Pigment cell research / sponsored by the European Society for Pigment Cell Research and the International Pigment Cell Society, 2005
Tyrosinase serves as a key enzyme in the synthesis of melanin. In humans mutations in the TYR gen... more Tyrosinase serves as a key enzyme in the synthesis of melanin. In humans mutations in the TYR gene are associated with type 1 oculocutaneous albinism (OCA1) that leads to reduced or absent pigmentation of skin, hair and eye. Various mutations causing OCA in man, mouse, rabbit and cattle have been identified throughout the Tyrosinase gene including nonsense, missense, frameshift and splice site alterations. Here we report a missense substitution at codon R299H in exon 2 of the Tyr gene in the albino Wistar rat. As this very exchange has already been described in OCA patients, our findings reinforce the significance of this region for normal catalytic activity of tyrosinase protein.
Multiple sclerosis (Houndmills, Basingstoke, England), Jan 5, 2014
Whereas cellular immune function depends on energy supply and mitochondrial function, little is k... more Whereas cellular immune function depends on energy supply and mitochondrial function, little is known on the impact of immunotherapies on cellular energy metabolism. The objective of this paper is to assess the effects of interferon-beta (IFN-β) on mitochondrial function of CD4(+) T cells. Intracellular adenosine triphosphate (iATP) in phytohemagglutinin (PHA)-stimulated CD4(+) cells of multiple sclerosis (MS) patients treated with IFN-β and controls were analyzed in a luciferase-based assay. Mitochondrial-transmembrane potential (ΔΨm) in IFN-β-treated peripheral blood mononuclear cells (PBMCs) was investigated by flow cytometry. Expression of genes involved in mitochondrial oxidative phosphorylation (OXPHOS) in CD4(+) cells of IFN-β-treated individuals and correlations between genetic variants in the key metabolism regulator PGC-1α and IFN-β response in MS were analyzed. IFN-β-treated MS patients exhibited a dose-dependent reduction of iATP levels in CD4(+) T cells compared to cont...
Recent evidence suggests that brain-derived neurotrophic factor (BDNF) is an attractive candidate... more Recent evidence suggests that brain-derived neurotrophic factor (BDNF) is an attractive candidate for modifying age at onset (AO) in Huntington disease (HD). In particular, the functional Val66Met polymorphism appeared to exert a significant effect. Here we evaluate BDNF variability with respect to AO of HD using markers that represent the entire locus. Five selected tagging polymorphisms were genotyped across a 65 kb region comprising the BDNF gene in a well established cohort of 250 unrelated German HD patients. Addition of BDNF genotype variations or one of the marker haplotypes to the effect of CAG repeat lengths did not affect the variance of the AO. We were unable to verify a recently reported association between the functional Val66Met polymorphism in the BDNF gene and AO in HD. From our findings, we conclude that neither sequence variations in nor near the gene contribute significantly to the variance of AO.
A genomic region on chromosome 6p21.3, including HLA-DPB1, has been linked to Wegener's g... more A genomic region on chromosome 6p21.3, including HLA-DPB1, has been linked to Wegener's granulomatosis (WG). The basis of this association is difficult to evaluate because of the complex haplotype block architecture of this region. To identify the causative molecular genetic variation(s) using a detailed HapMap based fine-mapping approach. 282 patients with WG and 380 healthy controls were genotyped for HLA-DPB1 as well as for 35 informative single nucleotide polymorphisms (SNPs) within the respective region. 25 of these SNPs have been selected as tagging SNPs for another 219 associated SNPs. Allele and genotype frequencies were analysed separately by contingency tables and logistic regression. Finally, the coding region of RING1 was directly sequenced in subjects who carried haplotypes that were correlated with contrasting WG risks. The previously reported strong association of WG with the HLA-DPB1*0401 allele was confirmed in an independent WG sample (n = 108, p(c) = 6.4 x 10(-8)). When the complete cohort (n = 282) was considered, the association remained highly significant in ANCA-positive (p(c) = 1.26 x 10(-22)), but not in ANCA-negative patients. An SNP 3' of HLA-DPB1 yielded the smallest p value and was associated with WG partly independently from the HLA-DPB1 alleles. Another informative SNP in the vicinity of RING1 showed significant WG association that was also partly independent of HLA-DPB1. RING1 sequencing, however, did not show any variation potentially predisposing to WG. The HLA-DPB1/RING1 region is strongly associated with WG in ANCA-positive subjects. Further analyses of potential cis regulatory sequences of candidate genes HLA-DPB1, RING1 and RXRB appear warranted.
