Gene/Protein Disease Symptom Drug Enzyme Compound
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Few autosomal recessive disorders display the degree of pleiotropism and genetic heterogeneity found in Bardet-Biedl syndrome (BBS), a genetic disorder characterized primarily by retinal dystrophy, obesity, polydactyly, cognitive impairment and gonadal and renal dysgenesis. This relatively rare condition has been reported frequently, but we have only recently begun to appreciate the genetic complexities that give rise to this constellation of clinical findings. During the last 12 months, the first three of at least six BBS genes have been identified, providing us for the first time with the ability to formulate hypotheses regarding the molecular etiology of the disorder. Here we review the key elements of the phenotype and discuss the significance of the discovery of the first three BBS genes on the effort to identify the cellular causes of this syndrome.
Hum Mol Genet 2001 Oct 01
PMID:Exploring the molecular basis of Bardet-Biedl syndrome. 1167 13

The autosomal dominant mutation causing myotonic dystrophy (DM1) is a CTG repeat expansion in the 3'-UTR of the DM protein kinase (DMPK) gene. This multisystemic disorder includes myotonia, progressive weakness and wasting of skeletal muscle and extramuscular symptoms such as cataracts, testicular atrophy, endocrine and cognitive dysfunction. The mechanisms underlying its pathogenesis are complex. Recent reports have revealed that DMPK gene haploinsufficiency may account for cardiac conduction defects whereas cataracts may be due to haploinsufficiency of the neighboring gene, the DM-associated homeobox protein (DMAHP or SIX5) gene. Furthermore, mice expressing the CUG expansion in an unrelated mRNA develop myotonia and myopathy, consistent with an RNA gain of function. We demonstrated that transgenic mice carrying the CTG expansion in its human DM1 context (>45 kb) and producing abnormal DMPK mRNA with at least 300 CUG repeats, displayed clinical, histological, molecular and electrophysiological abnormalities in skeletal muscle consistent with those observed in DM1 patients. Like DM1 patients, these transgenic mice show abnormal tau expression in the brain. These results provide further evidence for the RNA trans-dominant effect of the CUG expansion, not only in muscle, but also in brain.
Hum Mol Genet 2001 Nov 01
PMID:Mice transgenic for the human myotonic dystrophy region with expanded CTG repeats display muscular and brain abnormalities. 1172 59

Neuronal nicotinic receptor binding sites as well as mRNA levels encoding for subunits alpha4, beta2, and alpha7 were analysed in 3-mo-old transgenic mice generated with a neuronal overexpression of human acetylcholinesterase and in age-matched controls. The acetylcholinesterase transgenic mice display progressive cognitive impairment in spatial learning and memory. We here report a significantly increased [3H]epibatidine and [125I]alphabungarotoxin binding in the cortex and the caudate putamen of these mice. Quantitativein situ hybridization showed significant upregulation of mRNA corresponding to the nicotinic receptor subunits alpha4, beta2, and alpha7 in various brain regions in the transgenic mice compared to nontransgenic controls. Our results suggest that disruption of balanced cholinergic transmission by constitutive overexpression of acetylcholinesterase is accompanied by variable upregulation of several nicotinic receptor subtypes, in particular these associated with cholinergic terminals participating in compensatory response.
J Mol Neurosci 2002 Jun
PMID:Upregulation of neuronal nicotinic receptor subunits alpha4, beta2, and alpha7 in transgenic mice overexpressing human acetylcholinesterase. 1205 39

This progress report briefly describes the rationale and study design for the first cross-national clinical study of a positive AMPA-type glutamate receptor modulator in subjects with mild cognitive impairment (MCI). The study medication for the double-blind, placebo-controlled trial, the AMPAKINE CX516, represents a novel pharmacological approach to the treatment of memory disorders. Previous preclinical and pilot clinical studies have shown that CX516 has the ability to enhance memory and cognition. Design of the trial, including outcome measures and inclusion criteria, was aided by an international panel of experts in the newly emerging field of MCI.
J Mol Neurosci
PMID:Randomized, double-blind, placebo-controlled international clinical trial of the Ampakine CX516 in elderly participants with mild cognitive impairment: a progress report. 1221 80

