Irene M. Predazzi

LOX-1/LOXIN: the yin/yang of atheroscleorosis.

Atherosclerosis is the first cause of death in industrialized countries. Together with traditional risk factors (male gender, hypercholesterolemia, hypertension, diabetes, smoking and age), non-traditional risk factors have also been described as predisposing to this disease. Among these, oxidized low density lipoproteins (OxLDL) have been described in correlation to many proatherogenic processes. Many of the effects of OxLDL are mediated by the lectin like oxidized low density lipoprotein receptor 1 (LOX-1), expressed on endothelial cells, macrophages, SMCs and platelets. LOX-1 is encoded by the lectin like oxidized low density lipoprotein receptor 1 (OLR1) gene, located in the p12.3–p13.2 region of human chromosome 12. Variations on this gene have been studied extensively both at the functional and epidemiological level. Despite the fact that functional roles for two variants have been demonstrated, the epidemiological studies have provided inconsistent and inconclusive results. Of particular interest, it has been demonstrated that a linkage disequilibirum block of SNPs located in the intronic sequence of the OLR1 gene modulates the alternative splicing of OLR1 mRNA, leading to different ratios of LOX-1 full receptor and LOXIN, an isoform lacking part of the functional domain. As demonstrated, LOXIN acts by blocking the negative effective of LOX-1 activation. Here we review the state of the art regarding LOX-1, LOXIN, and the functional effects that are associated with the interaction of these molecules.

G6PD A- deficiency and severe malaria in The Gambia: heterozygote advantage and possible homozygote disadvantage.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is frequent in Africa, because it confers resistance to Plasmodium falciparum malaria; however, the nature of the protection and the genotypes associated with it have been controversial. In 1972, Bienzle and others described protection from malaria in West African females heterozygous for G6PD A-. They determined that G6PD A- heterozygotes had lower parasite counts than A- homozygotes, hemizygous males, and normal individuals. However, other studies have reached different conclusions about the protective genotypes. DNA samples from 135 children with severe malaria and 146 children with mild malaria from The Gambia were genotyped for the G6PD A- mutation that is most frequent among Gambians (G6PD 968 T->C); there was a marked deficiency of heterozygotes and an excess of homozygotes with severe malaria, producing a strong deviation from Hardy-Weinberg equilibrium. Our results support the protective effect in G6PD A- heterozygous females and suggest that homozygotes might be more susceptible to severe malaria attacks.

Association between OLR1 K167N SNP and intima media thickness of the common carotid artery in the general population.

Background and Purpose The lectin-like oxidised LDL receptor-1 (OLR1) gene encodes a scavenger receptor implicated in the pathogenesis of atherosclerosis. Although functional roles have been suggested for two variants, epidemiological studies on OLR1 have been inconsistent. Methods - We tested the association between the non-synonymous substitution K167N (rs11053646) and intima media thickness of the common carotid artery (CCA-IMT) in 2,141 samples from the Progression of Lesions in the Intima of the Carotid (PLIC) study (a prospective population-based study). Results Significantly increased IMT was observed in male carriers of the minor C (N) allele compared to GC and GG (KN and KK) genotype. Functional analysis on macrophages suggested a decreased association to Ox-LDL in NN carriers compared to KN and KK carriers which is also associated with a reduced OLR1 mRNA expression. Macrophages from NN carriers present also a specific inflammatory gene expression pattern compared to cells from KN and KK carriers. Conclusions These data suggest that the 167N variant of LOX-1 receptor affects the atherogenic process in the carotid artery prior to evidence of disease through an inflammatory process.

In silico and in vitro comparative analysis to select, validate and test SNPs for human identification

BackgroundThe recent advances in human genetics have recently provided new insights into phenotypic variation and genome variability. Current forensic DNA techniques involve the search for genetic similarities and differences between biological samples. Consequently the selection of ideal genomic biomarkers for human identification is crucial in order to ensure the highest stability and reproducibility of results.ResultsIn the present study, we selected and validated 24 SNPs which are useful in human identification in 1,040 unrelated samples originating from three different populations (Italian, Benin Gulf and Mongolian). A Rigorous in silico selection of these markers provided a list of SNPs with very constant frequencies across the populations tested as demonstrated by the Fst values. Furthermore, these SNPs also showed a high specificity for the human genome (only 5 SNPs gave positive results when amplified in non-human DNA).ConclusionComparison between in silico and in vitro analysis showed that current SNPs databases can efficiently improve and facilitate the selection of markers because most of the analyses performed (Fst, r2, heterozigosity) in more than 1,000 samples confirmed available population data.

Role of genomics in cardiovascular medicine.

As all branches of science grow and new experimental techniques become readily accessible, our knowledge of medicine is likely to increase exponentially in the coming years. Recently developed technologies have revolutionized our analytical capacities, leading to vast knowledge of many genes or genomic regions involved in the pathogenesis of congenital heart diseases, which are often associated with other genetic syndromes, coronary artery disease and non-ischemic cardiomyopathies and channelopathies. The knowledge-base of the genesis of cardiovascular diseases is likely going to be further revolutionized in this new era of genomic medicine. Here, we review the advances that have been made over the last several years in this field and discuss different genetic mechanisms that have been shown to underlie a variety of cardiovascular diseases.

