Giuseppe Novelli Laboratorio di Genetica Medica Azienda Ospedaliera Policlinico Tor Vergata Viale Oxford 1 00133 Roma (Italy) Tel. 06/20900665 or 20900664 Web site: www.geneticaumana.net
Abstract: Africa is the ultimate source of modern humans and as such harbors more genetic variation than any other continent. For this reason, studies of the patterns of genetic variation in African populations are crucial to understanding how genes affect phenotypic variation, including disease predisposition. In addition, the patterns of extant genetic variation in Africa are important for understanding how genetic variation affects infectious diseases that are a major problem in Africa, such as malaria, tuberculosis, schistosomiasis, and HIV/AIDS. Therefore, elucidating the role that genetic susceptibility to infectious diseases plays is critical to improving the health of people in Africa. It is also of note that recent and ongoing social and cultural changes in sub-Saharan Africa have increased the prevalence of non-communicable diseases that will also require genetic analyses to improve disease prevention and treatment. In this review we give special attention to many of the past and ongoing studies, emphasizing those in Sub-Saharan Africans that address the role of genetic variation in human disease.
Abstract: An RNA gain-of-function of expanded transcripts is the most accredited molecular mechanism for myotonic dystrophy type 1 (DM1) and 2 (DM2). To disclose molecular parallels and divergences in pathogenesis of both disorders, we compared the expression profile of muscle biopsies from DM1 and DM2 patients to controls. DM muscle tissues showed a reduction in the major skeletal muscle chloride channel (CLCN1) and transcription factor Sp1 transcript levels and an abnormal processing of the CLCN1 and insulin receptor (IR) pre-mRNAs. No essential differences were observed in the muscle blind-like gene (MBNL1) and CUG binding protein 1 (CUGBP1) transcript levels as well as in the splicing pattern of the myotubularin-related 1 (MTMR1) gene. Macroarray analysis of 96 neuroscience-related genes revealed a considerable similar expression profile between the DM samples, reflective of a common muscle pathology origin. Using a twofold threshold, we found six misregulated genes important in calcium and potassium metabolism and in mitochondrial functions. Our results indicate that the DM1 and DM2 overlapping clinical phenotypes may derive from a common trans acting mechanism that traps and influences shared genes and proteins. An RNA gain-of-function of expanded transcripts is the most accredited molecular mechanism for myotonic dystrophy type 1 (DM1) and 2 (DM2). To disclose molecular parallels and divergences in pathogenesis of both disorders, we compared the expression profile of muscle biopsies from DM1 and DM2 patients to controls. DM muscle tissues showed a reduction in the major skeletal muscle chloride channel (CLCN1) and transcription factor Sp1 transcript levels and an abnormal processing of the CLCN1 and insulin receptor (IR) pre-mRNAs. No essential differences were observed in the muscle blind-like gene (MBNL1) and CUG binding protein 1 (CUGBP1) transcript levels as well as in the splicing pattern of the myotubularin-related 1 (MTMR1) gene. Macroarray analysis of 96 neuroscience-related genes revealed a considerable similar expression profile between the DM samples, reflective of a common muscle pathology origin. Using a twofold threshold, we found six misregulated genes important in calcium and potassium metabolism and in mitochondrial functions. Our results indicate that the DM1 and DM2 overlapping clinical phenotypes may derive from a common trans acting mechanism that traps and influences shared genes and proteins.
Abstract: Cystic fibrosis (CF) is caused by mutations in the gene encoding the cystic fibrosis conductance transmembrane regulator (CFTR). Symptoms are pancreatic insufficiency, chronic obstructive lung disease, liver disease, chronic sinusitis and infertility in male patients. The phenotypic variability may be explained only in part by the more than 1200 CFTR mutations, which are grouped into six different classes, according to their effect on the protein ranging from a severe (no synthesis or blocked processing) to mild mutation (altered conductance or reduced synthesis). However, it is now accepted that other genes (CF modifiers) influence the phenotypic spectrum of the disease. In order to identify CF modifier genes, we built a low-density home-made oligoarray containing 144 genes selected according to biochemical criteria and evaluated their expression in two CF bronchial epithelial cell lines (CuFi1 F508del/F508del; CuFi3 F508del/R553X). If we consider both cell lines, 38 genes (26.3%) show an altered expression pattern with a threshold > +/-1.5. Of these 38 genes, 12 are altered in CuFi1, and 26 in CuFi3. Some of these genes share the same expression pattern in both cell lines, while others have a different behaviour. These results were validated by a QRT-PCR assay (R2 CuFi1 = 0.81 and R2 CuFi3 = 0.91). These data could suggest that the presence of a class I allele (R553X) determines a more profound alteration of gene expression pattern than the presence of a class II allele (F508del). The identification of the genes altered by a specific CF mutation could lead to the development of a pharmacological approach specific for different CFTR genotypes.
