| 1. |
- Hackman, Peter
(författare)
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HPRT mutational spectra and microsatellite DNA instability in HNPCC and lung cancer patients
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The, general aims of this work have been to explore the use of microsatellite DNA length variation and mutational spectra of the hypoxanthine guanine phosphoribosyltransferase (HPRT) locus in T-cells as tools for a better understanding of human somatic mutagenesis in vivo. In particular (a) how inherited mismatch repair (MMR) deficiency may affect the stability of microsatellite DNA and the mutational spectrum at the HPRT locus, and (b) how the mutational spectrum at the HPRT locus is influenced by smoking, and by predisposition to lung cancer among never smokers. Microsatellite DNA length variation (MSDLV) was studied in DNA from T-cell clones and peripheral blood lymphocytes, using suitable markers for PCR analysis and polyacrylamide gel electrophoresis. T-cell cloning in medium containing 6-thioguanine was used to select for HPRT mutant clones, and the mutations were further classified and characterised by PCR-based methods and DNA sequencing. The background frequency of MSDLV in peripheral lymphocytes was determined using three microsatellite markers (D2S123, D9S180, D10S197). 3 out of 1028 alleles studied in T-cell clones of normal healthy subjects, showed altered microsatellite size compared to other clones from the same individual. Thus the background MSDLV was estimated to 2.9 x 10-3. We then analysed the MSDLV and HPRT mutant frequency (MF) in a breast cancer patient belonging to a hereditary nonpolyposis colorectal carcinoma (HNPCC) family, with two different mutations in her hMLH1 genes. This compound heterozygote showed a frequency of microsatellite length variation of 18.9 % per allele, which was 50 times higher than the background frequency. The HPRT MF of 34.5 x 10-6 was elevated 2-3 times compared to controls. The HPRT mutational spectrum of this patient was significantly different from normal, with a shift from base pair substitutions towards frameshifts, especially + 1bp insertions, and deletions. Also two new basepair mutations not reported earlier were seen and two of the clones studied had two mutations each, which is very unusual. We concluded that the patient was likely to have a mild MMR deficiency in her somatic cells due to the mutations in both of her hMLH1 genes, and that this was the cause of her microsatellite instability (MSI), increased HPRT MF and abnormal HPRT mutational spectrum. The HPRT mutational spectrum was studied in 73 T-cell clones each from smoking and nonsmoking lung cancer patients. The proportions of different types of mutations, were not significantly different between smokers and nonsmokers, although the smokers had less deletions. The distribution of basepair substitutions was nonrandom, with clustering at previously identified hotspots at positions 143, 197 and 617 of the HPRT coding sequence. One additional hotspot at position 606 was observed, in smokers only. The frequency of GC>TA transversions (13%) was higher in smokers than in nonsmokers (6%). Conversely smokers had a lower frequency of GC>AT transitions (24 %) than nonsmokers (35 %). We concluded that there was a minor effect of smoking on the HPRT mutational spectra, with a trend for increase of GC>TA transversions and decrease of GC>AT transitions, in the smokers compared to the nonsmokers. This is consistent with the in vitro mutagenicity of benzo(a)pyrene, one of the prominent carcinogens of tobacco smoke. In conclusion, these results show that analysis of HPRT mutations may contribute to the understanding of somatic mutagenesis in vivo, and that the mutational spectrum at the HPRT locus may reflect abnormalities of repair and extensive environmental exposure, such as tobacco smoking.
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| 2. |
- Palmio, Johanna, et al.
(författare)
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Hereditary myopathy with early respiratory failure: occurrence in various populations
- 2014
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Ingår i: Journal of Neurology, Neurosurgery and Psychiatry. - : BMJ. - 1468-330X .- 0022-3050. ; 85:3, s. 345-353
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Tidskriftsartikel (refereegranskat)abstract
- Objective Several families with characteristic features of hereditary myopathy with early respiratory failure (HMERF) have remained without genetic cause. This international study was initiated to clarify epidemiology and the genetic underlying cause in these families, and to characterise the phenotype in our large cohort. Methods DNA samples of all currently known families with HMERF without molecular genetic cause were obtained from 12 families in seven different countries. Clinical, histopathological and muscle imaging data were collected and five biopsy samples made available for further immunohistochemical studies. Genotyping, exome sequencing and Sanger sequencing were used to identify and confirm sequence variations. Results All patients with clinical diagnosis of HMERF were genetically solved by five different titin mutations identified. One mutation has been reported while four are novel, all located exclusively in the FN3 119 domain (A150) of A-band titin. One of the new mutations showed semirecessive inheritance pattern with subclinical myopathy in the heterozygous parents. Typical clinical features were respiratory failure at mid-adulthood in an ambulant patient with very variable degree of muscle weakness. Cytoplasmic bodies were retrospectively observed in all muscle biopsy samples and these were reactive for myofibrillar proteins but not for titin. Conclusions We report an extensive collection of families with HMERF with five different mutations in exon 343 of TTN, which establishes this exon as the primary target for molecular diagnosis of HMERF. Our relatively large number of new families and mutations directly implies that HMERF is not extremely rare, not restricted to Northern Europe and should be considered in undetermined myogenic respiratory failure.
