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PubMed2006

Splice variant of mouse Stam2 mRNA in nervous and muscle tissue contains additional exon with stop codon within region coding for VHS domain.

AIM: To analyze the alternatively spliced variant of Stam2 mRNA and determine its distribution in mouse tissues. METHODS: We identified a novel alternatively spliced exon by cloning and sequencing of Stam2 cDNA obtained from tissue samples of 3-5 months old male C57Bl/6NCrl mice. The sequence of the alternatively spliced exon was analyzed by bioinformatic tools. The tissue distribution of different Stam2 mRNA variants was determined by reverse transcription-polymerase chain reaction, and the consequences of the alternative splicing at the protein level were analyzed by western blot with the polyclonal anti-STAM2 antibody. RESULTS: The novel alternatively spliced exon 1A of mouse Stam2 gene was inserted within Stam2 coding region and it contained a stop codon. The exon did not bear similarities to any other cDNA or protein sequence in the mouse, rat, or human databases. Both mRNA variants, with and without exon 1A, were present in the cortex, hippocampus, olfactory bulb, medulla oblongata, spinal cord, cerebellum, and the skeletal and heart muscle, while the other analyzed organs contained only the variant without the additional exon. The mRNA with the included exon did not give rise to a protein form detectable by western blotting with the polyclonal anti-STAM2 antibody. CONCLUSION: The alternatively spliced exon 1A was included in mRNA splice variant present in the nervous and muscle tissues. The alternative splicing event did not have major impact on STAM2 production and functionality. It seems that exon 1A is an evolutionary new exon created by exonization of an intronic sequence.

Adaptor Proteins, Signal Transducing↗

PubMed2006

[Exon rearrangement analysis of parkin gene in patients with isolated early-onset parkinsonism using semi-quantitative PCR].

OBJECTIVE: To investigate the value of fluorescence semi-quantitative PCR in analysis of the exon rearrangement of parkin gene in Chinese patients with isolated early-onset parkinsonism (EOP). METHODS: fluorescence semi-quantitative PCR was used to analyze the exon rearrangements of parkin gene in 61 isolated patients with EOP. RESULTS: Exon deletions in parkin gene were found in 4 of the 61 isolated patients with EOP. One of them failed to show the PCR product of exon 4 and had homozygous deletions of exon 4. The normalized ratios (NRs) of exon 2, exon 3, and exon 4 of the other 3 patients were 0.47, 0.52, and 0.49 respectively, showing that they had heterozygous deletions of exon 2, 3, and 4 respectively. No exon multiplication was found in this study. CONCLUSION: Exon rearrangement of parkin gene exists in Chinese patients with isolated EOP.

Adolescent↗

PubMed1995

p53 gene mutations inside and outside of exons 5-8: the patterns differ in breast and other cancers.

Most studies of mutations in the p53 tumor suppressor gene in tumors have examined only exons 5-8. Our laboratory previously found 64 mutations in exons 5-8 of the p53 gene in 194 primary breast cancers. Herein, we report 18 additional mutations found outside of exons 5-8. Mutations are present in exons 4, 9 and 10, and flanking splice junctions, but not in the promotor region or in exons 1, 2, 3 and 11. No missense mutations are found outside of exons 5-8. Instead, there is a predominance of frameshift mutations with lesser numbers of nonsense and splice site mutations. In contrast, the majority of mutations in exons 5-8 in this sample are missense changes and all of these are at amino acids that are identical in the 11 known p53 sequences that represent about 1.6 billion years of evolutionary divergence. The difference in mutational pattern between these two regions of the p53 gene is due to a lack of missense mutations and inframe microdeletions outside of exons 5-8. A review of our database of p53 mutations (De Vries et al., in preparation) shows that the patterns of mutation inside and outside of exons 5-8 differ in other types of cancers as well. The paucity of missense mutations in exons 2-4 and 9-11 in breast and other cancers (even at amino acids identical throughout p53 gene evolution) suggest that at least some missense mutations result in a phenotype other than malignant transformation. These data also illustrate the importance of examining identical exons when comparing the pattern of p53 gene mutations in different populations.

