[Show abstract][Hide abstract] ABSTRACT: Many neurodegenerative disorders present with sensory loss. In the group of hereditary sensory and autonomic neuropathies loss of nociception is one of the disease hallmarks. To determine underlying factors of sensory neurodegeneration we performed whole-exome sequencing in affected individuals with the disorder. In a family with sensory neuropathy with loss of pain perception and destruction of the pedal skeleton we report a missense mutation in a highly conserved amino acid residue of atlastin GTPase 3 (ATL3), an endoplasmic reticulum-shaping GTPase. The same mutation (p.Tyr192Cys) was identified in a second family with similar clinical outcome by screening a large cohort of 115 patients with hereditary sensory and autonomic neuropathies. Both families show an autosomal dominant pattern of inheritance and the mutation segregates with complete penetrance. ATL3 is a paralogue of ATL1, a membrane curvature-generating molecule that is involved in spastic paraplegia and hereditary sensory neuropathy. ATL3 proteins are enriched in three-way junctions, branch points of the endoplasmic reticulum that connect membranous tubules to a continuous network. Mutant ATL3 p.Tyr192Cys fails to localize to branch points, but instead disrupts the structure of the tubular endoplasmic reticulum, suggesting that the mutation exerts a dominant-negative effect. Identification of ATL3 as novel disease-associated gene exemplifies that long-term sensory neuronal maintenance critically depends on the structural organisation of the endoplasmic reticulum. It emphasizes that alterations in membrane shaping-proteins are one of the major emerging pathways in axonal degeneration and suggests that this group of molecules should be considered in neuroprotective strategies.
[Show abstract][Hide abstract] ABSTRACT: Retinitis pigmentosa (RP) and Leber congenital amaurosis (LCA) are major causes of blindness. They result from mutations in many genes which has long hampered comprehensive genetic analysis. Recently, targeted next-generation sequencing (NGS) has proven useful to overcome this limitation. To uncover "hidden mutations" such as copy number variations (CNVs) and mutations in non-coding regions, we extended the use of NGS data by quantitative readout for the exons of 55 RP and LCA genes in 126 patients, and by including non-coding 5' exons. We detected several causative CNVs which were key to the diagnosis in hitherto unsolved constellations, e.g. hemizygous point mutations in consanguineous families, and CNVs complemented apparently monoallelic recessive alleles. Mutations of non-coding exon 1 of EYS revealed its contribution to disease. In view of the high carrier frequency for retinal disease gene mutations in the general population, we considered the overall variant load in each patient to assess if a mutation was causative or reflected accidental carriership in patients with mutations in several genes or with single recessive alleles. For example, truncating mutations in RP1, a gene implicated in both recessive and dominant RP, were causative in biallelic constellations, unrelated to disease when heterozygous on a biallelic mutation background of another gene, or even non-pathogenic if close to the C-terminus. Patients with mutations in several loci were common, but without evidence for di- or oligogenic inheritance. Although the number of targeted genes was low compared to previous studies, the mutation detection rate was highest (70%) which likely results from completeness and depth of coverage, and quantitative data analysis. CNV analysis should routinely be applied in targeted NGS, and mutations in non-coding exons give reason to systematically include 5'-UTRs in disease gene or exome panels. Consideration of all variants is indispensable because even truncating mutations may be misleading.
PLoS ONE 01/2013; 8(11):e78496. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report a Mexican girl showing the full blown clinical picture of mucopolysaccharidosis type II. Iduronate-2-sulfatase (IDS) activity was low and she carried a heterozygous de novo c.1327C>T transition in exon 9, that changes codon 443 for a premature stop (TGA; p.Arg443*). Analysis of X-chromosome inactivation in AR showed a highly skewed ratio of 92:8 suggesting a functional hemizygosity with dominant expression of the mutant IDS and explaining the disease manifestation. This is one of the rare cases of females affected by MPSII due to the combined effect of a skewed X-chromosome inactivation and a de novo IDS mutation. We recommend that clinicians should consider the diagnosis of MPS II even in a girl without positive family history for this condition.
European journal of medical genetics 12/2012; · 1.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Das Marfan-Syndrom ist eine autosomal-dominant vererbte Bindegewebserkrankung mit Beteiligung des skelettalen, okulären und
kardiovaskulären Systems. Die Erkrankung wird durch Mutationen im FBN1-Gen verursacht, das für das Glykoprotein Fibrillin,
eine elementare Strukturkomponente der elastischen Fasern kodiert. Die Diagnose des Marfan-Syndroms basiert auf zwei Säulen,
erstens der klinischen Evaluierung der Patienten, zweitens dem direkten Mutationsnachweis im FBN1-Gen. Inter- und intrafamiliäre
Unterschiede im klinischen Erscheinungsbild erschweren die phänotypische Diagnostik. In dieser Arbeit wird die indirekte Genotypanalyse,
in welcher die Segregation von allelischen DNA-Polymorphismen verfolgt wird, als ein zusätzliches Verfahren für die Diagnose
vorgestellt. Mittels indirekter Genotypdiagnostik und in Kombination mit den klinischen Untersuchungsbefunden kann die Diagnose
oder der Ausschluss des Marfan-Syndroms noch sicherer gestellt werden, insbesondere bei klinischen Grenzfällen.
