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Increased nicotine response in iPSC-derived human neurons carrying the CHRNA5 N398 allele.

ABSTRACT: Genetic variation in nicotinic receptor alpha 5 (CHRNA5) has been associated with increased risk of addiction-associated phenotypes in humans yet little is known the underlying neural basis. Induced pluripotent stem cells (iPSCs) were derived from donors homozygous for either the major (D398) or the minor (N398) allele of the nonsynonymous single nucleotide polymorphism (SNP), rs16969968, in CHRNA5. To understand the impact of these nicotinic receptor variants in humans, we differentiated these iPSCs to dopamine (DA) or glutamatergic neurons and then tested their functional properties and response to nicotine. Results show that N398 variant human DA neurons differentially express genes associated with ligand receptor interaction and synaptic function. While both variants exhibited physiological properties consistent with mature neuronal function, the N398 neuronal population responded more actively with an increased excitatory postsynaptic current response upon the application of nicotine in both DA and glutamatergic neurons. Glutamatergic N398 neurons responded to lower nicotine doses (0.1??M) with greater frequency and amplitude but they also exhibited rapid desensitization, consistent with previous analyses of N398-associated nicotinic receptor function. This study offers a proof-of-principle for utilizing human neurons to study gene variants contribution to addiction.

SUBMITTER: Oni EN

PROVIDER: S-EPMC5048107 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Increased nicotine response in iPSC-derived human neurons carrying the CHRNA5 N398 allele.

Oni Eileen N EN Halikere Apoorva A Li Guohui G Toro-Ramos Alana J AJ Swerdel Mavis R MR Verpeut Jessica L JL Moore Jennifer C JC Bello Nicholas T NT Bierut Laura J LJ Goate Alison A Tischfield Jay A JA Pang Zhiping P ZP Hart Ronald P RP

Scientific reports 20161004

Genetic variation in nicotinic receptor alpha 5 (CHRNA5) has been associated with increased risk of addiction-associated phenotypes in humans yet little is known the underlying neural basis. Induced pluripotent stem cells (iPSCs) were derived from donors homozygous for either the major (D398) or the minor (N398) allele of the nonsynonymous single nucleotide polymorphism (SNP), rs16969968, in CHRNA5. To understand the impact of these nicotinic receptor variants in humans, we differentiated these ...[more]

PMID: 27698409

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Project description:Many addictive drugs such as nicotine mediate reward and reinforcing mechanisms within the mesolimbic pathway involving midbrain dopaminergic (mDA) neurons via nicotinic acetylcholine receptors (nAChRs). Previously, genome-wide association analyses (GWAs) identified several nucleotide polymorphism (SNP) associated with increased risk of addictive phenotypes including the nonsynonymous rs16969968 SNP encoding D398->N398 variation in the CHRNA5 gene (Bierut et al., 2008; Saccone et al., 2007) . However, the etiology and the pathophysiology associated with the N398 allele is unknown. Previous animal studies using a knock-in of human CHRNA5 N398 revealed increased nicotine consumption. However, given the evolutionary distance between mice and humans, identifying intrinsic factors that affect addiction may correlate poorly, limiting the conclusiveness of these studies. In this study, induced pluripotent stem cell (iPSC) lines were derived from cryopreserved lymphocytes drawn from patients with homozygous minor alleles (N398) of rs16969968 and demonstrated nicotine addiction as well as age- and gender-matched unaffected controls carrying the major allele (D398). Cultures of primarily mDA neurons were prepared from these iPSC lines. Gene expression analysis using RT-PCR and RNAseq revealed similar expression of mRNAs encoding subunits of nAChR in mDA neurons derived from both D398 and N398 iPSC lines, however, gene ontology (GO) analysis revealed an increased enrichment of genes associated with neuroactive ligand-receptor interactions and Ca2+ signaling pathways in N398 neurons. Moreover, the N398 neuronal population responded more actively to application of nicotine in both electrophysiological analysis and Ca2+-imaging analysis. Together, these results suggest that the N398 variation affects Ca2+-signaling in neurons, which may explain the predisposition of subjects carrying this mutation for addictive behavior in subjects carrying the nonsynonymous rs16969968 SNP (Sherva et al., 2008).

Project description:Midbrain dopamine (DA) neurons are considered a critical substrate for the reinforcing and sensitizing effects of nicotine and tobacco dependence. While the role of the α4 and β2 subunit containing nicotinic acetylcholine receptors (α4β2∗nAChRs) in mediating nicotine effects on DA release and DA neuron activity has been widely explored, less information is available on their role in the morphological adaptation of the DA system to nicotine, eventually leading to dysfunctional behaviors observed in nicotine dependence. In particular, no information is available on the role of α6∗nAChRs in nicotine-induced structural plasticity in rodents and no direct evidence exists regarding the occurrence of structural plasticity in human DA neurons exposed to nicotine. To approach this problem, we used two parallel in vitro systems, mouse primary DA neuron cultures from E12.5 embryos and human DA neurons differentiated from induced pluripotent stem cells (iPSCs) of healthy donors, identified using TH+ immunoreactivity. In both systems, nicotine 1-10 μM produced a dose-dependent increase of maximal dendrite length, number of primary dendrites, and soma size when measured after 3 days in culture. These effects were blocked by pretreatments with the α6∗nAChR antagonists α-conotoxin MII and α-conotoxin PIA, as well as by the α4β2nAChR antagonist dihydro-β-erythroidine (DHβE) in both mouse and human DA neurons. Nicotine was also ineffective when the primary DA neurons were obtained from null mutant mice for either the α6 subunit or both the α4 and α6 subunits of nAChR. When pregnant mice were exposed to nicotine from gestational day 15, structural plasticity was also observed in the midbrain DA neurons of postnatal day 1 offspring only in wild-type mice and not in both null mutant mice. This study confirmed the critical role of α4α6∗nAChRs in mediating nicotine-induced structural plasticity in both mouse and human DA neurons, supporting the translational relevance of neurons differentiated from human iPSCs for pharmacological studies.

Dataset Information

Increased nicotine response in iPSC-derived human neurons carrying the CHRNA5 N398 allele.

Publications

Increased nicotine response in iPSC-derived human neurons carrying the CHRNA5 N398 allele.

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