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Identification and characterization of two splice variants of human diacylglycerol kinase eta.

Diacylglycerol kinase (DGK) participates in regulating the intracellular concentrations of two bioactive lipids, diacylglycerol and phosphatidic acid. DGK eta (eta 1, 128 kDa) is a type II isozyme containing a pleckstrin homology domain at the amino terminus. Here we identified another DGK eta isoform (eta 2, 135 kDa) that shared the same sequence with DGK eta 1 except for a sterile alpha motif (SAM) domain added at the carboxyl terminus. The DGK eta 1 mRNA was ubiquitously distributed in various tissues, whereas the DGK eta 2 mRNA was detected only in testis, kidney, and colon. The expression of DGK eta 2 was suppressed by glucocorticoid in contrast to the marked induction of DGK eta 1. DGK eta 2 was shown to form through its SAM domain homo-oligomers as well as hetero-oligomers with other SAM-containing DGKs (delta 1 and delta 2). Interestingly, DGK eta 1 and DGK eta 2 were rapidly translocated from the cytoplasm to endosomes in response to stress stimuli. In this case, DGK eta 1 was rapidly relocated back to the cytoplasm upon removal of stress stimuli, whereas DGK eta 2 exhibited sustained endosomal association. The experiments using DGK eta mutants suggested that the oligomerization of DGK eta 2 mediated by its SAM domain was largely responsible for its sustained endosomal localization. Similarly, the oligomerization of DGK eta 2 was suggested to result in negative regulation of its catalytic activity. Taken together, alternative splicing of the human DGK eta gene generates at least two isoforms with distinct biochemical and cell biological properties responding to different cellular metabolic requirements.

Alternative Splicing↗

Regulation of Drosophila hypoxia-inducible factor (HIF) activity in SL2 cells: identification of a hypoxia-induced variant isoform of the HIFalpha homolog gene similar.

Although hypoxia-inducible factor-alpha (HIFalpha) subunit-specific hydroxylation and proteolytic breakdown explain the binary switch between the presence (hypoxia) and absence (normoxia) of HIFs, little is known of the mechanisms that fine-tune HIF activity under constant, rather than changing, oxygen tensions. Here, we report that the Drosophila HIFalpha homolog, the basic helix-loop-helix/PAS protein Sima (Similar), in hypoxic cultures of SL2 cells is expressed in full-length (fl) and splice variant (sv) isoforms. The following evidence supports the role of flSima as functional HIFalpha and the role of SL2 HIF as a transcriptional activator or suppressor. The pO(2) dependence of Sima abundance matched that of HIF activity. HIF-dependent changes in candidate target gene expression were detected through variously effective stimuli: hypoxia (strong) > iron chelation, e.g. desferrioxamine (moderate) >> transition metals, e.g. cobalt approximately normoxia (ineffective). Sima overexpression augmented hypoxic induction or suppression of different targets. In addition to the full-length exon 1-12 transcript yielding the 1510-amino acid HIFalpha homolog, the sima gene also expressed, specifically under hypoxia, an exon 1-7/12 splice variant, which translated into a 426-amino acid Sima truncation termed svSima. svSima contains basic helix-loop-helix and PAS sequences identical to those of flSima, but, because of deletion of exons 8-11, lacks the oxygen-dependent degradation domain and nuclear localization signals. Overexpressed svSima failed to transactivate reporter genes. However, it attenuated HIF (Sima.Tango)-stimulated reporter expression in a dose-dependent manner. Thus, svSima has the potential to regulate Drosophila HIF function under steady and hypoxic pO(2) by creating a cytosolic sink for the Sima partner protein Tango.

Amino Acid Sequence↗

Endothelin-converting enzyme-1, abundance of isoforms a-d and identification of a novel alternatively spliced variant lacking a transmembrane domain.

