| 291. |
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| 292. |
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| 293. |
- Nordin, Angelica, et al.
(författare)
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Extensive size variability of the GGGGCC expansion in C9orf72 in both neuronal and non-neuronal tissues in 18 patients with ALS or FTD
- 2015
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 24:11, s. 3133-3142
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Tidskriftsartikel (refereegranskat)abstract
- A GGGGCC-repeat expansion in C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) among Caucasians. However, little is known about the variability of the GGGGCC expansion in different tissues and whether this correlates with the observed phenotype. Here, we used Southern blotting to estimate the size of hexanucleotide expansions in C9orf72 in neural and non-neural tissues from 18 autopsied ALS and FTD patients with repeat expansion in blood. Digitalization of the Southern blot images allowed comparison of repeat number, smear distribution and expansion band intensity between tissues and between patients. We found marked intra-individual variation of repeat number between tissues, whereas there was less variation within each tissue group. In two patients, the size variation between tissues was extreme, with repeat numbers below 100 in all studied non-neural tissues, whereas expansions in neural tissues were 20-40 times greater and in the same size range observed in neural tissues of the other 16 patients. The expansion pattern in different tissues could not distinguish between diagnostic groups and no correlation was found between expansion size in frontal lobe and occurrence of cognitive impairment. In ALS patients, a less number of repeats in the cerebellum and parietal lobe correlated with earlier age of onset and a larger number of repeats in the parietal lobe correlated with a more rapid progression. In 43 other individuals without repeat expansion in blood, we find that repeat sizes up to 15 are stable, as no size variation between blood, brain and spinal cord was found.
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| 294. |
- Ochala, Julien, et al.
(författare)
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Congenital myopathy-causing tropomyosin mutations induce thin filament dysfunction via distinct physiological mechanisms
- 2012
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 21:20, s. 4473-4485
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Tidskriftsartikel (refereegranskat)abstract
- In humans, congenital myopathy-linked tropomyosin mutations lead to skeletal muscle dysfunction, but the cellular and molecular mechanisms underlying such dysfunction remain obscure. Recent studies have suggested a unifying mechanism by which tropomyosin mutations partially inhibit thin filament activation and prevent proper formation and cycling of myosin cross-bridges, inducing force deficits at the fiber and whole-muscle levels. Here, we aimed to verify this mechanism using single membrane-permeabilized fibers from patients with three tropomyosin mutations (TPM2-null, TPM3-R167H and TPM2-E181K) and measuring a broad range of parameters. Interestingly, we identified two divergent, mutation-specific pathophysiological mechanisms. (i) The TPM2-null and TPM3-R167H mutations both decreased cooperative thin filament activation in combination with reductions in the myosin cross-bridge number and force production. The TPM3-R167H mutation also induced a concomitant reduction in thin filament length. (ii) In contrast, the TPM2-E181K mutation increased thin filament activation, cross-bridge binding and force generation. In the former mechanism, modulating thin filament activation by administering troponin activators (CK-1909178 and EMD 57033) to single membrane-permeabilized fibers carrying tropomyosin mutations rescued the thin filament activation defect associated with the pathophysiology. Therefore, administration of troponin activators may constitute a promising therapeutic approach in the future.
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| 295. |
- Ohta, Yasuyuki, et al.
(författare)
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Sex-dependent effects of chromogranin B P413L allelic variant as disease modifier in amyotrophic lateral sclerosis
- 2016
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Ingår i: Human Molecular Genetics. - : OXFORD UNIV PRESS. - 0964-6906 .- 1460-2083. ; 25:21, s. 4771-4786
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Tidskriftsartikel (refereegranskat)abstract
- Recent genetic studies yielded conflicting results regarding a role for the variant chromogranin B (CHGB)(P413L) allele as a disease modifier in ALS. Moreover, potential deleterious effects of the CHG(BP413L) variant in ALS pathology have not been investigated. Here we report that in transfected cultured cells, the variant CHGB(L413) protein exhibited aberrant properties including mislocalization, failure to interact with mutant superoxide dismutase 1 (SOD1) and defective secretion. The CHGB(L413) transgene in SOD1(G37R) mice precipitated disease onset and pathological changes related to misfolded SOD1 specifically in female mice. However, the CHGB(L413) variant also slowed down disease progression in SOD1(G37R) mice, which is in line with a very slow disease progression that we report for a Swedish woman with ALS who is carrier of two mutant SOD1(D90A) alleles and two variant CHGB(P413)L and CHGB(R458Q) alleles. In contrast, overexpression of the common CHGB(P413) allele in SOD1(G37R) mice did not affect disease onset but significantly accelerated disease progression and pathological changes. As in transgenic mice, the CHGB(P413L) allele conferred an earlier ALS disease onset in women of Japanese and French Canadian origins with less effect in men. Evidence is presented that the sex-dependent effects of CHGB(L413) allelic variant in ALS may arise from enhanced neuronal expression of CHGB in females because of a sex-determining region Y element in the gene promoter. Thus, our results suggest that CHGB variants may act as modifiers of onset and progression in some ALS populations and especially in females because of higher expression levels compared to males.
