ORCID Profile
0000-0001-9190-4336
Current Organisations
Institute for Molecular Medicine Finland
,
University of Helsinki
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Publisher: Hindawi Limited
Date: 2006
DOI: 10.1002/HUMU.20370
Abstract: Nemaline myopathy (NM) is a clinically and genetically heterogeneous disorder of skeletal muscle caused by mutations in at least five different genes encoding thin filament proteins of the striated muscle sarcomere. We have previously described 18 different mutations in the last 42 exons of the nebulin gene (NEB) in 18 families with NM. Here we report 45 novel NEB mutations detected by denaturing high-performance liquid chromatography (dHPLC) and sequence analysis of all 183 NEB exons in NM patients from 44 families. Altogether we have identified, including the deletion of exon 55 identified in the Ashkenazi Jewish population, 64 different mutations in NEB segregating with autosomal recessive NM in 55 families. The majority (55%) of the mutations in NEB are frameshift or nonsense mutations predicted to cause premature truncation of nebulin. Point mutations (25%) or deletions (3%) affecting conserved splice signals are predicted in the majority of cases to cause in-frame exon skipping, possibly leading to impaired nebulin-tropomyosin interaction along the thin filament. Patients in 18 families had one of nine missense mutations (14%) affecting conserved amino acids at or in the vicinity of actin or tropomyosin binding sites. In addition, we found the exon 55 deletion in four families. The majority of the patients (in 49/55 families) were shown to be compound heterozygous for two different mutations. The mutations were found in both constitutively and alternatively expressed exons throughout the NEB gene, and there were no obvious mutational hotspots. Patients with more severe clinical pictures tended to have mutations predicted to be more disruptive than patients with milder forms.
Publisher: Hindawi Limited
Date: 24-11-2014
DOI: 10.1002/HUMU.22693
Publisher: Portland Press Ltd.
Date: 27-01-2012
DOI: 10.1042/BJ20111030
Abstract: NM (nemaline myopathy) is a rare genetic muscle disorder defined on the basis of muscle weakness and the presence of structural abnormalities in the muscle fibres, i.e. nemaline bodies. The related disorder cap myopathy is defined by cap-like structures located peripherally in the muscle fibres. Both disorders may be caused by mutations in the TPM2 gene encoding β-Tm (tropomyosin). Tm controls muscle contraction by inhibiting actin–myosin interaction in a calcium-sensitive manner. In the present study, we have investigated the pathogenetic mechanisms underlying five disease-causing mutations in Tm. We show that four of the mutations cause changes in affinity for actin, which may cause muscle weakness in these patients, whereas two show defective Ca2+ activation of contractility. We have also mapped the amino acids altered by the mutation to regions important for actin binding and note that two of the mutations cause altered protein conformation, which could account for impaired actin affinity.
Publisher: Proceedings of the National Academy of Sciences
Date: 02-03-1999
Abstract: The congenital nemaline myopathies are rare hereditary muscle disorders characterized by the presence in the muscle fibers of nemaline bodies consisting of proteins derived from the Z disc and thin filament. In a single large Australian family with an autosomal dominant form of nemaline myopathy, the disease is caused by a mutation in the α-tropomyosin gene TPM3 . The typical form of nemaline myopathy is inherited as an autosomal recessive trait, the locus of which we previously assigned to chromosome 2q21.2-q22. We show here that mutations in the nebulin gene located within this region are associated with the disease. The nebulin protein is a giant protein found in the thin filaments of striated muscle. A variety of nebulin isoforms are thought to contribute to the molecular ersity of Z discs. We have studied the 3′ end of the 20.8-kb cDNA encoding the Z disc part of the 800-kDa protein and describe six disease-associated mutations in patients from five families of different ethnic origins. In two families with consanguineous parents, the patients were homozygous for point mutations. In one family with nonconsanguineous parents, the affected siblings were compound heterozygotes for two different mutations, and in two further families with one detected mutation each, haplotypes are compatible with compound heterozygosity. Immunofluorescence studies with antibodies specific to the C-terminal region of nebulin indicate that the mutations may cause protein truncation possibly associated with loss of fiber-type ersity, which may be relevant to disease pathogenesis.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 27-10-2021
