PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “splicing variant”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources

CD44 splice variants: expression during lymphocyte activation and tumor progression.

A recently described splice variant of CD44 has been shown to confer metastatic potential to non-metastasizing rat pancreatic carcinoma and sarcoma cell lines. Using antibodies raised against a bacterial fusion protein encoded by variant CD44 sequences, we have explored the expression of variant CD44 glycoproteins in human lymphoid cells and tissues, in non-Hodgkin's lymphomas, and in colorectal neoplasia. Normal lymphohematopoietic cells express barely detectable low levels of variant CD44 glycoproteins, while T lymphocytes, upon activation by mitogen or antigen, transiently upregulate expression of specific CD44 variant glycoproteins. The reaction pattern of various antibodies indicates that these CD44 variants contain the domain encoded by exon v6, which is part of the variant that in the rat confers metastatic capability. Interestingly, overexpression of v6 was also found in several aggressive, but not in low-grade, non-Hodgkin's lymphomas (NHL). In human colorectal neoplasia we also observed strong overexpression of CD44 splice variants in all invasive carcinomas and carcinoma metastasis. Interestingly, focal expression was already observed in adenomatous polyps, expression being related to areas of dysplasia. The findings establish CD44 variants as tumor progression markers in colorectal cancer.

Alternative Splicing↗

Novel Cav2.1 splice variants isolated from Purkinje cells do not generate P-type Ca2+ current.

The alpha(1)2.1 (alpha(1A)) subunits of P-type and Q-type Ca(2+) channels are encoded by a single gene, Cacna1a. Although these channels differ in the inactivation kinetics and sensitivity to omega-agatoxin IVA, the mechanism underlying these differences remains to be clarified. Alternative splicings of the Cacna1a transcript have been postulated to contribute to the respective properties, however, the splice variants responsible for P-type Ca(2+) channels have not been identified. To explore P-type-specific splice variants, we aimed at cloning alpha(1)2.1 from isolated mouse Purkinje cells using single-cell reverse transcription-PCR, because in Purkinje cells P-type currents dominate over the whole currents (>95%) with Q-type currents undetected. As a result, two novel splice variants were cloned. Compared with the previously cloned mouse alpha(1)2.1, two novel variants had additional 48 amino acids at the amino termini, six single amino acid changes, and splicing variations at the exon 46/47 boundary, which produced different carboxyl termini. Furthermore, one variant had one RNA editing site. However, electrophysiological and pharmacological studies indicated that these variants did not generate P-type current in cultured cells. These results suggest that P-type-specific splice variants may exist but that post-translational processing or modification by uncharacterized interacting proteins is also required for generating the P-type current.

Alternative Splicing↗

A splice variant of the N-methyl-D-aspartate (NMDAR1) receptor.

A splice variant of the NMDA receptor (NMDAR1) was discovered containing a deletion of 37 amino acids near the carboxyl tail and has been designated NMDAR1b. The 111 nucleotides corresponding to the deleted amino acid sequence were found in a separate exon bounded by consensus intron/exon junction sequences in rat genomic DNA. A partial restriction map of genomic DNA bounding this region placed the deleted exon approximately 600 base pairs (bp) downstream of the upstream exon. RT/PCR analysis of RNA from different brain regions showed that the deletion variant is more abundantly expressed in the brain stem and cerebellum while the full-length form is expressed more abundantly in the olfactory bulb, striatum, hippocampus, and cortex. Northern analysis of poly(A)+ RNA from different brain regions with probes specific for the deleted exon (i.e., full-length form) and for the splice junction (deletion form) indicated approximately 4.4 kb transcripts. The probe for the deleted exon hybridized to transcripts in olfactory bulb, cortex, striatum, and hippocampus while the splice junction probe hybridized most strongly to transcripts in cerebellum. The results suggest an interesting rostral to caudal shift in the expression of splice variants of the NMDAR1 which may signify important functional differences in native forms of NMDA receptors.

Alternative Splicing↗

Estrogen receptor-alpha splice variants in the medial mamillary nucleus of Alzheimer's disease patients: identification of a novel MB1 isoform.

