Myotonia congenita and myotonic dystrophy in the same family: coexistence of a CLCN1 mutation and expansion in the CNBP (ZNF9) gene.

Myotonia is characterized by hyperexcitability of the muscle cell membrane. Myotonic disorders are divided into two main categories: non-dystrophic and dystrophic myotonias. The non-dystrophic myotonias involve solely the muscle system, whereas the dystrophic myotonias are characterized by multisystem involvement and additional muscle weakness. Each category is further subdivided into different groups according to additional clinical features or/and underlying genetic defects. However, the phenotypes and the pathological mechanisms of these myotonic disorders are still not entirely understood. Currently, four genes are identified to be involved in myotonia: the muscle voltage-gated sodium and chloride channel genes SCN4A and CLCN1, the myotonic dystrophy protein kinase (DMPK) gene, and the CCHC-type zinc finger, nucleic acid binding protein gene CNBP. Additional gene(s) and/or modifying factor(s) remain to be identified. In this study, we investigated a large Norwegian family with clinically different presentations of myotonic disorders. Molecular analysis revealed CCTG repeat expansions in the CNBP gene in all affected members, confirming that they have myotonic dystrophy type 2. However, a CLCN1 mutation c.1238C>G, causing p.Phe413Cys, was also identified in several affected family members. Heterozygosity for p.Phe413Cys seems to exaggerate the severity of myotonia and thereby, to some degree, contributing to the pronounced variability in the myotonic phenotype in this family.

Oncogenic potentials of the human polyomavirus regulatory proteins.

The polyomaviruses BK, JC and SV40 are common in the human population. Their DNA genomes encode large T-antigen, small t-antigen, agnoprotein, and the capsid proteins VP1-3. Studies with these viruses have contributed extensively to the understanding of processes such as replication, transcriptional and posttranscriptional regulation, and cell cycle control. All three viruses can transform human cells in vitro, can induce tumours in animal models, and are strongly association with certain human cancers. It is generally assumed that large T-antigen is the major protein involved in neoplastic processes and that large T-antigen predominantly exerts its effect through deregulation of the tumour suppressors p53 and the retinoblastoma family members. However, additional properties of large T-antigen as well as the other viral proteins contribute to oncogenic processes. This review presents the different mechanisms by which the polyomavirus proteins can induce transformation and discusses which mechanisms may be operational in polyomavirus-positive cancers.

The multifunctional roles of the four-and-a-half-LIM only protein FHL2.

Numerous cellular processes require the concerted action of multiple proteins that assemble in functional complexes. Protein-protein interaction domains allow specific proteins to combine with certain partners. Specificity of protein-protein association can be obtained by an interaction code predicted by conserved amino acid sequences. One of the protein-protein interaction motifs is the LIM domain, a conserved cysteine-rich module present in more than 100 different human proteins. The human four-and-a-half-LIM-only protein family consists of the members FHL1, FHL2, FHL3, FHL4 and ACT. They are expressed in a cell- and tissue-specific manner and participate in various cellular processes, including regulation of cell survival, transcription and signal transduction. Here, we review the current knowledge of the best-studied member of this family, FHL2. We describe the transcription regulation, the expression profile, the interaction partners, the subcellular localization, the biological functions and discuss the possible involvement of FHL2 in human diseases.

Simian virus 40 large T-antigen, but not small T-antigen, trans-activates the human cytomegalovirus major immediate early promoter.