In the past few years, a series of molecular-genetic, biochemical, cellular and behavioral studies in fruit flies, sea slugs and mice have confirmed a long-standing notion that long-term memory formation depends on the synthesis of new proteins. Experiments focused on the cAMP-responsive transcription factor, CREB, have established that neural activity-induced regulation of gene transcription promotes a synaptic growth process that strengthens the connections among active neurons. This process constitutes a physical basis for the engram--and CREB is a "molecular switch" to produce the engram. Helicon Therapeutics has been formed to identify drug compounds that enhance memory formation via augmentation of CREB biochemistry. Candidate compounds have been identified from a high throughput cell-based screen and are being evaluated in animal models of memory formation. A gene discovery program also seeks to identify new genes, which function downstream of CREB during memory formation, as a source for new drug discoveries in the future. Together, these drug and gene discovery efforts promise new class of pharmaceutical therapies for the treatment of various forms of cognitive dysfunction.
J Mol Neurosci
PMID:CREB and the discovery of cognitive enhancers. 1221 77

Although men do not experience an abrupt cessation of gonadal hormone production at midlife as do women, levels of testosterone (T) decrease gradually with aging. Because estradiol (E2) arises mainly from the conversion of T in men, the availability of E2 also decreases with increasing age. In randomized clinical trials, E2 replacement therapy has been shown to maintain aspects of cognition in postmenopausal women, specifically with regard to verbal memory. The present prospective, randomized, cross-over trial is being undertaken in order to determine whether E2 will enhance verbal memory in men with Mild Cognitive Impairment (MCI). Men with MCI will randomly receive E2 or placebo for the first 3 mo of treatment and will then be crossed-over to the other treatment for an additional 3 mo. A battery of neuropsychological tests will be administered at pretreatment and, again, following each 3-mo treatment phase. It is hypothesized that elderly men with MCI will perform better on tests of explicit memory when they are being treated with E2 compared to their performance under placebo conditions.
J Mol Neurosci
PMID:Estrogen and cognitive functioning in men with mild cognitive impairment. 1221 85

High circulating levels of glucocorticoid hormones adversely affect cognition. Previous studies exploring the hypothalamic-pituitary-adrenal (HPA) axis and basal cortisol levels in the elderly reported that subjects with mid-range cortisol levels outperformed subjects with high cortisol levels on assessments of memory and attention. This study examines the efficacy of mifepristone, a glucocorticoid-antagonist, in decelerating the rate of cortisol-related cognitive decline in subjects with mile-to-moderate Alzheimer's disease (AD). Rate of cognitve decline is compared in AD subjects randomized to receive 200 mg of mifepristone daily for 6 mo or placebo. The Alzheimer's Disease Assessment Scale (ADAS) and the Folstein Mini Mental Status Exam (MMSE) will be the primary measures used to assess change in cognitve function over the 6 mo period, supplemented by a neuropsychological battery testing memory and language and reasoning skills. During each visit, subjects will have samples collected for determination of plasma adrenocorticotropin (ACTH), serum cortisol and salivary cortisol levels to assess HPA axis activity. The placebo arm of this study also investigate whether subjects with high baseline cortisol levels experience greater declines in cognitive impairment over time relative to subjects with Ad who have low baseline cortisol levels. Additionally, this study test the hypothesis that AD subjects with elevated cortisol at baseline will perform more poorly on neuropsychological exams that do subjects with low cortisol.
J Mol Neurosci
PMID:Slowing the progression of cognitive decline in Alzheimer's disease using mifepristone. 1221 81

