A 4-base pair deletion mutation of Gs alpha gene in a Japanese patient with pseudohypoparathyroidism

Mutations in the guanine nucleotide binding protein alpha subunit (Gs alpha) have been found in patients with pseudohypoparathyroidism (PHP). We have screened the Gs alpha gene for mutations in a Japanese patient with this disorder and identified a novel 4-base pair deletion in exon 7 in codons 189-190. This deletion causes a frameshift and if synthesis of a truncated form of Gs alpha occurred, it would likely be biologically inactive. The patient was heterozygous for this deletion. The patient's mother and an unaffected brother were tested for the presence of this mutation. His mother had the same mutation, and although her serum calcium and parathyroid hormone levels were within the normal range, she had subcutaneous calcifications. Thus, this mutation appears to be necessary but not sufficient to cause the complete pseudohypoparathyroidism phenotype and thus, other unknown factors, either genetic or acquired, may be necessary for the full syndrome to occur.     

A nonsense mutation (G15059A) in the cytochrome b gene in a patient with exercise intolerance and myoglobinuria

We describe a new mitochondrial DNA mutation in the cytochrome b gene in a patient presenting with progressive exercise intolerance and myoglobinuria associated with complex III deficiency in muscle. The point mutation results in the replacement of a glycine at amino acid position 190 with a stop codon. This change predicts premature termination of translation, leading to a truncated protein missing 244 amino acids at the C-terminus of cytochrome b. The mutation fulfills all the accepted criteria for pathogenicity, suggesting that this is the primary cause of the myopathy in the patient.     

A novel nonsense mutation associated with an exon skipping in a patient with hereditary protein S deficiency type I

The genetic defect in a patient with hereditary type I protein S (PS) deficiency was investigated. All the exons and intron-exon junctions of the patient's PS gene were amplified by PCR and subjected to heteroduplex screening. Only the PCR product of exon 4 revealed heteroduplex bands. A novel nonsense mutation, Ser62 (TCA) to Stop (TGA) was found in exon 4. RT-PCR detected the aberrant mRNA in the patient's platelets, which was markedly reduced in amount and lacked the region of exon 4, suggesting that the nonsense mutation affected the mutated mRNA metabolism and induced exon skipping. The skipping of exon 4 causes an in-frame deletion of 29 amino acids which just construct the thrombin-sensitive region of the PS molecule. The loss of such an important domain as well as the quantitative decrease in the mutated mRNA appear to be responsible for the type I PS deficiency in this patient.     

Maternally inherited cardiomyopathy and hearing loss associated with a novel mutation in the mitochondrial tRNA(Lys) gene (G8363A)

A novel G8363A mutation in the mtDNA tRNA(Lys) gene was associated, in two unrelated families, with a syndrome consisting of encephalomyopathy, sensorineural hearing loss, and hypertrophic cardiomyopathy. Muscle biopsies from the probands showed mitochondrial proliferation and partial defects of complexes I, III, and IV of the electron-transport chain. The G8363A mutation was very abundant (>95%) in muscle samples from the probands and was less copious in blood from 18 maternal relatives (mean 81.3% +/- 8.5%). Single-muscle-fiber analysis showed significantly higher levels of mutant genomes in cytochrome (c) oxidase-negative fibers than in cytochrome (c) oxidase-positive fibers. The mutation was not found in >200 individuals, including normal controls and patients with other mitochondrial encephalomyopathies, thus fulfilling accepted criteria for pathogenicity.     

Missense mutation in a von Willebrand factor type A domain of the alpha 3(VI) collagen gene (COL6A3) in a family with Bethlem myopathy

OBJECTIVE: The purpose of this retrospective study was to examine the value of whole-body nuclear medicine imaging and to evaluate the typical scintigraphic pattern of sternocostoclavicular hyperostosis (SCCH) and/or pustulotic arthroosteitis (PAO). In this entity the correct diagnosis is frequently missed because of uncharacteristic changes in other imaging modalities. MATERIALS AND METHODS: Forty-nine patients (age range 15-65 years old, mean age 36 years) with sternocostoclavicular hyperostosis (SCCH) and/or pustulotic arthroosteitis (PAO) were examined with whole-body scintigraphy and conventional radiography. RESULTS: Forty-three of 49 patients with SCCH/PAO showed a characteristic "bullhead"-like high tracer uptake of the sternocostoclavicular region with the manubrium sterni representing the upper skull and the inflamed sternoclavicular joints corresponding to the horns (= bullhead sign). Scintigraphy revealed additional skeletal manifestations (spondylitis, sacroiliitis, osteitis) in 33 of 49 patients with SCCH and/or PAO. CONCLUSIONS: Bone scintigraphy is the imaging modality of choice for the diagnosis of skeletal involvement in PAO. Nuclear medicine reveals unexpected locations and shows the typical pattern of focal hot spots of the spine, sacroiliac joints and/or appendicular skeleton in the large majority of cases in combination with a bullhead-like tracer uptake of the sternocostoclavicular region. The bullhead sign is the typical and highly specific scintigraphic manifestation of SCCH and PAO in radionuclide bone scans and helps to avoid unnecessary biopsies.     

