Latest Activity: Feb 3, 2017
Started by Rahul Deshpande. Last reply by Tuyet Lan Thi Tran Jul 26, 2014.
Started by Kira Mullaly. Last reply by vishal wadhwani Jul 25, 2014.
Started by Tammy. Last reply by Ramya Srinivassan May 2, 2014.
What Keith describes is often the case when the mutation is in the exons at the very beginning or end of the gene.
In-frame mutatations don't always result in Becker, or even a milder phenotype of Duchenne. This generalization is what's called the "reading frame rule", and there's a study that showed it was correct about 90% of the time. Not all exons are of equal importance either. Some are more important than others.
Andrew, Thanks so much for the link to the Diagram! Acording to the diagram, if my son is missing Exxons 2-21, exxons 1 and 22 should fit together just fine, making it an in-frame deletion, meaning that he should have a much more milder form of Duchenne, or even Becker. But as I said before, He has great dificulty on stairs, and on a bad day, askes for help to get up from the floor. I am confused and worried about the diagnosis, it just doesn't seem to make sense.
"In Frame" generally means that the missing exon(s) don't interrupt the reading frame which generally they will produce some dystrophin. This is basically what exon skipping does, skips another exon which will then but the mutation back in-frame (where the individual exons sort of fit together).
There's a diagram here. In your case (and mine), 45 is missing and 44 and 46 don't fit together. However, if we skip over 44, then you can see that 43 and 46 will fit together.
My son was diagnosed when he was 5 and know he is almost eight. We went to the doctors originally just because he could not get on the couch or off the ground. Jacob also does not run, but he is a great fast walker. Jacob is a deletion of 45, and what is "in frame" mean?
Hi everyone, My son Nicky has deletions of exons 2-21. We live in Alaska, so there isn't a huge amount of Duchenne patients locally. I am a bit confused because I e-mailed one of the Genetic specialist that spoke in the webinar about exon skipping to ask her if there were any current clinical trails for deletions in the 20's, and she told me that she thought my son's deletion was an "in frame" deletion. That doesn't sound right though, because at 4 years old, he sometimes has great difficulty getting up from the floor, or getting up on the couch, and he can't really run at ALL. So I don't know if the testing was off, or what, or it it even matters at this point...any thoughts?
Dear Donna: Your son has a premature stop codon. PTC124/ataluren is the one on trial for this situation. Try this link for more info:
hhmm, interesting - I guess I don't know. He's also on the PTC124/ataluren drug. I thought that was for deletions, but maybe not... I'll have to clarify with his nurse. Thanks.
I think that describes a stop codon, not a deletion. I'm not sure if exon skipping is applicable to stop codons. I'm not an expert, though. Try Sharon or Pat.
Keith - here's the official verbage - looks like a deletion of 58:
This sequence analysis identified a hemizygous C to T change at nucleotide 8608 (c.8608C>T) in exon 58 of the DMD gene. This nucleotide change lies in the MLPA exon 58 probe ligation site and appears to account for the observed failure of amplification of exon 58 by MLPA. The c.8608C>T substitution results in an amino acid change of Arginine to a premature stop at codon 2870 (p.R2870X). This nonsense mutation has been previously reported in the Leiden Muscular Dystrophy Database (http://www.dmd.nl), and it is predicted to produce a premature translation termination. This nucleotide change is therefore interpreted as a disease-causing DMD mutation (ACMG Sequence Interpretation Guidelines, www.acmg.net).
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