Loss of neuronal GSK3ß reduces dendritic spine stability and attenuates excitatory synaptic transmission via ß-catenin.

Central nervous glycogen synthase kinase 3ß (GSK3ß) is implicated in a number of neuropsychiatric diseases, such as bipolar disorder, depression, schizophrenia, fragile X syndrome or anxiety disorder. Many drugs employed to treat these conditions inhibit GSK3ß either directly or indirectly. We studied how conditional knockout of GSK3ß affected structural synaptic plasticity. Deletion of the GSK3ß gene in a subset of cortical and hippocampal neurons in adult mice led to reduced spine density. In vivo imaging revealed that this was caused by a loss of persistent spines, whereas stabilization of newly formed spines was reduced. In electrophysiological recordings, these structural alterations correlated with a considerable drop in the frequency and amplitude of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-dependent miniature excitatory postsynaptic currents. Expression of constitutively active ß-catenin caused reduction in spine density and electrophysiological alterations similar to GSK3ß knockout, suggesting that the effects of GSK3ß knockout were mediated by the accumulation of ß-catenin. In summary, changes of dendritic spines, both in quantity and in morphology, are correlates of experience-dependent synaptic plasticity; thus, these results may help explain the mechanism of action of psychotropic drugs inhibiting GSK3ß.

GSK3beta, a centre-staged kinase in neuropsychiatric disorders, modulates long term memory by inhibitory phosphorylation at serine-9.

Accumulating evidence implicates deregulation of GSK3ss as a converging pathological event in Alzheimer's disease and in neuropsychiatric disorders, including bipolar disorder and schizophrenia. Although these neurological disorders share cognitive dysfunction as a hallmark, the role of GSK3ss in learning and memory remains to be explored in depth. We here report increased phosphorylation of GSK3ss at Serine-9 following cognitive training in two different hippocampus dependent cognitive tasks, i.e. inhibitory avoidance and novel object recognition task. Conversely, transgenic mice expressing the phosphorylation defective mutant GSK3ss[S9A] show impaired memory in these tasks. Furthermore, GSK3ss[S9A] mice displayed impaired hippocampal L-LTP and facilitated LTD. Application of actinomycin, but not anisomycin, mimicked GSK3ss[S9A] induced defects in L-LTP, suggesting that transcriptional activation is affected. This was further supported by decreased expression of the immediate early gene c-Fos, a target gene of CREB. The combined data demonstrate a role for GSK3ss in long term memory formation, by inhibitory phosphorylation at Serine-9. The findings are fundamentally important and relevant in the search for therapeutic strategies in neurological disorders associated with cognitive impairment and deregulated GSK3ss signaling, including AD, bipolar disorder and schizophrenia.

Synthesis of 18F-labelled 2-(4'-fluorophenyl)-1,3-benzothiazole and evaluation as amyloid imaging agent in comparison with [11C]PIB.

2-(4'-[(18)F]fluorophenyl)-1,3-benzothiazole was synthesized as a fluorine-18 labelled derivative of the Pittsburg Compound-B (PIB), which has known affinity for amyloid beta and promising characteristics as tracer for in vivo visualisation of amyloid deposits in patients suffering from Alzheimer's disease (AD). Both the nitro-precursor 2-(4'-nitrophenyl)-1,3-benzothiazole and the non-radioactive reference compound were synthesized using a 1-step synthesis pathway. Labelling was achieved by direct aromatic nucleophilic substitution of the nitro-precursor using [(18)F]fluoride by heating for 20 min at 150 degrees C and with a radiochemical yield of 38%. The reference compound showed high affinity for amyloid in an in vitro competition binding study using human AD brain homogenates (K(i)=9.0 nM) and fluorescence imaging of incubated transgenic APP mouse brain slices confirmed binding to amyloid plaques. A biodistribution study in normal mice showed a high brain uptake at 2 min pi (3.20%ID/g) followed by a fast washout (60 min pi: 0.21%ID/g). A dynamic microPET study was performed in a transgenic APP and normal WT mouse, but, similar to [(11)C]PIB, no difference was seen in tracer retention between both kind of mice. The new (18)F-labelled 2-phenylbenzothiazole showed excellent preclinical characteristics comparable with those of the (11)C-labelled PIB.