Adult↗

PubMed1993

Alternative splicing of exons encoding the calmodulin-binding domains and C termini of plasma membrane Ca(2+)-ATPase isoforms 1, 2, 3, and 4.

Rat plasma membrane Ca(2+)-ATPase (PMCA) mRNAs were examined by S1 nuclease protection (isoform 1) and polymerase chain reaction (isoforms 1, 2, 3, and 4) and the corresponding genes were analyzed to determine the tissue-specific splicing patterns involving exons encoding the calmodulin-binding domains and C termini. Splicing of PMCA1 involves a single 154-nucleotide exon that can be either included or excluded; when the exon is included four different splice donor sites, at positions 87, 114, 152, and 154, can be utilized. PMCA2 mRNAs are generated either by the inclusion of a 172-nucleotide exon, by the inclusion of both the 172-nucleotide exon and a 55-nucleotide exon, or by the exclusion of both exons. Four PMCA3 mRNAs arise by alternative splicing of a 154-nucleotide exon, in patterns that are analogous to those of PMCA1, and additional mRNAs are generated by the inclusion of a 68-nucleotide exon immediately before the 154-nucleotide exon. The simplest splicing pattern occurs in PMCA4, where a single 175-nucleotide exon is either included or excluded. The alternative mRNAs for each of the four genes are expressed in a tissue-specific manner and encode enzyme variants with different combinations of calmodulin-binding domains and C termini.

Alternative Splicing↗

PubMed1998

Role of an inhibitory pyrimidine element and polypyrimidine tract binding protein in repression of a regulated alpha-tropomyosin exon.

Splicing of exons 2 and 3 of a-tropomyosin (TM) involves mutually exclusive selection of either exon 3, which occurs in most cells, or of exon 2 in smooth muscle (SM) cells. The SM-specific selection of exon 2 results from the inhibition of exon 3. At least two essential cis-acting elements are required for exon 3 inhibition, the upstream and downstream regulatory elements (URE and DRE). These elements are essential for repression of TM exon 3 in SM cells, and also mediate a low level of repression of exon 3 in an in vitro 5' splice site competition assay in HeLa extracts. Here, we show that the DRE consists of at least two discrete components, a short region containing a number of UGC motifs, and an essential pyrimidine-rich tract (DY). We show that the specific sequence of the DY element is important and that DY is able to bind to factors in HeLa nuclear extracts that mediate a low background level of exon 3 skipping. Deletion of a sequence within DY identified as an optimal binding site for PTB impairs (1) regulation of splicing in vivo, (2) skipping of exon 3 in an in vitro 5' splice site competition, (3) the ability of DY competitors to affect the 5' splice site competition in vitro, and (4) binding of PTB to DY. Addition of recombinant PTB to in vitro splicing reactions is able to partially reverse the effects of the DY competitor RNA. The data are consistent with a model for regulation of TM splicing that involves the participation of both tissue-specific and general inhibitory factors and in which PTB plays a role in repressing both splice sites of exon 3.

Base Sequence↗

PubMed1991

Exon skipping during splicing of dystrophin mRNA precursor due to an intraexon deletion in the dystrophin gene of Duchenne muscular dystrophy kobe.

