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Mutation
- Question
- On our genetic result sheet the mutation "r334W/F508 del as well as p.Arg334 Tsp" is mentioned. The mutation 508 seems to be frequent. The other mutation seemingly not. Could you give us more detailed information on the above mentioned mutation? Many thanks.
- Answer
- Dear questioner,
we have forwarded your question to Prof. Tuemmler from the medical school, Hannover, Germany. He gave us per e-mail the following extended information on the genetic result:
Mutation F508del: most frequent mutation in CF, frequency in Germany: 70% of all CF chromosomes. F508del CFTR has only a CFTR-mediated chloride transport activity of 0-0.5% in comparison to normal CFTR (100%).
Mutation R334W (or also Arg334Trp): frequency in Germany: about 0.5% of all CF chromosomes. It codes instead of the amino acid arginin for the amino acid tryptophan at the position 334 in the CFTR protein which is about 1700 amino acids long. This exchange of amino acids changes the transport features of the CFTR ion channel for negative loaded ions.
This mutation belongs to class IV, PS (pancreatic sufficient), i.e. CF patients with this mutation are in childhood and adolescence in most cases pancreatic sufficient and the development of growth and weight is according to their age group. The involvement of the lung is however as severe as with the most common mutation F508del. R334W CFTR has a CFTR-mediated chloride transport activity of 1.1-1.5% in comparison to normal CFTR (100%).
Best regards,
Prof. B. Tuemmler - 30.07.2012
- 30.07.12
It has to be taken into account in general, that mutation analysis only gives a rough direction but it has clearly to be stated, that the individual clinical course and especially the degree of lung involvement cannot be predicted according to the genotype alone, as many other genetic (modifier genes etc.) and environmental factors play a role and severity of disease differs substantially even between patients with the exact same mutations.
Therefore, it is of high importance that the individual patient is seen regularly in a certified CF center and follows his individual treatment program.
D. d'Alquen
