This distinct white
pattern is characterized by the development of white over the body starting
from the head with facial markings often asymmetric and progressing back
(rearward) over the body leaving the head, neck, chest and front leg area
predominantly white. White can also extend past the withers and up the flank
from the belly area to cover the loin and back."
The inheritance of the Whitehead trait is not totally understood and "mismarks" caused by this trait are not to standard in several breeds. For example the AKC Australian Shepherd standard reads "white on the head should not predominate, and
the eyes must be fully surrounded by color and pigment."
Breeders can often be surprised by excessively whiteheaded offspring from 2 parents who are to standard,
as the following example demonstrates.
White around the area of the ears can be a cause for deafness as with Canon's example.
A better understanding of the inheritance of the trait and available genetic testing would be
helpful to many breeders.
GWAS is a statistical analysis technique that involves scanning markers across a full set of DNA to find a
genetic variant (mutation) associated with a specific trait. The geneticists look to identify an association
between genotypes at a particular marker/s and phenotypes observed with dogs involved in the research.
They search for markers where a given allele seems more prevalent in cases of dogs with full whiteheads
(white over both eyes) than control dogs with no white and no known white in the breed or line of dogs
within that breed.
In order to avoid false positive associations the testing uses a technique called Linear Mixed Models - LMM - which helps account for genetic relatedness. This is important information since there will be distinctive genetic markers found in different breed populations, related breeds and within related family lines.
Prof. Yuri Tani Utsunomiya DVM, MSc, PhD and Rafaela Beatriz Pintor Torrecilha DVM, MSc, PhD,
kindly offered their services to search for the genetic marker/s for the canine Whitehead trait. Their research uses the "Illumina CanineHD Array" chip, which is the same array that Embark uses for their testing.
The first stage of this research focused on mapping a genomic loci candidate.
SNP array can help in locating a chromosomal segment containing the variant, but will not provide
sufficient evidence to identify the precise mutation.
Identifying the mutation will need to be achieved using whole genome sequences.
So far there has been no cost involved with this research, however now we need to move forward with
Whole Genome Sequencing (WGS) and there will be cost involved.
Marco Milanesi PhD has recently joined our research team and kindly offered WGS testing for 2 dogs along with his expertise in reading the result. There is no-charge for the sequencing but there is a charge to extract the DNA and the cost for a blood draw and chilled shipping.
It would also be wonderful to include a third dog in the sequencing.
Moving forward we have started a Go Fund Me campaign to raise the needed funds.
Please consider donating :o)
The following video shows the typical spread of white over the body caused by Whitehead.
Video by Sandra Hansen