Episodic ataxia type 1 (EA1) is an autosomal dominant K(+) channelopathy which manifests with sho... more Episodic ataxia type 1 (EA1) is an autosomal dominant K(+) channelopathy which manifests with short attacks of cerebellar ataxia and dysarthria, and may also show interictal myokymia. Episodes can be triggered by emotional or physical stress, startle response, sudden postural change or fever. Here we describe a 31-year-old man displaying markedly atypical symptoms, including long-lasting attacks of jerking muscle contractions associated with hyperthermia, severe migraine, and a relatively short-sleep phenotype. A single nucleotide change in KCNA1 (c.555C>G) was identified that changes a highly conserved residue (p.C185W) in the first transmembrane segment of the voltage-gated K(+) channel Kv1.1. The patient is heterozygous and the mutation was inherited from his asymptomatic mother. Next generation sequencing revealed no variations in the CACNA1A, CACNB4, KCNC3, KCNJ10, PRRT2 or SCN8A genes of either the patient or mother, except for a benign variant in SLC1A3. Functional analysi...
Huntington disease (HD) is a fully penetrant, autosomal dominantly inherited disorder associated ... more Huntington disease (HD) is a fully penetrant, autosomal dominantly inherited disorder associated with abnormal expansions of a stretch of perfect CAG repeats in the 5' part of the IT15 gene. The number of repeat units is highly predictive for the age at onset (AO) of the disorder. But AO is only modestly correlated with repeat length when intermediate HD expansions are considered. Recently, suggestive association has been reported between a single nucleotide polymorphism (SNP; rs1801131, also known as A1298C) in the methyltetrahydrofolate reductase (MTHFR) gene and AO of HD. 5,10-MTHFR is a key enzyme in the folate metabolism, diverting metabolites toward methylation reactions or nucleotide synthesis. Using part of a previously established study cohort plus additional patients and appropriate statistical methods, we reinvestigated two polymorphisms in the MTHFR gene, C677T and A1298C, as well as their association with AO in 167 HD patients. There was no statistically significant...
Several candidate modifier genes which, in addition to the pathogenic CAG repeat expansion, influ... more Several candidate modifier genes which, in addition to the pathogenic CAG repeat expansion, influence the age at onset (AO) in Huntington disease (HD) have already been described. The aim of this study was to replicate association of variations in the N-methyl D-aspartate receptor subtype genes GRIN2A and GRIN2B in the "REGISTRY" cohort from the European Huntington Disease Network (EHDN). The analyses did replicate the association reported between the GRIN2A rs2650427 variation and AO in the entire cohort. Yet, when subjects were stratified by AO subtypes, we found nominally significant evidence for an association of the GRIN2A rs1969060 variation and the GRIN2B rs1806201 variation. These findings further implicate the N-methyl D-aspartate receptor subtype genes as loci containing variation associated with AO in HD.
Pigment cell research / sponsored by the European Society for Pigment Cell Research and the International Pigment Cell Society, 2005
Tyrosinase serves as a key enzyme in the synthesis of melanin. In humans mutations in the TYR gen... more Tyrosinase serves as a key enzyme in the synthesis of melanin. In humans mutations in the TYR gene are associated with type 1 oculocutaneous albinism (OCA1) that leads to reduced or absent pigmentation of skin, hair and eye. Various mutations causing OCA in man, mouse, rabbit and cattle have been identified throughout the Tyrosinase gene including nonsense, missense, frameshift and splice site alterations. Here we report a missense substitution at codon R299H in exon 2 of the Tyr gene in the albino Wistar rat. As this very exchange has already been described in OCA patients, our findings reinforce the significance of this region for normal catalytic activity of tyrosinase protein.
Multiple sclerosis (Houndmills, Basingstoke, England), Jan 5, 2014
Whereas cellular immune function depends on energy supply and mitochondrial function, little is k... more Whereas cellular immune function depends on energy supply and mitochondrial function, little is known on the impact of immunotherapies on cellular energy metabolism. The objective of this paper is to assess the effects of interferon-beta (IFN-β) on mitochondrial function of CD4(+) T cells. Intracellular adenosine triphosphate (iATP) in phytohemagglutinin (PHA)-stimulated CD4(+) cells of multiple sclerosis (MS) patients treated with IFN-β and controls were analyzed in a luciferase-based assay. Mitochondrial-transmembrane potential (ΔΨm) in IFN-β-treated peripheral blood mononuclear cells (PBMCs) was investigated by flow cytometry. Expression of genes involved in mitochondrial oxidative phosphorylation (OXPHOS) in CD4(+) cells of IFN-β-treated individuals and correlations between genetic variants in the key metabolism regulator PGC-1α and IFN-β response in MS were analyzed. IFN-β-treated MS patients exhibited a dose-dependent reduction of iATP levels in CD4(+) T cells compared to cont...
Recent evidence suggests that brain-derived neurotrophic factor (BDNF) is an attractive candidate... more Recent evidence suggests that brain-derived neurotrophic factor (BDNF) is an attractive candidate for modifying age at onset (AO) in Huntington disease (HD). In particular, the functional Val66Met polymorphism appeared to exert a significant effect. Here we evaluate BDNF variability with respect to AO of HD using markers that represent the entire locus. Five selected tagging polymorphisms were genotyped across a 65 kb region comprising the BDNF gene in a well established cohort of 250 unrelated German HD patients. Addition of BDNF genotype variations or one of the marker haplotypes to the effect of CAG repeat lengths did not affect the variance of the AO. We were unable to verify a recently reported association between the functional Val66Met polymorphism in the BDNF gene and AO in HD. From our findings, we conclude that neither sequence variations in nor near the gene contribute significantly to the variance of AO.