Previously we have reported an increased nuclear estrogen receptor-alpha (ERalpha) in the medial mamillary nucleus (MMN) in Alzheimer's disease (AD). In the present study, we addressed the presence of specific ERalpha mRNA splice variants in this brain area of five AD cases compared with five controls using the RT-PCR and quantitative RT-PCR approach. Indeed, the occurrence of isoforms with the deletion of exons 7 (del.7), 4 (del.4), or 2 (del.2) was determined in all patients. However, there were no significant differences in the relative transcription levels of each of the mentioned splice variants between AD and control cases, although the ratio of the del.7 isoform to the canonical ERalpha mRNA was higher in controls. Given that exons 7 and 4 encode the ligand-binding domain of the ERalpha, whereas exon 2 encodes the DNA-binding domain, abundant expression of these splice variants suggests that much of the available ERalpha in the MMN of AD and elderly control patients is nonfunctional because they will be unable to bind either the ligand (del.7 and del.4 variants) or the estrogen-responsive elements on appropriate DNA (del.2 variant). Yet, the wild-type ERalpha mRNA appeared to be 2- to 3-fold up-regulated in AD, confirming the rise in the nuclear immunocytochemical staining and pointing to the potential for a beneficial effect of estrogen replacement therapy on the MMN-associated cognitive functions in AD because it represents the availability of potentially functional ERalpha in the MMN. Noteworthy, the expression of the wild-type, del.7, and del.2 mRNAs declined with advanced age in both AD and control patients. Interestingly, we have identified in two AD and two control patients a novel ERalpha splice variant that we called MB1 (mamillary body, exon 1) with a 168-nucleotide deletion corresponding to a U2-type intron inside exon 1 encoding the major portion of the transactivation function 1 domain of the receptor.

Aged↗

Tissue-specific expression of splice variants of the mouse voltage-gated calcium channel alpha2/delta subunit.

Five different splice variants of mouse alpha2/delta subunit isoforms (alpha2a-e), which arose from various combinations of three alternatively spliced regions, were cloned with a combination of cDNA library screening and RT-PCR. Expression patterns and relative abundance of the various isoforms in mouse tissues were determined with an RNAse protection assay. Skeletal muscle and brain expressed single isoforms, alpha2a and alpha2b, respectively; however, the cardiovascular system expressed all five isoforms. Heart expressed mainly isoforms alpha2c and alpha2d while, in contrast to other species, aorta expressed predominantly alpha2a, the 'skeletal muscle' isoform. Smooth muscle-containing tissues expressed alpha2d and alpha2e. Thus, alpha2/delta isoforms are restricted in their tissue expression, suggesting an important functional role for the differentially spliced variants.

Alternative Splicing↗

Genomic organization of mouse orexin receptors: characterization of two novel tissue-specific splice variants.

In humans and rat, orexins orchestrate divergent actions through their G protein-coupled receptors, orexin-1 (OX1R) and orexin-2 (OX2R). Orexins also play an important physiological role in mouse, but the receptors through which they function are not characterized. To characterize the physiological role(s) of orexins in the mouse, we cloned and characterized the mouse orexin receptor(s), mOX1R and mOX2R, using rapid amplification of cDNA (mouse brain) ends, RT-PCR, and gene structure analysis. The mOX1R cDNA encodes a 416-amino acid (aa) receptor. We have identified two alternative C terminus splice variants of the mOX2R; mOX2 alpha R (443 aa) and mOX2 beta R (460 aa). Binding studies in human embryonic kidney 293 cells transfected with mOX1R, mOX2 alpha R, and the mOX2 beta R revealed specific, saturable sites for both orexin-A and -B. Activation of these receptors by orexins induced inositol triphosphate (IP(3)) turnover. However, human embryonic kidney 293 cells transfected with mOXRs demonstrated no cAMP response to either orexin-A or orexin-B challenge, although forskolin and GTP gamma S revealed a dose-dependent increase in cAMP. Although, orexin-A and -B showed no difference in binding characteristics between the splice variants; interestingly, orexin-B led to an increase in IP(3) production at all concentrations in the mOX2 beta R variant. Orexin-A, however, showed no difference in IP(3) production between the two variants. Additionally, in the mouse, we demonstrate that these splice variants are distributed in a tissue-specific manner, where OX2 alpha R mRNA was undetectable in skeletal muscle and kidney. Moreover, food deprivation led to a greater increase in hypothalamic mOX2 beta R gene expression, compared with both mOX1R and mOX2 alpha R. This potentially implicates a fundamental physiological role for these splice variants.

