Large German Family Research Articles

Consequences of a novel caveolin-3 mutation in a large German family.

Mutations in the human caveolin-3 gene (cav-3) on chromosome 3p25 have been described in limb girdle muscular dystrophy, rippling muscle disease, hyperCKemia, and distal myopathy. Here, we describe the genetic, myopathological, and clinical findings in a large German family harboring a novel heterozygous mutation (GAC-->GAA) in codon 27 of the cav-3 gene. This missense mutation causes an amino acid change from asparagine to glutamate (Asp27Glu) in the N-terminal region of the Cav-3 protein, which leads to a drastic decrease of Cav-3 protein expression in skeletal muscle tissue. In keeping with an autosomal dominant mode of inheritance, this novel cav-3 mutation was found to cosegregate with neuromuscular involvement in the reported family. Ultrastructural analysis of Cav-3-deficient muscle showed an abnormal folding of the plasma membrane as well as multiple vesicular structures in the subsarcolemmal region. Neurological examination of all nine subjects from three generations harboring the novel cav-3 mutation showed clear evidence of rippling muscle disease. However, only two of these nine patients showed isolated signs of rippling muscle disease without muscle weakness or atrophy, whereas five had additional signs of a distal myopathy and two fulfilled the diagnostic criteria of a coexisting limb girdle muscular dystrophy. These findings indicate that mutations in the human cav-3 gene can lead to different and overlapping clinical phenotypes even within the same family. Different clinical phenotypes in caveolinopathies may be attributed to so far unidentified modifying factors/genes in the individual genetic background of affected patients.

Complete form of X-linked congenital stationary night blindness: refined mapping and evidence of genetic homogeneity.

A number of distinct, partly non-overlapping genetic loci have been reported for the complete type of X-linked congenital stationary night blindness (CSNB1), suggesting genetic heterogeneity. In order to refine the localization of the CSNB1 gene and to demonstrate genetic homogeneity, linkage analysis was performed in two large CSNB1 families. Clinical features consistent with the diagnosis of CSNB1 were documented in five patients from a German seven-generation kindred by full ophthalmological examination including psychophysical and electroretinographical testing. Haplotype analysis in 30 members of the large German family was performed with 38 polymorphic markers predominantly covering the critical region. Linkage analyses defined a locus for CSNB1 with flanking markers DXS8042 and DXS228, refining the interval to 2.5 cM in Xp11.4. In addition, two-point linkage analysis was carried out using the MLINK computer program. In agreement with meiotic breakpoints, lod scores of 3.0 and greater were obtained for markers located to the proximal site of the former 5 cM CSNB consensus interval. A large Dutch CSNB1 family was re-evaluated with markers from the Xp11.4 region, and supports the CSNB1 minimal interval found in the German family. Together with previous results from three unrelated families from Sweden, Sardinia and Great Britain, our results provide evidence of genetic homogeneity in the disorder. Subsequent mutation analyses in CSNB1 patients revealed no pathogenic sequence alterations in DFFRX and CASK genes, but retain candidates for other diseases mapping to that region.

A distinct gene close to the hairless locus on chromosome 8p underlies hereditary Marie Unna type hypotrichosis in a German family.

Hypotrichosis of the Marie Unna type (HMU) is a rare autosomal dominant disorder characterized by male-pattern hair loss with childhood onset and anomalies of the hair shaft. We aimed to evaluate a number of chromosomal loci as possible candidate regions for HMU. A linkage analysis was performed in a large German family using microsatellite markers spanning candidate regions on chromosomes 8, 12 and 17. We found that the HMU locus maps to chromosomal region 8p21 in a 13.01-cM interval between markers D8S1145 and D8S1771. This interval harbours the hairless gene (HR). Mutational analysis of HR on the genomic and transcript levels revealed no pathogenic mutation. Our findings, together with a recent report of two unrelated families of Dutch and British origin, provide evidence for a hair growth regulatory gene distinct from HR in chromosomal region 8p21.

PGL3, a third, not maternally imprinted locus in autosomal dominant paraganglioma.