A genomic region on chromosome 6p21.3, including HLA-DPB1, has been linked to Wegener's g... more A genomic region on chromosome 6p21.3, including HLA-DPB1, has been linked to Wegener's granulomatosis (WG). The basis of this association is difficult to evaluate because of the complex haplotype block architecture of this region. To identify the causative molecular genetic variation(s) using a detailed HapMap based fine-mapping approach. 282 patients with WG and 380 healthy controls were genotyped for HLA-DPB1 as well as for 35 informative single nucleotide polymorphisms (SNPs) within the respective region. 25 of these SNPs have been selected as tagging SNPs for another 219 associated SNPs. Allele and genotype frequencies were analysed separately by contingency tables and logistic regression. Finally, the coding region of RING1 was directly sequenced in subjects who carried haplotypes that were correlated with contrasting WG risks. The previously reported strong association of WG with the HLA-DPB1*0401 allele was confirmed in an independent WG sample (n = 108, p(c) = 6.4 x 10(-8)). When the complete cohort (n = 282) was considered, the association remained highly significant in ANCA-positive (p(c) = 1.26 x 10(-22)), but not in ANCA-negative patients. An SNP 3' of HLA-DPB1 yielded the smallest p value and was associated with WG partly independently from the HLA-DPB1 alleles. Another informative SNP in the vicinity of RING1 showed significant WG association that was also partly independent of HLA-DPB1. RING1 sequencing, however, did not show any variation potentially predisposing to WG. The HLA-DPB1/RING1 region is strongly associated with WG in ANCA-positive subjects. Further analyses of potential cis regulatory sequences of candidate genes HLA-DPB1, RING1 and RXRB appear warranted.
Episodic ataxia type 1 (EA1) is an autosomal dominant K(+) channelopathy which manifests with sho... more Episodic ataxia type 1 (EA1) is an autosomal dominant K(+) channelopathy which manifests with short attacks of cerebellar ataxia and dysarthria, and may also show interictal myokymia. Episodes can be triggered by emotional or physical stress, startle response, sudden postural change or fever. Here we describe a 31-year-old man displaying markedly atypical symptoms, including long-lasting attacks of jerking muscle contractions associated with hyperthermia, severe migraine, and a relatively short-sleep phenotype. A single nucleotide change in KCNA1 (c.555C>G) was identified that changes a highly conserved residue (p.C185W) in the first transmembrane segment of the voltage-gated K(+) channel Kv1.1. The patient is heterozygous and the mutation was inherited from his asymptomatic mother. Next generation sequencing revealed no variations in the CACNA1A, CACNB4, KCNC3, KCNJ10, PRRT2 or SCN8A genes of either the patient or mother, except for a benign variant in SLC1A3. Functional analysi...
Huntington disease (HD) is a fully penetrant, autosomal dominantly inherited disorder associated ... more Huntington disease (HD) is a fully penetrant, autosomal dominantly inherited disorder associated with abnormal expansions of a stretch of perfect CAG repeats in the 5' part of the IT15 gene. The number of repeat units is highly predictive for the age at onset (AO) of the disorder. But AO is only modestly correlated with repeat length when intermediate HD expansions are considered. Recently, suggestive association has been reported between a single nucleotide polymorphism (SNP; rs1801131, also known as A1298C) in the methyltetrahydrofolate reductase (MTHFR) gene and AO of HD. 5,10-MTHFR is a key enzyme in the folate metabolism, diverting metabolites toward methylation reactions or nucleotide synthesis. Using part of a previously established study cohort plus additional patients and appropriate statistical methods, we reinvestigated two polymorphisms in the MTHFR gene, C677T and A1298C, as well as their association with AO in 167 HD patients. There was no statistically significant...
Several candidate modifier genes which, in addition to the pathogenic CAG repeat expansion, influ... more Several candidate modifier genes which, in addition to the pathogenic CAG repeat expansion, influence the age at onset (AO) in Huntington disease (HD) have already been described. The aim of this study was to replicate association of variations in the N-methyl D-aspartate receptor subtype genes GRIN2A and GRIN2B in the "REGISTRY" cohort from the European Huntington Disease Network (EHDN). The analyses did replicate the association reported between the GRIN2A rs2650427 variation and AO in the entire cohort. Yet, when subjects were stratified by AO subtypes, we found nominally significant evidence for an association of the GRIN2A rs1969060 variation and the GRIN2B rs1806201 variation. These findings further implicate the N-methyl D-aspartate receptor subtype genes as loci containing variation associated with AO in HD.
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