DOI: 10.1212/NXG.0000000000000632
Abstract: To determine the genetic cause of the disease in the previously reported family with adult-onset autosomal dominant distal myopathy (myopathy, distal, 3 MPD3). Continued clinical evaluation including muscle MRI and muscle pathology. A linkage analysis with single nucleotide polymorphism arrays and genome sequencing were used to identify the genetic defect, which was verified by Sanger sequencing. RNA sequencing was used to investigate the transcriptional effects of the identified genetic defect. Small hand muscles (intrinsic, thenar, and hypothenar) were first involved with spread to the lower legs and later proximal muscles. Dystrophic changes with rimmed vacuoles and cytoplasmic inclusions were observed in muscle biopsies at advanced stage. A single nucleotide polymorphism array confirmed the previous microsatellite-based linkage to 8p22-q11 and 12q13-q22. Genome sequencing of three affected family members combined with structural variant calling revealed a small heterozygous deletion of 160 base pairs spanning the second last exon 10 of the heterogeneous nuclear ribonucleoprotein A1 ( HNRNPA1) gene, which is in the linked region on chromosome 12. Segregation of the mutation with the disease was confirmed by Sanger sequencing. RNA sequencing showed that the mutant allele produces a shorter mutant mRNA transcript compared with the wild-type allele. Immunofluorescence studies on muscle biopsies revealed small p62 and larger TDP-43 inclusions. A small exon 10 deletion in the gene HNRNPA1 was identified as the cause of MPD3 in this family. The new HNRNPA1-related phenotype, upper limb presenting distal myopathy, was thus confirmed, and the family displays the complexities of gene identification.
Publisher: Springer Science and Business Media LLC
Date: 10-1999
DOI: 10.1038/13837
Abstract: Muscle contraction results from the force generated between the thin filament protein actin and the thick filament protein myosin, which causes the thick and thin muscle filaments to slide past each other. There are skeletal muscle, cardiac muscle, smooth muscle and non-muscle isoforms of both actin and myosin. Inherited diseases in humans have been associated with defects in cardiac actin (dilated cardiomyopathy and hypertrophic cardiomyopathy), cardiac myosin (hypertrophic cardiomyopathy) and non-muscle myosin (deafness). Here we report that mutations in the human skeletal muscle alpha-actin gene (ACTA1) are associated with two different muscle diseases, 'congenital myopathy with excess of thin myofilaments' (actin myopathy) and nemaline myopathy. Both diseases are characterized by structural abnormalities of the muscle fibres and variable degrees of muscle weakness. We have identified 15 different missense mutations resulting in 14 different amino acid changes. The missense mutations in ACTA1 are distributed throughout all six coding exons, and some involve known functional domains of actin. Approximately half of the patients died within their first year, but two female patients have survived into their thirties and have children. We identified dominant mutations in all but 1 of 14 families, with the missense mutations being single and heterozygous. The only family showing dominant inheritance comprised a 33-year-old affected mother and her two affected and two unaffected children. In another family, the clinically unaffected father is a somatic mosaic for the mutation seen in both of his affected children. We identified recessive mutations in one family in which the two affected siblings had heterozygous mutations in two different exons, one paternally and the other maternally inherited. We also identified de novo mutations in seven sporadic probands for which it was possible to analyse parental DNA.
