Center for Human Genetics - Molecular and Developmental GeneticsResearch
Alzheimer's disease - Parkinson's disease - Spinal Muscular Atrophy (SMA) - Tools and techniques
Alzheimer’s disease
Our working hypothesis is the amyloid hypothesis, i.e. that the amyloid peptide provides the initial trigger of the disease. This peptide is generated by proteolytic processing of the Amyloid Precursor Protein by the consecutive action of a beta-secretase and a gamma-secretase. Alternatively an alpha-secretase cleaves Abeta peptide precluding further Abeta generation. We tackle several questions that are central to the understanding of the disease and can possibly lead to novel cures.
Gamma-secretase - Beta-secretase - Alpha-secretase - APP biology - Sporadic Alzheimer's disease and the microRNA network - Oligomer Abeta toxicity
Gamma-secretase
Gamma-secretase is in fact a family of at least 4 different protease complexes. We have evidence that these complexes have different biological and biochemical properties. We use biochemical reconstitution assays, drug screens, mutagenesis and other methods to unravel structure-function relationships. We also use mouse models to investigate the role of the individual complexes and their constituents in health and disease models.
Beta-secretase
Beta-Secretase is a membrane bound aspartyl protease called BACE. We are generating specific monoclonal antibodies in mouse and camel that interfere with its activity to explore the possibility of blocking beta-secretase activity in the brain of patients.
Alpha-secretase
Alpha-Secretase is an underexplored drug target for AD. We study pharmacological approaches to modulate this activity in the central nervous system. Furthermore we are systematically investigating what proteases contribute to this activity in the brain, using knock out approaches in mice. One of our hypothesis is that alpha-Secretase has a protective effect in the brain.
APP biology
Although APP has been identified 20 years ago, we still do not fully understand its biological function in the central nervous system. One of the problems is that two additional homologues of APP exist and can compensate for its function. The triple knock out mice has a lethal phenotype and can only be generated via complex breeding schemes. We have derived therefore triple knock out stem cells that lack all forms and which we can now differentiate into primary neurons in vitro. We analyze neuronal survival, axonal and dendritic outgrowth, mobility, adhesion, synaptic activity and finally axonal transport. We will rescue phenotypes with APP and APP mutants to make a structure-function analysis of APP and its different subdomains.
A second line of work is focused on the identification of the APP receptor postulated many years ago.
Sporadic Alzheimer's discease and the microRNA network
We reasoned that gene dosage is important for the pathogenesis of Alzheimer’s Disease and therefore that loss of control of gene expression could be an important determinant for the age related increase in sporadic AD. We have analyzed micro-RNA expression using micro-array and identified several micro-RNA that are changed in AD and regulate APP or BACE expression. We have work in cell culture and AD brain providing strong evidence that AD could be partially caused by dysregulation of the micro-RNA network in the aging brain. We are developing mouse models to explore this hypothesis.
Oligomer Abeta toxicity
The crucial question to be addressed for the amyloid hypothesis is how Abeta peptides cause neuronal dysfunction and death. We have generated in collaboration with the SWITCH group in Brussels a protocol to generate toxic variants of Abeta oligomers from inert amyloid fibrils (“reversed oligomers”). We use these species now to investigate the mechanism of toxicity analyzing the effects on dendritic spines. A second line of research investigates the role of Tau in the observed toxicity (using Tau knock out neurons and mice).
Parkinson’s disease
Our working hypothesis is that mitochondrial dysfunction is an important part of the neurodegenerative process in Parkinson's disease. We approach this hypothesis using a series of mitochondrial assays (fusion-fission, oxygen consumption, cytochrome c release, respiratory chain function etc) and evaluating the effects of loss of functions of proteins involved or potentially involved in Parkinson's disease.
Pink-1
Pink-1 is a mitochondrial located kinase and mutations cause recessive forms of PD. We know very little about the function in the mitochondria in general and in neurons in particular. We have obtained knock out cells and Drosophila and have evidence that Pink-1 regulates oxidative phosphorylation and synaptic activity.
Lrrk-2
Lrrk-2 is the major cause of dominant inherited PD. We are generating a recombination cassette exchange protocol to target Lrrk-2 gene in embryonic stem cells. We will use these cells to generate dopaminergic neurons and we will investigate the role of Lrrk-2 and mutants in these neurons, with particular focus on the mitochondrium.
Parl-1
Parl-1 is a protease that regulates cytochrome c release from the mitochondrium. We will generate a dopaminergic neuron specific knock out in mice and investigate the phenotype of these mice.
Spinal Muscular Atrophy
Spinal Muscular Atrophy (SMA) is a devastating neurodegenerative disease characterized by the selective loss of the motor neurons in the spinal cord, which results in progressive paralysis and eventual death. There is no effective cure. At the molecular level, SMA is caused by reduced levels of the Survival of Motor Neurons (SMN) protein, which has a crucial albeit indirect role in pre-mRNA splicing: it catalyses assembly of Sm proteins onto the spliceosomal snRNAs. Every cell, however, needs pre-mRNA splicing, and it remains a complete enigma why SMA affects only motor neurons. One hypothesis suggests that SMN might have a second, neuron-specific function. Dr. Tilmann Achsel, sr. scientist in Bart De Strooper's team, studies the Like-Sm (LSm) proteins that also interact with SMN and found that they do have a neuron-specific function, as they participate in the transport of mRNAs from the nucleus to the dendrites/axons. Combining biochemical (purification of mRNP complexes) and cell biological approaches, Tilmann is now investigating the importance of this process in neurodegeneration, and an eventual role SMN might have.
Tools and techniques
We use mouse models that we manipulate genetically by overexpression, knock in and knock out strategies for most of the genes we are investigating. We do molecular cell biology, confocal and electron microscopy, behavior, histology. We culture primary neurons and glia cells, and differentiate ES cells to neurons. We have excellent detection systems for Abeta generation, gamma-Secretase biology, Notch signaling, mitochondrial biology.
