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Background: Lactose intolerance with adult-onset is due to the inadequate enzymatic activity of lactase-phlorizin hydrolase (LPH). It is frequently seen in patients with Crohn disease, but the mechanism remains to be elucidated. Two DNA genotypes, C/C -13910 and G/G -22018 , located upstream from the LCT locus, the gene encoding for LPH, were recently identified as representing genetic markers for lactose intolerance. We utilized these two DNA genotypes to study their role in inflammatory bowel disease. Methods: We investigated the prevalence of these two DNA variants using specific restriction enzyme digest assays in 166 patients with Crohn disease, in 120 healthy first-degree relatives of Crohn disease patients, in 63 patients with ulcerative colitis and in 187 healthy individuals. Results: The analysis revealed a frequency of 21.4% of the 2 genotypes for adult-type hypolactasia in our studied German cohort of healthy individuals, which is higher than previously reported (15%) based on the hydrogen (H 2 ) breath test. This might indicate a higher sensitivity of genotyping, but it has to be confirmed in larger cohorts. No significant difference was detectable in the frequency of the C/C -13910 and G/G -22018 genotypes in patients with Crohn disease (C/C -13910 : 21.7%; G/G -22018 : 22.3%) compared to first-degree relatives (C/C -13910 : 21.7%; G/G -22018 : 20.8%), patients with ulcerative colitis (C/C -13910 : 20.3%; G/G -22018 : 20.3%) and healthy individuals (C/C -13910 : 21.4%; G/G -22018 : 21.4%). Conclusion: The C/C -13910 and G/G -22018 genotype of adult-type hypolactasia is not associated with susceptibility to the pathogenesis of Crohn disease and ulcerative colitis. [ABSTRACT FROM AUTHOR]

Eukaryotic MutLα (mammalian MLH1-PMS2 heterodimer; MLH1-PMS1 in yeast) functions in early steps of mismatch repair as a latent endonuclease that requires a mismatch, MutSα/β, and DNA-loaded proliferating cell nuclear antigen (PCNA) for activation. We show here that human PCNA and MutLα interact specifically but weakly in solution to form a complex of approximately 1:1 stoichiometry that depends on PCNA interaction with the C-terminal endonuclease domain of the MutLα PMS2 subunit. Amino acid substitution mutations within a PMS2 C-terminal 721 QRLIAP motif attenuate or abolish human MutLα interaction with PCNA, as well as PCNA-dependent activation of MutLα endonuclease, PCNA- and DNA-dependent activation of MutLα ATPase, and MutLα function in in vitro mismatch repair. Amino acid substitution mutations within the corresponding yeast PMS1 motif ( 723 QKLIIP) reduce or abolish mismatch repair in vivo. Coupling of a weak allele within this motif ( 723 AKLIIP) with an exo1 Δ null mutation, which individually confer only weak mutator phenotypes, inactivates mismatch repair in the yeast cell., Competing Interests: The authors declare no conflict of interest.

Repair of dsDNA breaks requires processing to produce 3'-terminated ssDNA. We biochemically reconstituted DNA end resection using purified human proteins: Bloom helicase (BLM); DNA2 helicase/nuclease; Exonuclease 1 (EXO1); the complex comprising MRE11, RAD50, and NBS1 (MRN); and Replication protein A (RPA). Resection occurs via two routes. In one, BLM and DNA2 physically and specifically interact to resect DNA in a process that is ATP-dependent and requires BLM helicase and DNA2 nuclease functions. RPA is essential for both DNA unwinding by BLM and enforcing 5' → 3' resection polarity by DNA2. MRN accelerates processing by recruiting BLM to the end. In the other, EXO1 resects the DNA and is stimulated by BLM, MRN, and RPA. BLM increases the affinity of EXO1 for ends, and MRN recruits and enhances the processivity of EXO1. Our results establish two of the core machineries that initiate recombinational DNA repair in human cells.

The DNA mismatch repair protein PMS2 was recently found to encode a novel endonuclease activity. To determine the biological functions of this activity in mammals, we generated endonuclease-deficient Pms2E702K knock-in mice. Pms2EK/EK mice displayed increased genomic mutation rates and a strong cancer predisposition. In addition, class switch recombination, but not somatic hypermutation, was impaired in Pms2EK/EK B cells, indicating a specific role in Ig diversity. In contrast to Pms2-/- mice, Pms2EK/EK male mice were fertile, indicating that this activity is dispensable in spermatogenesis. Therefore, the PMS2 endonuclease activity has distinct biological functions and is essential for genome maintenance and tumor suppression.

MutSbeta (MSH2-MSH3) mediates repair of insertion-deletion heterologies but also triggers triplet repeat expansions that cause neurological diseases. Like other DNA metabolic activities, MutSbeta interacts with proliferating cell nuclear antigen (PCNA) via a conserved motif (QXX(L/I)XXFF). We demonstrate that MutSbeta-PCNA complex formation occurs with an affinity of approximately 0.1 microM and a preferred stoichiometry of 1:1. However, up to 20% of complexes are multivalent under conditions where MutSbeta is in molar excess over PCNA. Conformational studies indicate that the two proteins associate in an end-to-end fashion in solution. Surprisingly, mutation of the PCNA-binding motif of MutSbeta not only abolishes PCNA binding, but unlike MutSalpha, also dramatically attenuates MutSbeta-MutLalpha interaction, MutLalpha endonuclease activation, and bidirectional mismatch repair. As predicted by these findings, PCNA competes with MutLalpha for binding to MutSbeta, an effect that is blocked by the cell cycle regulator p21(CIP1). We propose that MutSbeta-MutLalpha interaction is mediated in part by residues ((L/I)SRFF) embedded within the MSH3 PCNA-binding motif. To our knowledge this is the first case where residues important for PCNA binding also mediate interaction with a second protein. These findings also indicate that MutSbeta- and MutSalpha-initiated repair events differ in fundamental ways.

A purified system comprised of MutSalpha, MutLalpha, exonuclease 1 (Exo1), and replication protein A (RPA) (in the absence or presence of HMGB1) supports 5'-directed mismatch-provoked excision that terminates after mismatch removal. MutLalpha is not essential for this reaction but enhances excision termination, although the basis of this effect has been uncertain. One model attributes the primary termination function in this system to RPA, with MutLalpha functioning in a secondary capacity by suppressing Exo1 hydrolysis of mismatch-free DNA (Genschel, J., and Modrich, P. (2003) Mol. Cell 12, 1077-1086). A second invokes MutLalpha as the primary effector of excision termination (Zhang, Y., Yuan, F., Presnell, S. R., Tian, K., Gao, Y., Tomkinson, A. E., Gu, L., and Li, G. M. (2005) Cell 122, 693-705). In the latter model, RPA provides a secondary termination function, but together with HMGB1, also participates in earlier steps of the reaction. To distinguish between these models, we have reanalyzed the functions of MutLalpha, RPA, and HMGB1 in 5'-directed mismatch-provoked excision using purified components as well as mammalian cell extracts. Analysis of extracts derived from A2780/AD cells, which are devoid of MutLalpha but nevertheless support 5'-directed mismatch repair, has demonstrated that 5'-directed excision terminates normally in the absence of MutLalpha. Experiments using purified components confirm a primary role for RPA in terminating excision by MutSalpha-activated Exo1 but are inconsistent with direct participation of MutLalpha in this process. While HMGB1 attenuates excision by activated Exo1, this effect is distinct from that mediated by RPA. Assay of extracts derived from HMGB1(+/+) and HMGB1(-/-) mouse embryo fibroblast cells indicates that HMGB1 is not essential for mismatch repair.