Mild Cognitive Impairment (MCI) is considered a transitional stage in the pathogenesis of Alzheimer's disease; however, not all MCI patients progress to clinically defined AD or decline at identical rates. Hippocampal atrophy, as measured by Magnetic Resonance Imaging (MRI), may be a marker for hippocampal pathology in patients with MCI and predict a more rapid deterioration to clinical AD. In this study, we used MRI data from an ongoing MCI clinical trial to determine whether MRI hippocampal volume at baseline was associated with cognitive and functional performance in MCI subjects and whether it predicted those individuals who were more likely to develop AD. We performed correlational analyses between the MRI hippocampal volumes at study entry and the subjects' concurrent performance on neuropsychological measures and clinical ratings. Larger hippocampal volume was associated with better performance on tests of memory, general cognition, and overall clinical ratings. Further analyses suggested that a smaller baseline hippocampal volume may be associated with a higher risk of developing clinical AD. As the trial is still ongoing, these results require confirmation once the trial is completed. In summary, these data suggest that MRI hippocampal volume may be a useful correlate of disease severity in MCI subjects and a prognostic indicator of subsequent AD.
J Mol Neurosci
PMID:Brain MRI hippocampal volume and prediction of clinical status in a mild cognitive impairment trial. 1221 87

Coffin-Lowry syndrome (CLS) is characterized by cognitive impairment, characteristic facial and digital findings and skeletal anomalies. The gene implicated in CLS encodes RSK2, a serine/threonine kinase acting in the Ras/MAPK signalling pathway. In humans, RSK2 belongs to a family of four highly homologous proteins (RSK1-RSK4), encoded by distinct genes. RSK2 mutations in CLS patients are extremely heterogeneous. No consistent relationship between specific mutations and the severity of the disease or the expression of uncommon features has been established. Together, the data suggest an influence of environmental and/or other genetic components on the presentation of the disease. Obvious modifying genes include those encoding other RSK family members. In this study we have determined the expression of RSK1, 2 and 3 genes in various human tissues, during mouse embryogenesis and in mouse brain. The three RSK mRNAs were expressed in all human tissues and brain regions tested, supporting functional redundancy. However, tissue specific variations in levels suggest that they may also serve specific roles. The mouse Rsk3 gene was prominently expressed in the developing neural and sensory tissues, whereas Rsk1 gene expression was the strongest in various other tissues with high proliferative activity, suggesting distinct roles during development. In adult mouse brain, the highest levels of Rsk2 expression were observed in regions with high synaptic activity, including the neocortex, the hippocampus and Purkinje cells. These structures are essential components in cognitive function and learning. Based on the expression levels, our results suggest that in these areas, the Rsk1 and Rsk3 genes may not be able to fully compensate for a lack of Rsk2 function.
Hum Mol Genet 2002 Nov 01
PMID:Expression analysis of RSK gene family members: the RSK2 gene, mutated in Coffin-Lowry syndrome, is prominently expressed in brain structures essential for cognitive function and learning. 1239 4

Cerebral neurofibrillary tangles (NFTs) accumulate in a predictable sequence decades before the clinical symptoms of Alzheimer's disease emerge, and the degree of tangle degeneration correlates with the severity of cognitive impairment. A valid in vivo marker of tangle burden, therefore, would be useful for presymptomatic and symptomatic disease detection and treatment monitoring. Recent advances using positron emission tomography (PET) indicate the feasibility of in vivo imaging that provides a combined signal of both neurofibrillary tangles and senile plaques. Such results are encouraging that a tangle-specific marker will be found; however, several methodological issues first need to be addressed, including scanner spatial resolution in the relatively small brain regions where tangles accumulate. NFT-specific imaging probes will need to be lipophilic in order to cross the blood-brain barrier and neuronal membranes and have a high binding affinity to NFTs with minimal nonspecific binding, which would result in a high signal-to-background ratio in PET images.
J Mol Neurosci 2002 Dec
PMID:In vivo brain imaging of tangle burden in humans. 1254 59


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