Paragangliomas (glomus tumors) are slowly growing, mostly benign tumors of the parasympathetic ganglia which most frequently occur in the head and neck region. Between 10% and 50% of cases are familial and follow an autosomal dominant mode of inheritance. The trait is maternally imprinted and exclusively transmitted through the paternal line. To date, two loci have been implicated in this disorder: one at 11q23 (PGL1), the other one at 11q13 (PGL2). We have analyzed a large German family with hereditary paraganglioma, but no evidence of maternal imprinting. By linkage analysis with markers flanking both PGL1 and PGL2, we demonstrate that the trait does not segregate with either of the loci at 11q. Our findings show that a third locus, PGL3, can be involved in hereditary paraganglioma.

Oculopharyngeal muscular dystrophy in a northern German family linked to chromosome 14q, and presenting carnitine deficiency

We report the evaluation of oculopharyngeal muscular dystrophy (OPMD) in a large northern German family, which can be traced back six generations and is unrelated to French-Canadian families. The symptoms in this family start at about 50 years of age and include dysphagia, bilateral ptosis, and in some cases a slowly progressive atrophy and weakness of other extraocular, facial or limb girdle muscles. The muscle biopsies showed the pathognomonic ultrastructural finding of characteristic intranuclear filaments. Linkage analysis confirmed that this family is also linked to chromosome 14q markers. Haplotype analysis revealed that a unique haplotype segregates with the disease which is different from the one found in French-Canadian OPMD. Although approximately half of the probands with OPMD showed mild clinical and neurophysiological signs of a distal symmetrical neuropathy, the association between the neurogenic lesions and OPMD is still unclear. Some family members with or without OPMD complained of exercise related muscle pain, and a lipid storage myopathy with low muscular carnitine concentrations was found, while the carnitine contents in blood and urine samples as well as the activity of the carnitine-palmitoyl-transferase were normal, fitting the pattern of a primary muscular carnitine deficiency, independent of OPMD.

Autosomal dominant spastic paraplegia with anticipation maps to a 4-cM interval on chromosome 2p21-p24 in a large German family.

Autosomal dominant familial spastic paraplegias (AD-FSP) are a group of genetically heterogeneous diseases characterised by a progressive spasticity of the lower limbs. Three loci have already been identified by genetic linkage studies on chromosomes 2p, 14q and 15q. Here we present linkage data from a large German family displaying AD-FSP with anticipation which confirms the existence of the FSP2 locus on chromosome 2p. The recombination events observed in our family define the critical region for the FSP2 gene to be within a 4-cM interval, flanked by markers D2S400 and D2S367. Moreover, clinical data from our family show evidence of anticipation, a phenomenon caused by trinucleotide expansion in several other neurodegenerative diseases.

Linkage studies in alcohol-responsive myoclonic dystonia.

A large German family with "myoclonic dystonia with lightning jerks responsive to alcohol" was identified. Eleven affected pedigree members and six obligate gene carriers from five generations were identified. A description of one branch of this pedigree was published in 1964. Our examination 30 years after the initial report confirms the clinical syndrome of a nonprogressive movement disorder characterized by myoclonic jerks affecting the proximal muscles and the muscles of the trunk, accompanied by mild dystonic features in some affected family members. Segregation analysis favors autosomal dominant inheritance with high, but incomplete, penetrance in males and much lower penetrance in females. Linkage analysis was performed using simple sequence repeat polymorphisms (CA repeats) closely associated with or spanning the chromosomal regions containing 15 candidate genes: the gene for early-onset generalized torsion dystonia, DYT1 (chromosome 9q34); the genes for subunits alpha 2, beta 1, and gamma 1 (chromosome 4p12-4q13); for alpha 1, alpha 6, beta 2, and gamma 2 (chromosome 5q31.1-5q31.3); for alpha 4, alpha 5, beta 3, and gamma 3 (chromosome 15q11-15q13); for rho 1 and rho 2 (chromosome 6q14-6q21) of the gamma-aminobutyric acid A receptor; and for the alpha subunit of the glycine receptor (chromosome 5q31). By a combination of pairwise and multipoint linkage analysis, it could be excluded that any of these candidate gene-bearing chromosomal regions contain the disease gene in this family. We also excluded major portions of three chromosomal regions syntenic with mouse chromosome 3, which carries the murine beta subunit of the glycine receptor.

