maternal Gnas exon 1 disruption is more obese than the paternal disruption [82]. In contrast to these similarities between the mouse models of exon 1 ablation and PHP-Ia/PPHP, the serum PTH level seems to be moderately elevated in mice with paternal Gnas exon 1 ablation, suggesting the presence of PTH-resistance [41]. This finding is not observed in mice with paternal ablation of exon 2 and may therefore reflect the preservation of Gnas transcripts that use exon 2, such as XLαs. Although this conclusion is contrary to the evidence that XLαs can mimic Gsα [70, 71, 143], it correlates well with the notion that Gsα and XLαs, which are oppositely imprinted in certain tissues, mediate opposing actions [67].