Alternative Splicing↗

Identification of a novel alternative splicing of human FGF receptor 4: soluble-form splice variant expressed in human gastrointestinal epithelial cells.

Among four closely related members of the FGF receptor family, FGFR 1, 2, and 3 have alternative splicing forms encoded by different exons for the C-terminal half of the third Ig-like domain, but FGFR 4 has no such alternative exon. Furthermore, FGFR 1, 2, and 3 have another splice variant of nontransmembrane type; however, such a variant has not been reported for FGFR 4. While searching for a novel receptor-type tyrosine kinase by RT-PCR, we identified a non-transmembrane-type receptor of FGFR 4 in human intestinal epithelial cell lines (Intestine 407 and Caco-2). Sequence analysis of this receptor revealed that exon 9 coding the single transmembrane domain was displaced by intron 9. Consequently, this variant form was 120 bp shorter than the normal form and had no transmembrane portion. Moreover, the signal sequence in exon 2 was maintained, suggesting that this splice variant is a soluble receptor. This soluble receptor was detected in human gastrointestinal epithelial cells and pancreas, and also in gastric, colon, and pancreatic cancer cell lines. Single cell RT-PCR showed that this soluble receptor was expressed simultaneously with the transmembrane-type receptor in the same cell. Western blot analysis revealed that this receptor was secreted from the transfected COS7 cells. Thus, a soluble-form splice variant of FGFR 4 was identified in human gastrointestinal epithelial cells and cancer cells. This is the first report of alternative splicing of FGFR 4.

Alternative Splicing↗

Molecular cloning and functional characterization of a rat somatostatin sst2(b) receptor splice variant.

1. The mouse somatostatin (SRIF) sst2 receptor exists in two splice variants, sst2(a) and sst2(b), which differ in their intracellular carboxy-termini only. The murine sst2(b) receptor was reported to be less prone to agonist-induced desensitization as compared with the sst2(a) receptor. To determine whether a sst2(b) splice variant with similar functional characteristics exists in the rat, we have isolated a cDNA fragment from rat gastric mucosa encoding a sst2(b) receptor and expressed the full-length protein in CHO-K1 cells for functional characterization. 2. This study provides the first evidence for the occurrence in the rat of the sst2(b) receptor, which has a 15 amino acid carboxy-terminus differing in composition to the 38 amino acid C-terminus of the rat sst2(a) receptor. 3. In CHO-K1 cells expressing rat recombinant sst2(a) or sst2(b) receptors, SRIF caused concentration-dependent increases in extracellular acidification rates (EAR) with pEC50 values of 9.0 and 9.9, respectively. Pre-treatment with pertussis toxin (Ptx) caused a rightward displacement of the SRIF concentration-effect curves with pEC50 values of 8.3 (sst2(a) and 8.4 (sst2(b)). 4. SRIF (3 pM-3 nM) also caused concentration-dependent inhibition of forskolin-stimulated cyclic AMP formation in CHO-sst2(a) cells (pIC50 10.5) and CHO-sst2(b) cells (pIC50 10.4). The degree of inhibition was less with higher concentrations of SRIF resulting in bell-shaped concentration-effect curves. Following pre-treatment with Ptx, the inhibitory effect of SRIF was abolished and SRIF caused only increases in cyclic AMP formation. 5. Both the SRIF-induced increases in EAR and inhibition of cyclic AMP formation were susceptible to agonist-induced desensitization, but this was less apparent following pre-treatment with Ptx. 6. This demonstrates that the operational characteristics of the recombinant rat sst2(a) and sst2(b) receptors are broadly similar. Both isoforms couple to Ptx-sensitive as well as -insensitive G proteins and are equally prone to agonist-induced desensitization.

Adenylyl Cyclases↗

Identification of splicing variants of Rapostlin, a novel RND2 effector that interacts with neural Wiskott-Aldrich syndrome protein and induces neurite branching.