Deregulation of NMDA-receptor function and down-stream signaling in APP[V717I] transgenic mice.

Evidence is accumulating for a role for amyloid peptides in impaired synaptic plasticity and cognition, while the underlying mechanisms remain unclear. We here analyzed the effects of amyloid peptides on NMDA-receptor function in vitro and in vivo. A synthetic amyloid peptide preparation containing monomeric and oligomeric A beta (1-42) peptides was used and demonstrated to bind to synapses expressing NMDA-receptors in cultured hippocampal and cortical neurons. Pre-incubation of primary neuronal cultures with A beta peptides significantly inhibited NMDA-receptor function, albeit not by a direct pharmacological inhibition of NMDA-receptors, since acute application of A beta peptides did not change NMDA-receptor currents in autaptic hippocampal cultures nor in xenopus oocytes expressing recombinant NMDA-receptors. Pre-incubation of primary neuronal cultures with A beta peptides however decreased NR2B-immunoreactive synaptic spines and surface expression of NR2B containing NMDA-receptors. Furthermore, we extended these findings for the first time in vivo, demonstrating decreased concentrations of NMDA-receptor subunit NR2B and PSD-95 as well as activated alpha-CaMKII in postsynaptic density preparations of APP[V717I] transgenic mice. This was associated with impaired NMDA-dependent LTP and decreased NMDA- and AMPA-receptor currents in hippocampal CA1 region in APP[V717I] transgenic mice. In addition, induction of c-Fos following cued and contextual fear conditioning was significantly impaired in the basolateral amygdala and hippocampus of APP[V717I] transgenic mice. Our data demonstrate defects in NMDA-receptor function and learning dependent signaling cascades in vivo in APP[V717I] transgenic mice and point to decreased surface expression of NMDA-receptors as a mechanism involved in early synaptic defects in APP[V717I] transgenic mice in vivo.

11C-labelled PIB analogues as potential tracer agents for in vivo imaging of amyloid beta in Alzheimer's disease.

Pittsburgh Compound-B (PIB) is currently being evaluated clinically for in vivo visualization of amyloid plaques in patients with Alzheimer's disease (AD). We have synthesized three structural isomers of 6-hydroxy-2-(4'-aminophenyl)-1,3-benzothiazole, performed radiolabelling with carbon-11 and investigated their in vivo and in vitro properties. Specific binding to amyloid plaques was demonstrated in vitro using post-mortem brain homogenates of AD patients, transgenic AD mice brain sections and post-mortem human AD brain sections. In normal mice, initial brain uptake (at 2 min p.i.) was high and was followed by a fast wash-out. The three structural analogues have a high potential as tracer agents for in vivo visualization of amyloid plaques in AD patients.

Glycogen synthase kinase-3beta, or a link between amyloid and tau pathology?

Phosphorylation is the most common post-translational modification of cellular proteins, essential for most physiological functions. Deregulation of phosphorylation has been invoked in disease mechanisms, and the case of Alzheimer's disease (AD) is no exception: both in the amyloid pathology and in the tauopathy are kinases deeply implicated. The glycogen synthase kinase-3 (GSK-3) isozymes participate in diverse cellular processes and important signalling pathways and have been implicitly linked to diverse medical problems, i.e. from diabetes and cancer to mood disorders and schizophrenia, and in the neurodegeneration of AD. Here, we review specific aspects of GSK-3 isozymes in the framework of recent data that we obtained in novel transgenic mouse models that robustly recapitulate the pathology and mechanistical problems of AD.

Modulation of synaptic plasticity and Tau phosphorylation by wild-type and mutant presenilin1.

