Homozygous mutated cats should not be used for breeding. However, these cats generally die before becoming sexually mature and consequently don't pose any problem for selection as they are automatically removed from reproduction.
Heterozygous carrier cats can be used for breeding, but they should then only be bred to partners who do not carry the mutation, as proven by gene testing. Kittens from such a litter should be tested before sold as future breeding cats. Ideally, only homozygous negative kittens should be used for breeding, but exceptions can be made as long as the buyer of the kitten is well aware of the problem and will continue to follow these recommendations.
All buyers of carrier kittens and kittens of unknown status from combinations where both parents are not negative should be informed about the disease, the fact that a parent is a carrier, and the risks of using the kitten for breeding. Heterozygous carriers will never get any symptoms, so one might think it is irrelevant information for a pet buyer. However, since it isn't uncommon that pet buyers later get the idea to have a litter from their cat, and they might then go ahead without contacting the breeder of the cat, it is important that also pet buyers fully understand the nature of the disease and the situation with their kitten.
The aim should be to have eliminated all carrier cats from breeding by the year 2015.