RESUMEN
Many bipolar affective disorder (BD) susceptibility loci have been identified but the molecular mechanisms responsible for the disease remain to be elucidated. In the locus 4p16, several candidate genes were identified but none of them was definitively shown to be associated with BD. In this region, the PPP2R2C gene encodes the Bgamma-regulatory subunit of the protein phosphatase 2A (PP2A-Bgamma). First, we identified, in two different populations, single nucleotide polymorphisms and risk haplotypes for this gene that are associated to BD. Then, we used the Bgamma subunit as bait to screen a human brain cDNA library with the yeast two-hybrid technique. This led us to two new splice variants of KCNQ2 channels and to the KCNQ2 channel itself. This unusual K+ channel has particularly interesting functional properties and belongs to a channel family that is already known to be implicated in several other monogenic diseases. In one of the BD populations, we also found a genetic association between the KCNQ2 gene and BD. We show that KCNQ2 splice variants differ from native channels by their shortened C-terminal sequences and are unique as they are active and exert a dominant-negative effect on KCNQ2 wild-type (wt) channel activity. We also show that the PP2A-Bgamma subunit significantly increases the current generated by KCNQ2wt, a channel normally inhibited by phosphorylation. The kinase glycogen synthase kinase 3 beta (GSK3beta) is considered as an interesting target of lithium, the classical drug used in BD. GSK3beta phosphorylates the KCNQ2 channel and this phosphorylation is decreased by Li+.
Asunto(s)
Trastorno Bipolar/genética , Trastorno Bipolar/metabolismo , Canal de Potasio KCNQ2/genética , Canal de Potasio KCNQ2/metabolismo , Fosfoproteínas Fosfatasas/genética , Fosfoproteínas Fosfatasas/metabolismo , Tálamo/metabolismo , Animales , Antimaníacos/farmacología , Argentina , Células COS , Estudios de Casos y Controles , Chlorocebus aethiops , Inhibidores Enzimáticos/farmacología , Frecuencia de los Genes , Predisposición Genética a la Enfermedad , Glucógeno Sintasa Quinasa 3/antagonistas & inhibidores , Glucógeno Sintasa Quinasa 3/metabolismo , Glucógeno Sintasa Quinasa 3 beta , Haplotipos , Humanos , Desequilibrio de Ligamiento , Cloruro de Litio/farmacología , Potenciales de la Membrana , Oportunidad Relativa , Fosforilación , Polimorfismo de Nucleótido Simple , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteína Fosfatasa 2 , Medición de Riesgo , Factores de Riesgo , Tálamo/efectos de los fármacos , Transfección , Reino UnidoRESUMEN
Primary genetic maps based on highly informative markers are now available. The local density of these markers may, however, not be sufficient. There is thus a need for new means to generate polymorphic markers from targeted regions of the genome. This can be achieved by selectively cloning and sequencing (CA)n-positive human inter-Alu sequences from targeted YAC clones. This method was tested on 21 YACs and led to the development of seven new polymorphic microsatellite markers.