Homogenous Delta F508
I'm always glad to hear from CFers that were diagnosed early in life and are doing well later in life! It gives me hope for Ellie.
Genotype refers to a specific gene whether it determines eyecolor, height, etc.,...in the case of CF, genotype refers to the CFTR gene. A defect in this gene (of which there are into the 1000s) can cause CF. Delta 508 means there has been a deletion at a certain location within the CFTR gene....(see below from Wikipedia). As with all genes, there are two strands of DNA which make up the genotype. If someone has a "normal" CFTR sequence that is paired with an abnormal CFTR sequence, they won't have CF. Homozygous means that the paired DNA strands are identical (i.e., both delta 508). There are also heterozygous genotypes that produce CF (i.e., two different CF mutations). The actual CF symptoms are called the phenotype...which are caused by the genotype.
The phenotype is caused by the genotype and is the result of the "dominant" gene present among the paired DNA strands. I suppose a simplified example would consider eye color. The gene for brown eyes is dominant over the gene for blue eyes. If these two are paired, a person will have brown eyes. If two stands for blue eyes are paired, a person will have blue eyes. With CF, the mutated strand is considered recessive...a normal strand will dominate over the recessive strand and a person won't have CF. If the two strands that make up the genotype are mutated strands (i.e., both are recessive as a consequence) for CFTR, the person will have CF.
With delta 508, the CFTR protein is misfolded due to the deletion of a base pair and usually degrades within the cell while some may make it to the cell protein surface and have some level of sodium-chloride channeling ability. There are different classes of mutations (see: <a target=_blank class=ftalternatingbarlinklarge href="http://atlasgeneticsoncology.org/Educ/CistFibID30032ES.html).">http://atlasgeneticsoncology.o...istFibID30032ES.html).</a> PTC124 aims to "skip" the premature stop sequence/codon as the CFTR protein is being made - thus allowing the entire CFTR protein to be manufactured. This drug is in phase 2 trials and has shown promising results. It won't work for the other classes of CF mutations. <img src="i/expressions/face-icon-small-sad.gif" border="0"> Delta 508 is a class 2 mutation while PTC124 works for class 1 mutations. I hope my stab at explaining genetics was helpful!
Wikipedia:
Delta 508 = deletion of 3 base pairs at position 508 at CFTR (cystic fibrosis transmembrane conductance regulator) protein and prevents the codon for phenylalanine, should be ATC for isoleucine at 507 then TTT for phenylalanine at 508.
The three base pairs A-T-C at position 507 of the CFTR nucleotide sequence form the codon for the amino acid isoleucine, while the three base pairs T-T-T at the adjacent position 508 form the codon for phenylalanine. The ?F508 mutation is a deletion of the C pair from position 507 along with two T pairs from position 508, leaving the codon A-T-T at position 507 (see figure). Since A-T-T also codes isoleucine, position 507's amino acid is unchanged, and the mutation's net effect is equivalent to a deletion ("?") of the codon for phenylalanine ("F") at position 508.
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