Marfan syndrome (MFS) is an autosomal dominant disorder of connective tissue characterized by skeletal, ocular and cardiovascular
manifestations. The disease is caused by mutations in the FBN1 gene, encoding fibrillin, an important component of elastic
fibers. Diagnosis of Marfan syndrome is currently based on detailed clinical examination and/or mutation analysis in the fibrillin
gene. Clinical expression varies widely both among and within families, rendering clinical diagnosis extremely difficult.
In this study, we performed segregation analysis of allelic DNA polymorphisms to support diagnosis of Marfan syndrome. This
type of genotype analysis is a useful, additional diagnostic tool for families with Marfan syndrome and provides incremental
information of diagnosis or exclusion of Marfan syndrome based on clinical findings.
Schlüsselwörter–Marfan-Syndrom–Fibrillin 1-Gen–klinische Variabilität–indirekte GenotypdiagnostikKey words Marfan syndrome–fibrillin-1 gene–clinical variability–haplotype segregation analysis
Zeitschrift für Kardiologie 04/2012; 89(10):939-948. · 0.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mucopolysaccharidosis type IIIA (MPS IIIA, Sanfilippo syndrome) is a fatal inherited lysosomal storage disease accompanied by progressive neurologic degeneration. The gene underlying MPS IIIA, SGSH, encodes a lysosomal enzyme, N-sulfoglucosamine sulfohydrolase (sulfamidase). Mutational analysis of a large cohort of MPS IIIA patients showed a correlation of the missense mutation p.Ser298Pro and a slowly progressive course of the disease. We report here on the expression of the mutant p.Ser298Pro sulfamidase in BHK cells retaining low residual activity. Pulse-chase experiments showed that rapid degradation is responsible for the low steady state level of the mutant protein. Processing and secretion of p.Ser298Pro sulfamidase suggests that small amounts of the newly synthesized enzyme are transported to lysosomes. Most of the mutant sulfamidase exits the endoplasmic reticulum for proteasomal degradation. The ability to predict the clinical course of MPS IIIA in patients with the p.Ser298Pro mutation, as well as the residual enzymatic activity, and the reduced stability of the mutant sulfamidase suggest that this subgroup of patients is especially well suited to early sulfamidase replacement therapy or treatment with selective pharmacological chaperones.
American Journal of Medical Genetics Part A 07/2011; 155A(7):1634-9. · 2.30 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The fact that hereditary hearing loss is the most common sensory disorder in humans is reflected by, among other things, an extraordinary allelic and nonallelic genetic heterogeneity. X-chromosomal hearing impairment represents only a minor fraction of all cases. In a study of a Spanish family the locus for one of the X-chromosomal forms was assigned to Xp22 (DFNX4). We mapped the disease locus in the same chromosomal region in a large German pedigree with X-chromosomal nonsyndromic hearing impairment by using genome-wide linkage analysis. Males presented with postlingual hearing loss and onset at ages 3-7, whereas onset in female carriers was in the second to third decades. Targeted DNA capture with high-throughput sequencing detected a nonsense mutation in the small muscle protein, X-linked (SMPX) of affected individuals. We identified another nonsense mutation in SMPX in patients from the Spanish family who were previously analyzed to map DFNX4. SMPX encodes an 88 amino acid, cytoskeleton-associated protein that is responsive to mechanical stress. The presence of Smpx in hair cells and supporting cells of the murine cochlea indicates its role in the inner ear. The nonsense mutations detected in the two families suggest a loss-of-function mechanism underlying this form of hearing impairment. Results obtained after heterologous overexpression of SMPX proteins were compatible with this assumption. Because responsivity to physical force is a characteristic feature of the protein, we propose that long-term maintenance of mechanically stressed inner-ear cells critically depends on SMPX function.