Mismatch repair contributes to genetic stability, and inactivation of the mammalian pathway leads to tumor development. Mismatch correction occurs by an excision-repair mechanism and has been shown to depend on the 5' to 3' hydrolytic activity exonuclease 1 (Exo1) in eukaryotic cells. However, genetic and biochemical studies have indicated that one or more Exo1-independent modes of mismatch repair also exist. We have analyzed repair of nicked circular heteroduplex DNA in extracts of Exo1-deficient mouse embryo fibroblast cells. Exo1-independent repair under these conditions is MutL alpha-dependent and requires functional integrity of the MutL alpha endonuclease metal-binding motif. In contrast to the Exo1-dependent reaction, we have been unable to detect a gapped excision intermediate in Exo1-deficient extracts when repair DNA synthesis is blocked. A possible explanation for this finding has been provided by analysis of a purified system comprised of MutS alpha, MutL alpha, replication factor C, proliferating cell nuclear antigen, replication protein A, and DNA polymerase delta that supports Exo1-independent repair in vitro. Repair in this system depends on MutL alpha incision of the nicked heteroduplex strand and dNTP-dependent synthesis-driven displacement of a DNA segment spanning the mismatch. Such a mechanism may account, at least in part, for the Exo1-independent repair that occurs in eukaryotic cells, and hence the modest cancer predisposition of Exo1-deficient mammalian cells.

The error-free repair of double-stranded DNA breaks by homologous recombination requires processing of broken ends. These processed ends are substrates for assembly of DNA strand exchange proteins that mediate DNA strand invasion. Here, we establish that human BLM helicase, a member of the RecQ family, stimulates the nucleolytic activity of human exonuclease 1 (hExo1), a 5'-->3' double-stranded DNA exonuclease. The stimulation is specific because other RecQ homologs fail to stimulate hExo1. Stimulation of DNA resection by hExo1 is independent of BLM helicase activity and is, instead, mediated by an interaction between the 2 proteins. Finally, we show that DNA ends resected by hExo1 and BLM are used by human Rad51, but not its yeast or bacterial counterparts, to promote homologous DNA pairing. This in vitro system recapitulates initial steps of homologous recombination and provides biochemical evidence for a role of BLM and Exo1 in the initiation of recombinational DNA repair.

Wilson's disease (WD) is a rare inborn metabolic error characterized by deficient biliary copper excretion secondary to ATP7B gene mutations. Neurological presentations are variable in respect to both pattern and age of onset; commonly a movement disorder presents in the second or third decade. The aim of this study was to ascertain genotype correlations with distinct neurological manifestations in 41 WD patients in a Brazilian center for WD. A total of 23 distinct mutations were detected, and the frameshift 3402delC had the highest allelic frequency (31.7%). An association between 3402delC and dysphagia was detected (p=0.01) but the limited number of patients is insufficient to allow one to draw conclusions. Both clinical studies analyzing larger cohorts and basic research on ATP7B protein function could potentially shed more light on our understanding of WD.

Background: Inflammatory bowel disease (IBD) results from an aberrant immune response to the indigenous intestinal flora in genetically susceptible hosts. Therefore, the study of candidate genes involved in host pathogen interactions is of key interest., Methods: In this two-center, retrospective German and Hungarian cohort study, patients with Crohn's disease (CD) (n = 379; German n = 235, Hungarian n = 144) and ulcerative colitis (UC) (n = 263; German n = 145, Hungarian n = 118) and healthy controls (n = 605; German n = 403, Hungarian n = 202) were genotyped for the presence of the CD14 c.1-260C>T promoter variant and the TLR4 c.896A>G (p.D299G) variant by melting curve analysis using fluorescence resonance energy transfer probes. Data were stratified according to the presence of NOD2 (CARD15) mutations and a detailed genotype-phenotype analysis was performed., Results: In the German cohort the CD14 single-nucleotide polymorphism was associated with UC, but not CD (UC p = 0.016 vs. CD p = 0.190), while the opposite was found in the Hungarian cohort (UC p = 0.083 vs. CD p = 0.019). No association of IBD with the TLR4 single-nucleotide polymorphism was found in either cohort (UC p = 0.430, CD p = 0.783 vs. UC p = 0.745, CD p = 0.383)., Conclusion: IBD appears to be associated with the CD14 c.1-260C>T promoter variant in Germans and Hungarians, but not with the TLR4 c.896A>G (p.D299G) variant.

Background: One-third of cases of dilated cardiomyopathy (DCM) is of familial aetiology. Several genes have been reported to cause the autosomal dominant form of DCM., Aims: To analyze the lamin A/C gene (LMNA) in 31 unrelated patients with DCM and conduction system disease (CSD)., Methods: Patients and family members underwent physical examination, ECG/Holter-ECG, echocardiography, and selective coronary angiography. Genetic analysis of all coding exons of LMNA was performed using PCR and sequencing., Results: Three different LMNA mutations (Arg377His, c.1397delA, c.424_425ins21nt) were identified in three families with autosomal dominant disease comprised of 39 individuals. 21 individuals were mutation carriers, of whom 12 were symptomatic. We observed a progressive and age-dependent form of DCM with CSD and arrhythmias. First, the patients developed a moderate left ventricular dilatation without symptoms. Later, systolic function declined progressively and the patients became symptomatic resulting in a high mortality due to sudden death and heart failure., Conclusions: Genetic screening leads to the identification of symptomatic and asymptomatic mutant carriers. The latter at a young age should be regarded as "presymptomatic" because of the age-dependent disease manifestation. New guidelines are required for the management of these individuals.

Objectives: Genetic variants within DLG5 were recently reported to be associated with inflammatory bowel disease (IBD). The aim of our study was to test for allelic and haplotype associations of six DLG5 variants in 668 IBD patients from two European populations. Furthermore, we evaluated whether DLG5 variants alter gastrointestinal permeability in Crohn's disease (CD)., Methods: Six DLG5 variants (p.R30Q, p.P1371Q, p.G1066G, rs2289308, DLG_e26, p.D1507D) were genotyped in two study populations: (1) German IBD patients (CD n = 250; ulcerative colitis (UC) n = 150) and German healthy controls (n = 422); (2) Hungarian IBD patients (CD n = 144; UC n = 124) and Hungarian healthy controls (n = 205). Subtyping analysis was performed in respect of CARD15 mutations and clinical characteristics. We also tested for differences within DLG5 genotypes in German CD patients with respect to gastroduodenal and intestinal permeability measured by triple-sugar-test., Results: Allele as well as genotype frequencies of DLG5 variants did not differ between IBD patients and controls in either study population. Indeed, the p.R30Q polymorphism was found more frequently in controls than in patients. The distribution of DLG5 genotypes in German and Hungarian CD patients with CARD15 mutations was not different from patients without mutated CARD15. We did also not observe any association between DLG5 variants and clinical parameters. Importantly, DLG5 variants were not associated with gastroduodenal or intestinal permeability., Conclusions: We could not replicate that DLG5 is a relevant disease susceptibility gene for IBD in German or Hungarian subjects. In addition, we have no evidence that DLG5 variants are involved in altered gastrointestinal permeability in CD.