Recent molecular studies have shown that in a patient with Duchenne muscular dystrophy (DMD) Kobe, the size of exon 19 of the dystrophin gene was reduced to 36 bp due to the deletion of 52 bp out of 88 bp of the exon. The consensus sequences at the 5' and 3' splice sites of exon 19 were unaltered (Matsuo, M., et al. 1990. Biochem. Biophys. Res. Commun. 170:963-967). To further elucidate the molecular nature of the defect, we examined the primary structure of cytoplasmic dystrophin mRNA of the DMD Kobe patient across the junctions of exons 18, 19, and 20 by gel electrophoresis and sequencing of polymerase chain reaction-amplified cDNA. The mRNA coding for dystrophin was reverse transcribed using random primers, and the cDNA was then enzymatically amplified in vitro. The targeted fragment was smaller than expected from the genomic DNA analysis. By sequencing of the amplified product, we found that exon 18 was joined directly to exon 20, so that exon 19 was completely absent, suggesting that this exon was skipped during processing of the dystrophin mRNA precursor. All other bases in the amplified product were unaltered. Therefore, the data strongly suggest that the internal exon deletion generates an abnormally spliced mRNA in which the sequence of exon 18 is joined to the sequence of exon 20. We propose that the deletion is responsible for abnormal processing of the DMD Kobe allele. This finding has important implications regarding the determinants of a functional splice site.

Base Sequence↗

PubMed1999

SF2 and SRp55 regulation of CD45 exon 4 skipping during T cell activation.

CD45 is an alternatively spliced membrane phosphatase required for T cell activation. Exons 4, 5 and 6 can be included or skipped from spliced mRNA resulting in several protein isoforms that include or exclude epitopes referred to as RA, RB or RC, respectively. T cells reciprocally express CD45RA or CD45RO (lacking all three exons), corresponding to naive versus memory T cells. Overexpression of the alternative splicing regulators, SF2 or SWAP, induces skipping of CD45 exon 4 in transfected COS cells. We show here that the arginine/serine-rich domain of SWAP and the RNA recognition motifs of SF2 are required for skipping of CD45 exon 4. Unlike SWAP, SF2 specifically regulated alternative splicing of CD45 exon 4, having no effect on a non-regulated exon of CD45 (exon 9). Like SF2 and SWAP, the SR proteins SC35, SRp40 and SRp75, but not SRp55 also induced CD45 exon 4 skipping. In contrast, antisense inhibition of SRp55 induced exon 4 skipping. SF2 and SRp55 proteins were not detectable or expressed at a very low level in freshly isolated CD45RA+ and CD45RO+ T cells. Activation of CD45RA+ T cells shifted CD45 expression from CD45RA to CD45RO, and induced a large increase in expression of both SF2 and SRp55. Thus, SF2 at least in part determines splicing of CD45 exon 4 during T cell activation. SRp55, SR protein phosphorylation, or other splicing factors likely regulate CD45 splicing in CD45RO+ memory T cells. The different SR proteins expressed by memory and activated T cells emphasize the different phenotypes of these cell types that both express CD45RO.

Alternative Splicing↗

PubMed1992

Sequence of exons and the flanking regions of human bilirubin-UDP-glucuronosyltransferase gene complex and identification of a genetic mutation in a patient with Crigler-Najjar syndrome, type I.

Crigler-Najjar syndrome, type I is a heterogeneous disorder that may result from mutations of various regions of the bilirubin-UDP-glucuronosyltransferase gene complex that encodes two bilirubin-UDP-glucuronosyltransferase isoforms and a phenol-UDP-glucuronosyltransferase isoform in the human liver. The two bilirubin-UDP-glucuronosyltransferase messenger RNAs and the phenol-UDP-glucuronosyltransferase messenger RNA have identical 3' regions derived from four consecutive exons. The 5' region of each messenger RNA is unique and is derived from distinct single exons. By screening a human genomic library with probes corresponding to various regions of the messenger RNAs, we have isolated five cosmid clones containing overlapping segments of this large gene complex that spans at least 84 kb of the human genome. To facilitate the amplification of each exon by polymerase chain reaction and their adjacent splice junctions, we have delineated the intron-exon boundaries of the four common region exons and the two single exons that encode the unique regions of the two bilirubin-UDP-glucuronosyltransferase isoforms and have described sequences of the regions flanking each exon. All exons encoding the two bilirubin-UDP-glucuronosyltransferase isoforms and their splice junctions were amplified from the DNA of two control subjects and a Crigler-Najjar syndrome, type I patient. The DNA from the Crigler-Najjar syndrome, type I patient revealed a point mutation in exon 3 (a common region exon) resulting in a stop codon. RNA blot showed that the two bilirubin-UDP-glucuronosyltransferase messenger RNAs in the liver of the Crigler-Najjar syndrome, type I patient were of normal length but were reduced in concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed2006

