In search for a blood marker for febrile seizures

Children between the age of 6 months and 5 years are susceptible to seizures
during fever, the so called febrile seizures (FS). Genetic linkage and
association studies showed that a genetic component is involved in FS
susceptibility. In januari 2006 we started a research project to identify FS
susceptibility genes in mice using the mouse hyperthermia-induced seizure
model. In this model we expose mouse pups to a hot air stream to induce fever.
All animals develop seizures. Using video/EEG monitoring we established that
the latency to tonic-clonic seizures correlates with that of epileptic activity
in the brain. We use this so-called febrile seizure latency to determine
seizure susceptibility in different mouse inbred strains. We identified two
inbred stains with a a large difference in febrile seizure latency. The AJ was
rather resistant to febrile seizures, whereas the C57 was highly susceptible.
Interestingly a chromosome substitution strain (CSS) panel based on these two
strains is commercially available. This panel consists of 21 strains in which
in each strain one particular chromosome of the AJ strains is substituted into
an otherwise homogeneous C57 background. We have screened the whole CSS panel
for hyperthermia susceptibility and we identified 6 CSS with a febrile seizure
phenotype different from C57. This means that a part of each of these 6
chromosomes must be carry genes with contribute to the difference in febrile
seizure susceptibility between the CSS and C57. We fine-mapped this so-called
quantitative trait locus (QTL) on chromosome 1, by extensive breeding
generating an F1 and subsequently a large F2 generation. After complex
bioinformatics we selected 8 candidate genes, one of which we found to be
up-regulated in the brain of the C57, the more susceptible strain, compared to
the CSS1. We have recent experimental evidence suggesting that the expression
difference is due to a deletion in the FS1 promotor.
The ultimate proof that this gene (FS1) is a FS susceptibility gene came from
intervention studies. Reducing the expression of FS1 in C57 mice by
intracerebroventricular injection of FS1 antisense oligo*s decreased FS
susceptibility to the level of the CSS1 strain.
The next step was to study the FS1 gene in human. Recent studies in biopsies
from patients operated to treat pharmaco-resistant temporal lobe epilepsy (TLE)
showed that FS1 expression is increased in the hippocampus of TLE patients with
hippocampal sclerosis compared to autopsy controls and TLE patients without
hippocampal sclerosis. More than 50% of HS-TLE patients have antecedent complex
FS. Indeed, HS-TLE patients with antecedent complex FS have a higher FS1
expression than those without FS. This increase in FS1 expression was also
found in the neocortex, showing that the effect is not hippocampus specific.
Taken together our data indicate that FS1 may also be involved in conferring
febrile seizure susceptibility in patient with complex febrile seizures.

In this research, a small group of children known to suffer from complex
febrile seizures (FS) will be studied. An increase in expression of FS1 will be
investigated in blood in comparison with an control group. This will be done by
isolating FS1 mRNA and protein from bloodcells. Then the FS1 levels will be
determined by quantitative PCR and western blitting. DNA will be isolated to
possible sequence the FS1 gene. If an increase in FS1 expression will be found,
this will be the first step towards a diagnostic tool by young children to
determine their risk for complex febrile seizures. This will be very relevant
for the clinic. Around 5% of all children suffer from FS during childhood.
Luckely, FS are most of the times innocent, however children suffering from
complex FS have an increase risk of the development of temporal lobe epilepsy
during adulthood. We try to investigate why children suffer from FS and we
would like to find a prediction tool (blood marker) for FS in children.

This study will be an observational study with invasive treatment. Parents of
patients known with complex FS in the WKZ hospital will be contacted and asked
if they and their child are interested in participating in this research
project. If they agree, further information will be sent to them, so they can
make a decision about participation. If they agree to participate they will be
asked to make a single appointment in the WKZ to allow collection of 5ml blood
of their child. This is the only visit. During the visit a few questions
regarding the FS history and general health of the child will be asked and
blood will be collected by vena puncture. In total this will take 1 hour at the
most. Additional patients will be recruited during their visit to the *First
seizure polikliniek*.
Parents of control patients will be asked to participate during their scheduled
visit to the WKZ for the childs' preoperative screening. If they agree an
additional 5 ml blood will be drawn during the blood collection for the
screening.

Patients blood will be collected with a vena puncture. This will be no heavy
burdens, only a little bit anxiety of the child and possible pain. The risks
are pain, some bleeding afterwards and hematoma formation