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Results for “Splicing mutations”

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At least 217 records · Page 12Linked to original sources
PubMed1998

In vivo function of mutated spliced leader RNAs in Caenorhabditis elegans.

The role of spliced leader RNA (SL RNA) in trans-splicing in Caenorhabditis elegans has been studied through a combination of in vitro mutagenesis and in vivo complementation of rrs-1 mutant nematodes, which lack endogenous SL1 RNA. Three classes of mutant SL1 RNAs have been found-those that rescue the lethal phenotype at low concentration of transforming DNA, those that rescue at high but not low concentration, and those that do not rescue at all. These studies showed that some mutations in the otherwise highly conserved 22-nt spliced leader are tolerated for splicing and post-splicing events. A longer spliced leader also can be tolerated but only when present in high copy number. Changes in the first 16 nucleotides result in the appearance of no SL RNA, consistent with the in vitro studies by others showing that the SL1 RNA promoter partly resides within the spliced leader sequence.

Animals↗
PubMed1990

Characterization of a splicing mutation in group A xeroderma pigmentosum.

The molecular basis of group A xeroderma pigmentosum (XP) was investigated by comparison of the nucleotide sequences of multiple clones of the XP group A complementing gene (XPAC) from a patient with group A XP with that of a normal gene. The clones showed a G----C substitution at the 3' splice acceptor site of intron 3, which altered the obligatory AG acceptor dinucleotide to AC. Nucleotide sequencing of cDNAs amplified by the polymerase chain reaction revealed that this single base substitution abolishes the canonical 3' splice site, thus creating two abnormally spliced mRNA forms. The larger form is identical with normal mRNA except for a dinucleotide deletion at the 5' end of exon 4. This deletion results in a frameshift with premature translation termination in exon 4. The smaller form has a deletion of the entire exon 3 and the dinucleotide at the 5' end of exon 4. The result of a transfection study provided additional evidence that this single base substitution is the disease-causing mutation. This single base substitution creates a new cleavage site for the restriction nuclease AlwNI. Analysis of AlwNI restriction fragment length polymorphism showed a high frequency of this mutation in Japanese patients with group A XP: 16 of 21 unrelated Japanese patients were homozygous and 4 were heterozygous for this mutation. However, 11 Caucasians and 2 Blacks with group A XP did not have this mutant allele. The polymorphic AlwNI restriction fragments are concluded to be useful for diagnosis of group A XP in Japanese subjects, including prenatal cases and carriers.

Amino Acid Sequence↗
PubMed2005

Mild glycine encephalopathy (NKH) in a large kindred due to a silent exonic GLDC splice mutation.

BACKGROUND: Classic neonatal-onset glycine encephalopathy (GE) is devastating and life threatening. Milder, later onset variants have been reported but were usually sporadic and incompletely defined. OBJECTIVE: To determine the clinical and biochemical phenotype and molecular basis of mild GE in nine children from a consanguineous Israeli Bedouin kindred. METHODS: Genomic DNA was screened for GLDC, AMT, and GCSH gene mutations. GLDC expression in lymphoblasts was studied by Northern blot and reverse transcriptase PCR analysis. RESULTS: Clinical features included hypotonia, abnormal movements, convulsions, and moderate mental retardation with relative sparing of gross motor function, activities of daily living skills, and receptive language. Aggression and irritability were prominent. CSF-to-plasma glycine ratio was mildly to moderately elevated. All nine patients were homozygous and their parents heterozygous for a novel, translationally silent GLDC exon 22 transversion c.2607C>A. Lymphoblast GLDC mRNA levels were considerably reduced. Three aberrantly spliced cDNA species were identified: exon 22 and exon 22 to 23 skipping, and insertion of an 87-base pair cryptic exon. Homozygosity for c.2607C>A was also identified in an unrelated but haplotypically identical patient with an unusually favorable outcome despite severe neonatal-onset GE. Mutation analysis enabled prenatal diagnosis of three unaffected and one affected pregnancies. CONCLUSIONS: The mutation in this kindred led to missplicing and reduced GLDC (glycine decarboxylase) expression. The 4 to 6% of normally spliced GLDC mRNA in the patients may account for their relatively favorable clinical outcome compared with patients with classic glycine encephalopathy.

Adolescent↗
PubMed2006

Novel splicing mutation in the NEMO (IKK-gamma) gene with severe immunodeficiency and heterogeneity of X-chromosome inactivation.