Polypeptide encoded by mouse ZP3 exon-7 is necessary and sufficient for binding of mouse sperm in vitro.

Fertilization in mice is initiated by species-specific binding of sperm to mZP3, one of three mouse zona pellucida (ZP) glycoproteins. At nanomolar concentrations, purified egg mZP3 binds to acrosome-intact sperm heads and inhibits binding of sperm to eggs in vitro. Although several reports suggest that sperm recognize and bind to a region of mZP3 encoded by mZP3 exon-7 (so-called, sperm combining-site), this issue remains controversial. Here, exon-swapping and an IgG(Fc) fusion construct were used to further evaluate whether mZP3 exon-7 is essential for binding of sperm to mZP3. In one set of experiments, hamster ZP3 (hZP3) exon-6, -7, and -8 were individually replaced with the corresponding exon of mZP3. Stably transfected embryonal carcinoma (EC) cell lines carrying the recombinant genes were produced and secreted recombinant glycoprotein was purified and assayed for the ability to inhibit binding of sperm to eggs. While EC-hZP3, a recombinant form of hZP3 made by EC cells, is unable to inhibit binding of mouse sperm to eggs in vitro, the results suggest that substitution of mZP3 exon-7 for hZP3 exon-7, but not mZP3 exon-6 or -8, can impart inhibitory activity to EC-hZP3. In this context, a fusion construct consisting of human IgG(Fc) and mZP3 exon-7 and -8 was prepared, an EC cell line carrying the recombinant gene was produced, and secreted chimeric glycoprotein, called EC-huIgG(Fc)/mZP3(7), was purified and assayed. It was found that the chimeric glycoprotein binds specifically to plasma membrane overlying sperm heads to a similar extent as egg mZP3 and, at nanomolar concentrations, inhibits binding of mouse sperm to eggs in vitro. Collectively, these observations provide new evidence that sperm recognize and bind to a region of mZP3 polypeptide immediately downstream of its ZP domain that is encoded by mZP3 exon-7. The implications of these findings are discussed.

Animals↗

PubMed2003

Target selection for antisense oligonucleotide induced exon skipping in the dystrophin gene.

BACKGROUND: Duchenne muscular dystrophy (DMD) is an X-linked recessive muscle wasting disorder characterised by the absence of the protein dystrophin. Antisense oligonucleotides have been used to re-direct dystrophin pre-mRNA processing by blocking sequences crucial to pre-mRNA splicing, thereby inducing skipping of specific exons. We wished to determine which splicing motifs are most amenable as targets for antisense oligonucleotide induction of efficient and specific skipping of selected exons. METHODS: Antisense oligonucleotides were directed at regions of dystrophin exon 19 involved in pre-mRNA splicing, including the donor and acceptor splice sites and the exon splicing enhancer (ESE). Cultured myotubes were transfected with antisense oligonucleotides at various concentrations and studies undertaken to determine both specificity and efficiency of induced exon 19 skipping. RESULTS: Antisense oligonucleotides as small as 12 nucleotides targeting the ESE induced consistent and specific skipping of only exon 19 in both human and normal and mdx mouse myotubes. Antisense oligonucleotides directed at the donor and acceptor splice sites also induced specific exon 19 skipping while mismatched antisense oligonucleotides could only induce skipping when delivered at higher concentrations. No other dystrophin exons were removed from the mature mRNA as a consequence of these antisense oligonucleotides treatments. CONCLUSIONS: Antisense oligonucleotides directed at the ESE tended to be marginally more efficient than those which targeted the donor or acceptor splice sites, based on their ability to induce specific skipping at lower concentrations. The specificity of exon removal does not appear to be a function of target selection, but may reflect the combination of the splicing motifs and position of that exon in the pre-mRNA.