The function of presenilin1 (PS1) in intra-membrane proteolysis is undisputed, as is its role in neurodegeneration in FAD, in contrast to its exact function in normal conditions. In this study, we analyzed synaptic plasticity and its underlying mechanisms biochemically in brain of mice with a neuron-specific deficiency in PS1 (PS1(n-/-)) and compared them to mice that expressed human mutant PS1[A246E] or wild-type PS1. PS1(n-/-) mice displayed a subtle impairment in Schaffer collateral hippocampal long-term potentiation (LTP) as opposed to normal LTP in wild-type PS1 mice, and a facilitated LTP in mutant PS1[A246E] mice. This finding correlated with, respectively, increased and reduced NMDA receptor responses in PS1[A246E] mice and PS1(n-/-) mice in hippocampal slices. Postsynaptically, levels of NR1/NR2B NMDA-receptor subunits and activated alpha-CaMKII were reduced in PS1(n-/-) mice, while increased in PS1[A246E] mice. In addition, PS1(n-/-) mice, displayed reduced paired pulse facilitation, increased synaptic fatigue and lower number of total and docked synaptic vesicles, implying a presynaptic function for wild-type presenilin1, unaffected by the mutation in PS1[A246E] mice. In contrast to the deficiency in PS1, mutant PS1 activated GSK-3beta by decreasing phosphorylation on Ser-9, which correlated with increased phosphorylation of protein tau at Ser-396-Ser-404 (PHF1/AD2 epitope). The synaptic functions of PS1, exerted on presynaptic vesicles and on postsynaptic NMDA-receptor activity, were concluded to be independent of alterations in GSK-3beta activity and phosphorylation of protein tau.

5-HT4 receptor agonists increase sAPPalpha levels in the cortex and hippocampus of male C57BL/6j mice.

BACKGROUND AND PURPOSE: A strategy to treat Alzheimer's disease (AD) is to increase the soluble form of amyloid precursor protein (sAPPalpha), a promnesic protein, in the brain. Because strong evidence supports beneficial effects of 5-hydroxytryptamine 5-HT(4) receptor agonists in memory and learning, we investigated the role of 5-HT(4) receptors on APP processing in 8 weeks-old male C57BL/6j mice. EXPERIMENTAL APPROACH: Mice were given, subcutaneously, prucalopride or ML 10302 (s.c.), two highly selective 5-HT(4) receptor agonists and, up to 240 min later, the hippocampus and cortex were analysed by Western blot for sAPPalpha determination. KEY RESULTS: Prucalopride (5 or 10 mg kg(-1)) significantly increased sAPPalpha levels in the hippocampus and cortex, but did not modify the expression level of APP mRNA as detected by quantitative RT-PCR. A selective 5-HT(4) receptor antagonist, GR125487 (1 mg kg(-1), s.c.) inhibited prucalopride induced- increase in sAPPalpha levels. In addition, levels of sAPPalpha were increased by ML10302 only at 20 mg kg(-1) and was limited to the cortex. Also, prucalopride increased sAPPalpha levels in the cortex of a transgenic mouse model of AD, expressing the London mutation of APP. Furthermore, the combined injection of a selective acetylcholinesterase inhibitor, donepezil and prucalopride induced a synergic increase in sAPPalpha levels in the cortex and hippocampus. CONCLUSIONS AND IMPLICATIONS: Our results demonstrate that the 5-HT(4) receptor plays a key role in the non-amyloidogenic pathway of APP metabolism in vivo and give support to the beneficial use of 5-HT(4) agonists for AD treatment.

Transgenic mouse models for Alzheimer's disease: the role of GSK-3B in combined amyloid and tau-pathology.