We report on a family with three stillborn males, three affected males who were small for gestational age and died within 8 months, and one male who died at age 5 years. This boy had cone-shaped teeth and oligoodontia. He had serious bacterial infections and inflammatory bowel disease. Mutations in the NF-kappaB essential modulator (NEMO) gene have recently been shown to be the cause of a group of ectodermal dysplasia and immunodeficiency disorders (EDA-ID). Analysis of the NEMO gene revealed a nucleotide change in the consensus sequence of the splicing donor site of exon 6 IVS6 + 5G --> A(1027 + 5G --> A), which has not previously been described in EDA-ID. RT-PCR analysis of fibroblast RNA from an aborted affected male fetus demonstrated a skipping of exons 4, 5, and 6 which resulted in a truncated protein of about 35 kDa revealed by NEMO antibody. The skipping of exons 4, 5, and 6 did not affect the ORF of the C-terminal of NEMO encoded by exons 7, 8, 9, and 10, which contains a coiled-coil motif (CC2), a leucin-zipper (LZ), and a zinc finger motif (ZF) sub-domains of NEMO. IkappaBalpha degradation was strongly impaired in the fetal fibroblasts, suggesting an impaired NF-kappaB signaling. One healthy carrier had a completely skewed X-inactivation pattern with the normal X active, whereas the two other carriers had a random X-inactivation pattern. This family may represent a new phenotype within the EDA-ID disorders. From the heterogeneity in X-inactivation phenotype, we conclude that this mutation is not deleterious enough to be lethal for peripheral blood cells.

Abnormalities, Multiple↗
PubMed1999

Prenatal diagnosis of sporadic neurofibromatosis type 1 (NF1) by RNA and DNA analysis of a splicing mutation.

Neurofibromatosis type 1 (NF1) is one of the most common genetic disorders in humans with an incidence of 1 in 3500. Most of the NF1 mutations reported so far (over 240 mutations) are unique. Specific prenatal diagnosis can only be provided to familial cases by an indirect linkage analysis or to families with a previously identified mutation. Here we report the first prenatal diagnosis in sporadic NF1 by direct characterization of the mutation. We first identified the skipping of exon 10b of NF1 in the mRNA from a woman affected by NF1 and without familial history of the disease. The analysis of genomic DNA identified mutation IVS10b+1G-->A as the cause of the skipping of exon 10b. Chorionic villus sampling (CVS) was performed at 10 weeks of gestation and total RNA was directly extracted from the sample. After reverse transcription (RT) and polymerase chain reaction (PCR) of the cDNA, the skipping of exon 10b was not identified in the CVS upon agarose gel electrophoresis. The fetal origin of the CVS was confirmed via polymorphic markers and the absence of the IVS10b+1G-->A mutation was confirmed by genomic analysis.

Adult↗
PubMed2006

Long-term FVII substitution in a preterm infant with severe gastrointestinal bleeding and FVII deficiency due to a homozygous donor splice mutation IVS4+1G-->A.

Congenital FVII deficiency is a rare bleeding disorder. Clinical complications are similar to those seen in hemophilia A, and an increased incidence of intracerebral hemorrhage related to birth trauma has been reported. The authors report on an infant who presented at the second day of life with melaena and hematemesis caused by congenital FVII deficiency with minimal activity of 4%. A homozygous mutation IVS4+G-->A, formerly described in 2 siblings, who died of brain hemorrhage within the first month of life, was identified. Severe bleeding events were prevented with prophylactic treatment. Early identification of the underlying mutation helps to assess the risk of hemorrhage and prevent severe bleeding by prophylactic FVII therapy.

Alternative Splicing↗
PubMed1992

Aspartylglycosaminuria in a non-Finnish patient caused by a donor splice mutation in the glycoasparaginase gene.

Aspartylglycosaminuria is a lysosomal storage disease caused by deficient activity of glycoasparaginase (EC 3.5.1.26), and it occurs with a high frequency among Finns. We have recently shown that the molecular defect in all Finnish aspartylglycosaminuria patients examined to date consists of two single base changes in the heavy chain of glycoasparaginase (Mononen, I., Heisterkamp, N., Kaartinen, V., Williams, J. C., Yates, J. R., III, Griffin, P. R., Hood, L. E., and Groffen, J. (1991) Proc. Natl. Acad. Sci U.S.A. 88, 2941-2945). This is the first report on the identification of the molecular defect causing aspartylglycosaminuria in a patient of non-Finnish origin. Total RNA from fibroblasts of a black American aspartylglycosaminuria patient was isolated, first-strand cDNA was synthesized, and the cDNA encoding glycoasparaginase was amplified by the polymerase chain reaction. The patient's mRNA nucleotide sequence was different from the normal sequence by a deletion of 134 nucleotides at positions 807-940. Nucleotide sequence analysis of the normal glycoasparaginase gene demonstrated that the deletion corresponded precisely to a 134-base pair exon. Moreover, analysis of the splice sites demonstrated a single base change, G to T, that altered the donor splice site of the exon deleted in the patient's mRNA. This change led to an exon-skipping event resulting in a frame shift and generation of a stop codon.

