Katariina Kainulainen

Apolipoprotein E, Dementia, and Cortical Deposition of β-Amyloid Protein

BACKGROUNDnThe epsilon 4 allele of apolipoprotein E has been associated with an increased risk of late-onset Alzheimers disease. In a cohort of elderly subjects we prospectively investigated the relation between the apolipoprotein E genotype, dementia, and the accumulation of beta-amyloid protein in the cerebral cortex.nnnMETHODSnAutopsy involving neuropathological analysis and DNA analysis of frozen blood samples were performed in 92 of 271 persons who were at least 85 years of age, who had been living in Vantaa, Finland, on April 1, 1991, and who had died between that time and the end of 1993. All subjects had been tested for dementia. Apolipoprotein E genotyping was done with a solid-phase minisequencing technique. The percentage of the cortex occupied by methenamine silver-stained plaques was used as an estimate of the extent of beta-amyloid protein deposition.nnnRESULTSnThe frequency of the epsilon 4 allele was significantly higher in the subjects with Alzheimers disease than in the subjects without dementia (30 percent vs. 8 percent, P < 0.001). There was a greater accumulation of beta-amyloid protein in the brain and more neurofibrillary tangles in the subjects with the epsilon 4 allele than in those without it (P < 0.001). The deposition of beta-amyloid protein varied according to the genotype in both the subjects with dementia and those without dementia: it was lowest in those with the epsilon 2/epsilon 3 genotype, intermediate in those with the epsilon 3/epsilon 3 genotype, and highest in those with the epsilon 3/epsilon 4 genotype. A single subject had the epsilon 4/epsilon 4 genotype and had dementia.nnnCONCLUSIONSnThe epsilon 4 allele of apolipoprotein E is significantly associated with Alzheimers disease. Even in elderly subjects without dementia, the apolipoprotein E genotype is related to the degree of deposition of beta-amyloid protein in the cerebral cortex.

Arrhythmic disorder mapped to chromosome 1q42–q43 causes malignant polymorphic ventricular tachycardia in structurally normal hearts

OBJECTIVESnThe purpose of this study was to provide clinical and anatomical characteristics as well as genetic background of a malignant arrhythmogenic disorder.nnnBACKGROUNDnAn inherited autosomally dominant cardiac syndrome causing stress-induced polymorphic ventricular tachycardia and syncope in the absence of structural myocardial changes was detected in two families.nnnMETHODSnTwo unrelated families with six victims of sudden death and 51 living members were evaluated. Resting and exercise electrocardiograms (ECG), echocardiography, magnetic resonance imaging (MRI), cineangiography, microscopic examination of endomyocardial biopsies and a drug testing with a class IC antiarrhythmic agent flecainide were performed. A genetic linkage analysis was carried out to map the gene locus.nnnRESULTSnOf the 24 affected individuals, 10 had succumbed with six cases of sudden death, and 14 survivors showed evidence of disease. Exercise stress test induced ventricular bigeminy or polymorphic ventricular tachycardia in affected individuals. Three children initially examined before 10 years of age developed arrhythmias during a four-year follow-up. Resting ECGs were normal in affected subjects except a slight prolongation of the QT intervals adjusted for heart rate (QTc) (430 +/- 18 vs. 409 +/- 19 ms, affected vs. nonaffected, p < 0.01). Administration of flecainide did not induce ECG abnormalities encountered in familial idiopathic ventricular fibrillation. Ventricular volumes, contractility and wall measurements were normal by echocardiography, right ventricular cineangiography and MRI. Histopathological examination showed no fibrosis or fatty infiltration. The cumulative cardiac mortality by the age of 30 years was 31%. The disease locus was assigned to chromosome 1q42-q43, with a maximal pairwise lod score of 4.74 in the two families combined. Only one heterozygous carrier was clinically unaffected suggesting high disease penetrance in adulthood.nnnCONCLUSIONSnA distinct cardiac disorder linked to chromosome 1q42-q43 causes exercise-induced polymorphic ventricular tachycardia in structurally normal hearts and is highly malignant. Delayed clinical manifestation necessitates repeated exercise electrocardiography to assure diagnosis in young individuals of the families.

Location on Chromosome 15 of the Gene Defect Causing Marfan Syndrome

BACKGROUNDnMarfan syndrome, the founding member of the heritable disorders of connective tissue, is a common autosomal dominant disorder with highly variable clinical manifestations in the skeletal, ocular, and cardiovascular systems. The fundamental defect leading to this disease has escaped definition despite decades of research efforts by several groups of investigators.nnnMETHODS AND RESULTSnUsing linkage analyses with polymorphic markers of the human genome, we mapped the genetic defect to chromosome 15 in five families with Marfan syndrome. With three polymorphic markers we obtained definitive proof of linkage in these families (lod score = 3.92, theta = 0.0 +/- 0.11). The most probable location of the gene for the disease is currently D15S45 (lod score = 3.32, theta = 0.0 +/- 0.12).nnnCONCLUSIONSnThe chromosomal localization of the mutation in Marfan syndrome is a first step toward the isolation and characterization of the defective gene and serves as a diagnostic test in families in which cosegregation of these markers with the disease has been confirmed.

