Genetic studies of osteoporosis in Malta : a review

Osteoporosis is a complex metabolic disease with a strong genetic component which results in a decrease in bone mineral density and deterioration in the microarchitecture of bone, leading to an increased risk of fractures. During the last decade, a number of genetic studies of the Maltese population were performed to determine a potential genetic component which increases the individual’s susceptibility to osteoporosis. Both family and population case-control approaches were used. Linkage analysis using large affected families has identified a region on chromosome 11p12, following which functional studies have shown that variations within two genes found in that region namely, TRAF6 and CD44, affect gene expression, and, more specifically, pre-mRNA splicing in the case of CD44. This is the first report of strong suggestive linkage of 11p12 to osteoporosis. Using the candidate gene approach, selected candidate genes, which had been studied in other populations and been found to increase susceptibility to osteoporosis to varying degrees in some of them, included those coding for the vitamin D and oestrogen receptors (VDR & ER1), osteoprotegerin (TNFRSF11B), collagen type 1 (COL1A1), methylenetetrahydrofolate reductase (MTHFR) and lipoprotein receptor related protein (LRP)-5. In the Maltese population, the most significant result showed that a polymorphism in the promoter region of TNFRSF11B, which codes for osteoprotegerin, had a significant effect on bone mineral density, thus increasing the susceptibility to osteoporosis. These studies have shown that variations within three different genes, namely TRAF6, CD44 and TNFRSF11B, all involved in osteoclast biology, might increase the risk of osteoporosis and could therefore serve as targets for novel therapeutic agents.peer-reviewe

Linkage to chromosome 11p12 in two Maltese families with a highly penetrant form of osteoporosis

Osteoporosis is a metabolic bone disease with a strong genetic component. Family-based linkage studies were performed by a number of investigators to try to identify loci that might contain genes responsible for an increased susceptibility to osteoporosis. A whole-genome linkage scan using 400 microsatellite markers was performed in 27 members from two Maltese families with a highly penetrant form of osteoporosis. The phenotype was defined by lumbar and femoral z-scores calculated after measurement of bone mineral density by DEXA. Both males and females were among the affected individuals. Multipoint parametric and non-parametric linkage analyses were performed by EasyLinkage v4.01 using GENEHUNTER v2.1, assuming dominant and recessive modes of inheritance with variable penetrance. Evidence of linkage was observed to a marker at 11p12 where a non-parametric LOD score of 5.77 (P¼0.0006) was obtained. A maximum heterogeneity LOD score of 2.55 for this region was obtained for the dominant mode of inheritance with 90% penetrance and a phenocopy rate of 1%. Following fine mapping, the critical interval was narrowed to a region that is 52.94cM from 11p-telomere. In this region, the gene for tumour necrosis factor receptor-associated factor 6 (TRAF6) is located approximately 1 cM away from the indicated marker. Sequencing of the promoter region and exons of the TRAF6 gene revealed three sequence variants, one of which was found in three affected members within one family.peer-reviewe

Biochemical predictors of bone mineral density and fracture susceptibility : results from a Maltese study

Osteoporosis is a multifactorial skeletal disease characterised by low bone mass and micro architectural deterioration, leading to increased fracture susceptibility [1,2]. In Malta, 20% of women and 6% of men aged 50 years and older are estimated to be affected with steoporosis [3]. Fracture is the most significant clinical consequence of osteoporosis, with the most common, debilitating, and costly fractures being those of the spine, hip and wrist [1]. A number of environmental and genetic risk factors are known to affect bone mineral density (BMD), which in turn impacts fracture outcome [4,5]. Furthermore, other parameters reflecting calcium homeostasis, matrix mineralisation, and bone formation can also be targeted and measured in blood. Levels of serum calcium, serum albumin, and total serum alkaline phosphatase (sALP) are suggested as potential indicative markers of osteoporosis and/or fracture susceptibility, and increased frailty [5,6].peer-reviewe

