Two New Susceptibility Genes Were Identified by Targeted Sequencing for Post-Stroke Depression in the Chinese Han Population

Background: Post stroke depression (PSD) is a common complication characterized by depressed mood, lack of interest or pleasure after stroke and leads to increased physical disability, poor functional outcome and raised mortality of stroke patients. Although several genes have been associated with PSD, the genetic basis of PSD remains poorly understood. In addition, no genome-wide association study (GWAS) has been carried out for PSD patients in China. Method: A 2-stage genome-wide association study was conducted involving 671 cases (321 PSD patients and 349 non-PSD patients) and 1746 non-stroke health controls. In the discovery stage (121 PSD, 131 non-PSD and 639 HC), logistic regression was used to test associations respectively in PSD and non-PSD groups, and analysis was restricted to sequenced single nucleotide polymorphisms (SNPs) and short indels. In the replication stage (200 PSD, 218 non-PSD and 983 HC), the selected SNPs were again genotyped in an independent cohort. Fixed-effects inverse variance-weighted meta-analysis was used in the combined discovery and replication samples. SNPs were functionally annotated by Annovar according to their location and expected effect on encoded gene products on the basis of information from the RefSeq, UCSU and eQTL database. In addition, functional network analysis and GO pathway enrichment analysis were performed to find the common biological processes mediated by the novel candidate genes. Results: The study identified 2 novel susceptibility genes for PSD [HTR3D (rs55674402, p=0.002512, odds ratio (OR)=0.7431); NEUROG3 (rs144643855, p=0.00325, OR=0.6523)] and 3 risk SNPs in one risk gene for non-PSD [PIK3C2B (rs17406271, p=0.0006801, OR=1.446; rs2271419, p=0.0005836, OR=1.497; rs2271420, p=0.001031, OR=1.431)] in two stages and meta-analysis. In addition, 2 previously studied genes [CREB1 (rs139164200, p=0.0001165, OR=2.281); SLC6A4 (rs25533, p=0.03166, OR=0.5293)] were identified in the discovery stage though they were not replicated in the second stage. No significant SNP showed evidence of heterogeneity between the 2 stages. HTR3D and NEUROG3 are both found expressed in central nervous system, while NEUROG3 shows highest expression level in hippocampus compared with other regions of body. HTR3D encodes the D subunit of type 3 serotonin receptor and is found to be associated with neuro-gastrointestinal dysfunctions. NEUROG3 encodes a transcription factor critical for the development of central nervous system and is found to associated with the neural and synaptic plasticity of hippocampus. PIK3C2B encodes the β isoform of the class II PI3K which involves in the intracellular signaling pathway related to the neuron survival and inflammatory process after stroke. Furthermore, GO pathway enrichment analysis shows that these susceptibility genes for PSD, including 2 novel genes identified in this study and those previously published, are involved in chemical synaptic transmission and regulation of lipid synthetic process. Conclusion: This study identified 2 novel susceptibility genes for PSD and 1 novel susceptibility genes for stroke. The association with 5-HT synaptic transmission, neural plasticity, neuron survival, lipid metabolism and inflammatory process of susceptibility genes suggest that the pathogenesis of PSD may be implicated in these pathways and therapeutic interventions targeting these pathways may be effective approaches for PSD treatment. Trial Registation Number: ChiCTR-OCH-13003133 Funding: This work was supported by Jiangsu Provincial Special Program of Medical Science (BL2012025, Yonggui Yuan). Declaration of Interest: There are no conflicts of interest. Ethical Approval: This study has been approved by IEC for clinical research of Zhongda Hospital, Affiliated to Southeast University. Approved No. of ethic committee2013ZDSYLL011.0