APOE haplotypes are associated with human longevity in a Central Italy population: Evidence for epistasis with HP 1/2 polymorphism

BACKGROUND Apolipoprotein E (APOE) functional haplotypes determined by rs429358 and rs7412 SNPs have been extensively studied and found to be one of the most consistent association in human longevity studies. However, the search for longevity-determining genes in human has largely neglected the operation of genetic interactions. METHODS APOE haplotypes have been determined for 1072 unrelated healthy individuals from Central Italy, 18-106 years old, divided into three gender-specific age classes defined according to demographic information and accounting for the different survival between sexes. The epistasis between APOE haplotypes and Haptoglobin (HP) 1/2 polymorphism was tested according to three-way contingency table analysis by a log-linear model. RESULTS APOE genotype and haplotype distributions differ significantly along the age classes (Genotype: p=0.014; Haplotype: p=0.005) with APOE*ε4 genotype status and haplotype displaying negative association (Genotype: O.R.=0.377, p=0.002, Haplotype: O.R.=0.447, p=0.005). A significant interaction between APOE*ε4 genotype status, HP 1/2 genotype and age classes is reported (p=0.006). CONCLUSION APOE haplotypes are significantly associated with longevity in our population. Of note, HP*1/*1 genotype seems to protects APOE*ε4 carriers from age-related negative selection. Collectively, these results also suggest and claim for further investigations on APOE/HP interaction in other age-related diseases such as Alzheimers disease, atherosclerosis and Parkinsons disease.

Putting Pleiotropy and Selection into Context Defines a New Paradigm for Interpreting Genetic Data

Background—Natural selection shapes many human genes, including some related to complex diseases. Understanding how selection affects genes, especially pleiotropic ones, may be important in evaluating disease associations and the role played by environmental variation. This may be of particular interest for genes with antagonistic roles that cause divergent patterns of selection. The lectin-like low-density lipoprotein 1 receptor, encoded by OLR1, is exemplary. It has antagonistic functions in the cardiovascular and immune systems because the same protein domain binds oxidized low-density lipoprotein and bacterial cell wall proteins, the former contributing to atherosclerosis and the latter presumably protecting from infection. We studied patterns of selection in this gene, in humans and nonhuman primates, to determine whether variable selection can lead to conflicting results in cardiovascular disease association studies. Methods and Results—We analyzed sequences from 11 nonhuman primate species, as well as single-nucleotide polymorphisms and sequence data from multiple human populations. Results indicate that the derived allele is favored across primate lineages (probably because of recent positive selection). However, both the derived and ancestral alleles were maintained in human populations, especially European ones (possibly because of balancing selection derived from dual roles of LOX-1). Balancing selection likely reflects response to diverse environmental pressures among humans. Conclusions—These data indicate that differential selection patterns, within and between species, in OLR1 render association studies difficult to replicate even if the gene is etiologically connected to cardiovascular disease. Selection analyses can identify genes exhibiting gene–environment interactions critical for unraveling disease association.

Frequency assessment of SNPs for forensic identification in different populations

Allele frequencies for 16 previously described autosomal SNPs were tested in 1020 unrelated individuals originating from three different continents (Africa, Asia and Europe). The populations analyzed included Africans from Benin Gulf (180), Asians from Mongolia (160) and Europeans from Italy (680).

PTX3 genetic variation and dizygotic twinning in the Gambia: could pleiotropy with innate immunity explain common dizygotic twinning in Africa?

Dizygotic (DZ) twinning has a genetic component and is common among sub‐Saharan Africans; in The Gambia its frequency is up to 3% of live births. Variation in PTX3, encoding Pentraxin 3, a soluble pattern recognition receptor that plays an important role both in innate immunity and in female fertility, has been associated with resistance to Mycobacterium tuberculosis pulmonary disease and to Pseudomonas aeruginosa infection in cystic fibrosis patients. We tested whether PTX3 variants in Gambian women associate with DZ twinning, by genotyping five PTX3 single nucleotide polymorphisms (SNPs) in 130 sister pairs (96 full sibs and 34 half sibs) who had DZ twins. Two, three and five SNP haplotypes differed in frequency between twinning mothers and those without a history of twinning (from P= 0.006 to 3.03e‐06 for two SNP and three SNP haplotypes, respectively). Twinning mothers and West African tuberculosis‐controls from a previous study shared several frequent haplotypes. Most importantly, our data are consistent with an independently reported association of PTX3 and female fertility in a sample from Ghana. Taken together, these results indicate that selective pressure on PTX3 variants that affect the innate immune response to infectious agents, could also produce the observed high incidence of DZ twinning in Gambians.

Population differences in allele frequencies at the OLR1 locus may suggest geographic disparities in cardiovascular risk events

Abstract Background: Several studies have demonstrated a link between cardiovascular disease (CVD) susceptibility and the genetic background of populations. Endothelial activation and dysfunction induced by oxidized low-density lipoprotein (ox-LDL) is one of the key steps in the initiation of atherosclerosis. The oxidized low density lipoprotein (lectin-like) receptor 1 (OLR1) gene is the main receptor of ox-LDL. We have previously characterized two polymorphisms (rs3736235 and rs11053646) associated with the risk for coronary artery disease (CAD) and acute myocardial infarction (AMI). Aim: Given their clinical significance, it is of interest to know the distribution of these variants in populations from different continents. Subjects and methods: A total of 1229 individuals from 17 different African, Asian and European populations was genotyped for the two considered markers. Results: The high frequencies of ancestral alleles in South-Saharan populations is concordant with the African origin of our species. The results highlight that African populations are closer to Asians, and clearly separated from the Europeans. Conclusion: The results confirm significant genetic structuring among populations and suggest a possible basis for varying susceptibility to CVD among groups correlated with the geographical location of populations linked with the migrations out of Africa, or with different lifestyle.