Endothelin-converting enzyme-1 (ECE-1) cleaves big endothelins, as well as bradykinin and beta-amyloid peptide. Several isoforms of ECE-1 (a-d) have been identified to date; they differ only in their NH(2) terminus but share the catalytic domain located in the COOH-terminal end. Using quantitative PCR, we found ECE-1d to be the most abundant type in several endothelial cells (EC) types. In addition to full-length ECE-1 forms we have identified novel, alternatively spliced mRNAs of ECE-1 b-d. These splice variants (SVs) lack exon 3', which codes for the transmembrane region and is present in full-length forms. SVs mRNA were highly expressed in EC derived from macro and microvascular beds but much less so in other, non-endothelial cells expressing ECE-1, which suggests that the splicing mechanism is cell-specific. Analyses of ECE-1d and its SV form in stably transfected HEK-293 cells revealed that both proteins were recognized by anti COOH-terminal ECE-1 antibodies, but anti NH(2)-terminal antibodies only bound ECE-1d. The novel protein, designated ECE-1 sv, has an apparent molecular mass of 75 kDa; by using site-directed mutagenesis its start site was identified in a region common to all ECE-1 forms suggesting that ECE-1 b-d SV mRNAs are translated into the same protein. In agreement with the findings demonstrating common COOH terminus for ECE-1sv and ECE-1d, both exhibited a similar catalytic activity. However, immunofluorescence staining and differential centrifugation revealed a distinct intracellular localization for these two proteins. The presence of ECE-1sv in different cellular compartments than full-length forms of the enzyme may suggest a distinct physiological role for these proteins.

Alternative Splicing↗

Identification of rare maternal copy number variants by genome-wide analysis of noninvasive prenatal screening data in 113,017 pregnant women.

OBJECTIVES: Knowledge of copy number variants (CNVs) is relevant to maternal and fetal health and can be obtained from noninvasive prenatal screening (NIPS) of pregnancy. However, genome-wide analysis of maternal CNVs using NIPS data has not been conducted in large populations. METHODS: For CNV analysis, the human genome was segmented into 10 kilobase pairs (Kb) bins, and the relative sequencing depth of each bin was calculated. The circular binary segmentation algorithm was used to estimate CNVs. Detected CNVs from two pregnancies of the same participant were compared to validate the reproducibility. All CNVs were merged into CNV regions (CNVRs) to evaluate their frequency, distributions, and relationship with disease-related genes and regions. RESULTS: In this study, 113,017 pregnant women were recruited. A total of 363,886 CNVs larger than 50 Kb were detected in 101,779 individuals and merged into 43,005 CNVRs. For evaluating the reproducibility of CNVs, 90.18% of deletions and 88.07% of duplications were consistent. In general, 78.13% of individuals carried CNVRs that overlapped protein-coding genes, while 14.76% overlapped OMIM genes. We detected 246 novel CNVRs, 134 (54.47%) involving protein-coding genes. For the perspective of maternal-fetal health, we identified 4,984 (4.41%) individuals as carriers of 5,243 CNVs containing known pathogenic or likely pathogenic regions, including 22q11.2 region and DMD gene.. CONCLUSIONS: NIPS sequencing data is a reliable source for maternal CNV detection. These CNVs constitute an integrate component in maternal-fetal health management.

Humans↗

Identification of hepatitis B surface antigen variants with alterations outside the "a" determinant in immunized Singapore infants.

Vaccine-associated hepatitis B surface antigen (HBsAg) mutations have been mainly identified within the "a" determinant (aa 124-147). Now changes have been detected that are located outside the "a" determinant from immunized Singapore infants born to hepatitis B virus (HBV) carrier mothers. These include Asn116 to Thr116, Val118 to Ala118, Pro120 to Ser120, Ala159 to Val159, Phe183 to Cys183, and Val184 to Ala184. Decreased binding to "a" determinant-specific monoclonal antibody was observed for variants Pro120 to Ser120, Ala159 to Val159, and Phe183 to Cys183. Unlike other HBsAg variants, the Asn116-to-Thr116 HBsAg variant had the wild type threonine in the infant, whereas the mutated asparagine was found in the mother. Vertical transmission is indicated for Phe183-to-Cys183 and Val184-to-Ala184 HBsAg variants, as they were found in both the infants and mothers. Detailed analysis of these HBsAg variants would provide further understanding of the antigenic structure of HBV.

Adolescent↗

Androgen regulation of murine beta-glucuronidase expression: identification and characterization of a nonresponse variant.