Palmoplantar Keratoderma in Association with Carcinoma of the Esophagus Maps to Chromosome 17q Distal to the Keratin Gene Cluster

Palmoplantar keratoderma is a group of hereditary disorders of keratinization involving hyperkeratosis of palms and soles. Two different forms of palmoplantar keratoderma have recently been shown to be caused by mutations in the body site-specific keratin 9 gene and in the keratin 1 gene, respectively. Now we have analyzed a large German family with autosomal dominantly inherited palmoplantar keratoderma in association with carcinoma of the esophagus. Linkage to both the type I keratin gene cluster on chromosome 17q and the type II keratin gene cluster on chromosome 12q could be excluded. In contrast, we mapped palmoplantar keratoderma in this family to chromosome 17q distal to the type I keratin genes. Two-point linkage data at D17S801 gave a lod scoreZmax= 5.1 at θ = 0.00. Therefore, palmoplantar keratoderma is shown to be heterogeneous clinically as well as genetically and may be caused by mutations in keratins as well as in nonkeratins.

Molecular defect of truncated beta-spectrin associated with hereditary elliptocytosis. Beta-spectrin Gottingen

A large German family with autosomal dominantly inherited elliptocytosis, associated with truncated beta-spectrin missing the phosphorylated C-terminal peptide, has been described (Eber, S.W., Morris, S. A., Schroeter, W., and Gratzer, W. B. (1988) J. Clin. Invest. 81, 523-530). We have attempted to delineate the molecular defect of this abnormality at the gene level. Southern blot analyses revealed no evidence of a partial gene deletion or rearrangement. We used polymerase chain reaction (PCR) and amplified several relevant portions of the beta-spectrin gene, using genomic DNA from two different heterozygous patients. No abnormality was found in the last four exons of the beta-spectrin gene produced by PCR. Examination of the introns connecting the last four exons revealed a T to A substitution in the 5' splice site following the exon X in four of eight clones prepared from two affected individuals, but not from a normal subject of this family. To examine the effect of the T to A substitution in these patients, we made cDNA from the reticulocyte mRNA of the patient and examined its composition by PCR. Two distinct PCR fragments produced from the patient's beta-spectrin cDNA were found. One matched the predicted size for normal spectrin, while the other was 197 base pairs shorter. The mutant cDNA sequence revealed that the entire exon preceding the T to A substitution was spliced out, while the two terminal exons were preserved. The deletion of this exon resulted in a frameshift giving a different terminal amino acid (serine instead of leucine) as well as a new termination codon causing a deletion of 129 amino acids including potentially phosphorylated residues.

Clinical and molecular genetic study of a large German kindred with Gerstmann‐Straussler‐Scheinker syndrome

We have verified, by full open reading frame sequencing, the presence of an amino-acid-altering mutation in codon 102 of the scrapie amyloid protein gene in three affected members of a large and well-documented German family with experimentally transmitted Gerstmann-Sträussler-Scheinker syndrome. In addition, we identified the mutation by partial sequencing or DNA restriction enzyme analysis in three of 12 presently healthy family members with an affected parent, and none of 12 members without an affected parent. Thus, a total of six of 15 family members at risk for the disease (including the three established cases) had the same codon 102 mutation, a proportion consistent with the autosomal dominant inheritance pattern of disease expression. It is undetermined whether the mutation influences susceptibility to infection by an exogenous agent or is itself a proximate cause of disease.