Rho family GTPases regulate neuronal morphology. Rnd subfamily is a new branch of Rho family GTPases. Of these GTPases, Rnd2 is specifically expressed in brain. We recently identified Rapostlin as a novel effector of Rnd2. Rapostlin induces neurite branching in response to Rnd2 in PC12 cells. During the cloning of Rapostlin, we have found two mainly expressed splicing variants of Rapostlin (renamed as RapostlinL), RapostlinM and RapostlinS, lacking 29 residues and 61 residues within the unique insert region at the center, respectively, and three minor variants, RapostlinLd, RapostlinMd, and RapostlinSd, each with the identical five-amino acid deletion from RapostlinL, RapostlinM, and RapostlinS, respectively. RapostlinL is predominantly expressed in brain, whereas RapostlinS is expressed ubiquitously. In a dot-blot assay, all splicing variants bind to Rnd2 in a GTP-dependent manner. However, RapostlinM and RapostlinS induce less neurite branching when coexpressed with Rnd2 in PC12 cells, indicating that the insert region is important for the branching activity of RapostlinL. All splicing variants bind to N-WASP in vitro and in vivo through the SH3 domain at the carboxyl terminus, and the SH3 domain is essential for branching activity of RapostlinL. In immunoprecipitation experiments, Rnd2 reduces RapostlinL-N-WASP interaction, whereas it has little effect on the interaction of RapostlinM or RapostlinS with N-WASP. Therefore, we found that functionally different splicing variants of Rapostlin have different responses to Rnd2 in association with N-WASP.

Alternative Splicing↗

Vascular endothelial growth factor splice variants and their prognostic value in breast and ovarian cancer.

PURPOSE: Vascular endothelial growth factor (VEGF) is a promotor for tumor angiogenesis, and is known to be elevated in breast and ovarian cancers. Through alternative splicing six VEGF isoforms were identified. We studied VEGF isoform expression in breast and ovarian cancer cell lines, as well as in breast carcinomas and ovarian tumors, and correlated the expression pattern with the in vitro invasiveness of the breast carcinoma cell lines and the clinicopathologic characteristics of the tumors. EXPERIMENTAL DESIGN: Reverse transcription-PCR and automated laser fluorescence fragment analysis were used to determine the expression of each splice variant. This method allowed the detection of all of the splice variants simultaneously, especially VEGF145 for the first time in tumor tissue. RESULTS: VEGF121 and VEGF165 were the most dominantly expressed variants in all of the tumor samples and cell lines investigated. VEGF145 was very weakly or not expressed in breast and ovarian cancers. Statistical analysis showed no correlation between VEGF splice variant expression in the tumors and histological type, differentiation grade, tumor size, Fédération Internationale des Gynaecologistes et Obstetristes, and nodal status from cancer patients. There was also no correlation between the invasive capacity of breast cell lines and VEGF isoform expression. CONCLUSIONS: Even though expression levels of VEGF have been shown to be important for tumor invasion and progression, the present data indicate no relation of VEGF isoform pattern with invasion and progression.

Alternative Splicing↗

Characterization of an alternative splice variant of human nucleoside triphosphate diphosphohydrolase 3 (NTPDase3): a possible modulator of nucleotidase activity and purinergic signaling.

Nucleoside triphosphate diphosphohydrolase 3 (NTPDase3) is a cell surface, membrane-bound enzyme that hydrolyzes extracellular nucleotides, thereby modulating purinergic signaling. An alternatively spliced variant of NTPDase3 was obtained and analyzed. This alternatively spliced variant, termed "NTPDase3beta", is produced through the use of an alternative terminal exon (exon 11) in place of the terminal exon (exon 12) in the full-length NTPDase3, now termed "NTPDase3alpha". This results in an expressed protein lacking the C-terminal cytoplasmic sequence, the C-terminal transmembrane helix, and apyrase conserved region 5. The cDNA encoding this truncated splice variant was detected in a human lung library by PCR. Like the full-length NTPDase3alpha, the alternatively spliced NTPDase3beta was expressed in COS cells after transfection, but only the full-length NTPDase3alpha is enzymatically active and properly trafficked to the plasma membrane. However, when the truncated NTPDase3beta was co-transfected with full-length NTPDase3alpha, there was a significant reduction in the amount of NTPDase3alpha that was properly processed and trafficked to the plasma membrane as active enzyme, indicating that the truncated form interferes with normal biosynthetic processing of the full-length enzyme. This suggests a role for the NTPDase3beta variant in the regulation of NTPDase3 nucleotidase activity, and therefore the control of purinergic signaling, in those cells and tissues expressing both NTPDase3alpha and NTPDase3beta.

