Multifactor effects and evidence of potential interaction between complement factor H Y402H and LOC387715 A69S in age-related macular degeneration.

BACKGROUND: Variants in the complement cascade genes and the LOC387715/HTRA1, have been widely reported to associate with age-related macular degeneration (AMD), the most common cause of visual impairment in industrialized countries. METHODS/PRINCIPAL FINDINGS: We investigated the association between the LOC387715 A69S and complement component C3 R102G risk alleles in the Finnish case-control material and found a significant association with both variants (OR 2.98, p = 3.75 x 10(-9); non-AMD controls and OR 2.79, p = 2.78 x 10(-19), blood donor controls and OR 1.83, p = 0.008; non-AMD controls and OR 1.39, p = 0.039; blood donor controls), respectively. Previously, we have shown a strong association between complement factor H (CFH) Y402H and AMD in the Finnish population. A carrier of at least one risk allele in each of the three susceptibility loci (LOC387715, C3, CFH) had an 18-fold risk of AMD when compared to a non-carrier homozygote in all three loci. A tentative gene-gene interaction between the two major AMD-associated loci, LOC387715 and CFH, was found in this study using a multiplicative (logistic regression) model, a synergy index (departure-from-additivity model) and the mutual information method (MI), suggesting that a common causative pathway may exist for these genes. Smoking (ever vs. never) exerted an extra risk for AMD, but somewhat surprisingly, only in connection with other factors such as sex and the C3 genotype. Population attributable risks (PAR) for the CFH, LOC387715 and C3 variants were 58.2%, 51.4% and 5.8%, respectively, the summary PAR for the three variants being 65.4%. CONCLUSIONS/SIGNIFICANCE: Evidence for gene-gene interaction between two major AMD associated loci CFH and LOC387715 was obtained using three methods, logistic regression, a synergy index and the mutual information (MI) index.

Molecularly defined adult-type hypolactasia among working age people with reference to milk consumption and gastrointestinal symptoms.

AIM: To study milk consumption and subjective milk-related symptoms in adults genotyped for adult-type hypolactasia. METHODS: A total of 1900 Finnish adults were genotyped for the C/T(-13910) variant of adult-type hypolactasia and filled in a structured questionnaire concerning milk consumption and gastrointestinal problems. RESULTS: The C/C(-13910) genotype of adult-type hypolactasia was present in 18% of the study population. The prevalence of the C/C(-13910) genotype was higher among subjects who were undergoing investigations because of abdominal symptoms (24%, P < 0.05). Those with the C/C(-13910) genotype drank less milk than subjects with either the C/T(-13910) or the T/T(-13910) genotype of lactase persistence (18% vs 38%; 18% vs 36%, P < 0.01). Subjects with the C/C(-13910) genotype had experienced more gastrointestinal symptoms (84%) during the preceding three-month period than those with the C/T(-13910) (79%, P < 0.05) or the T/T(-13910) genotype (78 %, P < 0.05). Only 9% (29/338) of the subjects with the C/C(-13910) genotype consumed milk and reported no symptoms from it. CONCLUSION: Gastrointestinal symptoms are more common among adults with the C/C(-13910) genotype of adult-type hypolactasia than in those with genotypes of lactase persistence.

Sequence analysis of the genes encoding for H+/K+-ATPase in autoimmune gastritis.

BACKGROUND: H+/K+-ATPase is the target autoantigen in autoimmune gastritis (AIG), an organ-specific autoimmune disease with a strong hereditary component. AIM: To detect possible polymorphisms in H+/K+-ATPase alpha- and beta-subunits in AIG patients. METHODS: Blood samples from 12 Finnish AIG patients were sequenced for the coding regions of genes encoding for H+/K+-ATPase alpha- and beta-subunits; 50-52 Finnish anonymous blood donors served as controls. Additionally, parietal cell and Helicobacter pylori antibodies and serum pepsinogen I levels (PG I) were analysed. RESULTS: In the alpha-subunit, all patients and controls had C-allele at the non-synonymous c.824T>C single nucleotide polymorphism (SNP) resulting in valine substitution for alanine (Val265Ala). In the beta-subunit, a previously unknown non-synonymous SNP resulting in a substitution of alanine residue for valine (Ala248Val) was found in exon 7 in a single patient and none of the controls. All patients had low serum PG I levels and elevated parietal cell antibodies; three had positive H. pylori serology. CONCLUSIONS: At the non-synonymous SNP c.824T>C in the alpha-subunit of H+/K+-ATPase most Finnish individuals with or without AIG have C allele. Genetic variants of the coding regions of genes for H+/K+-ATPase alpha- and beta-subunits are not associated with AIG in Finnish patients.

Molecular genetics of adult-type hypolactasia.

Adult-type hypolactasia (lactase non-persistence; primary lactose malabsorption) is characterized by the down-regulation of the lactase enzyme activity in the intestinal wall after weaning. The down-regulation is genetically determined and a mutation has occurred that has made part of mankind tolerate milk (lactase persistence). A DNA-variant, single nucleotide polymorphism C/T-13910 located 13 910 base pairs (bp) upstream of the lactase gene (LCT) at chromosome 2q21-22 has been shown to associate with the lactase persistence/non-persistence trait both in family and case-control studies. The C/T-13910 variant is located in a non-coding region in the genome in intron 13 of the minichromosome maintenance type 6 gene (MCM6). Significant correlation between the C/T-13910-variant and lactase activity in the intestinal biopsy specimens has been demonstrated. Molecular epidemiological studies on the prevalence of the C/C-13910 genotype associated with low lactase activity are in agreement with the prevalence figures for adult type hypolactasia in>70 diverse ethnic groups studied. Recent functional studies have suggested that this variant has an enhancer effect over the lactase gene. Based on the biochemical, functional, genetic and molecular epidemiological studies of the C/T-13910 variant, genetic testing for adult type hypolactasia has been introduced into clinical practice in Finland. Identification of the genetic change has highlighted the role of non-coding variants in the regulation of common genes and created new tools to study the mechanism of lactase enzyme activation.