A mitochondrial tRNA(Val) gene mutation (G1642A) in a patient with mitochondrial myopathy, lactic acidosis, and stroke-like episodes

We studied a patient with the diagnosis of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) for mitochondrial DNA mutations in muscle. Established MELAS mutations were excluded. Mitochondrial DNA was further analyzed for mutations in the 22 tRNA genes by single-strand conformation polymorphism (SSCP) analysis; a tRNA(Val) mutation (G1642A) was found. The structure of the altered tRNA, the heteroplasmy, and the absence of the mutation in the mother and in 100 control subjects suggests that the tRNA(Val) mutation is associated with the MELAS syndrome.     

Mitochondrial myopathy with predominant respiratory dysfunction in a patient with A3243G mutation in the mitochondrial tRNA(Leu(UUR))gene

Two treatment regimens for disseminated Lyme borreliosis (mainly neurologic and musculoskeletal manifestations) were compared in a randomized trial. A group of 30 patients received oral cefixime 200 mg combined with probenecid 500 mg three times daily for 100 days. Another group of 30 patients received intravenous ceftriaxone 2 g daily for 14 days followed by oral amoxicillin 500 mg combined with probenecid 500 mg three times daily for 100 days. There was no statistically significant difference in the outcome of infection between the two groups. However, the total number of patients with relapses or no response at all and the number of positive polymerase chain reaction findings after therapy were greater in the cefixime group. The general outcomes of infection in patients with disseminated Lyme borreliosis after 3-4 months of therapy indicate that prolonged courses of antibiotics may be beneficial in this setting, since 90% of the patients showed excellent or good treatment responses.     

A novel point mutation in the intracellular domain of the ret protooncogene in a family with medullary thyroid carcinoma

Specific mutations in the ret protooncogene have been found associated with multiple endocrine neoplasia type 2A (MEN 2A) and type 2B (MEN 2B) and familial medullary thyroid carcinoma (FMTC). Mutations in one of five cysteine residues in the extracellular domain have been found in over 95% of families with MEN 2A and 88% of families with FMTC. In MEN 2B patients, a specific mutation at codon 918, substituting a threonine for a methionine, has been found in 95% of cases. In FMTC, in addition to the mutations of the extracellular cysteines, three intracellular base pair changes have been reported at codons 768 and 804. Here we describe a novel intracellular mutation in exon 15 of the ret gene that leads to the substitution of an alanine for a serine at codon 891 in a family with medullary thyroid carcinoma. This amino acid change may be important in determining substrate specificity or, alternatively, may play a role in ATP binding.     

Alternative pre-mRNA splicing of the sterol 27-hydroxylase gene (CYP 27) caused by a G to A mutation at the last nucleotide of exon 6 in a patient with cerebrotendinous xanthomatosis (CTX)

Proline effectively inhibits protein aggregation during the refolding of bovine carbonic anhydrase. Other osmolytes used such as glycine and ethylene glycol fail to exhibit the 'aggregation-blockade' role shown by proline. Results of viscosity and ANS fluorescence (1-anilino-8-naphthalene sulphonic acid) experiments suggest that proline at high concentrations forms an ordered supramolecular assembly. Based on these results, it is proposed that proline behaves as a protein folding chaperone due to the formation of an ordered, amphipathic supramolecular assembly. To our knowledge, this is the first report wherein proline is proposed as a protein folding aid.     

Increased functional activity of elongation factor G with G16V mutation in the GTP-binding domain

Oligonucleotide-directed mutagenesis was used to obtain elongation factor G from Thermus thermophilus with the G16V mutation in its GTP-binding domain. Functional studies of the mutated protein and elongation factor G from E. coli were carried out. The data revealed that the G16V mutant retains high thermostability, has an increased ribosome-dependent GTPase activity, and its translation activity in cell-free translation system is equal to that of the factor G from E. coli. The mutated protein with an uncleavable GTP analog also has an increased affinity to the ribosomes.     

A novel lysosomal acid lipase gene mutation in a patient with cholesteryl ester storage disease

The International Classification for Nursing Practice (ICNP) is a collaborative project under the auspices of the International Council of Nurses. The alpha version is available online for comment in preparation for the release of the beta version in 1999. The authors answer the most-frequently asked questions about the ICNP and encourage nurses in the United States to participate in the revision by sending comments and suggestions to the American Nurses Association.     