Cytomegalovirus infection is a major cause of morbidity in immunocompromised patients. The major immediate early promoter/enhancer (MIEP) of the human cytomegalovirus controls the expression of the immediate early genes 1 and 2 which play a central role both in primary and reactivated human cytomegalovirus (HCMV)-infections. Our previous studies have shown that co-infection of A549 cells with human cytomegalovirus and human polyomavirus BK resulted in enhanced expression of the immediate early genes 1 and 2 and that the early gene products of BK virus trans-activated the MIEP. However, neither the MIEP sequences required for mediating this trans-activation, nor the contribution of the individual BK virus early gene products were examined. The MIEP contains multiple binding sites for the transcription factors CREB, AP1, Sp1 and NFkappaB, which may mediate polyomavirus large T- or small t-antigens-induced promoter activation. Transient transfection studies in A549 cells demonstrated that SV40 large T-antigen, but not small t-antigen, trans-activated MIEP activity approximately 9-fold. Mutations in individual binding motifs in the context of the complete MIEP did not impair traits-activation by large T-antigen. The level of induction of a truncated MIEP consisting of a single set of CRE/AP1, NFkappaB, and Sp1 binding motifs by large T-antigen was reduced 2-fold compared to the full length MIEP. Extended truncations diminished trans-activation by large T-antigen. To determine the contribution of a single binding motif in the trans-activation by large T-antigen, a CRE/AP1, an NFkappaB, an Sp1, or a non-consensus Sp1-motif, respectively, was linked to the MIEP TATA-sequence respecting the natural spacing between the two transcription regulatory elements. Only the MIEP TATA-box with the correctly spaced non-consensus Sp1 binding site (GT-motif) was stimulated by large T-antigen. These results suggest that an isolated non-consensus Sp1-motif is important for trans-activation of the MIEP by large T-antigen, but that other cis-acting elements can compensate for this element in the context of the whole MIEP.

Analysis of FMR1 (CGG)(n) alleles and DXS548-FRAXAC1 haplotypes in three European circumpolar populations: traces of genetic relationship with Asia.

Fragile X syndrome, the most common form of inherited mental retardation, is caused by expansion of a (CGG)(n) repeat located in the FMR1 gene. The molecular factors involved in the mutation process from stable (CGG)(n) alleles towards unstable alleles are largely unknown, although family transmission studies and population studies have suggested that loss of AGG interruptions in the (CGG)(n) repeat is essential. We have analysed the AGG interspersion pattern of the FMR1 (CGG)(n) repeat and the haplotype distribution of closely located microsatellite markers DXS548 and FRAXAC1, in three circumarctic populations: Norwegians, Nenets and Saami. The data confirm the conservation, reported in all human populations studied so far, of an AGG interruption for each 9-10 CGG and support the stabilising effect of AGG interruptions. The data also indicate the existence of chromosomes of Asian origin in the Saami and Nenets population, thereby confirming a genetic relationship between Northern Europe and Asia. DXS548-FRAXAC1 haplotype frequencies were compared between 24 Norwegian fragile X males and 119 normal males. Significant linkage disequilibrium were found between the fragile X mutation and haplotype 6-4 and between normal (CGG)(n) alleles and haplotype 7-3.

Neuronal cell death in the visual cortex is a prominent feature of the X-linked recessive mitochondrial deafness-dystonia syndrome caused by mutations in the TIMM8a gene.

The Mohr-Tranebjaerg syndrome (MIM 304700) and the Jensen syndrome (MIM 311150) were previously reported as separate X-linked recessive deafness syndromes associated with progressive visual deterioration, dystonia, dementia, and psychiatric abnormalities. In the most extensively studied Norwegian family, the Mohr-Tranebjaerg syndrome was reported to be caused by a one-basepair deletion (151delT) in the deafness/dystonia peptide (DDP) gene at Xq22. This gene has been renamed TIMM8a. We identified a stop mutation (E24X) in the TIMM8a gene segregating with the disease in the original Danish family with the Jensen syndrome, which confirms that the two disorders are allelic conditions. We also report abnormal VEP examinations and neuropathological abnormalities in affected males from the two unrelated families with different mutations. The findings included neuronal cell loss in the optic nerve, retina, striate cortex, basal ganglia, and dorsal roots of the spinal cord. The demonstration of mitochondrial abnormalities in skeletal muscle biopsies in some patients is compatible with the suggestion from recent research that the TIMM8a protein is the human counterpart of an intermembrane mitochondrial transport protein, Tim8p, recently characterized in yeast. The clinical and neuropathological abnormalities associated with mutations in the TIMM8a gene support that this X-linked deafness-dystonia-optic neuropathy syndrome is an example of progressive neurodegeneration due to mutations in a nuclear gene necessary for some, yet unknown mitochondrial transport function. We recommend sequencing the TIMM8a gene, thorough ophthalmological examination, and measuring visual evoked potentials in clinically suspected male patients with either progressive hearing impairment, dystonia, or visual disability in order to establish an early diagnosis and provide appropriate genetic counselling.

Spectrum of CLCN1 mutations in patients with myotonia congenita in Northern Scandinavia.

