Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1999-03-26
2004-11-30
Chen, Shin-Lin (Department: 1632)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S023100
Reexamination Certificate
active
06825332
ABSTRACT:
Migraine is a frequent paroxysmal neuro-vascular disorder, characterized by recurrent attacks of disabling headache, vomiting, photo/phonophobia, malaise, and other general symptoms (migraine without aura). Up to 20% of patients may, in addition, experience transient neurological (aura) symptoms during attacks (migraine with aura) (HCC, 1988). Up to 24% of females and 12% of males in the general population are affected, however with variable attack frequency, duration and severity (Russell et al., 1995). Knowledge about the mechanisms of the final common pathway of migraine attacks has increased substantially the last five years, resulting in improved, though still only symptomatic (and sub-optimal) acute treatment for the attack. There is, however, still very little knowledge about the etiology of migraine attacks, i.e. why and how attacks begin and recur. Accordingly, prophylactic treatment for migraine is non-specific and has only limited efficacy.
Family, twin and population-based studies suggest that genetic factors are involved In migraine, most likely as part of a multifactorial mechanism (reviewed by Haan et al., 1996). The complex genetics has hampered identification of candidate genes for migraine. Familial Hemiplegic Migraine (FHM) is a rare, autosomal dominant, subtype of migraine with aura, associated with ictal hemiparesis and, in some families cerebellar atrophy (HCC, 1988). Otherwise, the symptoms of the headache and aura phase of FHM and “normal” migraine attacks are very similar and both types of attacks may alternate within subject and co-occur within families. FHM is thus part of the migraine spectrum and can be used as a model to study the complex genetics of the more common-forms of migraine (Haan et al., 1996). A gene for FHM has been assigned to chromosome 19p13 in about half of the families tested (Joutel et al., 1993; Ophoff et al., 1994; Joutel et al., 1995). Remarkably, cerebellar atrophy was found only in families with FHM linked to chromosome 19p13, but not in unlinked families. Recently, we showed the 19p13 FHM locus to be also involved in “normal” migraine (May et al., 1995).
Episodic ataxia type 2 (EA-2) is another, autosomal dominant, paroxysmal neurological disorder, characterized by acetazolamide-responsive attacks of cerebellar ataxia and migraine-like symptoms, and interictal nystagmus and cerebellar atrophy. Recently, a gene for EA-2 was assigned to chromosome 19p13, within the same interval as for FHM (Kramer et al., 1995). This finding, as well as the clinical similarities, raise the possibility of EA-2 and FHM being allelic disorders.
Since other hereditary episodic neurological disorders responding to acetazolamide (such as hypokalaemic and hyperkalaemic periodic paralysis), as well as EA type-1 A (which, in contrast to EA-2, is associated with continuous myokymia and non-responsive to acetazolamide) have all been associated with mutations in genes encoding for ion channels (Ptacek et al., 1991; Ptacek et al., 1994; Brown et al., 1994), we specifically looked for similar genes within the FHM and EA-2 candidate region.
In view of the above, the FHM/EA-2 locus can, since FHM is part of the migraine spectrum, thus be used to study the genetic factors and biological mechanisms that are related to various episodic neurological disorders such as FHM, EA-2, common migraine and others such as epilepsy.
Calcium channels are multisubunit complexes composed of at least an &agr;1, an &agr;2&dgr;, and a &bgr; subunit. The central &agr;1 subunit is functionally the most important component, acting as a voltage sensor and forming the ion-conducting pore. The other subunits have auxiliary regulatory roles. The membrane topology of the &agr;1 subunit consist of four hydrophobic motifs (I to IV), each containing six transmembrane &agr;-helices (S1-S6) and one hairpin (P) between S5-S6 that spans only the outer part of the transmembrane region.
