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C Zühlke

Publications and source records attributed to C Zühlke.

At least 37 records · Page 2Linked to original sources
PubMed1999

Spinocerebellar ataxia type 6: evidence for a strong founder effect among German families.

The authors found a strong geographic cluster of spinocerebellar ataxia type 6 (SCA6) families in the Northrhine-Westfalia area, suggesting a founder effect in the German SCA6 population. Genotyping with DNA markers linked to the CACNL1A4 gene on chromosome 19p13 revealed a common haplotype and shared allelic characteristics in the majority of German families. The observed founder effect may be related to the relative meiotic stability of CAG repeats in this type of autosomal dominant cerebellar ataxia.

Alleles↗
PubMed1999

Linkage disequilibrium and haplotype analysis in German Friedreich ataxia families.

The main mutation causing Friedreich ataxia (FRDA) is the expansion of a GAA repeat localized within the intron between exon 1 and exon 2 of the gene X25. This expansion has been observed in 98% of FRDA chromosomes. To analyze frequencies of markers tightly linked to the Friedreich ataxia gene and to investigate wheter a limited number of ancestral chromosomes are shared by German FRDA families, a detailed analysis employing nine polymorphic markers was performed. We found strong linkage disequilibria and association of FRDA expansions with a few haplotypes. FRDA haplotypes differ significantly from control haplotypes. Our results confirm that GAA repeat expansions in intron 1 of the frataxin gene are limited to a few chromosomes and indicate an obvious founder effect in German patients. Based on these analyses, we estimate a minimum age of the mutation of 107 generations.

Evolution, Molecular↗
PubMed1999

Isolation and characterization of novel CAG repeat containing genes expressed in human brain.

Neurodegenerative diseases may be caused by expansion of triplet repeats in human genes. To identify novel genes with CAG repeats, we screened a human brain cDNA library with an oligonucleotide probe. Four of the isolated cDNAs were sequenced, analyzed for polymorphisms, chromosomal localization, evolutionary conservation and expression. One of the repeats is bi-allelic with 10 triplets (80% of chromosomes) and 7 triplets (20% of chromosomes). In one of the genes two CAG repeats coding for 10 and 17 glutamines are localized in the same reading frame.

Animals↗
PubMed1999

hSKCa3: a candidate gene for schizophrenia?

Recently, case-control studies have suggested an association between the polymorphic CAG repeat in the neuronal potassium channel gene hSKCa3 and an increased susceptibility to schizophrenia, with larger repeats being overrepresented in schizophrenic patients. Therefore, we have examined the CAG repeat polymorphism in hSKCa3 and four adjacent microsatellite markers in 12 multiplex schizophrenia families. On performing the extended transmission/disequilibrium test (ETDT), neither allele-wise (P = 0.67) nor genotype-wise (P = 0.071) analysis yielded evidence to support linkage disequilibrium between schizophrenia and the hSKCa3 CAG repeat alleles. No significant results were produced performing parametric and non-parametric linkage analysis between schizophrenia and hSKCa3, as well as the four microsatellite markers. Thus, our study does not support the involvement of hSKCa3 in schizophrenia. Furthermore, we refined the physical localization on chromosome 1q21.3 using linkage analysis. No recombination was seen between markers D1S2624 and D1S1600 and the polymorphic CAG repeat in hSKCa3. LOD scores of 19.44 and 12.97, respectively, were obtained at a recombination fraction of 0.00.

Chromosome Mapping↗
PubMed1998

Mutation of the start codon in the FRDA1 gene: linkage analysis of three pedigrees with the ATG to ATT transversion points to a unique common ancestor.

Friedreich ataxia (FRDA) is a progressive neurodegenerative disorder caused by loss-of-function mutations in the gene encoding frataxin. Most patients with FRDA have trinucleotide repeat expansions in both alleles of the FRDA 1 gene. In patients heterozygous for the expansion the second allele may be inactivated by a point mutation. We identified the ATG-->ATT (M11) mutation of the start codon in three independent families. Individuals with symptoms of FRDA in these families are compound heterozygous for the repeat expansion and the ATG mutation. To look for a common founder of the M11 mutation, a detailed linkage analysis employing six polymorphic chromosome 9 markers was performed. We found complete haplotype identity for two of the three chromosomes with the point mutation. The third case shows partial conformity and may be the result of a single recombination event.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Slow saccades and other eye movement disorders in spinocerebellar atrophy type 1.

