate genetic engineering and other techniques (which, IMHO, are not yet adequate, although we might reasonably assume that they will be in a half-century), we could increase the genetic diversity of cheetahs by injecting new genes into zygotes, anything from other big cats’ DNA to completely synthetic material (again, assuming suitable technology).

If we were to do so, would we have given the cheetah the means to surmount its “genetic bottleneck”, or would we have created worthless “cheetoids” that ought not to be allowed to contaminate pure cheetah stock, no matter the consequences?

2

This is a very good question. Unfortunately, I am swamped at work right now and can’t contribute much at this time. I will say that the inbreeding problem with cheetahs has been known for some time, and it does look bad for the fitness of this species.

I’m not sure where I fall in regards to genetic manipulation with the DNA of other species in order to strenghten cheetah stock. My chosen career relates directly to endangered species issues. Many times, there are conflicting and difficult situations/questions when it comes to species management and protection. My gut reaction is that the solution presented in the OP is not a good idea. However, I will think about this more, read the link provided, and get back to this thread later.

3

The obvious concern is that whatever genes you insert won’t be cheetah genes. They may be closely related, but they won’t be identical. Also, if you want to increase genetic diversity significantly, you’ll need to throw in a whole boatload of genes, which compounds the problem. Personally, I think a simpler and more viable solution would be to preserve DNA samples of what we have now and in the future throw in clones of long-dead individuals into the mix.

And, of course, work toward preserving their habitats. If they don’t have any place to live it won’t matter if they’re genetically diverse or not.

4

Like Smeghead said.

The problem with inbreeding is the preponderance of autosomal or sex linked recessive diseases that may be carried. Take for instance a small relatively inbred population – Ashkenazi Jews – they have an increased rate of a whole host of diseases (Tay Sachs, Cystic Fibrosis, Gaucher’s, Factor XII deficiency, Inflammatory Bowel Syndrome, etc. etc.) Before my wife and I (Ashkenazis) have kids, we will get tested for these and more diseases.

Now imagine that the population was small enough that these types of diseases became more prevalent, such that they would threaten the population. That’s what’s going on with cheetahs.

What tends to happen when the population shrinks is that all genes get a reduced number of alleles. Polymorphisms are the name given to small changes of the DNA that differ highly from individual to individual, that determine what makes each individual different. These are what make different alleles – they change protein coding sequence or regulatory level or temporal/spatial expression (when, where, and what level the gene comes on). When these are reduced, things tend to homozygose (get two copies of the same allele) more often – and this leads to diseases or reduction in fitness often. Let’s say you have a gene that needs 60% level in order for you to be normal. You have one allele that gives you 45% and one that gives you 20%. You are dandy. Let’s say you have kids with your sister, who has the same alleles. Your kids have a one in four chance of getting 2 20% alleles, and thus not being normal.

Also, sensitive pathways requiring many genes (like intelligence) are affected often because there are additional targets.

Interestingly, this is how we make lab mice – we breed brother versus sister for 40 generations or so to get rid of polymorphisms. Offspring of that cross are incredibly stupid, yet incredibly similar.

Inserting exogenous DNA will not help this – chances are that another big cat gene will work worse than the cheetah gene you are trying to replace. That, and it is often hard to track down these specific loci (polymorphisms which change the expression of a gene made are hard to find). Also, as Smeghead mentioned, it will have to be done on thousands of loci, which is well beyond feasibility right now.

5

I checked out the link, but I was hoping to see a discussion of the ‘DNA enhancement’ postulated by the OP. I thought meybe this was an idea being batted around in the scientific community for cheetah survival. Your idea is thought-provoking, Akatsukami. Do you perchance have a source for this inspiration?

Having said that, I’m not sure at what stage the genetic technology exists or would exist to help the cheetahs out. I do know that there is a movement to clone the Asian cheetah subspecies that has been extinct for about 50 years. Presumably, there are tissue samples (or other DNA source) from the last known individuals from India. Either that, or they would try to clone one of the few remaining (about 50 left in the wild) cheetahs from Iran. I’m not sure if this is a separate subspecies of the African cheetah, or just a geographically isolated population. Of course cloning doesn’t answer the question of improving species fitness. In fact, it heads in the opposite direction.

Didn’t we just have a recent situation where a rare guar embryo was implanted into a surragate domestic cow to birth and raise? It’s amazing the things science can do these days; however, limitations and ethical concerns are still present. Some people are afraid that cloning species or otherwise manipulating with genetics will give people excuses not to pay enough attention to habitat or conservation issues. “Who cares if we shoot a few, we can just clone them back.”

Sad to say, the cheetah seems destined for the way of the passenger pigeon, dodo bird, and other animals that are no longer with us. This is a shame, but the reasons are not all anthropomorphic. When I was a kid, the cheetah was my favorite animal. Combine my cat-loving nature with the speed and elegance of these cats, and, well, let me repeat that I hate to see the likely end for this species.

I am going to stick with my original assessment that inserting the genes of other cats in an effort to keep cheetahs around would be a misguided effort. Noble intentions, but as the OP suggested would lead to the creation of “cheetoids” instead of improving the fitness of the existing species. What may make matters more difficult is that cheetahs are the least catlike of all the big cats. Oh sure, then we may have animals that look like cheetahs, and maybe that would make zoos happy, but the species we know as “cheetah” would be no less extinct.