A double mutation (A8296G and G8363A) in the mitochondrial DNA tRNA (Lys) gene associated with myoclonus epilepsy with ragged-red fibers

OBJECTIVE: To define potential pathogenic mitochondrial DNA (mtDNA) point mutations in a patient with myoclonus epilepsy with ragged-red fibers (MERRF) syndrome. BACKGROUND: MERRF syndrome is typically associated with point mutations in the mtDNA tRNALys gene. METHODS: We performed morphologic, biochemical, and genetic analysis of muscle samples from the patient and four relatives. Molecular genetic studies included sequencing, PCR, and restriction enzyme analysis on whole muscle, blood, and single muscle fibers. RESULTS: Muscle biopsy showed cytochrome c oxidase (COX), negative ragged-red fibers (RRF), and a defect of complex I of the mitochondrial respiratory chain. We found an A8296G transition and a G8363A mutation in the mtDNA tRNALYs gene. The A8296G was almost homoplasmic in muscle and blood from the propositus and his oligosymptomatic maternal relatives. The G8363A mutation was heteroplasmic and more abundant in muscle than in blood, and its proportion correlated with clinical severity. Single muscle fiber analysis showed significantly higher levels of G8363A genomes in COX-negative than in normal fibers, and almost homoplasmic levels of mutant A8296G mtDNA in both COX-negative and normal fibers. The two mutations affect highly conserved nucleotides and were not found in controls. CONCLUSIONS: The G8363A mutation is pathogenic; the co-occurrence of the A8296G mutation is of unclear significance and is likely to be a rare polymorphism.     

A novel TP53 splicing mutation in a Li-Fraumeni syndrome family: a patient with Wilms'' tumour is not a mutation carrier

The authors describe the case of a patient with treatment-resistant schizophrenia who became pregnant after switching from conventional neuroleptic medications to clozapine, an atypical antipsychotic medication that does not cause hyperprolactinemia. Gestational diabetes, possibly exacerbated by clozapine, complicated management of her pregnancy. Comprehensive community support and psychiatric rehabilitation, combined with a positive response to clozapine, contributed to satisfying the patient's goal of having a healthy baby and being able to take the baby home to live with her and her husband.     

A novel mutation of the GTP-cyclohydrolase I gene in a patient with hereditary progressive dystonia/dopa-responsive dystonia

PURPOSE: To evaluate re-treatment with an additional course of low-dose irradiation in patients with progressive or recurrent choroidal neovascular membranes (CNVMs). MATERIALS AND METHODS: Ten patients who had received 14 Gy of external-beam radiation therapy in seven fractions for subfoveal CNVMs were found to have recurrent or persistent neovascularization at follow-up. They received an additional 15 Gy of radiation therapy administered in five daily fractions with a standard lens-sparing technique. Before reirradiation, visual acuity ranged from 20/80 to counting fingers. The median time between radiation courses was 6.5 months (range, 2-16 months). After re-treatment, the patients were followed up with angiography and visual field testing. The median follow-up was 18.5 months (range, 12-21 months). RESULTS: Eight of 10 patients (80%) maintained their visual acuity at 1 year and three of seven (43%) at 18 months. Visual acuity was stabilized in five of the 10 patients at their last follow-up. No acute or late side effects of irradiation were noted. CONCLUSION: Additional radiation therapy in selected patients with CNVMs who have failed to benefit from previous irradiation is well tolerated and appears to stabilize the disease process in a substantial proportion of these patients.     

A novel thrombomodulin gene mutation in a patient suffering from sagittal sinus thrombosis

Thrombomodulin is an endothelial cell membrane glycoprotein that promotes protein C activation. It has been clearly demonstrated that the anticoagulant functions of the protein C system are important in the prevention of thromboembolic disease. Patients with protein C or protein S deficiency and/or resistance to activated protein C (APC resistance) are at higher risk for developing thromboembolic disease. The first mutation in the thrombomodulin gene was discovered in an American patient suffering from pulmonary embolism at the age of 45 (Ohlin and Marlar 1995). Here we report a case of sagittal sinus thrombosis in a 42-year-old Swedish woman. She was found to carry a heterozygous point mutation changing G127 to A, predicting an Ala25 to a Thr change in the mature thrombomodulin protein. This mutation was also found in her 16-year-old daughter, who so far has not suffered from any thrombotic events. The patient had no other detectable prothrombotic genetic defects associated with the coagulation system. This case supports the hypothesis of an association between mutations in the thrombomodulin gene and venous thrombosis.