Background and Aims: A genetically impaired intestinal barrier function has long been suspected to be a predisposing factor for Crohn's disease (CD). Recently, mutations of the capsase recruitment domain family, member 15 (CARD15) gene have been identified and associated with CD. We hypothesise that a CARD15 mutation may be associated with an impaired intestinal barrier., Methods: We studied 128 patients with quiescent CD, 129 first degree relatives (CD-R), 66 non-related household members (CD-NR), and 96 healthy controls. The three most common CARD15 polymorphisms (R702W, G908R, and 3020insC) were analysed and intestinal permeability was determined by the lactulose/mannitol ratio., Results: Intestinal permeability was significantly increased in CD and CD-R groups compared with CD-NR and controls. Values above the normal range were seen in 44% of CD and 26% of CD-R but only in 6% of CD-NR, and in none of the controls. A household community with CD patients, representing a common environment, was not associated with increased intestinal permeability in family members. However, 40% of CD first degree relatives carrying a CARD15 3020insC mutation and 75% (3/4) of those CD-R with combined 3020insC and R702W mutations had increased intestinal permeability compared with only 15% of wild-types, indicating a genetic influence on barrier function. R702W and G908R mutations were not associated with high permeability., Conclusions: In healthy first degree relatives, high mucosal permeability is associated with the presence of a CARD15 3020insC mutation. This indicates that genetic factors may be involved in impairment of intestinal barrier function in families with IBD.

We compared the effect of the p.H1069Q mutation and other non-p.H1069Q mutations in ATP7B on the phenotypic expression of Wilson's disease (WD), and assessed whether the clinical phenotype of WD in compound heterozygotes depends on the type of mutation coexisting with the p.H1069Q. One hundred forty-two patients with clinically, biochemically, and genetically diagnosed WD were studied. The mutational analysis of ATP7B was performed by direct sequencing. A total number of 26 mutations in ATP7B were identified. The p.His1069Gln was the most common mutation (allelic frequency: 72%). Seventy-three patients were homozygous for this mutation. Of compound heterozygotes, 37 had frameshift/nonsense mutation, and 20 had other missense mutation on one of their ATP7B alleles. Twelve patients had two non-p.H1069Q mutations. Patients homozygous for the p.H1069Q mutation had the less severe disturbances of copper metabolism and the latest presentation of first WD symptoms. The most severely disturbed copper metabolism and the earliest age at initial disease manifestation was noticed in non-p.H1069Q patients. In compound heterozygotes, the type of mutation coexisting with the p.H1069Q to a small extent influenced WD phenotype. The phenotype of WD varied considerably among patients with the same genotype. The p.H1069Q mutation is associated with late WD manifestation and with a mild disruption of copper metabolism. In compound heterozygotes, the phenotype of WD to a small extent depends on the type of mutation coexisting with the p.H1069Q. Besides genotype, additional modifying factors seem to determine WD manifestations., (Copyright (c) 2005 Movement Disorder Society.)

The reaction responsible for replication error correction by mismatch repair proceeds via several steps: mismatch recognition, mismatch-provoked excision, repair DNA synthesis, and ligation. Key steps in this process are the recognition and subsequent exonucleolytic removal of the mispair. A minimal system comprised of human MutSalpha (MSH2*MSH6), MutLalpha (MLH1*PMS2), exonuclease I (EXOI), replication protein A (RPA), proliferating cell nuclear antigen (PCNA), and replication factor C (RFC) is sufficient to support mismatch-provoked excision in vitro. This chapter describes methods for analysis of the reconstituted excision reaction.

Wilson's disease (WD) is an autosomal recessive disorder of copper metabolism. The clinical phenotype of the disease is varied. It is proposed that this variation may be a result of differential functional disruption of ATPase7B (ATP7B) resulting from mutations in the gene ATP7B. We aimed to assess the relationship between specific mutational defects in ATP7B and divergence in the phenotypic expression of WD. One hundred and forty-two patients with clinically, biochemically and genetically diagnosed WD were included in the study. The phenotypic expression of WD was compared between patients with different types of mutations in ATP7B, detected by direct sequencing of exons 1-21 of the gene. Twenty-six mutations were identified in ATP7B; eleven of them were mutations predicted to result in the absence of a full-length normal protein [frameshift/nonsense mutations; classified as 'severe' mutations (SMs)], 14 were missense mutations (MMs) and one was a splice site mutation. Patients with one or two SMs on their alleles had lower serum copper and ceruloplasmin and were younger when the first symptoms of the disease appeared, compared with individuals with two MMs. The effect of SMs on the WD phenotype was dose-dependent. It is concluded that mutations within ATP7B are very heterogeneous. Frameshift and nonsense mutations are associated with a severe phenotype of WD.

Dunnigan-type familial partial lipodystrophy (FPLD) is caused by mutations in LMNA, the gene that encodes nuclear lamins A and C. FPLD is characterized by peripheral fat loss, excess central adiposity, insulin resistance, and hyperlipidaemia, which are difficult to treat. We present our 2 years' experience of treatment with rosiglitazone in a subject with FPLD. Insulin requirement decreased significantly from 240 IU/day to 76 IU/day (range 20-240 IU/day) and serum triglyceride concentration was lowered from 13.7 +/- 14.4 mmol/l to 4.5 +/- 4.3 mmol/l and remained stable. Mean HbA(1c) prior to rosiglitazone therapy was 9.4 +/- 1.32% and decreased to 7.4 +/- 0.6% during therapy with rosiglitazone. This case demonstrates the benefits of PPARgamma-agonists on glycaemic control and dyslipidaemia in a patient with FPLD. This in turn implies that PPARgamma may play a pathophysiological role in FPLD.