I would be interested, from the standpoint of scientific curiosity, whether we could do as the OP suggested. what would the result be? Would there be subtle (or not so subtle) changes in behavior? Would the new and improved cheetahs be able to produce viable offspring? Or would the species be at the absolute mercy of science to maintain some sort of existence?

6

At least I got to pet one when I was in South Africa in May. It was at a World Wildlife Fund reserve…

7

Would you elaborate for this layman? How are cheetahs less catlike? How would this lack of ‘catness’ affect efforts at genetic rehabilitation?

8

Here are some characteristics:

  1. Vocalization. Cheetahs are unable to roar like other big cats. A cheetah’s yelp is more like a dog. It also commonly emits a birdlike ‘chirp.’

  2. Claws. Not fully retractable. Through use, they become dulled and ineffective as weapons or as climbing aids. Other foot morphology differs as well. Consequently, hunting strategy differs.

  3. Unlike other big cats, cheetahs do not normally feed on carrion. They tend not to guard remains or return to a carcass after gorging on a fresh kill.

  4. Cheetahs tend to be less aggressive than other big cats. Most cats prefer to be left alone, but cheetahs moreso than others. I am not aware of any documented instance where a cheetah attacked a human.

  5. Limbs are proportionately longer and head is smaller (comapred to body size) than other cats. Adaptation for speed. Other unique structural adaptations in the respiratory system present in cheetahs but not in other cats allow increased air intake when running or recovering from a sprint.

In fact, cheetahs fit into a unique category. They are dissimilar enough from both the “big cats” (lions, tigers, leopards, jaguars) and the “small cats” (cougar and smaller) to fit in with either.

some of this information came from: http://lynx.uio.no/catfolk/jubssa1a.htm The rest from my memory, so someone feel free to add/revise what I have said.

As far as genetic rehabilitiation would go, I don’t really know. Genetics is not my strong suit. I have no idea how genes from, say, a leopard would affect the adaptations specific to cheetahs, as listed above. Maybe there would be enough morphological or behavioral changes for cheetahs to have to adapt to many new strategies. Maybe there would be absolutely no noticeable difference. I can’t even begin to speculate.

9

divemaster, thanks for the info and the link.

10

Actually, I wouldn’t go so far as to say they are less cat-like. They are cats, and are placed firmly within the Felidae Family. That they have their own Genus is more a result of their extreme specialization rather than having little in common with the other big cats (note that the clouded leopard, Neofelis, also has its own Genus).

Much of the cheetah’s seemingly-divergent morphology is a result of its extreme adaptation for speed. All cats run fast, so have the longer limb proportions common to cursors. Cheetahs, however, run faster, and the limbs are even more elongate. Canine teeth are reduced so as to not impede air flow through the nasal cavity, claws are duller and non-retractile to increase traction, spinal flexibility is increased, etc. Because of these adaptations for speed, the cheetah cannot grapple with its prey the way a lion or leopard can; it should be expected that its hunting behavors should therefore differ. Even the vocalization differences might be attributable to alterations in the trachea and larynx to benefit respiration.

So, it is not that cheetahs are less catlike that gives them their unique appearance and classification; it is that they are more specialized for speed than any other animal, cat or otherwise.

As for the effect of introducing foreign DNA, might it not be possible to only alter those aspects which relate to the immune system, since death due to disease is the biggest threat caused by the diminished gene pool? This would seemingly not diminish their inherent ‘cheetah-ness’, so should not threaten their survival as a species, yes?

11

divemaster writes:

SFAIK, this idea is not seriously proposed in the scientific community. However, you undoubtedly know of the debate over hybridizing the dusky sparrow in the 1970s. This seemed to me to be a logical extension, given the technology, of that debate.

We did recently, although I believe that it has been done before (on a proof-of-concept, rather than a serious need, level). Of course, while the offspring is not strictly a gaur (it’s a gaur from a cow environment, so to speak), it is far less of a contamination that what I suggested in the OP might be done. The biochemical environment may (or may not) be as different as allows the fetus to be carrie to term, but no foreign genetic material is introduced, and whatever interference the biochemistry of the womb causes will presumably correct itself in a couple of generations.

smeghead writes:

As I understand it (and, of course, anyone with more information is invited to contradict me), the genetic variability of existing cheetahs (and, presumably, all of the cheetahs that have lived in the past 10,000 or so years) is so low that almost no help could be provided if all individuals could be cloned and added, through natural or artificial breeding, back into the mix.

An difficulty with cloning is suggested by divemaster’s mention of the cow giving birth to a gaur. Suppose a gaur nucleus were to be inserted into a cow’s egg, induced to develop, implanted, and brought to term (again, I am assuming a level of technology that may not currently exist). Although the nuclear genetic material would be 100% gaur, the mitochondrial genetic material would be 100% cow. Again, is this a (morally) viable method of preserving, if not a species, at least its genetic lineage, or, if this point is reached, do we ay, “This game is over; time to concentrate on the next endangered species”.

12

Well, yeah. I guess my strategy would be to preserve what we do have now with the hope than in the future cheetahs would be in a better position - more habitat, less poaching, etc. At this point, we could replace anything that was lost between now and then. After all, if we don’t improve their conditions, no amount of genetic fiddling will be worth anything.

Regardless, over time some of the gene alleles that exist now will disappear by random chance, even if things are getting better and diversity increases. We could then reintroduce them, increasing overall diversity with a purely cheetah source.

13

If a male cheetah feels like it needs to change itself into a female cheetah, I fully support hir decision.

Oh wait. I thought the thread was transgendered cheetahs…