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Laura Campello, Adriana Izquierdo, Belén Prados, Madalina Raducu, Oihane Fano, Jesús Cruces, Nicolás Cuenca, José Martín-Nieto; The Dystroglycanopathy-Associated POMT1 Gene, Encoding Protein O-Mannosyltransferase 1, Is Alternatively Spliced In The Mammalian Retina. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5372.
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The POMT1 gene, causative of the Walker-Warburg syndrome and other dystroglycanopathies, has been shown by us to be expressed in the embryonic rodent retina. This gene contains 20 canonical exons, and its mRNA undergoes alternative splicing in a number of tissues including brain and muscle. In this work we have investigated POMT1 mRNA and protein expression in the retina of adult mammals. We have also focused on the possibility of alternative splicing of the POMT1 mRNA in the mammalian retina.
RNA from primate (human, monkey), bovine and rodent (rat, mouse) eyes was subjected to RT-PCR using primers flanking at least one particular POMT1 exon, as well as flanking the whole protein-coding sequence. PCR products corresponding to full-length transcript variants (TVs) were subcloned, sequenced and translated into amino-acid sequences in silico. Also, retinal extracts from different species were subjected to immunoblotting analysis with POMT1-specific antibodies.
We have found expression of the POMT1 gene at the mRNA and protein levels in the adult neural retina of all species analyzed. We have cloned a good number of alternatively-spliced TVs from the retina of various mammals. These mRNA molecules contained optional exons that can be either skipped or included in the mature mRNA, some of which were newly identified, creating in many instances -but not all- premature termination codons. Immunoblots revealed, in addition to the POMT1 expected band, lower-MW isoforms of this protein.
Our results indicate that the POMT1 gene and its protein product are expressed in the adult retina of all mammals studied. Its mRNA is subjected to alternative splicing in the mammalian retina, although most of the TVs generated are likely targets for nonsense-mediated mRNA decay (NMD). The different POMT1 isoforms detected by immunoblotting could be encoded by particular TVs or produced by post-translational modification.
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