Sunday, March 16, 2008

Glow in the Dark Snake?

*FYI - If you are a grant proposal reviewer then yes, I have a 2009 GC Round 4 proposal submitted for review.
That’s how it began for me – I wanted to make a snake that would glow in the dark. I wanted to insert a gene for luciferase (from the firefly) into a snake. What an awesome pet! It would be great but there was a catch – how do you do in vitro gene insertion into the embryo of a reptile? Mammals are relatively easy since you take the eggs out, modify them, and then put them back in the uterus. Although some reptiles give birth to live young, most reptiles lay eggs and must deposit a shell around the embryo when they ovulate. I suppose live bearing reptiles would be easiest but either way it gets very complicated to put the modified zygote back into the reproductive tract where it can be properly excreted.
But it also occurred to me that birds have a similar problem – the fertilized egg must pass through the magnum and isthmus to be coated with a shell when the egg is ovulated. Certainly the poultry industry would very interested in this strategy - Tyson Foods I'm looking at you! So I started thinking about how I would accomplish this. Might it be possible by doing in vivo laparoscopic follicular aspiration, followed by a quick ex vivo egg surgery, and finished with laparoscopic re-implantation? But these eggs are relatively large - could you even use laparoscopy? Wow! There were a lot of things to consider. But is there an easier way?

There was once a crazy idea about attaching a gene to the head of a sperm and letting the sperm carry the DNA to the egg. It was known as Sperm Mediated Gene Transfer (SMGT). But there were many technical problems including the fact that the gene did not insert into the chromosomes and therefore did not last through multiple replications of the cells. It was just present in the egg for a little while but apparently not permanent. Also, if the gene did insert into a chromosome it would not necessarily be expressed. So this idea basically fizzled out on a technicality. Incidentally, multi-generational SMGT could not be reproduced in other labs making the initial reports suspect.

Well, I really want to see a snake that glows in the dark! So I started thinking – what does a gene need in order to replicate? Well a gene sits on a chromosome and this chromosome needs at least an Origin of Replication, a centromere, and a telomere. When you really want to win the Tour de France you don't send just one cyclist - you send the whole team. So, what if we sent a whole chromosome instead of just a DNA fragment?

Hypothesis: Sperm Mediated Chromosome Transfer (SMCT) – use a sperm to deliver an entire chromosome to the egg.
Go to part 2 to some interesting notes about this hypothesis
- Just a peasant
Photo of two cats - the one on the right is expressing a gene that glows red under UV black light. From Gyeongsang National University in South Korea - video here.

6 Comments:

Anonymous Anonymous said...

This is an interesting read and it seems you have put some serious thought into this, are you going to try any of these techniques your self? Its just weird that you wrote this so recently, I've been going back and forth with a few friends(last night)on how we could get that to work in a ball python. Good luck with it if you are going to follow through, I'd love to see a glow in the dark snake.

9:04 AM  
Anonymous justapeasant said...

Hi anonymous,

Thanks for the comment. A Ball python would be really cool! In order to keep going you need more funding. We couldn't find anyone to loan us some chicken chromosomes and blew our tiny budget on trying to sort our own chromosomes. We never even got to do the cool part - mixing the semen and isolated chromosomes to prove step 1. I'll put some more stuff in part 2 in case you and your friends work in a lab or know investors. I'd really like to see someone succeed with it.

7:57 AM  
Anonymous Alex @PSU said...

I'm currently in talks with a few faculty members now, it seems they are hesitant to start this as the amount of time needed to carry out this research could be relatively long. I'm wondering though if birds (chickens) are close enough as far as development that already proven techniques could be used(http://dwb.sacbee.com/content/news/story/14289415p-15116929c.html). I don't really know, but the fact that ball python eggs are extremely expensive (although we do have a breeding pair) is probably going to be a pretty big factor. Have you thought of any other snake as a model? Something maybe with a bit quicker turn around? Really best case scenario with the ball python we're looking atleast a year to a year and a half.

4:06 AM  
Anonymous justapeasant said...

Hi Alex,

Your faculty are right - it will take a lot of time no matter which approach you pick. I picked chickens because we had a whole poultry house full of them and they were free. I like artificial chromosomes because I don't need to worry about transgene silencing, random insertions, viral promoters, etc. However, if you approach it from Origen's PGC modification method you will need to isolate snake PGC's and try to culture them as your first step. I'll bet that Dr. Mary Delany at UC Davis might even collaborate with you if you provide the snakes. She's got the xp and tools to start you so you should at least ask her. Incidentally, if it were me I'd probably go with corn snakes. Make sure your animal protocols are in order.

12:09 PM  
Blogger YeahIused tobereal said...

I noticed that this was posted in 2008, so have you gotten any closer? All of this sounds so interesting, being a Bio-chem student I understand your drawbacks. I wish you much luck in reaching your goals, and if you ever have any success, I will most definitely be snagging one. :)

Good luck!

12:32 PM  
Anonymous just a peasant said...

Hi YeahIused tobereal,

I only got one step closer before leaving grad school. It's still open game. The real reason I had wanted to do this was to use artificial chromosomes in human stem cells. Some labs have now done that. This is ultimately a powerful tool in medicine and, with your background, I encourage you to look more into it. Of course, making freaky pets would be cool too. Here's a link: http://www.genengnews.com/gen-news-highlights/researchers-combine-stem-cell-with-artificial-chromosome-to-treat-duchenne-muscular-dystrophy-in/81245566/

5:30 PM  

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