The present invention provides an isolated and/or recombinant nucleic acid, or fragments thereof, encoding a Ca
2
+-channel &agr;1 subunit related to familial hemiplegic migraine and/or episodic ataxia type-2, derived from a gene present on chromosome 19p13.1-19p13.2; a gene encoding the &agr;1 (ion-conducting) subunit of a P/Q-type voltage gated calcium channel. The present invention also provides access to and methods to study the genetic background and identify other subunits of the calcium channel subunit complexes and the proteins related therewith that are associated with the genetic factors and biological mechanisms that are related to various episodic neurological disorders such as FHM, EA-2, common migraine and others such as epilepsy which are related to cation channel dysfunction.
The sequence of the cDNA of the gene is highly related (≧90%) to a brain-specific rabbit and rat voltage gated P/Q-type calcium channel al subunit (Mori et al., 1991; Starr et al., 1991), and the open reading frame consists of 2261 amino acid residues. Northern blot analysis showed a brain-specific expression, especially in the cerebellum. Primary study of a cosmid contig harbouring the gene already indicated an exon distribution over at least 300 kb of genomic DNA. Recently, a neuronal Ca
2+
&agr;1A subunit gene was localized to chromosome 19p13.1-p13.2 by FISH analysis (Diriong et al, 1995). The gene symbol is CACNL1A4 and the al subunit is classified as a P/Q-type. No sequence data for the CACNL1A4 gene have been provided by Diriong or others, but the same localization (chromosome 19p13.1) and the identical classification (P/Q-type) suggests that the Ca
2
+ channel &agr;1 subunit we have identified is very similar to CACNL1A4. No relation with migraine has been disclosed for CACNL1A4. The genomic structures of three other human Ca
2
+ channel &agr;1 subunit genes (CACNL1A1, CACNL1A2 and CACNL1A3) have been published to date (Hogan et al, 1994; Soldatov, 1994; Yamada et al, 1995). Both CACNL1A1 and CACNL1A2 span about 150 kb and consist of 50 and 49 exons, respectively. The smaller CACNL1A3 gene is composed of 44 exons, distributed over 90 kb.
The present invention also provides an isolated and/or recombinant nucleic acid comprising alleles of the invented gene which contain mutations relevant to the occurence of migraine and other neurological disorders which are related to cation channel dysfunction. Such mutations are for example a mutation at codon 192 resulting in the replacement of arginine by glutamine (R192Q), and/or a mutation at codon 666 resulting in the replacement of threonine by methionine, and/or a mutation at codon 714 resulting in a replacement of valine by alanine and/or a mutation at codon 1811 resulting in a replacement of isoleucine by leucine, but also other mutations of alleles of said gene which bear relationships with cation channnel dysfunction.
The present invention also provides isolated and/or recombinant nucleic acid comprising alleles of said gene which contain a polymorphic CA-repeat sequence specific for various alleles of said gene. The present invention also provides isolated and/or recombinant nucleic acids comprising alleles of said gene which contain a CAG repeat.
The present invention also provides methods and tests (such as PCR, but also other tests to detect or amplify nucleic acids are known in the art) to detect, identify and localize or distinguish genes and alleles of such genes, or fragments thereof, encoding for proteins or &agr;, &bgr; or &khgr; sub-units of specific cerebral cation channels, more specifically the invented gene and its various alleles encoding the &agr;1 subunit of a P/Q-type voltage gated calcium channel and the gene encoding the &bgr;2 sub-unit, which are involved in the primary pathogenesis of neurological disorders such as FHM, migraine, EA-2 and SCA6. With such methods and tests one can study abnormalities of said gene.
The invention also provides recombinant expression vectors comprising isolated and/or recombinant nucleic acid comprising alleles of said genes or fragments therof, and provides host cells or animals that comprise
Ferrari Michel Dominique
Frants Rune Robert Isak Erik
Ophoff Roel André
Terwindt Gisela Marie
Chen Shin-Lin
Rae-Venter Law Group P.C.
Rijksuniversiteit Tel Leiden
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