Objectives: Characterization of familial clusters of subjects with metabolic derangements predisposing to hepatic steatosis and nonalcoholic steatohepatitis could facilitate genomic studies to identify risk factors for their development. Dunnigan-type familial partial lipodystrophy (FPLD) is an autosomal dominantly inherited disorder caused by mutations in the LMNA gene. Affected subjects have loss of subcutaneous fat from the extremities and symptoms similar to those characterizing the metabolic syndrome, including insulin resistance and dyslipidemia. The goal of this study was to determine the prevalence of steatosis in subjects with FPLD., Methods: We examined 18 subjects from six families with FPLD for mutations in LMNA and analyzed plasma lipid and serum glucose concentrations. Liver ultrasound and serum aminotransferase activities were used as indicators of steatosis or steatohepatitis. In two subjects, histological examination of hepatic tissue was performed., Results: All subjects had FPLD-causing mutations in LMNA. Plasma lipids were measured in 17 subjects, 16 of whom had hyperlipidemia and 14 presented with either documented insulin resistance or diabetes mellitus. Hepatic steatosis was present in 15 subjects who had ultrasound examinations and 9 of these had elevated serum aminotransferase activities. Liver biopsy confirmed steatosis in 2 subjects., Conclusions: Hepatic steatosis is part of the clinical phenotype of FPLD. This familial disorder may provide a human metabolic model system to facilitate genomic and environmental studies to determine risk factors for hepatic steatosis and nonalcoholic steatohepatitis.

Wilson disease (WD) is an autosomal recessive disorder of copper metabolism. The disorder is caused by mutations in the ATP7B gene, encoding a copper transporting P-type ATPase. The worldwide incidence is in the order of 30 cases per million, with a gene frequency of 0.56% and a carrier frequency of 1 in 90. The increased number of Wilson disease patients in the island of Crete led us to study the spectrum of mutations in a small village close to the city of Heraklion, from where many patients have been referred during the last 25 years. In order to estimate the frequency of the disease, we firstly investigated the number of births and the number of WD patients in the village since 1978. Six out of 90 births were diagnosed as WD patients, presenting the highest prevalence of WD reported so far. Analysis of the whole gene in three Wilson disease patients, and relatives of a boy who died from WD, led to the detection of 4 different point mutations. Two of them were missense (p.I1148T and p.G1176R) and cosegregated in cis in the same patient; the other allele of this patient carried a nonsense mutation (p.Q289X). This is the first report in the literature of three mutations co-segregating in the same WD patient. The fourth mutation identified was a novel frameshift mutation (c.398delT) with documented cosegregation. When screening 200 inhabitants originating from the same area, 18 were found to be carriers of one of these mutations. These findings indicate the need for health education intervention, genetic counselling and newborn screening for the Wilson disease.

Aim: To analyse the impact of NOD2/CARD15 mutations on the clinical course of Crohn's disease patients from an eastern European country (Hungary)., Methods: We investigated the prevalence of the three common NOD2/CARD15 mutations (Arg702Trp, Gly908Arg, 1007finsC) in 148 patients with Crohn's disease, 128 patients with ulcerative colitis and 208 controls recruited from the University of Szeged, Hungary. In patients with Crohn's disease, the prevalence of NOD2/CARD15 mutations was correlated to the demographical and clinical parameters., Results: In total, 32.4% of Crohn's disease patients carried at least one mutant allele within NOD2/CARD15 compared to 13.2% of patients with ulcerative colitis (P = 0.0002) and to 11.5% of controls (P<0.0001). In Crohn's disease patients, the allele frequencies for Arg702Trp, Gly908Arg and 1007finsC were 7.1%, 3.0% and 10.8% respectively. Interestingly, only the 1007finsC mutation was associated with a distinct clinical phenotype. The patients positive for the 1007finsC mutation suffered more frequently from stenotic disease behaviour (P = 0.008). Furthermore, 51.9% of patients positive for the 1007finsC mutation underwent a surgical resection within the ileum compared to only 17.4% of patients without the 1007finsC mutation (P = 0.001). With respect to the other two mutations (Arg702Trp and Gly908Arg), no associations were found with all investigated clinical parameters., Conclusion: NOD2/CARD15 mutations are frequently found in Crohn's disease patients from Hungary. The 1007finsC mutation is associated with stenotic disease behaviour and frequent ileal resections.

Lamin A and C are components of the nuclear envelope, located at the nucleoplasmatic surface of the inner nuclear membrane within cells. Recently, mutations within LMNA encoding lamin A/C have been associated with various disease entities including cardiomyopathy. We screened heart transplant recipients suffering from dilated cardiomyopathy (DCM) with a positive family history of LMNA mutations. Four index patients and one relative belonging to four unrelated families carrying LMNA mutations were identified. The mutations p.Q355X and p.S22L have not been reported before, whereas p.R190W has already been reported in other studied DCM cohorts. In the patients of the present study, the mean age at manifestation of heart disease was 37.6 years (range 30-45 years), with progression to end-stage heart failure requiring transplantation at a mean age of 45.8 years (range 35-54 years). Three patients presented initially with atrial fibrillation. These data confirm the involvement of LMNA mutations in patients with DCM and extend the mutational spectrum of LMNA. The p.R190W mutation has been reported in different populations and may therefore be useful for analyzing the impact of a specific LMNA mutation on the phenotype of muscle disease., (Copyright 2005 S. Karger AG, Basel.)

Background and Aims: To evaluate genotyping for two DNA variants (c.1993+327C>T and c.1438+117G>A), recently found to be associated with adult-type hypolactasia, in the diagnosis of lactose intolerance., Methods: In total, 166 consecutive patients with gastrointestinal symptoms mimicking hypolactasia admitted to the clinic between March 2002 and December 2002 were included. Genotyping for the two DNA variants (c.1993+327C>T and c.1438+117G>A) and standard H2 breath test was performed., Results: Among 116 patients with positive H2 breath test, the c.1993+327C variant was detectable in 106 (91.4%) patients. Among 50 patients with negative H2 breath test, the c.1993+327C variant was seen in 2 patients. Sensitivity, specificity, positive and negative predictive values for the c.1993+327C variant were 91.4, 96.0, 98.1 and 82.8%, respectively. Genotyping for the c.1438+117G variant did not bring any additional information. Among 4 of the 10 patients with positive H2 breath test but negative for the c.1993+327C and the c.1438+117G variant,further evaluation revealed other diseases known to cause secondary hypolactasia such as celiac disease and short bowel syndrome., Conclusion: In symptomatic patients, genotyping for the DNA variant c.1993+327C is a reliable test for adult-type hypolactasia with high sensitivity and specificity and thus provides a new tool in the diagnostic workup of hypolactasia., (Copyright (c) 2005 S. Karger AG, Basel.)

Familial hypercholesterolemia (FH) is a clinical definition for a remarkable increase of cholesterol serum concentration, presence of xanthomas, and an autosomal dominant trait of either increased serum cholesterol or premature coronary artery disease (CAD). The identification of the low-density lipoprotein (LDL)-receptor (LDLR) as the underlying cause and its genetic characterization in FH patients revealed more insights in the trafficking of LDL, which primarily transports cholesterol to hepatic and peripheral cells. Mutations within LDLR result in hypercholesterolemia and, subsequently, cholesterol deposition in humans to a variable degree. This confirms the pathogenetic role of LDLR and also highlights the existence of additional factors in determining the phenotype. Autosomal dominant FH is caused by LDLR deficiency and defective apolipoprotein B-100 (APOB), respectively. Heterozygosity of the LDLR is relatively common (1:500). Clinical diagnosis is highly important and genetic diagnosis may be helpful, since treatment is usually effective for this otherwise fatal disease. Very recently, mutations in PCSK9 have been also shown to cause autosomal dominant hypercholesterolemia. For autosomal recessive hypercholesterolemia, mutations within the so-called ARH gene encoding a cellular adaptor protein required for LDL transport have been identified. These insights emphasize the crucial importance of LDL metabolism intra- and extracellularly in determining LDL-cholesterol serum concentration. Herein, we focus on the published European LDLR mutation data that reflect its heterogeneity and phenotypic penetrance., (Copyright 2004 Wiley-Liss, Inc.)