Adenosine Triphosphatases↗

Splice variants of the Drosophila PS2 integrins differentially interact with RGD-containing fragments of the extracellular proteins tiggrin, ten-m, and D-laminin 2.

Two new potential ligands of the Drosophila PS2 integrins have been characterized by functional interaction in cell culture. These potential ligands are a new Drosophila laminin alpha2 chain encoded by the wing blister locus and Ten-m, an extracellular protein known to be involved in embryonic pattern formation. As with previously identified PS2 ligands, both contain RGD sequences, and RGD-containing fragments of these two proteins (DLAM-RGD and TENM-RGD) can support PS2 integrin-mediated cell spreading. In all cases, this spreading is inhibited specifically by short RGD-containing peptides. As previously found for the PS2 ligand tiggrin (and the tiggrin fragment TIG-RGD), TENM-RGD induces maximal spreading of cells expressing integrin containing the alphaPS2C splice variant. This is in contrast to DLAM-RGD, which is the first Drosophila polypeptide shown to interact preferentially with cells expressing the alphaPS2 m8 splice variant. The betaPS integrin subunit also varies in the presumed ligand binding region as a result of alternative splicing. For TIG-RGD and TENM-RGD, the beta splice variant has little effect, but for DLAM-RGD, maximal cell spreading is supported only by the betaPS4A form of the protein. Thus, the diversity in PS2 integrins due to splicing variations, in combination with diversity of matrix ligands, can greatly enhance the functional complexity of PS2-ligand interactions in the developing animal. The data also suggest that the splice variants may alter regions of the subunits that are directly involved in ligand interactions, and this is discussed with respect to models of integrin structure.

Alternative Splicing↗

A new splicing variant of a type III POU gene from zebrafish encodes a POU protein with a distinct C-terminal.

A zebrafish POU protein cDNA clone was isolated and sequenced. It appears to be a novel splicing variant of the previously reported zebrafish POU gene zp-12. There are four splicing variants and at least three of them lead to different C-terminal amino acid sequences. The four splicing variants are differentially regulated during development, indicating that they may be functionally diversified.

Alternative Splicing↗

Splicing variants in sheep CLN3, the gene underlying juvenile neuronal ceroid lipofuscinosis.

Mutations in different genes underlie different forms of the neuronal ceroid lipofuscinoses (NCLs, Batten disease). Subunit c of mitochondrial ATP synthase specifically accumulates in most of them, including the juvenile CLN3 form and a sheep form orthologous to CLN6. Products of these genes are likely to be components of a complex or pathway for subunit c turnover, and their expression may be cross-regulated. Different bands, some with different subcellular distributions, were detected by antisera against different regions of CLN3 on Western blots of sheep tissues. Affected liver blots were the same as controls but a specific 50-kDa band was at higher concentration in affected brain homogenates than in controls. Others have also reported bands reacting differently to different CLN3 antibodies. When the 3' end of sheep CLN3 cDNA was amplified by RT-PCR, four mRNA splicing variants were found. Different CLN3 splicing variants at the 5' end of the human cDNA have been reported. These mRNA splicing variants may account the variation of epitope distribution and the different subcellular locations of the CLN3 gene product(s). The predicted size of the unmodified CLN3 protein is 48 kDa. Significantly higher molecular weight bands may correspond to oligomers of a CLN3 isoform or to a CLN3 isoform tightly bound to another protein.

Amino Acid Sequence↗

Partial expression defect for the SCN5A missense mutation G1406R depends on splice variant background Q1077 and rescue by mexiletine.

