First, I just want to say a massive thank you to all those who have sent me samples. I now have samples from 1,100 dogs of which about 100 have JKD and the rest are used as healthy controls for comparison. The first part of my study was completed in 2017 using a relatively crude analysis applied to about 600 samples. I was pleased to find a strong indication that the faulty gene lies in one particular region on one on the dog’s 38 chromosomes. I am 90% certain this is a robust result. I don’t say 100% because there remains some room for doubt. Having said this, Bruce told me about one top dog who he was sure was homozygous (carried two copies of the faulty gene). I have samples from 13 of his offspring and they all carry a trait that is much commoner in diseased compared with control dogs. Such a pattern would be highly unlikely unless Bruce was right and if the region was not involved with the disease.
With a good ‘hit’ I now want to find the gene. With so many new samples coming in over the last 4 months I am in a good position. My next experiment is to look much more closely at the candidate chromosome region by DNA sequencing (I will read the genetic code). As a trial run to make sure the method works, I will study about 500 dogs. Sequencing will take about 5 weeks and I will post the samples off on Monday 7th May. Fingers crossed! If this works well, I will analyse the full sample set. However, even with just the first half I should be able to say with confidence that the gene does (or does not) lie in this region, and may well be able to say what the gene is. I should also be able to start developing a simple genetic test to tell whether a dog is a carrier or not.
I should end on a slight cautionary note. While the disease clearly has a genetic basis and runs in families, it is not completely simple. You may already have asked yourself how a top dog can carry two copies of the faulty gene yet still be healthy. There are several possible answers: the disease could be very variable such that some puppies die before they are born while others live well into adulthood; it could be that there is a second gene involved that actually protects against the effects of the disease gene. The truth is that we do not yet know why. Thus, while I am confident that I am well on my way to tracking down the main player, this will not be the end of the story. In future I want to understand the disease fully. In this light, more samples will always be welcome! “