Animals↗

PubMed1994

The exon-intron organization of the genes (GAD1 and GAD2) encoding two human glutamate decarboxylases (GAD67 and GAD65) suggests that they derive from a common ancestral GAD.

We have cloned and characterized human genes (GAD1 and GAD2) encoding the two human glutamate decarboxylases, GAD67 and GAD65. The coding region of the GAD65 gene consists of 16 exons, spanning more than 79 kb of genomic DNA. Exon 1 contains the 5' untranslated region of GAD65 mRNA, and exon 16 specifies the protein's carboxy terminal and at least part of the mRNA's 3' untranslated sequence. Similarly, the coding region of the GAD67 gene consists of 16 exons, spread over more than 45 kb of genomic DNA. The GAD67 gene contains an additional exon (exon 0) that, together with part of exon 1, specifies the 5' untranslated region of GAD67 mRNA. Exon 16 specifies the entire 3' untranslated region of GAD67 mRNA. Exons 1-3 encode the most divergent region of GAD65 and GAD67. The remaining exon-intron boundaries occur at identical positions in the two cDNAs, suggesting that they derive from a common ancestral GAD gene.

Amino Acid Sequence↗

PubMed1998

Localization of 67 exons on a YAC contig spanning 1.5 Mb around the multidrug resistance gene region of human chromosome 7q21.1.

A contig of 21 nonchimeric yeast artificial chromosomes (YACs) was previously assembled across 1.5 Mb of the multidrug resistance (MDR) gene (PGY1 and PGY3) region of human chromosome 7q21.1. This region of the human genome has now been subjected to exon amplification to detect the presence of additional genes. Exon trapping was performed directly on the YACs. Sixty-seven gene fragments were isolated and characterized by sequence analysis and comparison with public databases. The localization of these exons in the 1.5-Mb region was determined by hybridization to YAC clones, and they were localized in 11 subregions of YAC contigs. The exon collection includes 21 exons that were identical to known cDNA sequences of PGY1, PGY3, sorcin (SRI), the cDNA similar to the delta subunit of the human amiloride-sensitive Na- channel (SCNED), and 4 cDNAs with unknown function; 43 exons that showed homology/similarity to known cDNA sequences of mouse DMP1, rat COT, mouse and human NADHD, human MDC, 3 cDNAs encoding possible membrane proteins, and 21 other cDNAs; and 3 exons that shared no homology/similarity with any sequence in public databases. The nucleotide sequences of all the PGY1 and PGY3 exons were identical to the corresponding cDNA sequences previously determined, and these exons were localized to the expected positions on the appropriate YAC clones. No other member of the MDR gene family thus appeared to be present in the 1.5-Mb region. The integrated physical and exon maps should prove valuable for both fine mapping and determination of a complete gene map of this segment of the genome.

ATP Binding Cassette Transporter, Subfamily B↗

PubMed1995

Identification and analysis of multigene families by comparison of exon fingerprints.