The American Journal of Human Genetics 05/2011; 88(5):621-7. · 11.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Posterior microphthalmos (MCOP) is a rare isolated developmental anomaly of the eye characterized by extreme hyperopia due to short axial length. The population of the Faroe Islands shows a high prevalence of an autosomal-recessive form (arMCOP) of the disease. Based on published linkage data, we refined the position of the disease locus (MCOP6) in an interval of 250 kb in chromosome 2q37.1 in two large Faroese families. We detected three different mutations in PRSS56. Patients of the Faroese families were either homozygous for c.926G>C (p.Trp309Ser) or compound heterozygous for c.926G>C and c.526C>G (p.Arg176Gly), whereas a homozygous 1 bp duplication (c.1066dupC) was identified in five patients with arMCOP from a consanguineous Tunisian family. In one patient with MCOP from the Faroe Islands and in another one from Turkey, no PRSS56 mutation was detected, suggesting nonallelic heterogeneity of the trait. Using RT-PCR, PRSS56 transcripts were detected in samples derived from the human adult retina, cornea, sclera, and optic nerve. The expression of the mouse ortholog could be first detected in the eye at E17 and was maintained into adulthood. The predicted PRSS56 protein is a 603 amino acid long secreted trypsin-like serine peptidase. The c.1066dupC is likely to result in a functional null allele, whereas the two point mutations predict the replacement of evolutionary conserved and functionally important residues. Molecular modeling of the p.Trp309Ser mutant suggests that both the affinity and reactivity of the enzyme toward in vivo protein substrates are likely to be substantially reduced.
The American Journal of Human Genetics 03/2011; 88(3):382-90. · 11.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Retinitis pigmentosa (RP) is a degenerative disease of the retina leading to progressive loss of vision and, in many instances, to legal blindness at the end stage. The RP28 locus was assigned in 1999 to the short arm of chromosome 2 by homozygosity mapping in a large Indian family segregating autosomal-recessive RP (arRP). Following a combined approach of chromatin immunoprecipitation and parallel sequencing of genomic DNA, we identified a gene, FAM161A, which was shown to carry a homozygous nonsense mutation (p.Arg229X) in patients from the original RP28 pedigree. Another homozygous FAM161A stop mutation (p.Arg437X) was detected in three subjects from a cohort of 118 apparently unrelated German RP patients. Age at disease onset in these patients was in the second to third decade, with severe visual handicap in the fifth decade and legal blindness in the sixth to seventh decades. FAM161A is a phylogenetically conserved gene, expressed in the retina at relatively high levels and encoding a putative 76 kDa protein of unknown function. In the mouse retina, Fam161a mRNA is developmentally regulated and controlled by the transcription factor Crx, as demonstrated by chromatin immunoprecipitation and organotypic reporter assays on explanted retinas. Fam161a protein localizes to photoreceptor cells during development, and in adult animals it is present in the inner segment as well as the outer plexiform layer of the retina, the synaptic interface between photoreceptors and their efferent neurons. Taken together, our data indicate that null mutations in FAM161A are responsible for the RP28-associated arRP.
The American Journal of Human Genetics 09/2010; 87(3):376-81. · 11.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hereditary sensory and autonomic neuropathy type II (HSAN II) leads to severe mutilations because of impaired nociception and autonomic dysfunction. Here we show that loss-of-function mutations in FAM134B, encoding a newly identified cis-Golgi protein, cause HSAN II. Fam134b knockdown results in structural alterations of the cis-Golgi compartment and induces apoptosis in some primary dorsal root ganglion neurons. This implicates FAM134B as critical in long-term survival of nociceptive and autonomic ganglion neurons.
[Show abstract][Hide abstract] ABSTRACT: Genetic factors contribute to the overall risk of developing nicotine addiction, which is the major cause of preventable deaths in western countries. However, knowledge regarding specific polymorphisms influencing smoking phenotypes remains scarce. In the present study we provide evidence that a common single nucleotide polymorphism (SNP) in the 5' untranslated region of CHRM2, the gene coding for the muscarinic acetylcholine receptor 2 is associated with nicotine addiction. CHRM2 was defined as a candidate gene for nicotine addiction based on previous evidence that linked variations in CHRM2 to alcohol and drug dependence. A total of more than 5,500 subjects representative of the German population were genotyped and assessed regarding their smoking habits. The impact of three SNPs in CHRM2 on smoking behavior/nicotine addiction was investigated using logistic regression models or a quasi-Poisson regression model, respectively. We found the T allele of SNP rs324650 to be associated with an increased risk of smoking/nicotine dependence according to three different models, the recessive models of regular or heavy smokers vs. never-smokers (odds ratio 1.17 in both analyses) and according to the Fagerström index of nicotine addiction. In the analysis stratified by gender this association was only found in females. Our data provide further evidence that variations in CHRM2 may be associated with the genetic risk of addiction in general or with certain personality traits that predispose to the development of addiction. Alternatively, variations in CHRM2 could modulate presynaptic auto-regulation in cholinergic systems and may thereby affect an individual's response to nicotine more specifically.
