Genomic organization of the human GRIK2 gene and evidence for multiple splicing variants.
Fast excitatory transmission in the vertebrate central nervous system is mediated mainly by L-glutamate. Here we present the genomic organization of the human GRIK2 gene, which codes for the kainate GluR6 receptor subunit, deduced from sequence data present in the public databases and analyzed by bioinformatic tools. By similarity search using the human GluR6 cDNA sequence against non-redundant databases, we found three positive entries (AP002528, AP002529, and AP002530 deposited by Hirakawa et al., 2000) which are part of a BAC contig of about 1 Mb spanning region 6q21. The GRIK2 gene was found to be split into 17 exons, covering about 670 kb of the region. The availability of the data on the genomic organization allowed the study of GRIK2 gene expression by RT-PCR analysis which was performed on human teratocarcinoma cell cultures (NT2) and on mRNA obtained from human hippocampus (Clontech). The study gives evidence for several different splicing variants in addition to the previously cloned human GluR6 cDNA (ID: U16126). The splicing mechanism leading to the different isoforms involves exons 11, 12 and 16. The mRNA containing exon 16 at the 3' end is the homolog to the mouse GluR6-2. The translation of this mRNA would code for a different intracellular C-terminus, as compared to that coded by the known human isoform. The newly identify isoform is the predominant form expressed in human teratocarcinoma NT2 cells. All the newly identified mRNAs isoforms are expressed in NT2 cells and in human hippocampus mRNA at variable levels and would be responsible for the production of five different putative GluR6 receptor subunits, some differing in the C-terminal domains (mouse homolog) and some lacking specific transmembrane domains.
Barbon
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Division of Biology and Genetics, Department of Biomedical Sciences and Biotechnologies, Brescia University Medical School, via Valsabbina 19, 25123 Brescia, Italy.
Vallini
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Barlati
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D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001483:Base Sequence; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D005091:Exons; D015870:Gene Expression; D005796:Genes / Q000235:genetics*; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic / Q000235:genetics; D021122:Protein Subunits; D012322:RNA Precursors / Q000737:chemistry / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018092:Kainic Acid Receptors / Q000235:genetics*; D017422:Sequence Analysis, DNA; D014407:Tumor Cells, Cultured; D000097806:GluK2 Kainate Receptor
D018076:DNA, Complementary; D021122:Protein Subunits; D012322:RNA Precursors; D012333:RNA, Messenger; D018092:Kainic Acid Receptors; D000097806:GluK2 Kainate Receptor