In order to study the relation between genotype and phenotype, a detailed study of the course of oculomotor deficits was performed in three patients with autosomal-dominant cerebellar ataxia, subtype spinocerebellar atrophy type 1 (SCA 1) using clinical testing and electrooculography. DNA analysis revealed a CAG repeat expansion of 65 in the SCA 1 gene on chromosome 6p in all patients. A progressive disorder of the saccadic system became obvious, leading to a marked slowing of saccadic eye movements and loss of pathological and physiological nystagmus. An upward gaze palsy developed early, followed by horizontal and downward gaze palsy at a later state of the disease. Smooth pursuit eye movements were disturbed to a lesser extent; the vestibulo-ocular reflex was reduced. As an additional feature, severe loss of visual acuity developed due to progressive optic nerve atrophy. The oculomotor deficits can be explained by progressive damage to the brain stem rather than to the cerebellum. Each combination of oculomotor deficits with or without optic atrophy may occur irrespective of the gene locus of the disease, making a correlation between clinical signs and genetic findings difficult.

Adult↗
PubMed1997

CAG repeat analyses in frozen and formalin-fixed tissues following primer extension preamplification for evaluation of mitotic instability of expanded SCA1 alleles.

Neurodegenerative disorders, including spin-ocerebellar ataxias (SCA), Huntington disease (HD) and dentatorubral-pallidoluysian atrophy (DRPLA), are associated with unstable CAG repeats. To investigate the mitotic stability of the repetitive element in the genes for SCA1, SCA3, HD, and DRPLA we extracted DNA from up to 13 tissue samples from four deceased individuals with progressive neurological disorders and neuropathological signs. Due to the formalin fixation of some tissues the genomic DNA was highly degraded and unsuitable for amplification of fragments longer than 150 bp. After size selection and primer extension preamplification, specific analyses could be performed even for expanded alleles. In all four patients the SCA1 mutation could be demonstrated, in one case with remarkable somatic heterogeneity of the elongated allele, whereas alleles of the normal range were stable in all tissues examined.

Adult↗
PubMed1997

SCA2 trinucleotide expansion in German SCA patients.

Autosomal dominant spinocerebellar ataxias (SCA) are a group of clinically and genetically heterogeneous neurodegenerative disorders which lead to progressive cerebellar ataxia. A gene responsible for SCA type 2 has been mapped to human chromosome 12 and the disease causing mutation has been identified as an unstable and expanded (CAG)n trinucleotide repeat. We investigated the (CAG)n repeat length of the SCA2 gene in 842 patients with sporadic ataxia and in 96 German families with dominantly inherited SCA which do not harbor the SCA1 or MJD1/SCA3 mutation, respectively. The SCA2 (CAG)n expansion was identified in 71 patients from 54 families. The (CAG)n stretch of the affected allele varied between 36 and 64 trinucleotide units. Significant repeat expansions occurred most commonly during paternal transmission. Analysis of the (CAG)n repeat lengths with the age of onset in 41 patients revealed an inverse correlation. Two hundred and forty-one apparently healthy octogenerians carried alleles between 16 and 31 repeats. One 50-year old, healthy individual had 34 repeats; she had transmitted an expanded allele to her child. The small difference between 'normal' and disease alleles makes it necessary to define the extreme values of their ranges. With one exception, the trinucleotide expansion was not observed in 842 ataxia patients without a family history of the disease. The SCA2 mutation causes the disease in nearly 14% of autosomal dominant SCA in Germany.

Adolescent↗
PubMed1997

SCA6 is caused by moderate CAG expansion in the alpha1A-voltage-dependent calcium channel gene.

Recently, moderate (CAG)>20 repeat expansions in the alpha1A-voltage-dependent calcium channel gene (CACNL1A4) have been identified in a previously unmapped type of SCA which has been named SCA6. We investigated the (CAG)n repeat length of the CACNL1A4 gene in 733 patients with sporadic ataxia and in 46 German families with dominantly inherited SCA which do not harbor the SCA1, SCA2, or MJD1/SCA3 mutation, respectively. The SCA6 (CAG)n expansion was identified in 32 patients most frequently with late manifestation of the disease. The (CAG)n stretch of the affected allele varied between 22 and 28 trinucleotide units and is therefore the shortest trinucleotide repeat expansion causing spinocerebellar ataxia. The (CAG)n repeat length is inversely correlated with the age at onset. In 11 parental transmissions of the expanded allele no repeat instability has been observed. Repeat instability was also not found for the normal allele investigating 431 meioses in the CEPH families. Analyzing 248 apparently healthy octogenerians revealed one allele of 18 repeats which is the longest normal CAG repeat in the CACNL1A4 gene reported. The SCA6 mutation causes the disease in approximately 10% of autosomal dominant SCA in Germany. Most importantly, the trinucleotide expansion was observed in four ataxia patients without obvious family history of the disease which necessitates a search for the SCA6 (CAG)n expansion even in sporadic patients.

Age of Onset↗
PubMed1996

Friedreich's ataxia with retained tendon reflexes: molecular genetics, clinical neurophysiology, and magnetic resonance imaging.