Gene for non‐specific X‐linked mental retardation maps in the pericentromeric region

Linkage analysis was carried out in a large four-generation German family segregating for non-specific X-linked mental retardation. Affected males have moderate intellectual handicap. Speech delay, deviant behaviour, and hyperactivity have also been reported. Head circumference and testicular volumes are normal. Cytogenetic analysis failed to show evidence for fragile site or structural abnormality of the X chromosome. None of the obligatory carriers shows any clinical symptoms. Close linkage without recombination (lod scores 1.74 to 2.05) has been found between the disease locus (MRX1) and the polymorphic DNA loci DXS7 (Xp11.4-p11.3), MAOA (Xp11.3-p11.23), DXS255 (Xp11.22), and DXS159 (Xq12) suggesting that the gene responsible for the disease in this family maps in the pericentromeric region of the X chromosome. Linkage data obtained with the flanking marker loci OTC (Xp21.1) and DXS95 (Xq21.2-q21.3) also were compatible with this localization of the MRX1 gene. Close linkage to loci from Xp22, Xq22, Xq24-25, or Xq28 could be excluded.

Evidence Supporting Tight Linkage of X-Linked Emery-Dreifuss Muscular Dystrophy to the Factor VIII: C Gene

In a large German family with Emery-Dreifuss muscular dystrophy (EDMD) linkage analysis was performed using the factor IX gene (F9), the factor VIII:C gene (F8), the anonymous DNA probe DXS52, and DXS15 as markers. Tight linkage was found between the EDMD locus and the F8 probe (Zmax = 1.19; theta max = 0.00), DXS15 (Zmax = 1.75; theta max = 0.00) and DXS52 (Zmax = 2.26; theta max = 0.00). Weak linkage was found to F9 (Zmax = 0.02; theta max = 0.43). The data from the literature and our results suggest that the gene locus of EDMD is close to F8 (confidence interval theta = 0-0.07). The new linkage data are useful for carrier detection and diagnosis of EDMD patients before onset of major clinical signs.

Interactions of spectrin in hereditary elliptocytes containing truncated spectrin beta-chains.

An abnormal spectrin, in which one subunit is truncated, has been detected in a large German family. The inheritance is autosomal dominant. The affected members of the family suffer in widely varying degree from a microcytic hemolytic anemia. The red cell morphology varies correspondingly from smooth elliptocytes to predominantly poikilocytes. The abnormal spectrin makes up approximately 30% of the total and is almost entirely present as the dimer. The truncated chain is not phosphorylated by the endogenous cAMP-independent kinase, and it has been identified as a chain of beta-type, using monoclonal antibodies. Because a univalent terminal spectrin alpha-chain fragment will bind to normal dimers with an association constant lower by only a factor of two than that for the self-association of the dimers, it would be expected that the mutant dimers (alpha beta') would readily enter into an association with normal (alpha beta) dimers to give alpha 2 beta beta' tetramers (though not with each other). In dilute solution this is indeed observed, and the diminution in tetramer concentration when 30% of normal spectrin is replaced by alpha beta' dimers, amounts to only a small proportion. Moreover, in the membrane skeleton, if there is pairwise apposition of dimer units, only 9% of pairings will be between units that cannot associate. We have shown that the failure of alpha beta' dimers to enter into heterologous associations in situ is not due to the elimination of the ankyrin binding site near the truncated end of the beta-chain: this site is fully functional, as judged by rebinding to spectrin-depleted vesicles. When the spectrin is extracted from the membrane in the cold, the material released initially consists almost entirely of alpha beta' dimers; when the spectrin of normal membranes is partly dissociated to dimers in situ by warming at low ionic strength, extraction in the cold then leads similarly to much more rapid release of the dimer than of the tetramer. The similar rates of liberation of normal and abnormal dimer make it unlikely that the interaction of the latter with the membrane is in any way defective. When mixtures of alpha beta and alpha beta' dimers are bound to spectrin-depleted inside-out membrane vesicles from normal cells and tetramers are allowed to form by equilibration at 30 degrees C, the proportion of the abnormal species appearing in the tetramer is much lower than would be expected on a statistical basis. The relation of the self-association equilibrium on the membrane to that of spectrin in dilute solution is analyzed.