Research Update CHF 02403-MOU MY and EY-3: Microphthalmia and Delayed Growth Syndrome in the Portuguese Water Dog

Objective A is 100% complete. A draft of the paper describing the clinicopathological findings had been written but we found more data on affected puppies, which were added to the paper. The paper is being submitted for publication within the next 4 weeks. A paper was published about microphthalmia in PWDs recently by a group out of Cornell. However, this paper described only the ocular changes in affected dogs. With our publication, we will show that there can be other abnormalities such as low platelet counts and stunted growth, which makes this a truly syndromic disorder. We have also included pedigree analyses showing the autosomal recessive mode of inheritance. In the meantime, we have decided to put all of the clinical data into the final paper describing the disease-causing variant, making this a large landmark paper.

For Objective B, we received enough DNA samples from affected dogs and their relatives to perform an initial genome wide association study (GWAS). The DNA was sent to Illumina (Neogen) the end of November 2018, and we received the results as expected in January 2019.

We are absolutely thrilled with the results: A single, very significant peak was seen on the “Manhattan plot”, which allows us to locate not only the chromosome but the general area of that chromosome in which the gene must be located. Indeed, there is a gene in this area that, when mutated in mice and humans, causes a microphthalmia-like syndrome. We sequenced this gene and did not find a clear disease-causing variant. Thus, we submitted and sequenced the entire genome of one affected dog and one normal PWD.

This allowed us to find a variant in a gene that is important for the development of the eye, and this variant is not present in any of the normal dogs including dogs of other breeds. We have made the test available to the breeders early this year and have already tested over 750 PWDs from at least 7 different countries.

Mid-Year and End-year-3 Research Update Dr. Casal for microphthalmia syndrome.