Myotonia congenita is a non-dystrophic muscle disorder affecting the excitability of the skeletal muscle membrane. It can be inherited either as an autosomal dominant (Thomsen's myotonia) or an autosomal recessive (Becker's myotonia) trait. Both types are characterised by myotonia (muscle stiffness) and muscular hypertrophy, and are caused by mutations in the muscle chloride channel gene, CLCN1. At least 50 different CLCN1 mutations have been described worldwide, but in many studies only about half of the patients showed mutations in CLCN1. Limitations in the mutation detection methods and genetic heterogeneity might be explanations. In the current study, we sequenced the entire CLCN1 gene in 15 Northern Norwegian and three Northern Swedish MC families. Our data show a high prevalence of myotonia congenita in Northern Norway similar to Northern Finland, but with a much higher degree of mutation heterogeneity. In total, eight different mutations and three polymorphisms (T87T, D718D, and P727L) were detected. Three mutations (F287S, A331T, and 2284+5C>T) were novel while the others (IVS1+3A>T, 979G>A, F413C, A531V, and R894X) have been reported previously. The mutations F413C, A531V, and R894X predominated in our patient material. Compound heterozygosity for A531V/R894X was the predominant genotype. In two probands, three mutations cosegregated with myotonia. No CLCN1 mutations were identified in two families. Our data support the presence of genetic heterogeneity and additional modifying factors in myotonia congenita.

A de novo missense mutation in a critical domain of the X-linked DDP gene causes the typical deafness-dystonia-optic atrophy syndrome.

We report the first de novo mutation in the DDP gene in a Dutch 11-year-old boy with deafness and dystonia. Previously reported mutations in the DDP gene have all been frameshifts/nonsense mutations or deletion of the entire gene as part of a larger deletion encompassing the BTK gene. The clinical presentation was uniformly characterised by sensorineural hearing loss, dystonia, mental deterioration, paranoid psychotic features, and optic atrophy, indicating progressive neurodegeneration. Our report illustrates that de novo mutations occur and that a missense mutation, C66W, may cause an equally severe clinical picture. The diagnosis of sensorineural hearing impairment associated with neurologic and visual disability in a male, therefore, should encourage the search for mutations in the DDP gene, even in sporadic cases. The association of deafness-dystonia syndrome with a missense mutation provides valuable information for in vitro investigations of the functional properties of the deafness-dystonia peptide which was recently shown to be the human homolog of a yeast protein, Tim8p, belonging to a family of small Tim proteins involved in intermembrane protein transport in mitochondria.

A longitudinal study of human cytomegalovirus serology and viruria fails to detect active viral infection in 20 systemic lupus erythematosus patients.

In this study, we investigated whether active human cytomegalovirus infection could be detected in 20 systemic lupus erythematosus (SLE) patients over a one-year observation period by polymerase chain reaction on serial urine specimens and by monitoring of IgG and IgM HCMV-specific antibody profiles in serial serum samples. Of 788 urine samples analysed for the presence of human cytomegalovirus DNA, only 2 specimens (0.25%) collected from two different patients contained genuine human cytomegalovirus sequences as determined by polymerase chain reaction and subsequent sequencing of the PCR products. These two patients had one positive sample out of 36 samples or 40 samples, respectively. Nineteen of the patients (95%) possessed IgG antibodies against human cytomegalovirus, while 9 (45%) produced IgM antibodies. However, none of the patients showed signs of an active virus infection as judged by the stable anti-HCMV IgG or IgM antibody levels during the observation period, nor was any correlation between disease activity and HCMV serology/viruria observed. Of single serum samples of 26 age- and sex-matched blood donors, 21 (81%) were HCMV IgG positive and 1 (3.8%) was IgM seropositive. In conclusion, our data fail to establish an active human cytomegalovirus infection in SLE patients.

BK and JC viruses in patients with systemic lupus erythematosus: prevalent and persistent BK viruria, sequence stability of the viral regulatory regions, and nondetectable viremia.

