does a mitochondrial polymorphism entirely explain the parent-of-origin difference in penetrance?
The Val30Met transthyretin familial amyloid polyneuropathy (TTR-V30M-FAP) is the most frequent familial amyloidosis, with autosomal dominant transmission. This severe disease shows important differences in age of onset and penetrance. Recently, a difference in penetrance according to the gender of the transmitting parent was elicited in different geographic areas with a higher penetrance in case of maternal transmission of the trait. In addition, differences in mitochondrial haplogroup distribution in early and late onset Swedish and French cases of TTR-V30M-FAP suggested that a polymorphism of mitochondrial DNA could be one underlying mechanism of the phenotypic variation. We further investigated this hypothesis by modeling the penetrance function with a parent-of-origin and/or a mitochondrial polymorphism effect in samples of Portuguese (n=33) and Swedish families (n=86) with TTR-V30M-FAP in which several individuals had been tested for mitochondrial haplogroups. Our analysis showed
