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Dear expert team,
our daughter has the mutation detal F508 and c.1730A>T. Is there any information about this combination?
Thank you
Dear questioner,
c.1730A>T is also known as Y577F. In this variant there is a change from A to T in position 1730 of the CFTR gene, so in the CFTR protein there is a change on position 577 from "Y" (amino acid tyrosin) to "F" (amino acid phenylalanin).
The variant Y577F had been found in the year 1997 in an Austrian CF patient. This patient had on the other allele alos deltaF508, however: besides Y577F there was another variant found in this patient, that causes CF (on the same chromosome as Y577F, not on the F508 CF gene).
Therefore it is up to now not possible to say exactly if Y577F causes or does not cause CF: the variant is seldom, in the database CFTR2 Y577F is not listed, in the "CFTR mutation data base" is besides the Austrian patient with the 3 sequence variants in two CF genes no further case listed. The literature data base Pub med does not know Y577F either, the database dbSNP is judging it as not classifiable.
Only from the description "at position 577 of a protein, that is 1480 pieces long, there is now an F instead of an Y, on cannot make a diganosis. In other words: this variant can cause CF, however it could also be a rare variant of the CF gene, that does not cause the disease.
This means: please contact your CF physician. This illness is a clinical diagnosis, the genetic finding helps only to make the diagnosis, if the consequences of the found variants can doubtlessly be derived. This is only possible for frequent CF muations, however not for the rare variant Y577F.
In single cases, like your daughter's case, the consequences of the variant Y577F could be concluded by the CF-physician: besides the genetic investigation, there are direct diagnostics procedures, in order to test the function of the CF protein. These are NPD (nasal potential difference measurement) and ICM (intestinal currency measurement), which can be done in some specialized centers in Germany. You should discuss that with your physician in charge.
Best regerds,
Frauke Stanke