Gene families are often recognised by sequence homology using similarity searching to find relationships, however, genomic sequence data provides gene architectural information not used by conventional search methods. In particular, intron positions and phases are expected to be relatively conserved features, because mis-splicing and reading frame shifts should be selected against. A fast search technique capable of detecting possible weak sequence homologies apparent at the intron/exon level of gene organization is presented for comparing spliceosomal genes and gene fragments. FINEX compares strings of exons delimited by intron/exon boundary positions and intron phases (exon fingerprint) using a global dynamic programming algorithm with a combined intron phase identity and exon size dissimilarity score. Exon fingerprints are typically two orders of magnitude smaller than their nucleic acid sequence counterparts giving rise to fast search times: a ranked search against a library of 6755 fingerprints for a typical three exon fingerprint completes in under 30 seconds on an ordinary workstation, while a worst case largest fingerprint of 52 exons completes in just over one minute. The short "sequence" length of exon fingerprints in comparisons is compensated for by the large exon alphabet compounded of intron phase types and a wide range of exon sizes, the latter contributing the most information to alignments. FINEX performs better in some searches than conventional methods, finding matches with similar exon organization, but low sequence homology. A search using a human serum albumin finds all members of the multigene family in the FINEX database at the top of the search ranking, despite very low amino acid percentage identities between family members. The method should complement conventional sequence searching and alignment techniques, offering a means of identifying otherwise hard to detect homologies where genomic data are available.

Animals↗

PubMed1993

Exon skipping due to a mutation in a donor splice site in the WT-1 gene is associated with Wilms' tumor and severe genital malformations.

A germline WT-1 point mutation is described in a patient with unilateral Wilms' tumor, nephritis and ambiguous external genitalia. The patient was diagnosed as a possible case of Denys Drash syndrome (DDS). Analysis of the WT-1 exons and intron borders revealed a G to C transversion in the +1 position of the splice donor consensus sequence in intron 6. Two transcripts of abnormal size were identified in tumor RNA. Sequencing of the altered WT-1 mRNA revealed that this point mutation leads to exon-skipping, resulting in transcripts either missing exon 6 or exons 5 and 6. The normally occurring alternative splicing of exon 5 in the WT-1 gene is not affected by this mutation. The reading frame is changed when either both exons 5 and 6 or exon 6 alone are missing and a stop codon follows immediately downstream in exon 7. Most mutations identified in DDS are missense mutations located in the zinc finger (ZF) region (exons 7, 8 and 9) but recently a patient with a germline mutation in exon 6 leading to premature chain termination was described. Therefore the site of the mutation in the WT-1 gene in this patient cannot exclude the possibility that he has DDS.

Base Sequence↗

PubMed1996

Allelic diversity at the primate Mhc-G locus: exon 3 bears stop codons in all Cercopithecinae sequences.

Twenty-seven major histocompatibility complex (Mhc)-G exon 2, exon 3, and exon 2 and 3 allelic sequences were obtained together with 12 different intron 2 sequences. Homo sapiens, Pan troglodytes, Pan paniscus, Gorilla gorilla, Pongo pygmaeus, Macaca fascicularis, Macaca mulatta, and Cercopithecus aethiops individuals were studied. Polymorphism does not follow the classical pattern of three hypervariable regions per domain and is found in all species studied; exon 3 (equivalent to the alpha 2 protein domain) shows stop codons in the Cercopithecinae group but not in the Pongidae and human groups. Dendrograms show that cotton top tamarin (Saguinus oedipus) Mhc-G sequences are closer to Homo sapiens and Pongidae than to Cercopithecinae, probably due to the stop codons existing at exon 3 of the latter. There is a clear trans-species evolution of allelism in Cercopithecinae and also in exon 2 of all the other apes studied, but a generation of allelism within each species may be present on exon 3 sequences. This discrepancy may be due to the preferential use of exon 2 over exon 3 at the mRNA splicing level within each species in order to obtain the appropriate functional G product. Mhc-G intron 2 shows conserved motifs in all species studied, particularly a 23 base pair deletion between positions 161 and 183 which is locus specific, and some of the invariant residues, important for peptide presentation, conserved in classical class I molecules from fish and reptiles to humans were not found in Mhc-G alleles; the intron 2 dendrogram also shows a particular pattern of allelism within each species. In summary, Mhc-G has substantial differences from other classical class I genes: polymorphism patterns, tissue distribution, gene structure, splicing variability, and probably an allelism variability within each species at exon 3. The G proteins may also be different. This indicates that the Mhc-G function may not be peptide presentation to the clonotypic T-cell receptor.