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| 3. |
- Raheem, Olayinka, et al.
(författare)
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Hartia-lantiodystrofioiden molekyyligenetiikka Suomessa
- 2006
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Ingår i: Duodecim; lääketieteellinen aikakauskirja. - 0012-7183. ; 122:17, s. 2130-2136
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Tidskriftsartikel (refereegranskat)abstract
- Hartia-lantiolihasdystrofia (limb girdle muscular dystrophy, LGMD) oli ennen kyseisen taudin geenien löytämistä käytetty diagnoosi potilasryhmälle, jolla ei ole todettu muuta tunnistettua dystrofiaa, kuten X-kromosomaalista Duchennen tai Beckerin lihasdystrofiaa, vallitsevasti periytyvää fasioskapulohumeraalista lihasdystrofiaa, distaalista myopatiaa tai synnynnäistä lihasdystrofiaa. Suomessa tämän ryhmän potilailla on usein ollut diagnoosina dystrophia musculorum progressiva NUD. Vuonna 1991 löydettiin ensimmäinen LGMD:tä aiheuttava geenivirhe, ja nykyään voidaan molekyyligeneettisesti eritellä 17 eri alalajia, eivätkä nämäkään kata kaikkia tapauksia. Joidenkin alalajien diagnoosi on ollut mahdollista tehdä proteiinipuutoksen osoittavalla immunohistokemiallisella biopsialeikkeen värjäyksellä, ja menetelmä on tarjolla maamme neuropatologian laboratorioissa. TAYS:aan perustetussa lihastautien erityisdiagnostiikan keskuksessa on mahdollista etsiä tämän ryhmän geeni- ja proteiinivirheitä DNA- ja Western blotting -menetelmin. Mutaatiot kalpaiini 3-, FKRP- (fukutin-related protein) ja alfasarkoglykaanigeeneissä näyttävät olevan tärkeimmät suomalaisessa väestössä.
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| 4. |
- Savarese, Marco, et al.
(författare)
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Genotype-phenotype correlations in recessive titinopathies.
- 2020
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Ingår i: Genetics in Medicine. - : Elsevier BV. - 1098-3600 .- 1530-0366. ; 22:12, s. 2029-2040
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: High throughput sequencing analysis has facilitated the rapid analysis of the entire titin (TTN) coding sequence. This has resulted in the identification of a growing number of recessive titinopathy patients. The aim of this study was to (1) characterize the causative genetic variants and clinical features of the largest cohort of recessive titinopathy patients reported to date and (2) to evaluate genotype-phenotype correlations in this cohort.METHODS: We analyzed clinical and genetic data in a cohort of patients with biallelic pathogenic or likely pathogenic TTN variants. The cohort included both previously reported cases (100 patients from 81 unrelated families) and unreported cases (23 patients from 20 unrelated families).RESULTS: Overall, 132 causative variants were identified in cohort members. More than half of the cases had hypotonia at birth or muscle weakness and a delayed motor development within the first 12 months of life (congenital myopathy) with causative variants located along the entire gene. The remaining patients had a distal or proximal phenotype and a childhood or later (noncongenital) onset. All noncongenital cases had at least one pathogenic variant in one of the final three TTN exons (362-364).CONCLUSION: Our findings suggest a novel association between the location of nonsense variants and the clinical severity of the disease.
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| 5. |
- Wallgren-Pettersson, Carina, et al.
(författare)
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Distal myopathy caused by homozygous missense mutations in the nebulin gene
- 2007
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Ingår i: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 130:Pt 6, s. 1465-1476
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Tidskriftsartikel (refereegranskat)abstract
- We describe a novel, recessively inherited distal myopathy caused by homozygous missense mutations in the nebulin gene (NEB), in which other combinations of mutations are known to cause nemaline (rod) myopathy (NM). Two different missense mutations were identified in homozygous form in seven Finnish patients from four unrelated families with childhood or adult-onset foot drop. Both mutations, when combined in compound heterozygous form with more disruptive mutations in NEB, are known to cause NM. Hitherto, no patients with NM have been found to have two missense mutations in NEB. Muscle weakness predominantly affected ankle dorsiflexors, finger extensors and neck flexors, a distribution different both from the patterns of weakness seen in NM caused by NEB mutations, and those of the known recessively inherited distal myopathies. Singleton cases need to be distinguished from the Laing type of distal myopathy. Histologically, this myopathy differs from NM in that nemaline bodies were not detectable with routine light microscopy, and they were inconspicuous or absent even with electron microscopy. Rimmed vacuoles, commonly seen in other distal myopathies, were not a feature. We conclude that homozygous missense mutations in NEB cause a novel distal myopathy, predominantly involving lower leg extensor muscles, finger extensors and neck flexors.
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