Evidence for Involvement of the Type 1 Angiotensin II Receptor Locus in Essential Hypertension

Components of the renin-angiotensin system play an important role in the normal regulation of blood pressure. We carried out a comprehensive genetic linkage study of the genes involved in the renin-angiotensin cascade in Finnish hypertensive twins and their affected siblings. We found no evidence for linkage between essential hypertension and the genes coding for renin, angiotensinogen, angiotensin-converting enzyme, or kallikrein 1 in the 329 hypertensive individuals of 142 families studied. In contrast, two intragenic markers for the type 1 angiotensin II receptor (AT1) showed some evidence for linkage in the total sample. A closer examination of this gene locus was carried out using subgroups of nonobese sibpairs with early onset of hypertension and uniform geographical origin. These stratifications yielded suggestive evidence for linkage of hypertension to the genetic area containing the AT1 gene, with a maximal multipoint logarithm of the odds (LOD) score of 2.9. A genetic association study carried out in an independent series of 50 hypertensive cases and 122 normotensive controls showed an increase in the frequency of the A1166-->C allele of the AT1 gene in the hypertensive individuals. In a novel variant of model-free multipoint linkage analysis allowing linkage disequilibrium in the calculations, an LOD score of 5.13 was obtained. Sequence analyses of the entire coding region and 848 bp of promoter region in the DNA sample on 8 index samples did not reveal previously unpublished sequence variations. The data provide evidence that a common genetic variant of the AT1 gene locus influences the risk of essential hypertension in the Finnish population.

Angiotensinogen gene M235T polymorphism predicts left ventricular hypertrophy in endurance athletes

OBJECTIVESnWe studied whether left ventricular mass in athletes associates with polymorphisms in genes encoding components of the renin-angiotensin system.nnnBACKGROUNDnAdaptive left ventricular hypertrophy is a feature of the athletes heart. However, similarly training athletes develop left ventricular mass to a different extent, suggesting that genetic factors may modulate heart size.nnnMETHODSnWe measured left ventricular mass by echocardiography in 50 male and 30 female elite endurance athletes aged 25 +/- 4 (mean +/- SD) years. Deoxyribonucleic acid samples were prepared for genotyping of angiotensinogen (AGT) gene M235T polymorphism, angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and angiotensin II type 1 receptor (AT1) gene A1166C polymorphism.nnnRESULTSnThe AGT gene M235T genotypes were significantly associated with left ventricular mass independently of blood pressure in both genders (p = 0.0036 for pooled data). TT homozygotes had greater mass compared with MM homozygotes in both men (147 +/- 12 g/m vs. 132 +/- 15 g/m, p = 0.032) and women (121 +/- 12 g/m vs. 101 +/- 13 g/m, p = 0.019). There was a gender difference in the relation between myocardial mass and AGT genotype, MT heterozygotes resembling MM homozygotes among women and TT homozygotes among men. The other studied gene polymorphisms were not associated with left ventricular mass.nnnCONCLUSIONSnAngiotensinogen gene M235T polymorphism is associated with the variability in left ventricular hypertrophy induced by endurance training, with athletes homozygous for the T allele having the largest hearts. We found no association between ACE gene I/D or AT1 gene A1166C polymorphisms and left ventricular mass.

Genome-wide scan of predisposing loci for increased diastolic blood pressure in Finnish siblings.

Objectives To review, on a genome-wide scale, a linkage result obtained in an earlier candidate gene analysis in this same study sample, and to look for other possible contributing genetic loci predisposing to hypertension in this population. Design An affected sibpair linkage study with highly polymorphic genetic markers spanning the genome at an average intermarker density of 10 cM. Participants A total of 47 families with two affected siblings (mostly dizygotic twins) and all available additional family members from the genetic isolate of Finland. The families were identified through the Finnish Twin Cohort Study, the total number of this follow-up cohort being 13 888. The study sample was selected on the basis of early-onset hypertension with minimal presence of other phenotypic risk factors such as obesity. Results The AT1 locus stood out as the most significant locus in this population (maximum likelihood score 4.04). Some evidence for linkage was also detected with markers on chromosomes 2q (maximum likelihood score 2.96), 22q (2.07), and Xp (2.41). Conclusions Our results establish the role of the AT1 locus, on a genome-wide scale, as a major contributing locus to essential hypertension in this study sample.

COMMON POLYMORPHISM OF THE VITAMIN D RECEPTOR GENE IS ASSOCIATED WITH VARIATION OF PEAK BONE MASS IN YOUNG FINNS

Abstract. Previous studies suggested a relation between polymorphism of the vitamin D receptor (VDR) gene and bone mineral density (BMD) at perimenopausal age. To enlighten the possible association of the VDR gene polymorphism and BMD, we studied young (20–29 years) adults whose BMD provides a measure of their maximal bone mass. After sequencing the DNA regions flanking the polymorphic BsmI site, we set up a specific solid-phase minisequencing technique to assay this allelic variation. BMD values were adjusted for age, sex, weight, physical activity, smoking, and calcium intake. Young subjects homozygous for the b allele (BsmI site present) had a significantly higher BMD in lumbar spine and femoral neck than those homozygous for the B allele (BsmI site absent). This data shows that the BsmI polymorphism of the VDR gene is associated with peak bone mass. The implication of this result regarding the prevention of osteoporosis deserves further attention.

