Frank Kooy, Ph.D.
Principal Investigator
University of Antwerp

FRAXA Awards:
  $50,000 in 2007
  $35,000 in 2000
  $30,000 in 1999

by Frank Kooy, 5/2007

Absence of only a single protein, FMRP in fragile X patients leads to a cascade of molecular events in the cell. To find out which other genes are involved the clinical symptoms, we have been looking for genes that are differentially expressed in the fragile X syndrome. One of the genes specifically under expressed was a part of the GABAA receptor. As GABAA receptors are the main inhibitory receptors in the brain, involved in processes like anxiety, mood swings, sleep and cognition, processes also disturbed in fragile X patients, we followed up on this finding. In subsequent studies, we demonstrated abnormalities in expression levels of multiple parts of the GABAA receptor, both in the mouse model as in the fly model, indicating under expression is an evolutionary conserved hallmark of the fragile X syndrome. Our case for involvement of the GABAergic system in the fragile X syndrome is supported by independent findings from other groups.

The purpose of the current grant is twofold: first we want to understand more of the molecular mechanisms leading to under expression of the GABA receptor. It is important to find out why and how absence of the fragile X protein results in under expression of the GABA system. Therefore we will analyze the expression of crucial compounds of the GABAergic system in different fragile X mouse models containing a premutation or extra copy of the Fmr1 gene to verify whether under expression it is a direct effect of absence of the FMR1 gene and whether decreased RNA or decreased protein is the cause. We will also perform experiments to determine if and which RNAs from the GABAergic system are bound to FMRP containing particles.

Second, we want to investigate whether drugs that work on the GABA system are able to influence the phenotype of the fragile X mouse model. The rationale behind these experiments is that if the GABAergic system is under expressed in fragile X syndrome, stimulation of the GABA system might be able to reverse specific symptoms of the disease. We therefore planned a series of tests of behavioral and cognitive performance, including open field, elevated plus maze and leverpress escape/avoidance as well as the audiogenic induction of seizures. Various drugs that interact with the GABAergic system will be tested to evaluate the effect on fragile X mouse behavior.

In summary, we hope to significantly increase our insights in the role of altered expression of the GABAergic system in the fragile X syndrome and to investigate whether drugs that act on the GABAA receptor are potentially suitable therapeutics.

Fellowship for Ilse Gantois, Graduate Student, 1999-2000
by Frank Kooy, 7/2000

The main objective of the Center for Medical Genetics in Antwerp, Belgium is to understand the molecular causes of Mental Retardation, including fragile X syndrome. Through increased understanding of the molecular causes of mental retardation, rational therapies might be developed.

The fragile X mouse model, our main research tool, has helped us to understand the nature of the cognitive deficit associated with the fragile X syndrome. Recently, we analyzed the effect of the introduction of a transgene capable of generating the fragile X protein (the gene missing in fragile X syndrome) in the fragile X knockout mouse. In initial trials, we observed significant amounts of fragile X protein in the knockout mice, but observed little rescue of the phenotype. Experiments to modify the experimental conditions to allow a full "rescue" the phenotype of the fragile X knockout mouse are ongoing.

We also identified ca 40 sequences that are differentially expressed in neurons of fragile X mice, e.g. that are significantly under or overrepresented in the fragile X mouse when compared with a control littermate. As the only difference between the control and the knockout is the fragile X gene, these sequences are potentially related to the pathogenesis of fragile X syndrome. Analysis of these genes is ongoing, and may provide insights in the molecular pathways of the fragile X syndrome. Such pathways might be interferable by drug treatment.

by Katie Clapp, President, FRAXA

Much of the recent research funded by FRAXA has focused on fragile X knockout mice. These animals are normal except that they lack the fragile X gene (FMR1). Like most humans with fragile X, the knockout mice do not produce the protein FMRP, potentially involved in normal learning and memory. The mouse model is critical to research because potential treatments can be tested in the animals. However, better behavioral, cognitive, molecular, and neuroanatomical tests are needed to distinguish between normal mice and fragile X knockout mice.