One of the major features of beta-glucuronidase (GUS) expression in inbred strains of the house mouse, Mus musculus, is the responsiveness of this enzyme to androgen stimulation in tubule cells of the kidney. Both GUS-specific and nonspecific mutations have been described which define genes that serve to control this response. During examination of the expression of GUS in the interbreeding subspecies, Mus hortulanus, a new GUS haplotype was uncovered that is characterized, in part, by a lack of GUS response to androgen stimulation in an apparently responsive kidney. Blot hybridization analyses of kidney RNA with a radiolabeled murine GUS cDNA shows this lack of response to be reflected in GUS mRNA levels. The difference in heat stability of GUS activity between M. hortulanus and a responsive inbred strain, ICR/Ha, was utilized to assess the contribution of each parent to kidney levels of GUS in androgen-treated and -untreated F1 progeny of these strains. The results, together with preliminary genetic studies, suggest that the element controlling this responsiveness (or the lack thereof) is cis-active and tightly linked to the GUS structural gene on chromosome 5. It is not known whether this element is identical to another GUS-specific, cis-active element, Gus-r, which also controls the androgen response of GUS in mouse kidney.

Androgens↗

Identification of non-functional allelic variant of CYP1A2 in dogs.

OBJECTIVES: Recently, we reported that AC-3933, a novel cognitive enhancer, is polymorphically hydroxylated in beagle dogs and that dogs could be phenotyped as extensive metabolizers (EM) or poor metabolizers (PM). AC-3933 polymorphic hydroxylation is caused by polymorphic expression of CYP1A2 protein in dog liver. METHODS: In order to clarify the mechanism of polymorphic expression of CYP1A2 protein in beagle dogs, we investigated, in this study, the sequence of CYP1A2 cDNA in EM and PM dogs. RESULTS: In PM dogs CYP1A2 gene, we discovered a nonsense mutation (C1117T) that induces a premature termination, and is associated with PM phenotype for AC-3933 hydroxylation. All PM dogs studied were homozygote of the mutant allele (m/m) and seemed to be CYP1A2-null phenotype as they lacked the heme-binding region in CYP1A2. These results indicate that the polymorphic expression of CYP1A2 protein observed in our previous study is caused by a single nucleotide polymorphism on CYP1A2 coding region. Furthermore, we developed a genotyping method for the mutant allele using a mismatch PCR-restriction fragment length polymorphism, and carried out frequency analysis in 149 beagle dogs. CONCLUSION: Our results indicate that more than 10% of the dogs studied were CYP1A2-null. Because CYP1A2-null phenotype in dogs affects the results of pharmacokinetic, toxicological and pharmacological studies of drug candidates, these findings are important in the pharmaceutical and the veterinary fields.

Alleles↗

Identification and functional analysis of genetic variants of the human beta-glucuronidase in a German population sample.

The deleterious consequences of total beta-glucuronidase deficiency, leading to symptomatic mucopolysaccharidosis type VII (MPS VII), have been firmly established. However, the question of whether sequence variations in beta-glucuronidase of non-MPS VII patients affect expression of the enzyme, thereby explaining the wide inter-individual expression, has not been addressed in a systematic manner. In the present study, a population of 965 subjects were screened for enzyme activity and relevant fractions of the beta-glucuronidase gene were sequenced in those individuals belonging to the highest or lowest decile of activity. The study showed a substantial inter-individual variability of beta-glucuronidase in plasma (range 0.5-150.2 micromol/min) and confirmed the association of beta-glucuronidase activity with gender (P < 0.001), age (r = 0.218; P < 0.001) and body mass index (r = 0.311; P < 0.001). We were able to identify six beta-glucuronidase single base substitutions (-1026A > G, -72G > T, -12G > A, +7728C > T, +14 209C > T and +14 604A > G) in 193 non-MPS VII patients at a rate of one single nucleotide polymorphism (SNP) per 520 bp sequenced. The GG genotype of +14 604A > G and the CT genotype of +14 209C > T were associated with higher beta-glucuronidase activity (P < 0.05). Subsequently, reporter gene assays were carried out to elucidate the effects of the SNPs -1026A > G, -72G > T and -12G > A, and the combined genotype -1026A > G and -12G > A observed in one of the subjects. Variant -12G > A reduced the promoter activity (75%; 95% confidence interval 70-84%, P < 0.05). The present study demonstrates that three of the described SNPs influence the activity and/or expression of beta-glucuronidase. Taken together, the data indicate a rather limited influence of genetic factors on inter-individual variability in beta-glucuronidase activity.