A role for polyomaviruses in the pathogenesis of systemic lupus erythematosus (SLE) has been suggested. BK virus (BKV) and JC virus (JCV) were demonstrated in single urine specimens from 7 (16%) of 44 and 5 (11%) of 44 patients with SLE and 0/88 and 18 (21%) of 88 matched healthy controls, respectively. During a 1-year follow-up study, episodes of polyomaviruria were detected in 16 (80%) of 20 patients, BKV in 13, and JCV in 3 patients. A group of 12 (60%) of 20 patients demonstrated persistent or recurrent polyomaviruria, BKV viruria (n=9), or JCV viruria (n=3) in 180 (70%) of 256 specimens. Polyomaviruria was not significantly associated with immunosuppressive therapy. The BKV and JCV isolates revealed predominantly stable archetypal regulatory regions over 3 years, indicating viral persistence rather than reinfection as a cause for urinary shedding. The demonstration of nondetectable viremia and stable archetypal BKV and JCV noncoding control regions during persistent viruria argue against the urinary tract as a focus for the creation of rearranged regulatory region variants.

Concerted expression of BK virus large T- and small t-antigens strongly enhances oestrogen receptor-mediated transcription.

Previous studies have shown that the human polyomavirus BK (BKV) genome contains an oestrogen response element (ERE). This isolated element binds its cognate receptor in vitro and can mediate 17beta-oestradiol-induced gene expression when linked to a heterologous promoter. The roles of the ERE- and the AP-1-binding sites in oestrogen receptor-directed transcription from the complete BKV promoter/enhancer (Dunlop strain) have been examined and the effects of the general co-activator CBP and large T- and small t-antigens on oestrogen receptor-mediated transcription have been investigated. A constitutive activated oestrogen receptor stimulated BKV promoter activity in HeLa cells. Mutations in either the ERE- or the AP-1-binding sites did not impair oestrogen receptor-induced activation of the BKV Dunlop promoter, while mutations in both binding motifs almost completely abolished oestrogen receptor-induced transcription. Simultaneous expression of large T- and small t-antigens strongly activated oestrogen receptor-mediated transcription. When expressed separately, only large T-antigen moderately stimulated oestrogen receptor-mediated transcription. The stimulatory effect of large T-antigen on the activity of the oestrogen receptor is probably indirect because no physical interaction between the two proteins was detected in a two-hybrid assay. Large T-antigen abrogated the synergistic effect on transcription between this nuclear receptor and the general co-activator CBP. The findings that the BKV early proteins amplify oestrogen receptor-mediated transcription may have important biological implications in individuals with raised oestrogen concentrations.

Sucrose synthase and enolase expression in actinorhizal nodules of Alnus glutinosa: comparison with legume nodules.

Two different types of nitrogen-fixing root nodules are known- actinorhizal nodules induced by Frankia and legume nodules induced by rhizobia. While legume nodules show a stem-like structure with peripheral vascular bundles, actinorhizal nodule lobes resemble modified lateral roots with a central vascular bundle. To compare carbon metabolism in legume and actinorhizal nodules, sucrose synthase and enolase cDNA clones were isolated from a cDNA library, obtained from actinorhizal nodules of Alnus glutinosa. The expression of the corresponding genes was markedly enhanced in nodules compared to roots. in situ hybridization showed that, in nodules, both sucrose synthase and enolase were expressed at high levels in the infected cortical cells as well as in the pericycle of the central vascular bundle of a nodule lobe. Legume sucrose synthase expression was studied in indeterminate nodules from pea and determinate nodules from Phaseolus vulgaris by using in situ hybridization.

The zebrafish homeobox gene hox[zf-114]: primary structure, expression pattern and evolutionary aspects.

It is gradually becoming accepted that vertebrate homeobox genes, like their counterparts in Drosophila, are crucial for normal development of the embryo. Most vertebrate homeoboxes reported so far are related to the Drosophila Antennapedia (Antp) sequence, and here we describe hox[zf-114], a novel Antp-like homeobox gene from the zebrafish. The sequence of the hox[zf-114] homeodomain indicates that this gene could be a member of a subfamily defined by the mouse Hox-1.5/-2.7/-4.1 genes. However, the evolutionary origin of hox[zf-114] is unclear and, based on the putative protein sequence, we conclude that it is not directly homologous to Hox-1.5, Hox-2.7 or Hox-4.1, or to other known mammalian homeobox genes. Nevertheless, as revealed by in situ hybridization, hox[zf-114] exhibits a spatial expression pattern typical for vertebrate Antp-like homeobox genes. Transcripts are detected in the posterior hindbrain, where a sharp anterior border of expression is observed, and throughout the spinal cord. The hox[zf-114] gene is also active in a region that gives rise to the pectoral fins. These findings suggest a role for hox[zf-114] in anteroposterior patterning of the neural tube and in pectoral fin development.