In our PA model (i.e., a model of maternal uniparental disomy, or UPD), bimaternal expression of STX16, did not affect the methylation status and expression of Exon1A as well as Exon1B. Furthermore, in comparison with other UPD-related imprinted loci that are significantly associated with genetic diseases [33,34], the overall effect of maternal UPD on the GNAS locus might not be substantial, because of biallelical expression of the predominant Gnas transcript and lower amounts of other parental-origin-specific transcripts (i.e., Nesp, Nespas, Gnasxl, Exon1B, and Exon 1A). Here, GNAS is linked to hereditary disease.