Mismatch-provoked excision directed by a strand break located 3' or 5' to the mispair has been reconstituted using purified human proteins. While MutSalpha, EXOI, and RPA are sufficient to support hydrolysis directed by a 5' strand break, 3' directed excision also requires MutLalpha, PCNA, and RFC. EXOI interacts with PCNA. RFC and PCNA suppress EXOI-mediated 5' to 3' hydrolysis when the nick that directs excision is located 3' to the mispair and activate 3' to 5' excision, which is dependent on loaded PCNA and apparently mediated by a cryptic EXOI 3' to 5' hydrolytic function. By contrast, RFC and PCNA have only a limited effect on 5' to 3' excision directed by a 5' strand break.

Background: Familial hypercholesterolaemia (FH) is caused by mutations in the low-density lipoprotein receptor gene and the gene encoding apolipoprotein B-100, affecting one in 500 individuals., Methods: One hundred and eighty-three Greek FH patients were screened for mutations on the LDLR and ApoB genes., Results: We identified mutations in 67 probands and 11 relatives. Sixteen mutations located in eight different exons and the promoter of the LDLR were discovered. Among them 10 were missense mutations (C6W, S265R, A370T, Q363P, D365E, V408M, A410T, A517T, G528D, G571E), two were nonsense mutations (Q363X and C660X), three were splice defects (2140 + 5G-->A and 2140 + 9C-->T, 1706 - 10G-->A), and one was a nucleotide substitution (- 45delT) on the promoter. None of the subjects carried any apoB mutation. The detection rate of mutations in this study was 43%. From the above mutations, A410T, A519T and the splice site defects 2140 + 9C-->T were detected for the first time in the Greek population. Among them V408M, G528D, C6W and S265R account for 73% of heterozygous FH probands. V408M mutation is more common in Central West, while C6W is more common in Central East. Separating the patients into two groups (receptor defective and receptor negative) we found that the receptor negative group had higher levels of total cholesterol, low-density lipoprotein cholesterol and higher prevalence of tendon xanthomas compared with the receptor-defective group., Discussion: The homogenous molecular basis of familial hypercholesterolaemia in Greece facilitates the application of a DNA diagnostic strategy based on the origin of the patient. The early mutation analysis would add valuable information on the severity of the disease.

Background: Keratin 8 is a major component of intermediate filaments in single-layered epithelia of the gastrointestinal tract. Keratin 8 deficient mice display signs of colitis and diarrhoea characteristic for inflammatory bowel disease. Very recently, two keratin 8 mutations, Y54H and G62C, were identified., Aims: We investigated if these keratin 8 missense mutations were associated with inflammatory bowel disease., Patients: In total, 217 German patients with Crohn' s disease, 131 German patients with ulcerative colitis, and 560 German control subjects were enrolled in this study., Methods: Samples were analysed by PCR amplification and subsequent melting curve analysis using fluorescence resonance energy transfer probes., Results: The G62C mutation was detected in five (2.3%) patients presenting with Crohn's disease and in three (2.3%) with ulcerative colitis. In comparison, 9 (1.6%) out of 560 controls were heterozygous for this mutation. No patient or control was homozygous for this mutation. Patients carrying one mutant allele did not show any noticeable characteristics in their corresponding phenotype. In contrast, the Y54H mutation was observed in neither any of the 348 patients with inflammatory bowel disease nor in any control subject., Conclusions: Our data indicate that both keratin 8 mutations, G62C and Y54H, do not play a relevant pathogenic role in inflammatory bowel disease.

Background: Mutations within the NOD2/CARD15 gene have recently been shown to be associated with Crohn's disease., Aims: To investigate the clinical impact of the three common NOD2/CARD15 mutations in patients with Crohn's disease., Methods: We investigated the prevalence of the three common NOD2/CARD15 mutations (Arg702Trp, Gly908Arg, 3020insC) in 180 patients with Crohn's disease, 70 patients with ulcerative colitis and 97 controls. In patients with Crohn's disease, prevalence of NOD2/CARD15 mutations were correlated to clinical and demographical parameters., Results: In Crohn's disease patients, 35.6% carried at least one mutant allele of NOD2/CARD15 mutations compared with 14.3% of patients with ulcerative colitis (P = 0.006) and to 15.5% of controls (P = 0.0001). Genotype phenotype analyses revealed that NOD2/CARD15 mutations determined younger age at disease diagnosis (P = 0.03), ileal disease location (P = 0.01) and ileocecal resections (P = 0.0002). Interestingly, reoperation with resection of the anastomosis was significantly more frequent in patients with NOD2/CARD15 mutations (P = 0.01)., Conclusions: Our investigations support the current hypothesis that NOD2/CARD15 mutations are associated with a phenotype of Crohn's disease with younger age at diagnosis, ileal involvement, ileocecal resections and a high risk of postoperative relapse and reoperation. NOD2/CARD15 mutations might therefore be used to identify high risk patients for relapse prevention strategies.

Noninvasive tools to quantitate transgene expression directly are a prerequisite for clinical gene therapy. We established a method to determine location, magnitude, and duration of low-density lipoprotein (LDL) receptor (LDLR) transgene expression after adenoviral gene transfer into LDLR-deficient Watanabe hypercholesterolemic rabbits by following tissue uptake of intravenously injected (111)In-labeled LDL using a scintillation camera. Liver-specific tracer uptake was calculated by normalizing the counts measured over the liver to counts measured over the heart that represent the circulating blood pool of the tracer (liver/heart (L/H) ratio). Our results indicate that the optimal time point for transgene imaging is 4 h after the tracer injection. Compared with control virus-injected rabbits, animals treated with the LDLR-expressing adenovirus showed seven-fold higher L/H ratios on day 6 after gene transfer, and had still 4.5-fold higher L/H ratios on day 30. This imaging method might be a useful strategy to obtain reliable data on functional transgene expression in clinical gene therapy trials of familial hypercholesterolemia.