Alleles↗

PubMed1987

Intron-dependent evolution: preferred types of exons and introns.

Exon insertions and exon duplications, two major mechanisms of exon shuffling, are shown to involve modules that have introns of the same phase class at both their 5'- and 3'-ends. At the sites of intronic recombinations exon insertions and duplications create new introns which belong to the same phase class as the recipient introns. As a consequence of repeated exon insertions and exon duplications introns of a single phase class predominate in the resulting genes, i.e. gene assembly by exon shuffling is reflected both by this nonrandom intron phase usage and by the correlation between the domain organization of the proteins and exon-intron organization of their genes. Genes that appeared before the eukaryote-prokaryote split do not show these diagnostic signs of exon shuffling. Since ancestral introns (e.g. self-splicing introns) did not favour intronic recombination, exon shuffling may not have been significant in the early part of protein evolution.

Animals↗

PubMed1996

The exon encoding the fibronectin type III-9 repeat is constitutively included in the mRNA from chick limb mesenchyme and cartilage.

The fibronectin monomer is comprised of three types of homologous repeating units, the types I, II, and III elements. Each type III repeat is encoded by two exons except for the two type III repeats involved in alternative splicing (IIIB and IIIA) and the type III-9 repeat which are all encoded by one exon. The fact that the type III-9 repeat is the only other type III repeat encoded by one exon has led to speculation that this exon may also be alternatively spliced. However, no evidence exists for alternative splicing of this exon in any tissues examined to date. The recent localization of a cell adhesion synergy site within the type III-9 repeat increases the likelihood of functional ramifications if the exon encoding this repeat is alternatively spliced in specific cells or tissues. We have shown previously that chick cartilage contains an unusual fibronectin mRNA splicing pattern and that the pattern changes during chondrogenesis from B+A+V+ to B+A-V+. In order to completely characterize the fibronectin mRNA in cartilage and other mesenchymal tissues for all possible alternative splicing events, we have determined whether or not the exon encoding the type III-9 repeat is alternatively spliced in these tissues. RNase protection and RT/PCR assays indicate that the fibronectin mRNA in all of these tissues, including cartilage, contains the type III-9 repeat as a constitutively included exon. Thus the exon encoding the type III-9 repeat will serve as a useful control exon for examining the regulation of tissue-specific alternative splicing during chondrogenesis.

Alternative Splicing↗

PubMed2006

Identification of three mouse mu-opioid receptor (MOR) gene (Oprm1) splice variants containing a newly identified alternatively spliced exon.

The mouse mu-opioid receptor gene, Oprm1, is recognized currently to contain 17 alternatively spliced exons that generate 24 splice variants encoding at least 11 morphine-binding isoforms of the receptor. Here, we identify three new MOR splice variants that contain a previously undescribed exon, exon 18, and provide evidence that they are expressed in two mouse strains. The transcripts containing the newly identified exon 18 encode two new putative mu-opioid receptor isoforms, MOR-1V and MOR-1W. In mouse Oprm1, exon 18 is located between the described exons 10 and 6. Exon 18 appears to be conserved in the rat genome between exons 4 and 7. A BLAST search of the non-redundant GenBank database suggests that human OPRM1 may also contain exon 18. Analysis of mouse brain mRNA by RT-PCR suggests that MOR-1Vii transcripts are expressed in all areas of the brain analyzed, whereas expression of MOR-1Vi transcripts was restricted to thalamus and striatum. MOR-1W transcripts are expressed most highly in the hypothalamus, thalamus and striatum. In summary, we have identified three brain expressed, alternatively spliced mouse MOR splice variants containing a novel exon and encoding new putative MOR isoforms, MOR-1V and MOR-1W.

Alternative Splicing↗