I just got this from google alerts and am confused. I note that the authors are not Steve Wilton's group, but what do the rest of you know about this? It sounds like they are saying that skipping multiple exon's is not feasible.....

Assessment of the feasibility of exon 45-55 multiexon skipping for duchenne muscular dystrophy


The specific skipping of an exon, induced by antisense oligonucleotides (AON) during splicing, has shown tobe a promising therapeutic approach for Duchenne muscular dystrophy (DMD) patients. As different mutations require skipping of different exons, this approach is mutation dependent.

The skipping of an entire stretch of exons (e.g. exons 45 to 55) has recently been suggested as an approach applicable to larger groups of patients.

However, this multiexon skipping approach is technically challenging. The levels of intended multiexon skips are typically low and highly variable, and may be dependent on the order of intron removal.

We hypothesized that the splicing order might favor the induction of multiexon 45-55 skipping.

Methods: We here tested the feasibility of inducing multiexon 45-55 in control and patient muscle cell cultures using various AON cocktails.

Results: In all experiments, the exon 45-55 skip frequencies were minimal and comparable to those observed in untreated cells.

Conclusion: We conclude that current state of the art does not sufficiently support clinical development of multiexon skipping for DMD.

Author: Laura van Vliet, Christa L de Winter, Judith CT van Deutekom, Gert-Jan B van Ommen and Annemieke Aartsma-Rus
Credits/Source: BMC Medical Genetics 2008, 9:105

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Thank you for your answer,but the reality is I didn't understand too much what is:Trialserve predictor?from where I'll get this?
We seen a neurologist for two times since last august I'm very upset that because she didn't explain to me how is his deletion,you know this new for me,
djamel fathi said:
Hi,you said an exon 45 deletion is out of frame,but what I have in the result , my son have an in frame shift,wich is consistent with dmd. is that different from what you saying or what? I appreciate your answer.
Keith said:
When we talk about in-frame or out-of-frame deletions, we're talking about how the mutation has disrupted the dna sequence. This is a complicated subject, and I'm by no means an expert.

To oversimplfy things, you can think of the DNA as a string of 3 letter words.

THE CAT ATE THE RAT

The DNA is "read" as cells are created in sequences of three. An out of frame deletion would disrupt the reading sequence. For example, if the deletion took out the T from CAT. The DNA would be read like this:

THE CAA TET HER AT

The result is a totally jumbled sequence, and the "recipe" for making the protein is lost.

By contrast, an in frame deletion takes out part of the DNA sequence such that it still makes "some" sense. For example, if the deletion took out ATE, you'd get

THE CAT THE RAT.

Here, there's still some resemblence to the original intent. You would get some type of protein created, although it might not be quite correct, or you might not get as much.

This general concept is referred to as the "reading frame rule". You can google it and find more, and better, explanations than this.

An exon 45 deletion is out of frame. There's a predictor to determine that at this website: http://www.dmdregistry.org/reports/predictor/


Good luck.
The trial serve predictor is online and you put in your sons mutation and it will tell you if the mutation is 'in frame' or 'out of frame' as well as what exons will need to be skipped for exon skipping to work. It was created by some very smart folks in the UK I believe.

djamel fathi said:
Thank you for your answer,but the reality is I didn't understand too much what is:Trialserve predictor?from where I'll get this?
We seen a neurologist for two times since last august I'm very upset that because she didn't explain to me how is his deletion,you know this new for me,
djamel fathi said:
Hi,you said an exon 45 deletion is out of frame,but what I have in the result , my son have an in frame shift,wich is consistent with dmd. is that different from what you saying or what? I appreciate your answer.
Keith said:
When we talk about in-frame or out-of-frame deletions, we're talking about how the mutation has disrupted the dna sequence. This is a complicated subject, and I'm by no means an expert.

To oversimplfy things, you can think of the DNA as a string of 3 letter words.

THE CAT ATE THE RAT

The DNA is "read" as cells are created in sequences of three. An out of frame deletion would disrupt the reading sequence. For example, if the deletion took out the T from CAT. The DNA would be read like this:

THE CAA TET HER AT

The result is a totally jumbled sequence, and the "recipe" for making the protein is lost.

By contrast, an in frame deletion takes out part of the DNA sequence such that it still makes "some" sense. For example, if the deletion took out ATE, you'd get

THE CAT THE RAT.

Here, there's still some resemblence to the original intent. You would get some type of protein created, although it might not be quite correct, or you might not get as much.

This general concept is referred to as the "reading frame rule". You can google it and find more, and better, explanations than this.

An exon 45 deletion is out of frame. There's a predictor to determine that at this website: http://www.dmdregistry.org/reports/predictor/


Good luck.
Thanks for your reply Roxanne :-)
The trialserve predictor is the weblink I have in my post, in red.
The exons are a puzzle which fit in together. My son is missing exons 48, 49 and 50. Out of frame. Exon 47 does not fit into exon 51 - the puzzle pieces do not fit. When exon 51 is skipped, in our case, the code can them be put right back in frame as exon 47 fits perfectly into exon 52. We are extremely lucky that if our son had to get MD, he got the best one. Skipping of exon 51 can help the greatest number of those afflicted with DMD - like 13%. But the hope is that if it works on 51, then it can be adjusted to skipping other exons.
You have to look at the strand as a puzzle and see for yourself which one fit and which ones do not. In your case, where you child is missing 49 and 50, if you look at the strand - 48 does not fit into 51, but if 51 is skipped, 48 then fits into 52 and the code can run on. You need to know if your child's deletion is out of frame or not. In our case, Liam is out of frame and skipping 51 pops him right back in frame. They know the drug works with amazing results, but they need to figure out the dosing with the IV and the dose for that trial starting right now is very low and may not yield any results, but when the trials start here in DC in the next year - Hoffman wants to really increase that dose. Yippie.
Here is a site that pictures the process - I found it to be very helpful in this confusing situation.
www.HumGen.nl/lab-aartsma-rus/ I hope this helps you out in some way. Hang in there.

Jennifer said:
My son has a deletion of exon 49 and 50. I thought that skipping exon 51 would help him, was I wrong?
Has your son had a muscle biopsy yet? That is the definitive way to tell.

Nadine Foley said:
Hi Lori

I looked up my newphew's deletions on the leiden trial serve and it says ....deletion exon 4-18 leads to ..an IN-FRAME deletion. I know exon skipping will only fix out of frame deletions and will not work for in-frame deletions. We are still waiting to hear from the doc for a way for get Travis a definite diagnosis not just based on age & symptoms. But we are 99% sure it is DMD, that last 1% is just the hope left in us.

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