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| 296. |
- Oldfors Hedberg, Carola, 1969, et al.
(författare)
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Cardiomyopathy with lethal arrhythmias associated with inactivation of KLHL24
- 2019
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 28:11, s. 1919-1929
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Tidskriftsartikel (refereegranskat)abstract
- Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiovascular disorder, yet the genetic cause of up to 50% of cases remains unknown. Here, we show that mutations in KLHL24 cause HCM in humans. Using genome-wide linkage analysis and exome sequencing, we identified homozygous mutations in KLHL24 in two consanguineous families with HCM. Of the 11 young affected adults identified, 3 died suddenly and 1 had a cardiac transplant due to heart failure. KLHL24 is a member of the Kelch-like protein family, which acts as substrate-specific adaptors to Cullin E3 ubiquitin ligases. Endomyocardial and skeletal muscle biopsies from affected individuals of both families demonstrated characteristic alterations, including accumulation of desmin intermediate filaments. Knock-down of the zebrafish homologue klhl24a results in heart defects similar to that described for other HCM-linked genes providing additional support for KLHL24 as a HCM-associated gene. Our findings reveal a crucial role for KLHL24 in cardiac development and function.
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| 297. |
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| 298. |
- Olive, M., et al.
(författare)
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New cardiac and skeletal protein aggregate myopathy associated with combined MuRF1 and MuRF3 mutations
- 2015
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 24:13, s. 3638-3650
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Tidskriftsartikel (refereegranskat)abstract
- Protein aggregate myopathies (PAMs) define muscle disorders characterized by protein accumulation in muscle fibres. We describe a new PAM in a patient with proximal muscle weakness and hypertrophic cardiomyopathy, whose muscle fibres contained inclusions containing myosin and myosin-associated proteins, and aberrant distribution of microtubules. These lesions appear as intact A- and M-bands lacking thin filaments and Z-discs. These features differ from inclusions in myosin storage myopathy (MSM), but are highly similar to those in mice deficient for the muscle-specific RING finger proteins MuRF1 and MuRF3. Sanger sequencing excluded mutations in the MSM-associated gene MYH7 but identified mutations in TRIM63 and TRIM54, encoding MuRF1 and MuRF3, respectively. No mutations in other potentially disease-causing genes were identified by Sanger and whole exome sequencing. Analysis of seven family members revealed that both mutations segregated in the family but only the homozygous TRIM63 null mutation in combination with the heterozygous TRIM54 mutation found in the proband caused the disease phenotype. Both MuRFs are microtubule-associated proteins localizing to sarcomeric M-bands and Z-discs. They are E3 ubiquitin ligases that play a role in degradation of sarcomeric proteins, stabilization of microtubules and myogenesis. Lack of ubiquitin and the 20S proteasome subunit in the inclusions found in the patient suggested impaired turnover of thick filament proteins. Disruption of microtubules in cultured myotubes was rescued by transient expression of wild-type MuRF1. The unique features of this novel myopathy point to defects in homeostasis of A-band proteins in combination with instability of microtubules as cause of the disease.
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| 299. |
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| 300. |
- Olsson, Angelica, 1982-, et al.
(författare)
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Myopathy with lactic acidosis is linked to chromosome 12q23.3-24.11 and caused by an intron mutation in the ISCU gene resulting in a splicing defect
- 2008
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 17:11, s. 1666-1672
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Tidskriftsartikel (refereegranskat)abstract
- We describe the mapping and identification of the gene for hereditary myopathy with lactic acidosis (HML). HML is characterized by low physical performance, resulting in physical exertion that causes early exhaustion, dyspnoea and palpitations. Using an autosomal recessive mode of inheritance, we mapped the trait to chromosome 12q23.3-24.11, with a maximum lod score of 5.26. The 1.6-Mb disease-critical region contained one obvious candidate gene-ISCU-specifying a protein involved in iron-sulphur cluster assembly. IscU is produced in two isoforms; one cytosolic and one mitochondrial, coded for by different splice variants of the ISCU gene. Mutational analysis of all exon and intron sequences as well as 1000 bp of the promoter of the ISCU gene revealed one intron mutation that was specific for the disease haplotype. The mutation is located in a region with homology to the interferon-stimulated response element (ISRE), but we could not see any effect of the mutation on expression levels in vitro or in vivo. We did, however, observe a drastic difference in the splicing pattern between patients and controls. In controls the mRNA was, as expected, mainly in the mitochondrial form, while in the patients a larger mRNA transcript was predominant. Sequencing of the product revealed that the mutation activates cryptic splice sites in intron 5 resulting in aberrant mRNA containing 100 bp of the intron. To conclude, our data strongly suggest that an intron mutation in the ISCU gene, leading to incorrectly spliced mRNA, is the cause of myopathy with lactic acidosis in this family.
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