Sub-Aortic Stenosis, also known as sub-valvular aortic
stenosis, is a polygenic dominant disease, although some of the data is
equivocal regarding whether it is incomplete penetrance or modifying
factors. Data on a study of Newfoundlands clearly showed that the disease
was dominant, most probably polygenic, and uncertain what the other factors
were.
Currently, research is being done on a significant
incidence in Bouviers, where the pedigrees indicate that it is polygenic
dominant.
The carrier modes, although "somewhat"
similar between polygenic-dominant and recessive--in that a series of genes
(multiple individual alleles in recessive, multiple single dominant loci in
polygenic dominant) are required--is different in polygenic dominant
inheritance in that one set of genes gets transmitted as carrier or affected
genes, and the other may get transmitted as clear (whereas in recessive,
both are carriers if bred to a clear, or are affected if bred to another
affected or carrier).
In polygenic dominant, if one of the parents of the
litter were not individually affected (which is possible in a sub-clinical
affected status), the BOTH of the lines are probably carriers. The disease
shows up when you have a combination of the critical genes loci brought in
from both sides of the lines, where if the lines were separated, the disease
would not be expressed. That is one of the unique factors of polygenic
dominant expression.....you need a series of gene loci ALL to be there for
the disease to be expressed.
References to read: Ettinger, Veterinary Internal
Medicine, SECTION VIII, Chapter 74, "The Cardiovascular
System/Congenital Heart Disease"; R.L. Pyle & D.F. Patterson, et.al.,
American Heart Journal, Sept 1976, Vol 92, No 3, pp. 324-334).
(Source: David J. Sheckler, DVM, Saratoga, CA)