Superoxide and superoxide dismutase in red blood cells

In 1969 a previously obscure copper protein of red blood cells, erythrocuprein, was shown to catalyse the dismutation of superoxide radicals. Erythrocuprein thus became superoxide dismutase and the object of intensive study. Superoxide dismutase is typically an enzyme of aerobic organisms which utilize oxygen as the major electron acceptor. The presence of superoxide dismutase in microorganisms has been found to parallel their tolerance for oxygen. We recently described the isolation and properties of two forms of superoxide dismutase from human erythrocytes, SOD I and SOD II (Bannister et al., 1976). These can be obtained from a haemolysate of red blood cells after precipitation of the hemoglobin with a mixture of ethanol and chloroform.peer-reviewe

Variants within protectin (CD59) and CD44 genes linked to an inherited haplotype in a family with coeliac disease

Coeliac disease (CD) is an autoimmune disorder characterised by inflammation, villous atrophy and hyperplasia of the small intestinal mucosa that affects genetically susceptible individuals. A genome-wide scan was performed in 17 family members with high incidence of CD. Highest nonparametric linkage (NPL) and logarithm of odds (LOD) scores were of 6.21 (P = 0.0107) and 2.57, respectively, to a region on chromosome 11p13-12. Following fine mapping, NPL and LOD scores did not change, but the linkage interval on chromosome 11 was narrowed to a region that is approximately 50.94 cM from pTer. Two inherited haplotypes on chromosomes 11p13-12 and 9q21 were observed in all affected members but not in the majority of clinically normal individuals. Sequencing of genes at region 11p13-12 showed a number of sequence variants, two of which were linked with the inherited haplotype. One of these variants in the CD59 gene was found at a very low frequency in the population and could possibly affect pre-messenger RNA splicing. This study is of particular importance for the identification of novel genes that might be responsible for CD other than human leukocyte antigen.peer-reviewe

Tumor-infiltrating B lymphocytes as an efficient source of highly specific immunoglobulins recognizing tumor cells

<p>Abstract</p> <p>Background</p> <p>There is much evidence that tumor cells elicit a humoral immune response in patients. In most cases, the presence of antibodies in peripheral blood is detected only in small proportion of patients with tumors overexpressing the corresponding antigen. In the present study, we analyzed the significance of local humoral response provided by tumor-infiltrating lymphocytes in breast cancer patients.</p> <p>Methods</p> <p>The ability of a patient's immune system to produce specific antibodies inside tumor tissue, capable of recognizing tumor cells, was explored through analysis of the oligoclonality of antibodies derived from tumor-infiltrating lymphocytes and construction of a series of recombinant antibody libraries in scFv format, derived from breast tumor-infiltrating B lymphocytes. These libraries and one from peripheral blood lymphocytes of a single breast cancer patient were panned against three purified surface tumor antigens, such as CEA, MUC1 and ED-B domain, and against intact MCF7 breast carcinoma cells.</p> <p>Results</p> <p>Application of novel display vector, pKM19, allowed isolation of a large panel of breast cancer-specific antibodies against known tumor antigens, as well as against breast carcinoma cells. Reactivity of novel scFvs was confirmed by ELISA, immunohistochemistry, fluorescence staining and flow cytometry. We demonstrated that seven of ten primary breast tumor specimens, obtained using discarded surgical material, could be exploited as an appropriate source for generation of phage display libraries, giving highly specific antitumor antibodies which recognize heterologous tumor cells.</p> <p>Conclusion</p> <p>Local humoral immune response within tumor tissue in breast cancer patients frequently has an oligoclonal character. Efficient selection of specific antitumor antibodies from recombinant antibody libraries, derived from such oligoclonal tumor-infiltrated B lymphocytes, indicates the presence of natural immune response against tumor antigens in these patients. The described method is very promising for development of antitumor antibodies, potentially useful for diagnostic and therapeutic approaches.</p