Wilson disease (WD) is a rare inherited autosomal recessive disorder caused by a defect in a metal transporting P-type ATPase, resulting in copper overload in various tissues and cells. The aim was to assess both the phenotype in Brazilian WD patients and the corresponding ATP7B genotype. Sixty subjects belonging to 46 pedigrees diagnosed as WD were included in this study. Direct sequencing of all 21 exons within ATP7B and their flanking introns was performed. Demographic, clinical, laboratory and histopathological data at the time of diagnosis were obtained. We identified twenty-five mutations, twelve of them reported for the first time. The c.3402delC mutation had the highest allelic frequency (30.8%), followed by the c.2123T>C (p.L708P) (16.7%). Exons 8 and 15 were the site of 62.5% of the mutations. The common European mutation c.3207C>A (p.H1069Q) was not present at all. Phenotype varied greatly among individuals with the same ATP7B genotype. Our data confirm the heterogeneity of ATP7B genotype in Brazilian WD patients. The mutational spectrum is compatible with the Brazilian history of Mediterranean immigration; however, new mutations, and different frequencies and phenotype associated with the previously known mutations characterize this population. Exons 8 and 15 should be preferentially screened in WD cases from Brazil. Phenotype variation among subjects with the same ATP7B genotype suggests that modifying factors play an additional role in the pathogenesis of WD., (Copyright 2004 Wiley-Liss, Inc.)

We used the denaturing gradient gel electrophoresis (DGGE) method to define mutations in the promoter region, the 18 exons, and their flanking intronic sequences of the low-density lipoprotein (LDL) receptor gene LDLR, causing familial hypercholesterolemia (FH) phenotype in 100 German and in 100 Greek hypercholesterolemic individuals. In addition, we tested all patients for the presence of mutations in codons 3456-3553 of the gene encoding apolipoprotein B-100 (APOB). Twenty-six aberrant DGGE patterns were identified and subsequently directly sequenced. In LDLR, two novel missense mutations (c.1957G>T/p.V653F, c.647 G>A/p.C216Y) and one novel homozygous base substitution c.1-156 C>T in the repeat 2 of the promoter region were identified among German FH patients; one novel splice site c.1060+10C>G was identified among Greek FH patients. One of the German FH patients was a carrier for the mutations c.1171G>A/p.A391T and p.V653F, and two of the Greek FH patients were compound heterozygotes for the mutations c.1150C>T/p.Q384X and c.1158C>G/p.D386E. Two German FH patients carried the mutation p.R3500Q within APOB. Comparing the mutations within the LDLR gene of the two European FH populations, the German population seems to be more heterogeneous than the Greek cohort. Further studies in progress are trying to elucidate the responsiveness to drug therapy in association with LDLR genotype and the nutritional habits of the two FH populations., (Copyright 2004 Wiley-Liss, Inc.)

We have developed a purified system that supports mismatch-dependent 5'-->3' excision. In the presence of RPA, ATP, and a mismatch, MutSalpha activates 5'-->3' excision by EXOI, and excision terminates after removal of the mispair. MutSalpha confers high processivity on EXOI, and termination is due to RPA-dependent displacement of this processive complex from the helix and a weak ability of EXOI to reload at the RPA-bound gap in the product, as well as MutSalpha- and MutLalpha-dependent suppression of EXOI activity in the absence of a mismatch cofactor. As observed in the purified system, excision directed by a 5' strand break in HeLa nuclear extract can proceed in the absence of MutLalpha or PCNA, although 3' excision in the extract system requires both proteins.

Genetic predisposition has been suggested to play an important role in the pathogenesis of inflammatory bowel diseases (IBDs). Linkage studies have identified a Crohn's disease susceptibility locus on chromosome 14 (14q11-12; IBD4). Interleukin-25 (IL-25) is a newly identified proinflammatory cytokine that has been shown to promote Th2 responses by inducing cytokines such as IL-4, IL-5 and IL-13. The IL-25 gene is located within this susceptibility region at 14q11.2. As IBDs are characterized by an imbalance of the Th1/Th2 cytokine response, we hypothesized that genetic alterations within the IL-25 gene might contribute to IBD. First, direct sequencing of the coding regions of the IL-25 gene in 40 patients with Crohn's disease or ulcerative colitis revealed only a newly reported polymorphism (c424C/A) in exon 2. Next, the frequency of this polymorphism was further investigated in 151 patients with Crohn's disease, 111 patients with ulcerative colitis, and 119 healthy controls to determine its clinical relevance. The genotypes of the c424C/A polymorphism did not reveal any significant differences between patients with Crohn's disease or ulcerative colitis and controls. Genoytype-phenotype relations in patients with Crohn's disease showed a comparable distribution of the c424C/A polymorphism in all subgroups of the Vienna classification. In summary, our data indicate that genetic alterations in the coding regions of the IL-25 gene are unlikely to play a role in IBDs, but the c424C/A polymorphism in the IL-25 gene should be investigated for a potential association with other chronic inflammatory and inherited disorders such as autoimmune diseases.

Familial partial lipodystrophy (FPL) and lipodystrophy observed in HIV-1 infected patients receiving highly active antiretroviral therapy (HAART) share multiple clinical and metabolic features. Recently, missense mutations of LMNA encoding lamin A/C have been described in FPL providing evidence for a pivotal role of lamin A/C in the regulation of adipocytes. Moreover, the cellular retinoic acid binding protein (CRABP) has been suggested to be involved in HAART associated lipodystrophy. In this study, we excluded mutations within the complete coding region and the promoter of LMNA and the CRABP II gene in HIV-1 infected patients with lipodystrophy and also any correlation of the nucleotide polymorphism at codon 566 in exon 10 of LMNA with metabolic abnormalities. Protease inhibitors including indinavir have been shown to reduce adipocyte cell differentiation and increase apoptosis of adipocytes in vitro. Indinavir leads to altered retinoic acid signaling most likely by an activation of the RAR/RXR heterodimer, perhaps by displacing all-trans-retinoic acid from CRABP. Since LMNA is regulated by a retinoic acid responsive element (L-RARE) in the promoter region, we propose that indinavir impairs retinoic acid homeostasis and/or interact via the L-RARE within the LMNA promoter. This results in altered LMNA expression and subsequent impaired adipocyte differentiation, lipodystrophic body habitus, and metabolic disturbances in HIV infected patients receiving HAART.

Background: Lactose intolerance with adult-onset is due to the inadequate enzymatic activity of lactasephlorizin hydrolase (LPH). It is frequently seen in patients with Crohn disease, but the mechanism remains to be elucidated. Two DNA genotypes, C/C(-13910) and G/G(-22018), located upstream from the LCT locus, the gene encoding for LPH, were recently identified as representing genetic markers for lactose intolerance. We utilized these two DNA genotypes to study their role in inflammatory bowel disease., Methods: We investigated the prevalence of these two DNA variants using specific restriction enzyme digest assays in 166 patients with Crohn disease, in 120 healthy first-degree relatives of Crohn disease patients, in 63 patients with ulcerative colitis and in 187 healthy individuals., Results: The analysis revealed a frequency of 21.4% of the 2 genotypes for adult-type hypolactasia in our studied German cohort of healthy individuals, which is higher than previously reported (15%) based on the hydrogen (H2) breath test. This might indicate a higher sensitivity of genotyping, but it has to be confirmed in larger cohorts. No significant difference was detectable in the frequency of the C/C(-13910) and G/G(-22018) genotypes in patients with Crohn disease (C/C(-13910): 21.7%; G/G(-22018): 22.3%) compared to first-degree relatives (C/C(-13910): 21.7%; G/G(-22018): 20.8%), patients with ulcerative colitis (C/C(-13910): 20.3%; G/G(-22018): 20.3%) and healthy individuals (C/C(-13910): 21.4%; G/G(-22018): 21.4%)., Conclusion: The C/C(-13910) and G/G(-22018) genotype of adult-type hypolactasia is not associated with susceptibility to the pathogenesis of Crohn disease and ulcerative colitis.