Describing and understanding the pathological processes which devastate the brain of Alzheimer's disease (AD) patients remains a major target for experimental biology. We approached this problem by generating different types of single and double transgenic mice that develop pathological hallmarks of AD. In APP-V717 mice, the progression from intracellular amyloid to diffuse and senile plaques with vascular deposits, is preceded by early defects in cognition and LTP. In Tau-P301L mice, the morbid tauopathy with intracellular filaments, cause mortality before age 1 year. Ageing APP-V717IxTau-P301L double tg mice (14-17 months) have combined AD-like pathology in hippocampus and cortex consisting of amyloid plaques and neurofibrillary tangles. Remarkably, while Tau-P301L mice die before age 1 year, the APP-V717IxTau-P301L double tg mice survive much longer, which correlates with alleviation of tauopathy in hindbrain, despite aggravation in forebrain. This hypothesis is corroborated in Tau-P301LxGSK-3B double transgenic mice, which have also an extended lifespan relative to Tau-P301L mice, that correlates with reduction of brainstem tauopathy. At the same time, Tau-P301LxGSK-3B mice have dramatic forebrain tauopathy, with "tangles in almost all neurons", although without hyper-phosphorylation of Tau. The data corroborate the hypothesis that GSK-3B is the missing link between the amyloid and tau-pathology, and position GSK-3B as prominent player in the pathogenesis in AD.

Noninvasive in vivo MRI detection of neuritic plaques associated with iron in APP[V717I] transgenic mice, a model for Alzheimer's disease.

Transgenic mice overexpressing the London mutant of human amyloid precursor protein (APP[V717I]) in neurons develop amyloid plaques in the brain, thus demonstrating the most prominent neuropathological hallmark of Alzheimer's disease. In vivo 3D T2*-weighted MRI on these mice (24 months of age) revealed hypointense brain inclusions that affected the thalamus almost exclusively. Upon correlating these MRI observations with a panel of different histologic staining techniques, it appeared that only plaques that were positive for both thioflavin-S and iron were visible on the MR images. Numerous thioflavin-S-positive plaques in the cortex that did not display iron staining remained invisible to MRI. The in vivo detection of amyloid plaques in this mouse model, using the intrinsic MRI contrast arising from the iron associated with the plaques, creates an unexpected opportunity for the noninvasive investigation of the longitudinal development of the plaques in the same animal. Thus, this work provides further research opportunities for analyzing younger APP[V717I] mouse models with the knowledge of the final outcome at 24 months of age.

Alpha-2 macroglobulin controls trophoblast positioning in mouse implantation sites.

In humans, functional deficiency of alpha-2M is not known, implying alpha 2M is essential for gestational success. Mice, deficient in two members of the alpha-2 Macroglobulin (alpha 2M) family, i.e. alpha-2 macroglobulin (MAM) and murinoglobulin-1 (MUG-1) are viable, fertile and phenotypically normal, unless stressed (Am J Pathol, 155 (1999), 983). Here, we analysed implantation sites in MAM(-/-)/MUG-1(-/-)mice during pregnancy, a strong physiological stressor. Despite some post-implantation fetal loss, mean litter size was comparable to congenic C57Bl/6J (B6) mice, but MAM(-/-)/MUG-1(-/-)pups were significantly lighter and the sex ratio was skewed towards males. Implantation sites appeared histologically normal up to gestational day (gd) 8. By gd 10, extensive over-development of trophoblasts was evident, accompanied by relative deficits in decidua, in the mural mesometrial lymphoid aggregates of pregnancy and in uterine Natural Killer cells. At gd 10-12, decidual spiral arteries were dilated but abnormally cuffed by trophoblasts that extended anomalously, for midgestation, to the myometrial circular smooth muscle. Ultrastructurally, trophoblasts in the mesometrial decidua made intimate contact with endothelial cells that were shedding membrane fragments. These findings demonstrate that alpha 2M, and thereby proteinases and/or cytokines whose bio-availability is regulated by alpha 2M, exert significant decidual regulation on trophoblast invasion.

Neonatal neuronal overexpression of glycogen synthase kinase-3 beta reduces brain size in transgenic mice.