Mutations in the cardiac Na(+) channel gene SCN5A cause loss of function and underlie arrhythmia syndromes. SCN5A in humans has two splice variants, one lacking a glutamine at position 1077 (Q1077del) and one containing Q1077. We investigated the effect of splice variant background on loss of function and rescue for G1406R, a mutation reported to cause Brugada syndrome. Mutant and wild-type (WT) channels in both backgrounds were transfected into HEK-293 cells and incubated for up to 72 h with and without mexiletine. At 8 h, neither current nor cell surface expression was observed for the mutant in either background, but both were present in WT channels. At 24 h, small (<10% compared with WT) currents were noted and accompanied by cell surface expression. At 48 h, current density was approximately 40% of WT channels for the mutant in the Q1077del variant background but remained at <10% of WT channels in Q1077. Current levels were stable by 72 h. Coexpression with beta(1)- or beta(3)-subunits or insertion of the polymorphism H558R in the background did not significantly affect current expression. Mexiletine restored current density of the mutant channel in both backgrounds to nearly WT levels. The mutant channels also showed a negative shift in inactivation, slower recovery, and enhanced slow inactivation, consistent with a loss of function phenotype. These data show that a trafficking defect may be partial and time dependent and may differ with the splice variant background. Also, expression defects and gating abnormalities may contribute to loss of function for the same mutation.

Alternative Splicing↗

Patterns of splice variant CD44 expression by normal human urothelium in situ and in vitro and by bladder-carcinoma cell lines.

CD44 core and splice variant exon expression was investigated in the stratified transitional epithelium of the urinary tract and in normal and malignant bladder epithelial cell lines in vitro. Antibodies against core CD44 epitopes and splice exon variants v3, v4/5, v5 and v6 showed an intense reaction in the basal and lower intermediate urothelial cell layers, which was consistently lost from the upper intermediate and superficial cell layers. Seven independent cell lines established from normal human urothelium expressed complex multiple-spliced CD44 mRNA transcripts when tested by RT-PCR and were positive with antibodies against CD44 core epitopes and splice variants v3, v4/5, v5 and v6. Of the 13 bladder-carcinoma cell lines, all were positive for CD44 core. The more differentiated cell lines had retained some splice-variant antibody reactivity and showed multiple but less complex CD44 mRNA transcript patterns, compared with normal cells. Anaplastic cell lines did not react with variant antibodies and did not contain multiple-spliced CD44 transcripts. These data suggest that loss of alternatively-spliced CD44 may reflect a selection pressure in the evolution of anaplastic bladder cancers.

Antigens, Neoplasm↗

Involvement of large tenascin-C splice variants in breast cancer progression.

Alternative splicing of fibronectin-like type III (FNIII) repeats of tenascin-C (Tn-C) generates a number of splice variants. The distribution of large variants, typical components of provisional extracellular matrices that are up-regulated during tumor stroma remodeling, was here studied by immunoblotting and immunohistochemistry using a monoclonal antibody against the FNIII B domain (named 4C8MS) in a series of human breast cancers. Large Tn-C variants were found at only low levels in normal breast tissues, but were highly expressed at invading sites of intraductal cancers and in the stroma of invasive ductal cancers, especially at invasion fronts. There was a positive correlation between the expression of large Tn-C variants and the cell proliferation rate determined by immunolabeling of the Ki-67 antigen. Of the Tn-C recombinant fragments (all FNIII repeats or mFNIII FL, the conserved FNIII domain only, the epidermal growth factor-like domain, and the fibrinogen-like domain) which were expressed by CHO-K1 cells transfected with mouse Tn-C cDNAs, only the mFNIII FL enhanced in vitro migration and mitotic activity of mammary cancer cells derived from a Tn-C-null mouse. Addition of 4C8MS blocked the function of mFNIII FL. These findings provide strong evidence that the FNIII alternatively spliced region has important roles in tumor progression of breast cancer.

Alternative Splicing↗

cDNA cloning and tissue-specific splicing variants of mouse hippostasin/TLSP (PRSS20).

Two splicing variants of mouse hippostasin/TLSP (PRSS20) were identified and termed brain-type and prostate-type, respectively. Mouse hippostasin/TLSP showed 76.8% identity to the human homologue. Transient expression showed that both translational products were secreted into the conditioned medium. Mouse hippostasin/TLSP was expressed preferentially in the fetal brain and the prostate, but not in the neonatal brain. The brain expressed only brain-type hippostasin/TLSP, while the prostate expressed both types.

Alternative Splicing↗