Background: Lactose intolerance with adult-onset is due to the inadequate enzymatic activity of lactase-phlorizin hydrolase (LPH). It is frequently seen in patients with Crohn disease, but the mechanism remains to be elucidated. Two DNA genotypes, C/C&#95;₁₃₉₁₀ and G/G&#95;₂₂₀₁₈, located upstream from the LCT locus, the gene encoding for LPH, were recently identified as representing genetic markers for lactose intolerance. We utilized these two DNA genotypes to study their role in inflammatory bowel disease., Methods: We investigated the prevalence of these two DNA variants using specific restriction enzyme digest assays in 166 patients with Crohn disease, in 120 healthy first-degree relatives of Crohn disease patients, in 63 patients with ulcerative colitis and in 187 healthy individuals., Results: The analysis revealed a frequency of 21.4% of the 2 genotypes for adult-type hypolactasia in our studied German cohort of healthy individuals, which is higher than previously reported (15%) based on the hydrogen (H₂) breath test. This might indicate a higher sensitivity of genotyping, but it has to be confirmed in larger cohorts. No significant difference was detectable in the frequency of the C/C&#95;₁₃₉₁₀ and G/G&#95;₂₂₀₁₈ genotypes in patients with Crohn Disease (C/C&#95;₁₃₉₁₀: 21.7%; G/G&#95;₂₂₀₁₈: 22.3%) compared to first-degree relatives (C/C&#95;₁₃₉₁₀: 21.7%; G/G&#95;₂₂₀₁₈: 20.8%), patients with ulcerative colitis (C/C&#95;₁₃₉₁₀: 20.3%; G/G&#95;₂₂₀₁₈: 20.3%) and healthy individuals (C/C&#95;₁₃₉₁₀: 21.4%; G/G&#95;₂₂₀₁₈: 21.4%)., Conclusions: The C/C&#95;₁₃₉₁₀ and G/G&#95;₂₂₀₁₈ genotype of adult-type hypolactasia is not associated with susceptibility to the pathogenesis of Crohn disease and ulcerative colitis.

We have partially purified a human activity that restores mismatch-dependent, bi-directional excision to a human nuclear extract fraction depleted for one or more mismatch repair excision activities. Human EXOI co-purifies with the excision activity, and the purified activity can be replaced by near homogeneous recombinant hEXOI. Despite the reported 5' to 3' hydrolytic polarity of this activity, hEXOI participates in mismatch-provoked excision directed by a strand break located either 5' or 3' to the mispair. When the strand break that directs repair is located 3' to the mispair, hEXOI- and mismatch-dependent gap formation in excision-depleted extracts requires both hMutSalpha and hMutLalpha. However, excision directed by a 5' strand break requires hMutSalpha but can occur in absence of hMutLalpha. In systems comprised of pure components, the 5' to 3' hydrolytic activity of hEXOI is activated by hMutSalpha in a mismatch-dependent manner. These observations indicate a hydrolytic function for hEXOI in 5'-heteroduplex correction. The involvement of hEXOI in 3'-heteroduplex repair suggests that it has a regulatory/structural role in assembly of the 3'-excision complex or that the protein possesses a cryptic 3' to 5' hydrolytic activity.

The vast majority of Caucasian patients presenting with hereditary hemochromatosis demonstrate a single homozygous missense mutation in the HFE gene (C282Y). The underlying genetic defects in hemochromatosis patients of non-Caucasian origin are largely unknown. A 48-year-old man of Vietnamese origin presented with insulin-dependent diabetes mellitus, tertiary adrenocortical insufficiency, and laboratory results highly indicative of hereditary hemochromatosis. Because the patient was negative for the known HFE gene mutations C282Y, H63D, and S65C HFE, the entire coding region and intron/exon boundaries of the HFE gene was investigated. Sequencing studies identified a homozygous G-to-A transition at position +1 of intron 5 (IVS5+1 G/A). This newly described mutation alters the invariant G at position +1 of the 5' splice site causing altered mRNA splicing and exon skipping with exon 4 being spliced to exon 6. Both heterozygously affected children (age 19 and 20 years) had moderately increased ferritin levels with normal serum iron concentration and transferrin saturation. The newly described mutation was not detected in a control group consisting of 220 Caucasian individuals as verified by allele-specific polymerase chain reaction. We describe for the first time a homozygous HFE splice site mutation (IVS5+1 G/A) in a non-Caucasian patient with hereditary hemochromatosis. Although the absence of this novel HFE gene mutation in Caucasian subjects suggests that the mutation is exclusive to this family, mutation screening in populations of different ethnic background is recommended to precisely define its contribution to hereditary hemochromatosis in non-Caucasian patients.

Lipatrophic diabetes, also referred to as familial partial lipodystrophy, is a rare disease that is metabolically characterized by hypertriglyceridemia and insulin resistance. Affected patients typically present with regional loss of body fat and muscular hypertrophic appearance. Variable symptoms may comprise pancreatitis and/or eruptive xanthomas due to severe hypertriglyceridemia, acanthosis nigricans, polycystic ovaria, and carpal tunnel syndrome. Mutations within the LMNA gene on chromosome 1q21.2 were recently reported to result in the phenotype of familial partial lipodystrophy. The genetic trait is autosomal dominant. We identified a family with partial lipodystrophy carrying the R482W (Arg(482)Trp) missense mutation within LMNA. Here we present the lipoprotein characteristics in this family in detail. Clinically, the loss of sc fat and muscular hypertrophy especially of the lower extremities started as early as in childhood. Acanthosis and severe hypertriglyceridemia developed later in life, followed by diabetes. The characterization of the lipoprotein subfractions revealed that affected children present with hyperlipidemia. The presence and severity of hyperlipidemia seem to be influenced by age, apolipoprotein E genotype, and the coexistence of diabetes mellitus. In conclusion, dyslipemia is an early and prominent feature in the presented lipodystrophic family carrying the R482W mutation within LMNA.