Glycogen synthase kinase-3beta (GSK-3beta) is important in neurogenesis. Here we demonstrate that the kinase influenced post-natal maturation and differentiation of neurons in vivo in transgenic mice that overexpress a constitutively active GSK-3beta[S9A]. Magnetic resonance imaging revealed a reduced volume of the entire brain, concordant with a nearly 20% reduction in wet brain weight. The reduced volume was most prominent for the cerebral cortex, without however, disturbing the normal cortical layering. The resulting compacted architecture was further demonstrated by an increased neuronal density, by reduced size of neuronal cell bodies and of the somatodendritic compartment of pyramidal neurons in the cortex. No evidence for apoptosis was obtained. The marked overall reduction in the level of the microtubule-associated protein 2 in brain and in spinal cord, did not affect the ultrastructure of the microtubular cytoskeleton in the proximal apical dendrites. The overall reduction in size of the entire CNS induced by constitutive active GSK-3beta caused only very subtle changes in the psychomotoric ability of adult and ageing GSK-3beta transgenic mice.

Increased Trypanosoma cruzi invasion and heart fibrosis associated with high transforming growth factor beta levels in mice deficient in alpha(2)-macroglobulin.

Trypanosoma cruzi proteinases are involved in host cell invasion in human patients and in mouse models. In mice, murine alpha(2)-macroglobulin (MAM) and murinoglobulin are circulating plasma proteinase inhibitors that also have important roles in inflammation and immune modulation. To define their role in experimental Chagas disease, we investigated the susceptibility to T. cruzi infection of mice that are deficient only in alpha2-macroglobulins (AM-KO) or in both MAM and monomeric murinoglobulin-1 (MM-KO), relative to the wild type (WT). Despite the high parasite load, parasitemia was lower in AM-KO and MM-KO mice than in WT mice. Nevertheless, we observed a significantly higher parasite load in the hearts of AM-KO and MM-KO mice, i.e., more amastigote nests and inflammatory infiltrates than in WT mice. This result demonstrates a protective role for MAM in the acute phase of murine T. cruzi infection. We further demonstrated in vitro that human alpha2-macroglobulins altered the trypomastigote morphology and motility in a dose-dependent way, and that also impaired T. cruzi invasion in cardiomyocytes. Finally, we demonstrated that the levels of transforming growth factor beta in AM-KO mice increased significantly in the third week postinfection, concomitant with high amastigote burden and important fibrosis. Combined, these in vivo and in vitro findings demonstrate that the MAM contribute to the resistance of mice to acute myocarditis induced by experimental T. cruzi infection.

Coexpression of GSK-3beta corrects phenotypic aberrations of dorsal root ganglion cells, cultured from adult transgenic mice overexpressing human protein tau.

Coexpression of constitutively active GSK-3beta[S9A] rescued the axonal pathology induced by overexpression of human tau in transgenic mice (Spittaels et al., (2000) J. Biol. Chem. 275, 41340-41349). We isolated dorsal root ganglion (DRG) neuronal cultures from adult tau4R- and tau4R x GSK-3beta-transgenic mice to define the mechanisms at the cellular and subcellular level. DRG from tau4R-transgenics showed a reduced sprouting capacity while density and stability of microtubules in the axonal processes were significantly increased. Video-enhanced contrast microscopy demonstrated a dramatic inhibition of fast axonal transport. Coexpression of GSK-3beta increased tau phosphorylation and reversed the effects on microtubule stability and saltatory motion. In DRG from GSK-3beta single transgenics, increased tau phosphorylation was evident without any major effects on microtubule stability or axonal transport. These observations support the hypothesis that excess tau competed with motor-proteins for binding to microtubules and/or that a rigid microtubular system inhibits axonal transport.

Unusual association of Hodgkin's disease and sarcoidosis.

We report a 51-year-old patient who developed abdominal lymphadenopathy following Hodgkin's disease seven years after she was diagnosed as having sarcoidosis. The patient had been treated with steroids, methotrexate and azathioprine. After three cycles of chemotherapy for Hodgkin's disease, the patient again developed sarcoidosis in the mediastinal lymph nodes. A greater awareness of the co-existence of sarcoidosis and Hodgkin's disease could circumvent the diagnostic difficulties.

Impact of genetic defects on atherosclerosis in patients suspected of familial hypercholesterolaemia.

