Aip regulates cAMP signalling and GH secretion in GH3 cells.

Mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene have been linked to predisposition to pituitary adenomas. However, the mechanism by which this occurs remains unknown. AIP interacts with a number of interesting proteins, including members of the cAMP signalling pathway that has been shown to be consistently altered in pituitary tumours. The functional role of Aip was investigated using both over-expression and knock down of Aip in GH3 cells. cAMP signalling and its downstream effectors, including GH secretion, were then investigated. cAMP signalling was analysed using cAMP assays, cAMP-response element-promoter luciferase reporter assays, real-time PCR and finally secreted GH quantification. Over-expression of wild-type (WT)-Aip reduced forskolin-induced cAMP signalling at the total cAMP level, luciferase reporter activity and target gene expression, when compared with empty vector and the non-functional R304X mutant. Additionally, GH secretion was reduced in WT-Aip over-expressing GH3 cells treated with forskolin. Knock down of endogenous Aip resulted in increased cAMP signalling but a decrease in GH secretion was also noted. Inhibition of phosphodiesterase activity using general and selective inhibitors did not completely ablate the effect of Aip on forskolin-augmented cAMP signalling. A mechanism by which Aip acts as a tumour suppressor, by maintaining a low cAMP signalling and concentration, is suggested. Mutations of Aip render the protein incapable of such activity. This effect appears not to be mediated by the AIP-PDE interaction, suggesting the involvement of other interacting partners in mediating this outcome.

Frequency of the CCR5-Delta32 polymorphism in the Maltese population at birth.

In this study, the frequency of the CCR5-Delta32 polymorphism was estimated in the human population of Malta. The frequency of the CCR5-Delta32 allele was found to be 1.1% which was similar to that of other island populations, and agree with the north to south gradient observed across Europe.

No effects of a synonymous variant within the CD59 gene on its protein product in duodenal biopsies of coeliac individuals.

A novel rare variant within the CD59 gene was linked with coeliac disease in a family with high incidence of disease. Functional analyses of this variant were performed using complementary DNA analysis and protein analysis in paraffin-embedded duodenal biopsies from affected individuals and controls. No effects on pre-mRNA or size of linear protein were observed, although these results do not exclude the possible effects of this variant on co-translational protein folding.

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.

TNFRSF11B gene variants and bone mineral density in postmenopausal women in Malta.

UNLABELLED: A number of polymorphisms in various genes have been identified and associated with bone mineral density (BMD) and with an increased risk of osteoporosis. OBJECTIVE: In this study, three single nucleotide polymorphisms (SNPs) within the TNFRSF11B gene were studied for association with an increased risk of osteoporosis in postmenopausal Maltese women (n=126). METHODOLOGY: Analysis was performed by PCR restriction fragment length polymorphism (RFLP) while BMD at the lumbar spine, femoral neck, Ward's triangle and trochanter was measured by DEXA. RESULTS: No significant association was observed between genotypes and BMD for all polymorphisms studied within this gene. Homozygotes CC (T(950)-C) were observed to have the highest BMD at all anatomical sites although statistical significance was not reached when comparing the three genotypes. A statistical significant difference was observed in the distribution of genotype frequencies for this polymorphism between normal individuals and those that were either osteopenic or osteoporotic at one or both anatomical sites, with the TT genotype associated more frequently with low BMD. The T(950)-C and G(1181)-C polymorphisms were in strong linkage disequilibrium with each other but not with the A(163)-G polymorphism further upstream in the OPG promoter. Statistical significance was reached when constructing haplotypes, where the A-T-G haplotype was found to be more frequent in individuals with low BMD. CONCLUSIONS: These results indicate the possible role of TNFRSF11B gene variants in postmenopausal bone loss in women in Malta.

Associations of polymorphisms in the vitamin D receptor gene (BsmI and FokI) with bone mineral density in postmenopausal women in Malta.

Previous studies have suggested that variations in the vitamin D receptor (VDR) gene are related to bone mineral density (BMD). In this study, the T-->C transition in the start codon and the G-->A polymorphism at the 3' end of the VDR gene, identified by endonucleases FokI and BsmI, respectively, were analysed and correlated with BMD in postmenopausal Maltese women ( n=104). Genotype frequencies observed for the VDR start codon polymorphism (SCP) were CC: 60.4%; CT: 30.7% and TT: 8.9%, while those observed for the 3' in this study were GG: 16.4%; GA: 51.9%; AA: 31.7%. In postmenopausal women, both lumbar and femoral BMD were observed to be highest in CC homozygotes for the FokI genotype and in GG homozygotes for the BsmI genotype, although in both groups the difference between the genotypes was not statistically significant, even after adjusting BMD for age, BMI and years since menopause. No evidence of linkage disequilibrium between the two alleles was observed.

Pyridinium crosslinks excretion in patients with rheumatoid arthritis. Correlation with disease activity and glucocorticoid treatment.

In patients with rheumatoid arthritis, significant positive correlations were found between urinary pyridinium crosslinks and C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and articular index. Also an inverse correlation was observed between pyridinium crosslinks excretion and grip strength. Glucocorticoid therapy, equivalent to daily doses of 7.5 mg of prednisolone or less, did not appear to have deleterious effect on bone metabolism in these patients as measured by urinary pyridinium crosslinks.