Hereditary amyloidosis is primarily caused by mutations within the transthyretin gene. More than 75 mutations within transthyretin have been reported in causing amyloidosis. The most common mutation is the val30met mutation in the transthyretin protein (TTR-met30) caused by a mononucleic substitution from G to A (GUC to AUC) in the transthyretin gene resulting in the exchange for the amino acids valine to methionine in the corresponding protein sequence. The aim of this work is the development of a specific cleavage of TTR-met30 mRNA in the cell culture system using hammerhead ribozymes. We showed previously that chemically modified nuclease stable Inosine(15.1)-Hammerhead ribozymes are able to target the TTR-met30 mRNA with high specificity on the RNA level (Biochem. Biophys. Res. Commun. 260, 313-317, 1999). Now we present data confirming our observations on the cellular level. We used the wild-type human normal (hn) TTR expressing cell line HepG2 and the stable transfected cell line 293-TTR-met30 for TTR-met30 experiments. We cleaved the TTR-met30 and hnTTR mRNA with specific nuclease stable chemically modified Inosine(15.1)-Hammerhead ribozymes and analyzed the protein after immunoprecipitation and subsequent Western blotting. We were able to downregulate the TTR concentration by 54.5% (100% = 1.5 mg/l TTR) and also specifically to target the TTR-met30 expression in the cell culture system. The therapeutic effect was improved using cationic liposomes resulting in a total downregulation by 92.1 and 62.7% targeting hnTTR mRNA and TTR-met30 mRNA, respectively. The successful employment of Inosine(15.1)-Hammerhead ribozymes in cell culture is therefore a promising tool for the development of a gene therapeutic strategy for hereditary amyloidosis.

Very recently, mutations within the LMNA gene on chromosome 1q21.2 were shown to result in forms of muscular dystrophy, conduction-system disease, cardiomyopathy, and partial lipodystrophy. The LMNA gene encodes for the nucleophilic A-type lamins, lamin A and lamin C. These isoforms are generated by different splicing within exon 10 of LMNA. Thus lamin A/C is, besides emerin, the first known nucleophilic protein which plays a role in human disease. To date, 41 different mutations, predominantly missense, in the LMNA gene are known causing variable phenotypes. Twenty-three different mutations of LMNA have so far been shown to cause autosomal-dominant Emery-Dreifuss muscular dystrophy (EDMD2), three mutations were reported to cause limb-girdle muscular dystrophy (LGMD1B), eight mutations are known to result in dilated cardiomyopathy (CMD1A), and seven mutations were reported to cause familial partial lipodystrophy (FPL). The reports of lamin mutations including the corresponding phenotype are of great interest in order to gain insights into the function of lamin A/C. Here we summarize the mutations published to date in LMNA encoding lamin A/C., (Copyright 2000 Wiley-Liss, Inc.)

The 3'-5' single-stranded DNA(ssDNA) degrading exonuclease I of E. coli directly interacts with the E. coli ssDNA binding protein (EcoSSB). Analytical ultracentrifugation shows that all 4 carboxy-termini of an EcoSSB tetramer bind exonuclease I. Binding is weakened by increasing salt concentrations, indicating the involvement of the negatively charged amino acids of the carboxy-terminus of SSB. Mutant SSB proteins EcoSSBP176S (ssb-113) and EcoSSBF177C do not bindtoexonuclease I while EcoSSBG15D (ssb-3) does bind. In a co-precipitation assay we show that the absence of the lastten amino acids (PMDFDDDIPF) completely abolishes binding of EcoSSB to exonuclease I. The interaction does not depend on the presence of the correct amino-terminal DNA binding domain or the amino acid sequences between the DNA binding domain and the last ten amino acids. A synthetic peptide (WMDFDDDIPF), corresponding to the last nine amino acids of EcoSSB, specifically inhibits the interaction. Both EcoSSBP176S and EcoSSBF177C SSBs bind DNA similar to wild-type EcoSSB, indicating that the phenotype of ssb-113 is not an indication of altered DNA binding. The repair deficiency of either ssb-3 or ssb-113 strain can be complemented by overexpression of the respective other mutant.

The most common cause of hereditary amyloidosis (HA) is the val30met mutation in the transthyretin protein (TTR-met30). The mutation is caused by a mononucleic substitution from G to A (GUC to AUC) in the transthyretin gene resulting in the exchange for the amino acids valine to methionine in the corresponding protein sequence. The aim of our work was the development of a specific cleavage of TTR-30 mRNA using hammerhead ribozymes. We chemically modified nuclease stable hammerhead ribozymes to target the TTR-30 mRNA with high specificity. The exchange of adenosine(15.1) with inosine(15.1) in the catalytic core of the hammerhead ribozyme resulted in a change of the cleavable target sequence from N(16.2)U(16.1)H(17) to N(16. 2)C(16.1)H(17) without loss in ribozymal activity (Nucleic Acids Res. 26, 2279-2285, 1998). This modification allowed a specific cleavage of the TTR-30 mutation ("gCC Gug" to "gCC Aug"). In vitro experiments with TTR-30 mRNA demonstrated that the RNase stable inosine(15.1) hammerhead ribozyme cleaved the TTR-30 mRNA with 100% specificity and with a velocity of 0.23 min(-1), whereas no cleavage occured in the wildtype mRNA of TTR. In conclusion, the development of this NCH specific hammerhead ribozyme represents a promising tool for future in vivo therapeutic application for TTR-met30 induced hereditary amyloidosis., (Copyright 1999 Academic Press.)

There is accumulating evidence that human immunodeficiency virus type 1 (HIV-1) protease inhibitors (PIs) can induce hyperlipidaemia. To evaluate the frequency and type of hyperlipidaemia in PI-treated patients, 98 outpatients were prospectively analysed for their lipoprotein characteristics at the Medizinische Hochschule in Hannover, Germany. Fifty-seven percent of the patients studied presented with hyperlipidaemia. Both hypertrigylceridaemia (type IV and V hyperlipoproteinaemia, 33%) and hypercholesterolaemia (type IIa hyperlipoproteinaemia, 6%) were detectable. The remaining 18% had a type IIb hyperlipoproteinaemia. Increased lipid levels were highly statistically significant compared to a control group of PI-naive HIV-1-infected patients [low-density lipoprotein (LDL) 146 mg/dl (range, 53-274 mg/dl) versus 105 mg/dl (range, 22-188 mg/dl; P=0.0006); very-low-density lipoprotein (VLDL) 35.5 mg/dl (5-253 mg/dl) versus 18 mg/dl (range, 3-94 mg/dl; P=0.0002)]. All PIs used (saquinavir, indinavir, nelfinavir and ritonavir) were associated with this variable form of hyperlipidaemia according to the Fredrickson classification. There was no significant correlation of any determined lipid value with the duration of treatment. A higher frequency of the apolipoprotein E2 allele and E4 allele was observed in the hyperlipidaemic subjects. Patients with excessive hypertriglyceridaemia showed a reduced lipoprotein lipase activity. Lipodystrophy was observed especially in hyperlipidaemic patients and to a lesser extent in normolipidaemic subjects. The frequency of hyperlipidaemic risk factors was surprisingly high in the group studied, which in turn may explain the proposed increased risk of atherogenesis in HIV-1 PI-treated patients. Therefore, PI-treated subjects should also be evaluated for their lipoprotein pattern, which may require antihyperlipidaemic interventions.