BACKGROUND: Among patients with severe hypercholesterolaemia and a family history of early cardiovascular disease, we assessed whether patients with mutations of low-density lipoprotein (LDL) receptor and apolipoprotein B genes related to familial hypercholesterolaemia (FH) have a different degree of atherosclerosis than those without such mutations. METHOD: In our lipid clinics, 273 patients were selected on the basis of a severe hypercholesterolaemia (cholesterol above 95th percentile) and a family history of early cardiovascular disease. By molecular genetic test, 122 patients were classified as FH. Atherosclerosis was evaluated by the ultrasonographic measurement of intima-media thickness (IMT) in the carotid and femoral arteries. RESULT: Despite the fact that non-FH individuals had a higher prevalence of obesity, hypertension, diabetes and hypertriglyceridaemia, FH individuals had significantly greater carotid and femoral IMT than non-FH patients: difference between carotid and femoral IMT, respectively, 0.19 mm (95% CI, 0.08-0.29; P < 0.001) and 0.20 mm (95% CI, 0.09-0.35; P = 0.001), respectively. These differences remained statistically significant after adjustment for the various risk factors as well as in sub-analysis restricted to the patients with LDL-cholesterol between 240 and 300 mg dL-1 (range with similar distribution in the two groups). When classified according to the severity of their mutations, FH individuals with null LDL receptor allele tended to have thicker carotid IMT than FH individuals carrying the LDL receptor-defective allele. CONCLUSION: Among patients with severe hypercholesterolaemia and a family history of early cardiovascular disease, the presence of a genetically ascertained FH is associated with a higher degree of atherosclerosis. This suggests that molecular genetic identification of FH may be helpful to evaluate better the coronary heart disease risk in these patients.

Differential expression of mRNA coding for the alpha-2-macroglobulin family and the LRP receptor system in C57BL/6J and C3H/HeJ male mice.

Expression of mouse A2M (MAM), murinoglobulin (MUG), the A2M receptor or LDL-Receptor related protein (A2MR/LRP) and the Receptor Associated Protein (RAP) were measured by northern blotting of mRNA isolated from liver, heart and peritoneal macrophages from C3H/HeJ and C57BL/6J (B6) mice. Marked differences between males of the two mouse strains were observed for MAM and MUG mRNA levels in liver, which were reflected in plasma levels of both proteinase inhibitors, as confirmed by immune-electrophoresis. C3H/HeJ mice had higher levels of the MAM and MUG mRNA and their corresponding plasma proteins than B6 mice. B6 mice expressed higher levels of LRP mRNA relative to C3H/HeJ mice but had lower levels of RAP mRNA. LRP receptor activity, assayed by fluoresceinated-A2M binding, was higher in B6 cells. The present data contribute to the knowledge of genetic background characteristics among male mouse of these two strains, which can take part in many biological events such as lipid metabolism, inflammation and immune response to different infectious agents.

Modelling Alzheimer's disease in multiple transgenic mice.

We have reported transgenic mice with neuronal overexpression of the clinical mutant beta-amyloid precursor protein (APP) known as London, which develop an AD-related phenotype [Moechers, Dewachter, Lorent, Reversé, Baekelandt, Nadiu, Tesseur, Spittaels, Van den Haute, Checler, et al. (1999) J. Biol. Chem. 274, 6483-6492]. Characterized early symptoms (3-9 months) include disturbed behaviour, neophobia, aggression, hypersensitivity to kainic acid, hyposensitivity to N-methyl-D-aspartate, defective cognition and memory, and decreased long-term potentiation. Late in life, at 12-15 months, amyloid plaques develop in the brain and correlate with increased levels of beta-amyloid (A beta)40/42 (the 40- and 42-amino-acid forms of A beta). The formation of amyloid plaques is dissociated in time from and not involved in the early phenotype. Hyperphosphorylated protein tau is present but no tangle pathology is observed. In double-transgenic mice, i.e. APP/London x Presenilin 1, the increased production of A beta 42 results in amyloid plaques developing by the age of 6 months. Transgenic mice with overexpression of either human apolipoprotein E4 (ApoE4) or human protein tau in central neurons develop severe axonopathy in the brain and spinal cord. Progressive degeneration of nerves and muscles is demonstrated by motor problems, wasting and premature death. Tau is hyperphosphorylated but there is no formation of filaments or neurofibrillary tangles. The tangle aspect of AD pathology is still missing from all current transgenic amyloid models. Its implementation will require insight into the cellular signalling pathways which regulate the microtubule-stabilizing function by phosphorylation of neuronal tau.