Abstract: BACKGROUND: Cystic fibrosis (CF) is a multisystem disorder characterised by mutations of the CFTR gene, which encodes for an important component in the coordination of electrolyte movement across of epithelial cell membranes. Symptoms are pulmonary disease, pancreatic exocrine insufficiency, male infertility and elevated sweat concentrations. The CFTR gene has numerous mutations (>1000) and functionally important polymorphisms (>200). Early identification is important to provide appropriate therapeutic interventions, prognostic and genetic counselling and to ensure access to specialised medical services. However, molecular diagnosis by direct mutation screening has proved difficult in certain ethnic groups due to allelic heterogeneity and variable frequency of causative mutations. METHODS: We applied a gene scanning approach using DHPLC system for analysing specifically all CFTR exons and characterise sequence variations in a subgroup of CF Italian patients from the Lazio region (Central Italy) characterised by an extensive allelic heterogeneity. RESULTS: We have identified a total of 36 different mutations representing 88% of the CF chromosomes. Among these are two novel CFTR mutations, including one missense (H199R) and one microdeletion (4167delCTAAGCC). CONCLUSION: Using this approach, we were able to increase our standard power rate of mutation detection of about 11% (77% vs. 88%).
Abstract: Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasians, with a frequency of approximately 1 in 3000 live births. The mutated gene is a defective chloride channel in epithelial cells, named cystic fibrosis transmembrane conductance regulator (CFTR). Several different protocols for the scanning of the entire gene have aided molecular diagnosis and improved our understanding of the disorder's pathophysiology, but also showed the disease's complexity. Therefore, CF phenotype remains difficult to predict from CFTR mutation data alone: several studies have suggested that additional genes could modulate its clinical outcome. Gene replacement therapy is still far from being used in patients with CF, mostly due to the difficulties with targeting the appropriate cells. In this review, we summarize recent advances, both in the pharmacological and gene therapy field, aimed for the treatment of the disease.
Abstract: OBJECTIVE: Cystic fibrosis (CF; OMIM# 219700) is caused by mutation in the CF transmembrane regulator (CFTR) gene. We investigate whether the (paternal) M348K mutation is a benign polymorphism or a disease-causing mutation in a patient clinically affected with CF, with the second (maternal) CFTR allele identified as N1303K. METHODS: The patient and his father were studied for the presence of mutations in the CFTR gene using the DHPLC system to analyze all CFTR exons. Amplicons showing an abnormal elution profile were sequenced. RESULTS: The CFTR gene from the healthy father has two mutations, M348K and G1244E. The affected son inherited only the G1244E paternal mutation from his father, and hence the two paternal mutations are trans and do not occur in the same CFTR gene. The patient's genotype is G1244E(paternal)/N1303K(maternal). This information was used to study an ongoing pregnancy of the couple, where the fetus inherited the same genotype as the affected proband and therefore is affected. CONCLUSION: M348K in the CFTR gene is not a mutation causing CF, but a rare polymorphism. These data are important for genetic counseling and prenatal diagnosis and illustrate the importance of full sequence data when studying rare mutations. Copyright (c) 2004 John Wiley & Sons, Ltd.
Abstract: Mandibuloacral dysplasia (MAD) is a rare autosomal recessive disorder caused basically by a missense mutation within the LMNA gene, which encodes for lamin A/C. We have used gene expression profiling to characterize the specificity of molecular changes induced by the prevalent MAD mutation (R527H). A total of 5531 transcripts expressed in human dermis were investigated in two MAD patients, both carrying the R527H mutation, and three control subjects (age and sex matched). Transcription profiles revealed a differential expression in MAD vs. control fibroblasts in at least 1992 genes. Sixty-seven of these genes showed a common altered pattern in both patients with a threshold expression level >+/-2. Nevertheless, a large number of these genes (43.3%) are ESTs or encode for protein with unknown function; the other genes are involved in biological processes or pathways such as cell adhesion, cell cycle, cellular metabolism, and transcription. Quantitative RT-PCR was applied to validate the microarray results (R2= 0.76). Analysis of the effect of the prevalent MAD mutation (R527H) over the transcriptional pattern of genes expressed in the human dermis showed that this LMNA gene mutation has pleiotropic effects on a limited number of genes. Further characterization of these effects might contribute to understanding the molecular pathogenesis of this disorder.