Publisher: Springer Science and Business Media LLC
Date: 02-04-2008
DOI: 10.1038/EJHG.2008.60
Abstract: To date, six genes are known to cause nemaline (rod) myopathy (NM), a rare congenital neuromuscular disorder. In an attempt to find a seventh gene, we performed linkage and subsequent sequence analyses in 12 Turkish families with recessive NM. We found homozygosity in two of the families at 1q12-21.2, a region encompassing the gamma-tropomyosin gene (TPM3) encoding slow skeletal muscle alpha-tropomyosin, a known NM gene. Sequencing revealed homozygous deletion of the first nucleotide of the last exon, c.913delA of TPM3 in both families. The mutation removes the last nucleotide before the stop codon, causing a frameshift and readthrough across the termination signal. The encoded alphaTm(slow) protein is predicted to be 73 amino acids longer than normal, and the extension to the protein is hypothesised to be unable to form a coiled coil. The resulting tropomyosin protein may therefore be non-functional. The affected children in both families were homozygous for the mutation, while the healthy parents were mutation carriers. Both of the patients in Family 1 had the severe form of NM, and also an unusual chest deformity. The affected children in Family 2 had the intermediate form of NM. Muscle biopsies showed type 1 (slow) fibres to be markedly smaller than type 2 (fast) fibres. Previously, there had been five reports, only, of NM caused by mutations in TPM3. The mutation reported here is the first deletion to be identified in TPM3, and it is likely to be a founder mutation in the Turkish population.
Publisher: Springer Science and Business Media LLC
Date: 07-03-2022
DOI: 10.1038/S41586-022-04576-6
Abstract: Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care 1 or hospitalization 2–4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from in iduals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill in iduals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling ( IL10RB and PLSCR1 ), leucocyte differentiation ( BCL11A ) and blood-type antigen secretor status ( FUT2 ). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase ( ATP11A ), and increased expression of a mucin ( MUC1 )—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules ( SELE , ICAM5 and CD209 ) and the coagulation factor F8 , all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease.
Publisher: Springer Science and Business Media LLC
Date: 08-07-2021
DOI: 10.1038/S41586-021-03767-X
Abstract: The genetic make-up of an in idual contributes to the susceptibility and response to viral infection. Although environmental, clinical and social factors have a role in the chance of exposure to SARS-CoV-2 and the severity of COVID-19 1,2 , host genetics may also be important. Identifying host-specific genetic factors may reveal biological mechanisms of therapeutic relevance and clarify causal relationships of modifiable environmental risk factors for SARS-CoV-2 infection and outcomes. We formed a global network of researchers to investigate the role of human genetics in SARS-CoV-2 infection and COVID-19 severity. Here we describe the results of three genome-wide association meta-analyses that consist of up to 49,562 patients with COVID-19 from 46 studies across 19 countries. We report 13 genome-wide significant loci that are associated with SARS-CoV-2 infection or severe manifestations of COVID-19. Several of these loci correspond to previously documented associations to lung or autoimmune and inflammatory diseases 3–7 . They also represent potentially actionable mechanisms in response to infection. Mendelian randomization analyses support a causal role for smoking and body-mass index for severe COVID-19 although not for type II diabetes. The identification of novel host genetic factors associated with COVID-19 was made possible by the community of human genetics researchers coming together to prioritize the sharing of data, results, resources and analytical frameworks. This working model of international collaboration underscores what is possible for future genetic discoveries in emerging pandemics, or indeed for any complex human disease.
Publisher: Springer Science and Business Media LLC
Date: 11-05-2021
DOI: 10.1007/S00401-021-02319-X
Abstract: Using deep phenotyping and high-throughput sequencing, we have identified a novel type of distal myopathy caused by mutations in the Small muscle protein X-linked ( SMPX ) gene. Four different missense mutations were identified in ten patients from nine families in five different countries, suggesting that this disease could be prevalent in other populations as well. Haplotype analysis of patients with similar ancestry revealed two different founder mutations in Southern Europe and France, indicating that the prevalence in these populations may be higher. In our study all patients presented with highly similar clinical features: adult-onset, usually distal more than proximal limb muscle weakness, slowly progressing over decades with preserved walking. Lower limb muscle imaging showed a characteristic pattern of muscle involvement and fatty degeneration. Histopathological and electron microscopic analysis of patient muscle biopsies revealed myopathic findings with rimmed vacuoles and the presence of sarcoplasmic inclusions, some with amyloid-like characteristics. In silico predictions and subsequent cell culture studies showed that the missense mutations increase aggregation propensity of the SMPX protein. In cell culture studies, overexpressed SMPX localized to stress granules and slowed down their clearance.
No related grants have been discovered for Kati Donner.