Untersuchungen zum Mutationsspektrum bei CADASIL

Summary CADASIL (cerebral autosomal arteriopathy with subcortical
infarcts and eukoencephalopathy) is a autosomal dominant
disease,which lead among other things to migraen headache and early
stroke. Shortly before beginning of this work Notch3 was identified
as responsible gene. Notch3 coded for a large transmembranereceptor
with 34 extracellularly located,epidermal growth factor (EGF)
similar domains. In this work 70 related families (70 index
patients and 13 relatives) with bioptisch secured diagnosis in
substantial two Exons (3 and 4) were examined, since within this
range the mutations accumulate. By sequencing of Exon 3 and Exon 4
mutations in 70 % of the cases were identified. Three types of
mutations were found: Point mutations ((n = 50), Dinukleotid
mutation (n = 1) and Deletionen (n= 2). In addition numerous
Polymorphismen was identified (n =43). Seven of the mutated
nucleotides mutations arose frequently, whereby transitions of
cytosine to thymine occure. All mutations including the Deletionen
led either to an acquisition or a loss of a Cystein. Therefore it
is to be accepted obviously that the change of a Cystein in a EGF
similar domain of Notch3 represents the crucial mutation mechanical
which is responsible for CADASIL. With the Polymorphismen no
changes of the Cystein arose. Genotyp/Phaenotyp correlations could
not be proven. This stands in the agreement with the uniformity of
the mutations. Due to the results of this work an improvement in
the procedure results for the existing diagnostics. Scinbiopsie and
MRT photographs can be supplemented by the sequencing of Exon 3 and
4. Thus 2/3 of the mutations are already discovered. If no
mutations are found there, still the remaining 22 Exons of the
extracellular domain can be sequenzed, whereby here first on Exon 6
(and 12) the emphasis should be put. This procedure is used
meanwhile as standard technique for the diagnostics. In this work
as the further supplementing diagnostic method the analysis with
mutation-specific restriction enzymes was developed. Under
consultation of the theoretically computed restriction enzymes of
the 7 most frequent mutations one receives 52% (amount of = 37) of
the mutations with 70 index patients (74% of the found mutations).
In families, in which a mutation already admits is, further family
members with this method let themselves be examined faster and more
economically, than by sequencing. In this work it could be shown
that forecasts of mutation effects make the development of protein
models possible on the protein structure. As possible working
hypothesis a Conformationchange ore a Surfacechange can be
accepted, the one effect on the connection partner be had can and
possibly the function affected. An incorrect dismantling of the
Notch3 of receptor leads to the fact that truncated receptor
fragments collect in the Media of the vessels in the proximity of
osmiophilen deposits. Because of the stereotyped mutations with
those frequently so-called CpG (modulators of the Epigenetic)is
present further possible mutations can be predicted.