The Utility of Next-Generation Sequencing for Identifying the Genetic Basis of Dementia

The clinical manifestations of dementia are often rapidly matched to a specific clinical syndrome, but the underlying neuropathology is not always obvious. A genetic factor often plays an important role in early onset dementia, but there are cases in which the phenotype has a different genetic basis than is assumed. Two patients, at different times, presented to the Memory Clinic because of memory problems and difficulty in performing daily activities and work. Neither caregiver complained of marked behavioural or personality changes, except for apathy. Patients underwent standard dementia evaluation procedures including clinical symptoms, family history, neuroimaging, neuropsychological evaluation, and genetic analysis of selected genes. Based on specific clinical phenotypes and genetic analysis of selected genes, both patients were diagnosed with frontal variant of Alzheimer’s disease. The presence of a rare polymorphism in PSEN2 in both patients allowed the discovery that they belong to the same family. This fact reinforced the belief that there is a strong genetic factor responsible for causing dementia in the family. Next-generation sequencing based on a panel of 118 genes was performed to identify other potential genetic factors that may determine the background of the disease. A mutation in the GRN gene was identified, and the previous diagnosis was changed to frontotemporal dementia. The described cases show how important it is to combine all diagnostic tests available in the diagnostic centre, including new generation genetic tests, in order to establish/confirm the pathological background of clinical symptoms of dementia. If there is any doubt about the final diagnosis, persistent efforts should be made to verify the cause.

Association between C677T polymorphism of MTHFR gene and risk of amyotrophic lateral sclerosis: Polish population study and a meta-analysis

OBJECTIVE

Genetic factors play a role in pathogenesis of amyotrophic lateral sclerosis (ALS). A few studies demonstrated that the TT genotype of C677T polymorphism of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene can increase the risk of sporadic ALS. The aim of our study was to determine the relationship between C677T polymorphism of MTHFR gene and the risk of sporadic ALS in Polish population and to perform the meta-analysis assessing the significance this polymorphism for the risk of ALS in Caucasian population.

METHODS

We included 251 patients with ALS and 500 control subjects recruited from Polish population and performed the meta-analysis of published data from Caucasian population. MTHFR C677T polymorphism was genotyped using a TaqMan assay and 7900HT Fast real Time PCR System.

RESULTS

The frequency of genotypes did not differ significantly between Polish ALS patients and control subjects (CC: 45.0 vs 45.8%, CT: 48.2 vs 45.0%, TT: 6.8 vs 9.2%, P=0.46). The meta-analysis including 863 ALS patients and 1362 controls revealed that TT genotype increases the risk of sporadic ALS in Caucasian population.

CONCLUSION

Although we did not find the association between C677T polymorphism of MTHRF gene and risk of ALS in Polish population, the results of meta-analysis suggest that the TT genotype can be a genetic risk factor for ALS in Caucasian population.

[Association of apoE polymorphism and treatment outcome in patients with traumatic brain injury]

A number of papers published in recent years indicate the importance of the apolipoprotein E gene (apoE) for the outcome of traumatic brain injury [TBI]. A majority of publications suggest that the presence of an epsilon 4 allele is associated with an unfavorable long-term outcome. A hypothesis has been recently posed that this phenomenon may be related to an increased risk of traumatic hypoxic brain damage or post-traumatic ischemic complications. The study group consisted of 95 consecutive TBI patients treated in the years 2000-2001 in the Neurotraumatology Clinic. The presence of apoE epsilon 4 was found in 16 cases. In the statistical analysis relationship was sought between the patient's age and state of consciousness at admission as assessed using the Glasgow Coma Scale, on the one hand, and on the other hand, treatment outcome at 6 months from injury, in patients differing in respect of apoE epsilon 4 presence. Although the number of apoE-negative patients was nearly five times as large as that of the apoE-positive, regression coefficients in both groups were statistically significant. The obtained results indicate that the presence of apoE epsilon 4 contributes to a less favorable clinical TBI outcome than the absence of this allele.

Calpain 10 gene polymorphisms and the risk of ischaemic stroke in a Polish population

Experimental studies showed that calpain inhibitors suppressed post-ischaemic changes in the brain. We examined whether an association exists between variants of three single nucleotide polymorphisms (SNPs) -43, -19, and -63 in the calpain 10 gene and either stroke or size of ischaemic lesions on the CT in a Polish population. We included 209 patients with a first ischaemic stroke and 148 controls. The patients were divided into four groups based on the infarct size assessed on the CT taken within two week after stroke. Alleles of SNP19 were determined by electrophoresis of the PCR product on agarose gel by size; while for SNP43 and -63 the RFLP method was used. The allele frequencies for patients and controls were similar in both groups: SNP43- G/A- 73.5%/26.5% vs. 71.0%/29%, SNP19-three 32 bp/two 32 bp repeats--65.7%/34.2% vs. 62.2%/37.7%; SNP63- C/T- 89.5%/10.5% vs. 90.9%/9.1%, respectively. The distribution of the genotypes, haplotypes, and haplotype combinations did not differ in both groups. The distribution in the subgroups of patients based on the size of the ischaemic lesions was similar to controls. Our study did not showed any association between calpain 10 SNPs: -43, -19, and -63 and ischaemic stroke, or with the size of post-ischaemic cerebral lesions in a Polish population.

