Bidirectional Imprinting of a Single Gene: GNAS1 Encodes Maternally, Paternally, and Biallelically Derived Proteins

• Published in: Proceedings of the National Academy of Sciences - PNAS 1998-12, Vol.95 (26), p.15475-15480
• Main Authors: Hayward, Bruce E., Moran, Veronica, Strain, Lisa, Bonthron, David T.
• Format: Article
• Language: English
• Subjects: Alleles; Amino Acid Sequence; Animals; Base Sequence; Biological Sciences; Cattle; Cloning, Molecular; Complementary DNA; DNA - chemistry; DNA - genetics; DNA Methylation; Exons; Eye - embryology; Eye - metabolism; Female; Fetus; Genes; Genetic inheritance; Genetics; Genomic Imprinting; Genomics; GTP-Binding Protein alpha Subunits, Gs - biosynthesis; GTP-Binding Protein alpha Subunits, Gs - chemistry; GTP-Binding Protein alpha Subunits, Gs - genetics; Humans; Kidney - embryology; Kidney - metabolism; Male; Messenger RNA; Methylation; Mice; Molecular Sequence Data; Muscle, Skeletal - embryology; Muscle, Skeletal - metabolism; Oncogene Proteins - genetics; Organ Specificity; Proteins; Pseudohypoparathyroidism - genetics; Recombinant Proteins - biosynthesis; Recombinant Proteins - chemistry; Reverse Transcriptase Polymerase Chain Reaction; Sequence Alignment; Sequence Homology, Amino Acid; Ungulates
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.95.26.15475

The GNAS1 gene encodes the α subunit of the guanine nucleotide-binding protein Gs, which couples signaling through peptide hormone receptors to cAMP generation. GNAS1 mutations underlie the hormone resistance syndrome pseudohypoparathyroidism type Ia (PHP-Ia), so the maternal inheritance displayed by PHP-Ia has raised suspicions that GNAS1 is imprinted. Despite this suggestion, in most tissues Gsα is biallelically encoded. In contrast, the large G protein XLα s, also encoded by GNAS1, is paternally derived. Because the inheritance of PHP-Ia predicts the existence of maternally, rather than paternally, expressed transcripts, we have investigated the allelic origin of other mRNAs derived from GNAS1. We find this gene to be remarkable in the complexity of its allele-specific regulation. Two upstream promoters, each associated with a large coding exon, lie only 11 kb apart, yet show opposite patterns of allele-specific methylation and monoallelic transcription. The more 5′of these exons encodes the neuroendocrine secretory protein NESP55, which is expressed exclusively from the maternal allele. The NESP55 exon is 11 kb 5′to the paternally expressed XLα s exon. The transcripts from these two promoters both splice onto GNAS1 exon 2, yet share no coding sequences. Despite their structural unrelatedness, the encoded proteins, of opposite allelic origin, both have been implicated in regulated secretion in neuroendocrine tissues. Remarkably, maternally (NESP55), paternally (XLα s), and biallelically (Gsα ) derived proteins all are produced by different patterns of promoter use and alternative splicing of GNAS1, a gene showing simultaneous imprinting in both the paternal and maternal directions.