Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Recombinant dna technique included in method of making a...
Reexamination Certificate
1999-05-17
2003-03-25
Duffy, Patricia A. (Department: 1645)
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Recombinant dna technique included in method of making a...
C435S071100, C435S071200, C435S320100, C435S325000, C435S252300, C435S254110, C435S257200, C435S440000, C536S023500
Reexamination Certificate
active
06537775
ABSTRACT:
The present invention relates to the demonstration of the involvement of the Notch3 protein in CADASIL thus allowing in particular a diagnosis of a predisposition to certain neurological disorders, in particular CADASIL, and models which make it possible to test the therapies possible for this type of pathology.
CADASIL or “Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy” has recently been identified as a cause of cerebral attacks and of dementia whose main characteristics include recidivous subcortical infarcts, migraines and a vascular dementia, in association with MRI images objectivizing diffuse abnormalities of the cerebral white substance.
An anatomicopathological examination shows multiple small deep cerebral infarcts, a leukoencephalopathy and a nonatherosclerotic and nonamyloid angiopathy involving essentially the small cerebral arteries.
As its name indicates, CADASIL is a hereditary disease with a dominant autosomal character. For more information, there may be found in particular a study of the clinical spectrum of CADASIL in H. Chabriat et al., The Lancet, Vol. 346, Oct. 7, 1995.
This highly incapacitating and very often lethal disease has probably remained so far largely undiagnosed as such; the study of about one hundred families since 1993 shows that erroneous diagnoses were most often given to the patient (multiple sclerosis, Alzheimer's disease and the like). Current studies would tend to demonstrate that it is a condition which is much more widespread than what was thought during its discovery.
The research studies currently pursued have the objective of identifying diagnostic tools for the disease and, by virtue, in particular of the models and the possibilities offered by genetic engineering, of developing a possible substitute therapy.
The gene involved in CADASIL has been localized on chromosome 19 and a finer localization is in particular mentioned in two patent applications with the same inventors.
It has now been possible to identify the gene involved in CADASIL which is the Notch3 gene.
The demonstration of the involvement of Notch3 in CADASIL has been possible given the previous limits which had been mentioned especially in the patent applications in question, the first interval (size 14 cM) was D19S221-D19S215 (first patent application), and then the second interval (size 2 cM) was D19S226-D19S199 (second patent application). The region of interest was cloned into a BAC and YAC contig (continuous nucleotide sequence) and its size was estimated at 800 kb. Analysis of this region with the aid of restriction enzymes showed a very high density of NotI, EagI and SacII sites which suggested the presence of numerous genes. Among the numerous transcripts identified by cDNA selection, one transcript showed a very strong homology with a sequence situated at the coding 5′ end of the mouse gene Notch3. Since other analytical factors seemed to corroborate this presence of the Notch3 gene in this situation, the latter was considered to be a good candidate gene by its position in the interval of interest.
The comparative studies carried out on known CADASIL families in comparison with healthy subjects have made it possible to identify mutations on this Notch3 gene in a large number of CADASIL subjects whereas such mutations were not observed on the healthy subjects analyzed. Since, finally, it has been possible to demonstrate the cosegregation of these mutations with the disease phenotype within effected families, the involvement of the Notch3 gene in CADASIL became incontestable.
All the point mutations observed lead to the creation or to the disappearance of a cysteine in one of the EGF domains of this protein. These mutations are clustered for a large part of them into the first six EGFs. The clustering of the mutations is certainly important in diagnostic terms especially for the “sequential” search for these mutations.
Moreover, all these mutations lead to the presence of an odd number of cysteines in one of the EGFs (either seven, or five cysteines) instead of the six cysteines normally present. These mutations could thus result in the formation of either intra- or intermolecular (and in this case in the formation of homo- or heterodimers) aberrant disulfide bridges.
The role of a normal or abnormal dimerization in the functioning of receptors, in particular their activation, is well known.
The Notch genes have been known for a very long time, especially in drosophila and their equivalent is known in vertebrates, in particular in mice. Its English name “notch” comes from the fact that some mutations of this gene produce a notch in the wings of flies. The article by Spyros Artavanis-Tskanas et al., Science 268, 225 (1995) as well as the references which it contains indicate that the Notch proteins are essentially involved, especially in drosophila, in the specification of the cellular destiny during development, and although the protein is always expressed in adult organisms, its functions in the latter remain unknown. More precisely, it appears that the product of the Notch3 gene, hereinafter “Notch3 protein”, is a cell receptor which controls a cascade of cellular events and whose mutation necessarily leads to greater or lesser disruptions in this cascade which may lead to many other neurological, especially cerebrovascular, disorders.
It should be recalled that, while in the text which follows there is interest more particularly in neurological disorders, in particular cerebrovascular-type disorders and most particularly CADASIL, it is probable, given the function of the cell receptor for the product of the Notch3 gene, that impairment of this receptor can lead to a disorganization of its interaction with various ligands but also with the various partners involved in the transduction cascade. Account should be taken, in addition, of the fact that the Notch3 protein might have other functions which have not yet been demonstrated. Under these conditions, it is highly probable that conditions exhibiting similarities with CADASIL may also be involved in the case of a mutation in the Notch3 gene.
Among the relevant diseases, there may be mentioned the sporadic forms of CADASIL, that is to say which occur without a family history but following a neomutation. Notch3 might moreover be involved in other conditions which may be classified into different groups:
Migraine and Hemiplegic Migraine
It was shown that at least one of the genes involved in familial hemiplegic migraine (FHM), the dominant autosomal form of migraine with aura, was located in the same region of chromosome 19 as the CADASIL gene. It should be noted that more than 30% of patients suffering from CADASIL, a condition characterized by the repeated onset of cerebrovascular accidents and of a vascular dementia, suffered from migraine with aura. However, the latter is observed in only about 5% of the population; it is this observation which led to testing the involvement of the CADASIL gene in the mechanisms of this condition. The involvement of this gene in a form of migraine with or without aura was of considerable diagnostic and therapeutic interest because of the frequency of migraine with aura and of migraine without aura in the general population.
Other Vascular (Cerebral Infarct) and/or Dementia Pathologies of Unknown Etiology
This group corresponds to a very large number of patients in neurology, psychiatric and internal medicine departments and it is everything to do reasonable to think that Notch3 or a partner in this signaling pathway may be involved in these conditions for the reasons stated above.
Familial Paroxytic Ataxia
The situation is the same as for FHM. A gene responsible for this condition has been located in the same region of chromosome 19 and Notch3 could be implicated in this condition.
Moreover, the mutations of this gene are responsible for developmental abnormalities which are well known in other species as well as for neoplastic-type pathologies. Malformative and/or neoplastic syndromes in which there may be demonstra
Bach Jean-François
Bousser Marie-Germaine
Joutel Anne
Tournier-Lasserve Elisabeth
Duffy Patricia A.
Finnegan Henderson Farabow Garrett & Dunner LLP
Institut National de la Sante et de la Recherche (INSERM)
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