Cross-Sectional Studies↗

Genetic landscape of pediatric seizures in Southeast China: identification of a novel GLI3 frameshift variant through whole-exome sequencing.

BACKGROUND: Pediatric seizure disorders are clinically and genetically heterogeneous. Whole-exome sequencing has improved the detection of rare genetic variants in childhood epilepsy; however, data from pediatric populations in Southeast China remain limited. This study aimed to characterize the genetic landscape of pediatric seizure disorders in Southeast China and to evaluate the clinical diagnostic yield of whole-exome sequencing. MATERIALS AND METHODS: This retrospective observational study included 21 pediatric patients with seizure disorders who were recruited at the Fifth Hospital of Xiamen, Fujian, China, between January 2021 and June 2024. Clinical data were extracted from medical records. Whole-exome sequencing was performed on DNA extracted from peripheral blood. Sequence variants were annotated, filtered, and classified according to the guidelines of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Copy-number variants were evaluated using exome-based algorithms. Descriptive statistics were used because of the limited sample size. RESULTS: WES identified three clinically relevant, likely pathogenic findings in 3 of 21 patients, corresponding to a provisional diagnostic yield of 14.3%. The remaining 62 of 65 variants were of uncertain significance (VUS). The three retained variants included a GLI3 frameshift variant (exon 2: c.90_91insCAGATGTGAGC; p.Glu31Glnfs*3) and two copy-number variants (16p13.12-16p13.11 duplication and Xp22.31 deletion) with established clinical significance. Functional analysis of all 65 variants revealed that ion channel genes and neurodevelopmental genes were the most frequently affected categories. CONCLUSION: Whole-exome sequencing identified clinically relevant genetic findings in a subset of Southeast Chinese children with seizure disorders. The novel GLI3 frameshift variant may suggest an expansion of the GLI3-associated phenotypic spectrum, but further segregation, functional validation, and larger cohort studies are needed. The high proportion of variants of uncertain significance highlights the ongoing challenges of genetic interpretation in pediatric seizure disorders.

GLI3 frameshift variant↗

Pole-tracking algorithms for the extraction of time-variant heart rate variability spectral parameters.

Various algorithms of autoregressive (AR) recursive identification make it possible to evaluate power spectral distribution in correspondence with each sample of a time series, and time-variant spectral parameters can be calculated through the evaluation of the pole positions in the complex z-plane. In traditional analysis, the poles are obtained by zeroing the denominator of the model transfer function, expressed as a function of the AR coefficients. In this paper, two algorithms for the direct updating and tracking of movements of poles of an AR time-variant model on the basis of the innovation given to the coefficients are presented and investigated. The introduced algorithms are based upon 1) the classical linearization method and 2) a recursive method to compute the roots of a polynomial, respectively. In the present paper, applications in the field of heart rate variability (HRV) signal analysis are presented and efficient tools are proposed for quantitative extraction of spectral parameters (power and frequency of the low-frequency (LF) and high-frequency (HF) components) for the monitoring of the action of the autonomic nervous system in transient patho-physiological events. These computational methods seem to be very attractive for HRV applications, as they inherit the peculiarity of recursive time-variant identification, and provide a more immediate comprehension of the spectral process characteristics when expressed in terms of poles and AR spectral components.

Algorithms↗

Identification of HLA-B*56 variant (B*560502) in the Korean population.

We report here a new HLA-B*56 allele, B*560502, identified by sequencing-based typing in the Korean population. HLA-B*560502 differs from B*560501 by a single nucleotide at position 141 in exon 2 (T(r)C). This single nucleotide substitution may not result in an amino acid difference in the alpha1 domain at residue 23. The putative haplotype involving B*560502 may be A*24-DRB1*1201-DQA1*0503-DQB1*0304-DPB1*0202.

Alleles↗

Identification of an HLA-C variant allele, Cw*0805, by sequencing based typing.