The use of Achilles tendon ultrasonography for the diagnosis of familial hypercholesterolemia.

Differentiating FH from other causes of hypercholesterolemia has important clinical and therapeutic implications but is often not possible by standard clinical criteria. As accumulation of cholesterol in tendon is generally considered as pathognomonic of FH, we evaluated the sensitivity and specificity of clinical and ultrasonographic tendon characteristics using the data of 127 genetically ascertained FH and 160 controls with various lipid profiles. Upon clinical examination, none of the controls and 29% of FH individuals (17% FH women and 38% FH men) presented with xanthomata in Achilles tendons, but no female and only 6% of male FH patients also showed xanthomata in the extensor tendon of the hand. Amongst all possible quantitative parameters (thickness, breadth, section and roundness) of Achilles tendon (AT) measured by ultrasonography, the thickness presented the best receiver operating curves. AT thickness above 5.8 mm was the most useful threshold for diagnosis of FH, procuring sensitivity of 75% and specificity of 85%. Analysis of variation of AT thickness with age and sex indicated that this clinical criterion performed better in females older than 45 and in males under 45. In patients carrying the APOB-R3500Q mutation, AT-thickness appeared significantly less important compared with those carrying LDLR mutations. In conclusion, this study recommends identification of possible FH individuals amongst hypercholesterolemic patients using a criteria of AT-thickness over 5.8 mm eventually associated with a specific genetic test for APOB-R3500Q mutation.

Mutant presenilins disturb neuronal calcium homeostasis in the brain of transgenic mice, decreasing the threshold for excitotoxicity and facilitating long-term potentiation.

Mutant human presenilin-1 (PS1) causes an Alzheimer's-related phenotype in the brain of transgenic mice in combination with mutant human amyloid precursor protein by means of increased production of amyloid peptides (Dewachter, I., Van Dorpe, J., Smeijers, L., Gilis, M., Kuiperi, C., Laenen, I., Caluwaerts, N., Moechars, D., Checler, F., Vanderstichele, H. & Van Leuven, F. (2000) J. Neurosci. 20, 6452-6458) that aggravate plaques and cerebrovascular amyloid (Van Dorpe, J., Smeijers, L., Dewachter, I., Nuyens, D., Spittaels, K., van den Haute, C., Mercken, M., Moechars, D., Laenen, I., Kuipéri, C., Bruynseels, K., Tesseur, I., Loos, R., Vanderstichele, H., Checler, F., Sciot, R. & Van Leuven, F. (2000) J. Am. Pathol. 157, 1283-1298). This gain of function of mutant PS1 is approached here in three paradigms that relate to glutamate neurotransmission. Mutant but not wild-type human PS1 (i) lowered the excitotoxic threshold for kainic acid in vivo, (ii) facilitated hippocampal long-term potentiation in brain slices, and (iii) increased glutamate-induced intracellular calcium levels in isolated neurons. Prominent higher calcium responses were triggered by thapsigargin and bradykinin, indicating that mutant PS modulates the dynamic release and storage of calcium ions in the endoplasmatic reticulum. In reaction to glutamate, overfilled Ca(2+) stores resulted in higher than normal cytosolic Ca(2+) levels, explaining the facilitated long-term potentiation and enhanced excitotoxicity. The lowered excitotoxic threshold for kainic acid was also observed in mice transgenic for mutant human PS2[N141I] and was prevented by dantrolene, an inhibitor of Ca(2+) release from the endoplasmic reticulum.