title: Rare missense variants of neuronal nicotinic acetylcholine receptor altering receptor function are associated with sporadic amyotrophic lateral sclerosis.
abstract: Sporadic amyotrophic lateral sclerosis (SALS) is a motor neuron degenerative disease of unknown etiology. Current thinking on SALS is that multiple genetic and environmental factors contribute to disease liability. Since neuronal acetylcholine receptors (nAChRs) are part of the glutamatergic pathway, we searched for sequence variants in CHRNA3, CHRNA4 and CHRNB4 genes, encoding neuronal nicotinic AChR subunits, in 245 SALS patients and in 450 controls. We characterized missense variants by in vitro mutagenesis, cell transfection and electrophysiology. Sequencing the regions encoding the intracellular loop of AChRs subunits disclosed 15 missense variants (6.1%) in 14 patients compared with only six variants (1.3%) in controls (P = 0.001; OR 4.48, 95% CI 1.7-11.8). The frequency of variants in exons encoding extracellular and transmembrane domains and in intronic regions did not differ. NAChRs formed by mutant alpha3 and alpha4 and wild-type (WT) beta4 subunits exhibited altered affinity for nicotine (Nic), reduced use-dependent rundown of Nic-activated currents (I(Nic)) and reduced desensitization leading to sustained intracellular Ca(2+) concentration, in comparison with WT-nAChR. The cellular loop has a crucial importance for receptor trafficking and regulating ion channel properties. Missense variants in this domain are significantly over-represented in SALS patients and alter functional properties of nAChR in vitro, resulting in increased Ca(2+) entry into the cells. We suggest that these gain-of-function variants might contribute to disease liability in a subset of SALS because Ca(2+) signals mediate nAChR's neuromodulatory effects, including regulation of glutamate release and control of cell survival.
authors.affiliation: Istituto di Neurologia, Università Cattolica del Sacro Cuore, Roma, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Sabatelli
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Eusebi
authors.forename: Ammar
authors.initials: A
authors.lastname: Al-Chalabi
authors.forename: Amelia
authors.initials: A
authors.lastname: Conte
authors.forename: Francesca
authors.initials: F
authors.lastname: Madia
authors.forename: Marco
authors.initials: M
authors.lastname: Luigetti
authors.forename: Irene
authors.initials: I
authors.lastname: Mancuso
authors.forename: Cristina
authors.initials: C
authors.lastname: Limatola
authors.forename: Flavia
authors.initials: F
authors.lastname: Trettel
authors.forename: Fabrizia
authors.initials: F
authors.lastname: Sobrero
authors.forename: Silvia
authors.initials: S
authors.lastname: Di Angelantonio
authors.forename: Francesca
authors.initials: F
authors.lastname: Grassi
authors.forename: Amalia
authors.initials: A
authors.lastname: Di Castro
authors.forename: Claudia
authors.initials: C
authors.lastname: Moriconi
authors.forename: Sergio
authors.initials: S
authors.lastname: Fucile
authors.forename: Serena
authors.initials: S
authors.lastname: Lattante
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Marangi
authors.forename: Marina
authors.initials: M
authors.lastname: Murdolo
authors.forename: Daniela
authors.initials: D
authors.lastname: Orteschi
authors.forename: Alessandra
authors.initials: A
authors.lastname: Del Grande
authors.forename: Pietro
authors.initials: P
authors.lastname: Tonali
authors.forename: Giovanni
authors.initials: G
authors.lastname: Neri
authors.forename: Marcella
authors.initials: M
authors.lastname: Zollino
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D016022:Case-Control Studies; D002460:Cell Line; D005260:Female; D014644:Genetic Variation; D006801:Humans; D008297:Male; D008875:Middle Aged; D016472:Motor Neuron Disease / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism*; D055815:Young Adult
chemical_list: D009419:Nerve Tissue Proteins; D011978:Receptors, Nicotinic; C447159:CHRNB4 protein, human