Molecular genetics of the long QT syndrome: Two novel mutations of the KVLQT1 gene and phenotypic expression of the mutant gene in a large kindred

At least three different gene loci were recently shown to account for the long QT syndrome (LQTS), a monogenic disorder with altered myocardial repolarization and occurrence of life‐threatening cardiac arrhythmias. We screened 44 unrelated probands for mutations of the gene encoding the cardiac potassium channel KVLQT1 using single‐strand conformational polymorphism (SSCP) and subsequent DNA sequencing. Two different mutations, T182I and D188N, were identified in two separate pedigrees. Cosegregation of the mutation with the disease phenotype was evident in both families. No mutations were identified at codon 212, previously suggested to represent a mutational hot spot of the KVLQT1 channel, in any of the 44 probands. The large pedigree with the D188N mutation (30 affected and 43 nonaffected individuals) permitted an analysis of expression of the mutant gene in its documented carriers. Although the mean (± SD) Qtc interval was markedly longer in affected (484 ± 38 ms) than in nonaffected individuals (406 ± 27 ms, P < 0.001), there was a marked overlapping of individual values in these two groups. QTc values in symptomatic and asymptomatic carriers of the mutant gene were not significantly different. In conclusion, we have identified two novel mutations of the KVLQT1 component of a cardiac potassium channel. Our data support the functional significance of the pore‐S6 domain of this membrane protein and emphasize the diagnostic usefulness of DNA analyses in families with LQTS. Hum Mutat 11:158–165, 1998.

Vitamin D receptor polymorphism and treatment of psoriasis with calcipotriol

SIR. Fibroblasts and keratinocytes contain intracellular receptors for 1.2 5-dihydroxyvitamin D;, suggesting that skin constitutes a target tissue for vitamin D. Indeed, vitamin D inhibits proliferation and induces terminal differentiation of cultured human keratinocytes, and both topical and oral vitamin D derivatives have proved to be a safe and effective treatment for psoriasis. However, clinical experience as well as cell culture studies have indicated that some patients with psoriasis show resistance to vitamin I) treatment. Rectjntly, an association between genetic polymorphism of the vitamin D receptor (TORI and bone mass density in perimenopausal women was reported. Although this finding has not been consistently confirmed in all subsequent investigations/ studies showing VDR genotype related differences in calcium absorption^ and the concentration of osteocalcin in serum.* both considered to be parameters regulated by 1.25-OHvitamin Dj. lend support to the idea that DNA polymorphism of the vitamin D receptor gene may be reflected at the physiological level. Recently, we found that vitamin U receptor polymorphism is significantly associated with maximal bone density measured at the age of 2 3 years. Thus, young Finns with the bb genotype {Bsml restriction site present in intron H of both allelesof the VDR gene) had a lumbar bone density H% higher than those with the genotype BB (Bsml site absent in both alleles). while heterozygous subjects (genotype Bb) had intermediate bone density values,

Novel polymorphism of the human ob gene promoter in lean and morbidly obese subjects

OBJECTIVE: Leptin, the circulating product of the human ob gene, may play role in control of appetite and metabolic rate. We screened the proximal promoter area of the ob gene for mutations and common polymorphisms in order to find out whether genetic variation in the regulatory area of this gene plays a role in human obesity. DESIGN: The technique of single‐strand‐conformation polymorphism (SSCP) was applied to screen for the promoter area of the ob gene for genetic alterations in morbidly obese patients. SUBJECTS: A total of 249 morbidity obese (present or past body mass index [BMI;[ge;40u2005kg/m2) and 141 lean (BMI≤25u2005kg/m2) subjects. MEASUREMENTS: DNA analysis was carried out using a single-strand conformation polymorphism (SSCP) technique and PCR followed by digestion with the restriction enzyme BssHII. Leptin was determined by radioimmunoassay in obese subjects. Serum lipids, glucose and insulin concentrations in the obese subjects were also determined. RESULTS: A new polymorphism C(-188)A was identified in the promoter region of the ob gene. This polymorphism was detected with allelic frequencies of 0.06 in morbidly obese subjects and 0.09 in lean controls (P=0.28). Initial studies failed to show an association of this polymorphism with serum leptin, response to treatment for obesity, history and extent of weight gain, or serum insulin, glucose of lipid concentrations. CONCLUSIONS: We have identified a common polymorphism in the promoter area of the human ob gene which appears to be very useful for genetic association and linkage studies. Further studies are needed to elucidate its potential role in the regulation of the human ob gene and in human metabolic disorders.