American Journal of Medical Genetics Part B Neuropsychiatric Genetics 08/2009; 153B(2):684-90. · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: RDH12 mutations are responsible for early-onset autosomal recessive retinal dystrophy, which results in profound retinal pathology and severe visual handicap in patients. To investigate the function of RDH12 within the network of retinoid dehydrogenases/reductases (RDHs) present in retina, we studied the retinal phenotype of Rdh12-deficient mice. In vivo rates of all-trans-retinal reduction and 11-cis-retinal formation during recovery from bleaching were similar in Rdh12-deficient and wild-type mice matched for an Rpe65 polymorphism that impacts visual cycle efficiency. However, retinal homogenates from Rdh12-deficient mice exhibited markedly decreased capacity to reduce exogenous retinaldehydes in vitro. Furthermore, in vivo levels of the bisretinoid compound diretinoid-pyridinium-ethanolamine (A2E) were increased in Rdh12-deficient mice of various genetic backgrounds. Conversely, in vivo levels of retinoic acid and total retinol were significantly decreased. Rdh12 transcript levels in wild-type mice homozygous for the Rpe65-Leu(450) polymorphism were greater than in Rpe65-Met(450) mice and increased during postnatal development in wild-type mice and Nrl-deficient mice having an all-cone retina. Rdh12-deficient mice did not exhibit increased retinal degeneration relative to wild-type mice at advanced ages, when bred on the light-sensitive BALB/c background, or when heterozygous for a null allele of superoxide dismutase 2 (Sod2(+/-)). Our findings suggest that a critical function of RDH12 is the reduction of all-trans-retinal that exceeds the reductive capacity of the photoreceptor outer segments.
Journal of Biological Chemistry 07/2009; 284(32):21468-77. · 4.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mutations in TOPORS cause autosomal dominant retinitis pigmentosa (adRP). Examination of 160 adRP patients from continental Europe revealed nine exonic single nucleotide variants, eight of which reside in the coding region; three synonymous single nucleotide polymorphisms (SNPs; c.2319T > C, c.2991T > C and c.1560A > G), three nonsynonymous SNPs (c.58C > T/p.P20S, c.74C >G/p.S25W and c.1730C > A/p.S577Y) and two novel missense mutations (c.1205A > C/p.Q402P and c.1818T > G/p.S606R). Whether the latter two variants represent adRP causing mutations awaits further analysis.
[Show abstract][Hide abstract] ABSTRACT: Although Fabry disease is X linked and considered to affect primarily male hemizygotes, female heterozygotes may experience all the signs and symptoms of this metabolic disorder. This prospective, single-center, open-label, clinical trial was performed to evaluate the long-term response of female patients with Fabry disease to enzyme replacement therapy.
Symptomatic women (average age = 47 years) enrolled in this 4-year study were treated with agalsidase alfa (Replagal, Shire HGT, Inc.) at a dose of 0.2 mg/kg, every other week for 4 years (N = 36). Clinical and biochemical assessments were conducted at 12-month intervals.
The Mainz Severity Score Index, a measure of total disease burden, was significantly reduced after 12 months (P < 0.01) of treatment and continuously improved over 4 years. Brief Pain Inventory "pain at its worst" score was reduced from 4.6 +/- 2.9 at baseline to 3.3 +/- 2.9 after 12 months (P = 0.001) and remained reduced through 4 years. Mean left-ventricular mass decreased from 89.4 +/- 29.3(2.7) g/m at baseline to 66.5 +/- 29.3(2.7) g/m after 12 months (P < 0.001) and remained reduced through 4 years. Average kidney function (estimated glomerular filtration rate and proteinuria) remained constant during the study. No safety issues were identified.
Long-term agalsidase alfa is effective and was well tolerated in women with Fabry disease.
Genetics in medicine: official journal of the American College of Medical Genetics 04/2009; 11(6):441-9. · 3.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mutations in IDH3B, an enzyme participating in the Krebs cycle, have recently been found to cause autosomal recessive retinitis pigmentosa (arRP). The MDH1 gene maps within the RP28 arRP linkage interval and encodes cytoplasmic malate dehydrogenase, an enzyme functionally related to IDH3B. As a proof of concept for candidate gene screening to be routinely performed by ultra high throughput sequencing (UHTs), we analyzed MDH1 in a patient from each of the two families described so far to show linkage between arRP and RP28.
With genomic long-range PCR, we amplified all introns and exons of the MDH1 gene (23.4 kb). PCR products were then sequenced by short-read UHTs with no further processing. Computer-based mapping of the reads and mutation detection were performed by three independent software packages.
Despite the intrinsic complexity of human genome sequences, reads were easily mapped and analyzed, and all algorithms used provided the same results. The two patients were homozygous for all DNA variants identified in the region, which confirms previous linkage and homozygosity mapping results, but had different haplotypes, indicating genetic or allelic heterogeneity. None of the DNA changes detected could be associated with the disease.
The MDH1 gene is not the cause of RP28-linked arRP. Our experimental strategy shows that long-range genomic PCR followed by UHTs provides an excellent system to perform a thorough screening of candidate genes for hereditary retinal degeneration.