Lower limb areflexia is generally regarded as an essential criterion for the diagnosis of Friedreich's ataxia (FRDA). We describe a family with a recessive form of early-onset ataxia in which one member had a phenotype typical of FRDA whereas another, with retained tendon reflexes in the lower limbs, did not have electrophysiologic evidence of the usual severe afferent axonal neuropathy of FRDA. In contrast, somatosensory evoked potentials, eye-movement recordings, and MRI of the head and cervical cord provided results highly suggestive of FRDA in both patients. We performed genetic linkage analysis in this family, using markers tightly linked to the FRDA locus on chromosome 9. Inheritance of identical paternal and maternal genotypes by the affected members, but not by their unaffected siblings, provided supporting evidence that this disorder may result from mutation within the FRDA gene or is tightly linked to the investigated loci on chromosome 9.

Adult↗
PubMed1996

[Huntington chorea. Molecular genetic principles, mutation detection and predictive diagnosis].

Predictive genetic testing offers the opportunity for persons at risk to obtain information about their carrier status concerning Huntington's disease (HD). HD is associated with the expansion of a (CAG) repeat in the gene IT15. HD chromosomes contain about 40-75 repeat units, whereas normal chromosomes show a range between 11 and 33 repeats. The HD repeat is highly unstable during transmission, involving both increases and decreases in size with the largest expansions occurring in male meioses. The number of (CAG) copies is inversely correlated with the onset age of the disorder. Investigation of sporadic cases revealed that new mutations for HD are more frequent than estimated. Analysis of the repeat length allows direct DNA diagnosis of affected individuals and asymptomatic persons at risk. From 1989 to March 1993 in our institute predictive testing by indirect DNA methods was requested by 108 persons at risk. After cloning of the HD gene in 1993, direct testing was requested by 113 persons at risk between April 1993 and April 1994 in Göttingen. In about 400 patients differential diagnosis was performed with the direct method. In approximately 82% of the patients the expanded (CAG) repeat was found, and the HD diagnosis could be confirmed.

Adult↗
PubMed1994

Subtractive cDNA cloning as a tool to analyse secondary effects of a muscle disease. Characterization of affected genes in the myotonic ADR mouse.

In myotonic ADR mice that are homozygous for a defect in the muscular chloride channel gene adr/Clc-1, the hyperexcitability of fast muscles is associated with secondary changes in gene expression and fibre type composition. cDNA clones derived from a set of genes down regulated in fast muscles of the myotonic ADR mouse were isolated by a subtractive cloning procedure. A total of 1200 clones were analysed for high expression in fast muscle of wild type and low expression in mutant mouse. Differential transcript levels were verified by northern blot hybridizations. The identities of the corresponding transcripts were determined by sequencing as myosin heavy chain IIB, alpha-tropomyosin, troponin C, a Ca2+ ATPase and parvalbumin mRNAs. Of these, mRNAs for parvalbumin and myosin heavy chain IIB were drastically downregulated in myotonic muscle (to < 10% of control). A full length cDNA clone for skeletal muscle alpha-tropomyosin was homologous to the mouse fibroblast tropomyosin isoform 2, except for the portion encoding the alpha-tropomyosin specific amino acids 258-284. A cDNA derived from the 1100 nucleotide parvalbumin transcript was cloned and the sequence for the as yet unknown 3' extended trailer, generated by alternative polyadenylation, was determined.

Animals↗
PubMed1994

Down syndrome and male fertility: PCR-derived fingerprinting, serological and andrological investigations.

Down syndrome, the most common birth defect causing mental retardation, is characterized by a specific phenotype including subfertility or sterility and hypogonadism in males. In contrast, several females with Down syndrome have borne offspring. Here, a male with trisomy 21 fathering an infant is described. This observation is verified by serological markers, DNA fingerprinting using different DNA micro- or minisatellites and andrological investigations.

Adult↗
PubMed1993

Mitotic stability and meiotic variability of the (CAG)n repeat in the Huntington disease gene.

The gene causing Huntington's disease, an autosomal dominantly inherited, neurodegenerative disorder, has been identified recently. The corresponding mutation is involving an expansion in the number of (CAG)n repeats in the coding region of the Huntington's disease gene on chromosome 4. In this report, we demonstrate the length variation of the repeat in 513 non-HD chromosomes from normal individuals and HD patients showing 23 alleles with 11 to 33 repeats. Analyzing the inheritance of the (CAG)n stretch we found meiotic instability for HD alleles ([CAG]40 to [CAG]75) with a mutation frequency of approximately 0.7, while in 431 meioses of normal alleles only two expansions were identified. The risk of expansion during spermatogenesis is enhanced compared to oogenesis explaining juvenile onset by transmission from affected fathers. Further, the number of (CAG)n copies in an affected individual in relation to the sex of the transmitting parent was evaluated and no significant differences were found. No mosaicism or differences in the repeat lengths were observed in the DNA from different tissues including brain and lymphocytes of two HD patients indicating mitotic stability of the mutation. Therefore, the determination of the repeat number in the DNA of blood lymphocytes is probably representative of all tissues in a patient.

Alleles↗