Amino Acid Sequence↗
PubMed1998

A novel splicing mutation in the ceruloplasmin gene responsible for hereditary ceruloplasmin deficiency with hemosiderosis.

Hereditary ceruloplasmin deficiency with hemosiderosis (aceruloplasminemia) is a newly recognized autosomal recessive disorder of copper-iron metabolism due to mutations in the ceruloplasmin (Cp) gene. We report here a novel mutation in the Cp gene in a 54-year-old Japanese woman with this disease. She showed clinical triad; diabetes mellitus, retinal degeneration and neurological disorder in her middle age. Laboratory findings were characteristic for no detectable serum ceruloplasmin and increased serum ferritin. Liver biopsy revealed excessive storage of iron in hepatocytes and magnetic resonance imaging of the brain was indicative of increased iron content in the basal ganglia, thalamus and dentate nucleus. The a-->g substitution at the splice acceptor site of the intron 6 (1209-2) caused a 8-bp deletion in Cp mRNA by defective splicing, resulting in a premature termination codon at the amino acid position 388. Truncation of Cp, even if effectively translated, may cause loss of its normal function because of drastic change in its triangular structure.

Alternative Splicing↗
PubMed1995

Splicing mutations in the COL4A5 gene in Alport's syndrome: different mRNA expression between leukocytes and fibroblasts.

The COL4A5 gene from 40 patients with Alport's syndrome was examined using single-strand conformation substitution at the acceptor site (-2) of intron 50 and a G-to-C substitution at the donor site (+1) of intron 47, respectively. The transcript in peripheral leukocytes from the former had a 10-nucleotide deletion. This shortened transcript was derived from abnormal splicing in a cryptic acceptor site within exon 51. This could be translated into a protein with an alteration of three amino acids followed by premature termination, which eliminated 23 amino acids from the carboxyl end. Gene tracking revealed that the mother and a brother carried the mutant allele. In the latter, the transcript in leukocytes was normal, but that in cultured skin fibroblasts showed skipping of exon 47, the result being that 71 amino acids were absent. Glomerular basement membrane from the patient did not react with the anti-alpha 5(IV) antibody. His maternal grandmother, mother, and a sister, all with abnormal urinalysis, carried the mutant allele. Thus, the appearance of exons of the COL4A5 gene in leukocytes may differ from that in fibroblasts. If kidney mRNA is not available, mRNAs from cultured skin fibroblasts, in addition to leukocytes, can be used for gene analysis in subjects with Alport's syndrome.

Adolescent↗
PubMed1998

A novel Alu-like element rearranged in the dystrophin gene causes a splicing mutation in a family with X-linked dilated cardiomyopathy.

We have identified and characterized a genomic sequence with some features typical of Alu-like mobile elements rearranged into the dystrophin gene in a family affected by X-linked dilated cardiomyopathy. The Alu-like sequence rearrangement occurred 2.4 kb downstream from the 5' end of intron 11 of the dystrophin gene. This rearrangement activated one cryptic splice site in intron 11 and produced an alternative transcript containing the Alu-like sequence and part of the adjacent intron 11, spliced between exons 11 and 12. Translation of this alternative transcript is truncated because of the numerous stop codons present in every frame of the Alu-like sequence. Only the mutant mRNA was detected in the heart muscle, but in the skeletal muscle it coexisted with the normal one. This result is supported by the immunocytochemical findings, which failed to detect dystrophin in the patient's cardiac muscle but showed expression of a reduced level of protein in the skeletal muscle. Comparative analysis of the Alu-like sequence showed high homology with other repeated-element-containing regions and with several expressed sequence tags. We suggest that this Alu-like sequence could represent a novel class of repetitive elements, reiterated and clustered with some known mobile elements and capable of transposition. Our report underlines the complexity of the pathogenic mechanism leading to X-linked dilated cardiomyopathy but suggests that differences in tissue-specific expression of dystrophin mutations may be a common feature in this condition.

Adult↗