We have identified a variant HLA-C allele, Cw*0805, in DNA isolated from a blood sample used in the UK National External Quality Assessment Scheme for Histocompatibility and Immunogenetics. The DNA was initially typed by PCR-SSP and PCR-SBT as Cw*0802, 1602 with a single mismatch in exon 2 of one of the alleles. The two HLA-C alleles were separated by locus- and allele-specific PCRs and sequencing analysis showed that the Cw*0802 allele was variant in this sample, with a single mismatch in exon 2 at position 289.

Alleles↗

Identification of three new alternatively spliced variants of the rat mu opioid receptor gene: dissociation of affinity and efficacy.

Mu opioid receptors mediate the pharmacological actions of morphine and morphine-like drugs, such as heroin. The mouse and human Oprm genes undergo splicing. In these present studies, we have identified and characterized three new MOR-1 splice variants from the rat Oprm gene. Using an RT-PCR approach, we isolated the new exons 7, 8 and 9 downstream of exon 3. The rat exons 7 and 9 were homologous to the mouse exons 7 and 9 while the rat exon 8 was not. Northern blot analysis with the new exon probes showed distinctive and abundant transcripts of the variants in the rat brain. Full-length cDNA clones containing the new exons, rMOR-1C1, rMOR-1C2 and rMOR-1D were obtained using an RT-PCR approach. Each contained the same exons 1, 2 and 3 as the original rMOR-1, followed by different combinations of the new exons in place of exon 4. In addition, we also isolated another new variant, rMOR-1A, which contains only exons 1, 2 and 3, and is homologous to the human variant MOR-1A previously identified. All the variants were highly mu-selective in binding studies with little difference in affinities for the mu ligands among the variants. However, functional evaluation of assessments of the variants using agonist stimulated [(35)S]GTPgammaS binding assays revealed marked differences among the variants, both in terms of potency and efficacy of the drugs. The relative efficacy of a series of mu opioids to each other varied depending upon the variant studied. Efficacy in the [(35)S]GTPgammaS assay did not correlate with either receptor binding affinity or with potency. Thus, selectivity of opioid action might be achieved by designing compounds with varying efficacies at different MOR-1 variants.

Alternative Splicing↗

Giardia lamblia: identification and characterization of a variant-specific surface protein gene family.

Giardia lamblia trophozoites undergo antigenic variation by modulating the expression of variant-specific surface proteins (VSP), which are encoded by a number of small multigene families. We characterized the genomic copy of the VSP gene expressed by the cloned trophozoite line H7, derived from the isolate GS/M, in addition to a related, but nonexpressed, family member. The coding regions of the two genes encode closely related polypeptides (86% identity). However, differences in the coding region of these genes reside solely in an 873 bp segment. Only four differences were found between the 5' flanking sequences (465 bp). The proximal 205 base pairs downstream from the coding regions were identical, but thereafter the sequences diverged (37% identity over the next 391 bp). Mapping studies indicated that no other VSP gene was located within 4 kb pairs of the expressed H7 VSP gene, and transcripts from the nonexpressed gene were detected in neither GS/H7 nor heterogeneous trophozoites populations derived from this cloned line. Any mechanisms responsible for the differential expression of VSP genes must reconcile the near identity of DNA sequences that flank the coding regions of expressed and nonexpressed VSP genes.

Amino Acid Sequence↗

Identification of a novel alternative splicing variant of RGS5 mRNA in human ocular tissues.