[A statistic study of airborne pollen grains]

Since 1969, authors have been doing a statistical analysis of airborne pollen grains, aiming at the clarification of their atmospheric behaviors, in connection with an increase in a number of pollinosis cases. The airborne pollens were collected three times a week starting from January 1 and ending December 31 with the help of cascade impactor, by which 6001 of air was suctioned at the rate of 51 per min for 2 h from 10:00 a.m. to 12:00 at the rooftop of one of the buildings (16 m high) in the Narashino Campus of Toho University, Funabashi, Chiba. The collected airborne pollens were numerated and classified under microscope according to the Ikuse's classification system for Japanese pollens. The number of days (n) was plotted as a function of daily number of a certain type of airborne pollens (x), not fitting to a simple normal distribution. However, the data were found to approximate a normal distribution when x was log-transformed as ln (x + 1). Among the statistical methods tested, semilogarithmic plot, Weibull plot, Edwards' plot and circular graph method were found to be useful in the follow-up of seasonal variation of environmental pollen grains, especially when used in combination.

A statistic study of atmospheric pollen in Japan

By using a volumetric method, the authors made an investigation on airborne pollen grains in connection with the incidence of pollinosis since 1969, in Toho University, Funabashi, Chiba, Japan. The airborne pollen grains in each sample were counted under the microscope to identify the pollen types, and the pollen grains were classified into seven types according to the classification of pollen grains in Japan reported by Ikuse. In this report, the accumulated number of each species was analyzed statistically by circular plot, semi-logarithmic plot and test of skewness (g1) and kurtosis (g2) of frequency distribution by G. W. Snedecor. From the investigation in the years of 1969, 1970, 1990, 1991, the most frequent airborne pollen grains belonged to the 1-aperturate 3C(ab) type pollen in 1969 and 1970, and to the 1-aperturate 3B type pollen in 1990 and 1991, reflecting the change of environment during twenty years. By the g1 and g2 statistics for almost all species, the mode of distribution curve was significantly smaller than the mean, indicating that the whole distribution significantly skewed from a normal distribution, and the peak was flat for the herbs, while sharp for the trees.

Are free radicals involved in Ca(2+)-induced membrane damage of mitochondria?

Ca(2+)-Induced membrane damage of energized mitochondria has been proposed to be due to lipid peroxidation induced by Ca2+. To examine this possibility, we studied the effects of the radical scavenger, 3,5-di-tert-butyl-4-hydroxytoluene (BHT), and its derivative, 3,5-di-tert-butyl-4-methoxytoluene (MeO-BHT), on membrane damage of respiring mitochondria induced by Ca2+ in the presence of inorganic phosphate. Both compounds inhibited Ca(2+)-induced damage almost completely at 20 microM, and their effects were identical, although MeO-BHT had no radical scavenging ability. These results indicate that the protective effects of BHT and MeO-BHT are not due to their radical scavenging ability. Thus, free radicals are concluded not to be involved in Ca(2+)-induced membrane damage of mitochondria.

Protective effect of the plasticizer di(2-ethylhexyl) phthalate against damage of the mitochondrial membrane induced by calcium: possible participation of the adenine nucleotide translocator

The effect of di(2-ethylhexyl) phthalate (DEHP) on the response of isolated rat liver mitochondria to Ca2+ was investigated. DEHP was found to inhibit more than 60% of the auto-accelerating release of respiration induced by 100 microM Ca2+, being maximally inhibitory at 40 microM. Prior addition of DEHP also partially inhibited Ca2+-induced swelling of the mitochondrial matrix. However, DEHP did not change the net rate of Ca2+ uptake measured by the steady-state infusion method. DEHP also reduced the rate of adenine nucleotide exchange across the mitochondrial membrane. Another alkyl phthalate and alkyl citrates had similar effects on Ca2+-induced membrane damage, but their potencies depended on the lengths of their alkyl chains. These results suggest that the effects of DEHP and other alkyl esters on mitochondrial functions are mainly based on their actions on membrane lipids surrounding adenine nucleotide translocator (AdNT), resulting in alteration of the interaction between these phospholipids and AdNT, and consequent modification of the state of the protein.

Effect of the plasticizer di-(2-ethylhexyl)phthalate on oxidative phosphorylation in rat liver mitochondria: modification of the function of the adenine nucleotide translocator

The effect of di-(2-ethylhexyl)phthalate (DEHP) on oxidative phosphorylation of isolated rat liver mitochondria was investigated. DEHP at concentrations of 20-1000 microM had no effect on state 4 respiration, but at 40 microM, DEHP decreased the rate of state 3 respiration by about 20%. Although DEHP had no effect on electron transport through the respiratory chain, it decreased the rate of adenosine triphosphate (ATP) synthesis. Its inhibition of ATP synthesis showed a similar concentration dependence to that of state 3 respiration. Furthermore, DEHP at 40 microM inhibited the uptake of [3H]adenosine diphosphate into mitochondria. DEHP also retarded the action of cationic uncoupling agents, which are known to modify the 29000-dalton protein involved in adenine nucleotide exchange. These results suggest that DEHP affects the activity of adenine nucleotide exchange and consequently partially decreases the rate of state 3 respiration. The action of DEHP on the 29000-dalton protein involves a protective effect against mitochondrial damage induced by hydrophobic cations or heavy metal cations.