Regulator of G protein signaling (RGS) proteins act as GTPase-activating proteins (GAPs) for Galpha subunits and negatively regulate G protein-coupled receptor signaling. Using RGS5 gene-specific RT-PCR, we have identified a novel alternative splicing variant of RGS5 mRNA in human ocular tissues. The alternative splicing of RGS5 mRNA occurred at position +44 (GenBank NM_003617), spliced out 174 bp (+44 to +218 bp) of the coding region, and encoded an RGS5s protein with a 108 amino acid N-terminal deletion. This study is the first to document alternative splicing of an RGS5 gene. We therefore studied RGS5 and RGS5s mRNA distribution in human tissues. In the eye, RGS5s was found to be highly expressed in the ciliary body and trabecular meshwork. It was also expressed in the kidney, brain, spleen, skeletal muscle and small intestine, but was not detectable in the liver, lung, heart. RGS5s was not found in monkey and rat ocular tissues, indicating species specificity for the eye. Comparing the recombinant RGS5 and RGS5s expression in HEK293/EBNA cells, RGS5s was present almost exclusively in the cytosolic fraction, whereas RGS5 was present in both membrane and cytosolic fractions. The data suggest that the N-terminal of RGS5 may be important for protein translocation to the cell membrane. Both RGS5 and RGS5s antagonized the rapid phosphorylation of p44/42 MAP kinase induced by Galphai coupled cannibinoid receptor-1 activation. RGS5, but not RGS5s, inhibited the Ca2+ signaling initiated by activation of Galphaq coupled angiotensin II receptors (AT1) and prostaglandin FP receptors. Cotransfection of RGS5s with RGS5 resulted in the blockade of RGS5 actions with respect to inhibition of the signal transduction initiated by activation of both AT1 and FP receptor, suggesting that RGS5s may contain functional domains that compete with RGS5 in the regulation of the Galphaq coupled AT1 and FP receptors. The unique expression pattern, cellular localization and functions of RGS5s suggest that RGS5s may play a critical role in the regulation of intracellular signaling pathways.

Alternative Splicing↗

Identification and functional characterization of genetic variants of human organic cation transporters in a Korean population.

Genetic variants of three human organic cation transporter genes (hOCTs) were extensively explored in a Korean population. The functional changes of hOCT2 variants were evaluated in vitro, and those genetic polymorphisms of hOCTs were compared among different ethnic populations. From direct DNA sequencing, 7 of 13 coding variants were nonsynonymous single-nucleotide polymorphisms (SNPs), including four variants from hOCT1 (F160L, P283L, P341L, and M408V) and three from hOCT2 (T199I, T201M, and A270S), whereas 6 were synonymous SNPs. The linkage disequilibrium analysis presented for three independent LD blocks for each hOCT gene showed no significant linkage among all three hOCT genes. The transporter activities of MDCK cells that overexpress the hOCT2-T199I, -T201M, and -A270S variants showed significantly decreased uptake of [(3)H]methyl-4-phenylpyridinium acetate (MPP(+)) or [(14)C]tetraethylammonium compared with those cells that overexpress wild-type hOCT2, and the estimated kinetic parameters of these variants for [(3)H]MPP(+) uptake in oocytes showed a 2- to 5-fold increase in K(m) values and a 10- to 20-fold decrease in V(max) values. The allele frequencies of the five functional variants hOCT1-P283L, -P341L, and hOCT2-T199I, -T201M, and -A270S were 1.3, 17, 0.7, 0.7, and 11%, respectively, in a Korean population; the frequency distributions of these variants were not significantly different from those of Chinese and Vietnamese populations. These findings suggest that genetic variants of hOCTs are not linked among three genes in a Korean population, and several of the hOCT genetic variants cause decreased transport activity in vitro compared with the wild type, although the clinical relevance of these variants remains to be evaluated.

1-Methyl-4-phenylpyridinium↗

Hemoglobins M: identification of Iwate, Boston, and Saskatoon variants.

Hemoglobin M variants, M Iwate, M Boston, M Saskatoon are easily and accurately identified by electron spin resonance with small amounts of patients' blood. In hemoglobin M Iwate and M Boston the electron spin resonance of both fresh blood (unprocessed) and isolated pure ferrihemoglobin M revealed similar signal shapes; whereas that of hemoglobin M Saskatoon was doublet in fresh blood and triplet in pure ferrihemoglobin M.

Electron Spin Resonance Spectroscopy↗

Identification of a naturally occurring transforming variant of the p65 subunit of NF-kappa B.

Transcription factor NF-kappa B comprises two proteins, p50 and p65, that have sequence similarity to the v-rel oncogene. In primary hematopoietic cell populations an alternatively spliced form of NF-kappa B p65 mRNA was observed that encoded a protein designated p65 delta. Expression of the p65 delta cDNA in Rat-1 fibroblasts resulted in focus formation, anchorage-independent growth in soft agar, and tumor formation in athymic nude mice, effects not obtained with expression of p65 or a p65 delta mutant that contains a disruption within the transcriptional activation domain. Thus, p65 delta, which associated weakly and interfered with DNA binding by p65, may sequester an essential limiting regulatory factor or factors required for NF-kappa B function.

Animals↗