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Response of risperidone treatment may be associated with polymorphisms of HTT gene in Chinese schizophrenia patients
Neuroscience Letters 414 (2007) 1–4
Response of risperidone treatment may be associated with polymorphisms of HTT gene in Chinese schizophrenia patients Lei Wang a,b,1 , Lan Yu b , Guang He a,b , Jing Zhang a,b , Ai-Ping Zhang a,b , Jing Du a,b , Rui-Qi Tang a,b , Xin-Zhi Zhao a,b , Jie Ma a,b , Jie-Kun Xuan a,b , Yue Xiao a,b , Niu-Fan Gu c , Guo-Ying Feng c , Ming-Qing Xu, Qing-He Xing a,b,∗,1 , Lin He a,b,∗ b
a Bio-X center, Shanghai Jiao Tong University, Shanghai, China Institute of Nutritional Science, Shanghai Institute for Biological Sciences, Chinese Academy of Sciences, Shanghai, China c Shanghai Institute of Mental health, Shanghai, China
Received 14 June 2006; received in revised form 3 September 2006; accepted 5 September 2006
Abstract Serotonin transporter (5-HTT) is a key component of the serotonergic neurotransmitter system. Few studies have focused on polymorphisms of the serotonin transporter and antipsychotic response and, in particular, there have so far been no published studies on the association between the serotonin transporter and response to risperidone. This study examined the relationship between two polymorphisms of the serotonin transporter and the efficacy of risperidone treatment in 129 patients with schizophrenia. Our results revealed that patients with l allele of HTTRLP showed a greater improvement than those without l allele on the overall brief psychiatric rating scale (BPRS) (P = 0.025). But no such relationship was found for the HTTVNTR. In haplotype analysis, the frequency of L-12 haplotype showed a significant difference between the responder group and the non-responder group (P = 0.005). Our study has, for the first time, produced evidence that the potential for therapy in patients with schizophrenia is related to the HTTRLP polymorphism in the HTT gene and haplotype L-12 may help to predict risperidone treatment efficiency. © 2007 Published by Elsevier Ireland Ltd. Keywords: Schizophrenia; 5-HTT; Polymorphisms; Risperidone treatment response
Risperidone, a new atypical antipsychotic drug, is effective on both positive and negative symptoms of schizophrenia. In clinical therapy, some patients recover completely from severe symptoms, while a large proportion of patients show no improvement. The different responses to antipsychotic drugs is greatly influenced by genetic factors and the genetic component is highly complex, polygenic and epistatic [14]. Some pharmacogenetic studies on the response to risperidone have been published [11,12,23]. But pharmacogenetic mechanism for individual differences in response to risperidone remains unclear. Components of the serotonin system are being studied as risk factors in depression, schizophrenia, obsessive–compulsive disorder, aggression, alcoholism, and autism [18] and are seen ∗ Corresponding authors at: Shanghai Jiao Tong University, Bio-X center, P.O. Box 501, Hao Ran Building, 1954 Hua Shan Road, Shanghai 200030, China. Fax: +86 21 62822491. E-mail addresses: [email protected] (Q.-H. Xing), [email protected] (L. He). 1 These two authors contributed equally to this work.
0304-3940/$ – see front matter © 2007 Published by Elsevier Ireland Ltd. doi:10.1016/j.neulet.2006.09.014
as playing an important role in the clinical effectiveness of antipsychotic drugs [17]. The serotonin transporter (solute carrier family 6, member 4, SLC6A4, also know as 5-HTT) is a key member of the serotonin system, which mediates high-affinity 5HT transport into the presynaptic neuron and has a predominant role in the termination of the extracellular effects of 5-HT [29]. Diminished 5-HT concentration within various brain regions, as well as changes in distribution and density of 5-HT1A and 5HT2A receptors, have been observed in knock out mice lacking the serotonin transporter gene [3]. On the other hand, current studies suggest that risperidone has an important effect on the serotonin system, affecting, for instant, the 5-HT1A, 5-HT2A, 5-HT2C receptors [16,27]. Variation of function of 5-HTT may affect the response to almost any agent affecting the 5HT system. Thus, individual differences in the serotonin transporter may affect the response to risperidone in schizophrenia patients. We therefore hypothesize that polymorphisms of 5-HTT may be associated with response to risperidone. Two 5-HTT polymorphisms, one consisting of a variable number of tandem repeat elements known as HTTVNTR in the intron2 and the other is a 44
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L. Wang et al. / Neuroscience Letters 414 (2007) 1–4
base pair insertion/deletion located upstream of the transcription start site known as HTTRLP, have been widely studied in both the context of complex traits and disorders [2,4,5,8,21,26] and of treatment response to antidepressants [10,22,25]. However, few studies have focused on polymorphisms of the serotonin transporter and response to antipsychotic drugs. Arranz et al. [1] studied the two polymorphisms of 5-HTT and found HTTRLP to be associated with response to clozapine, whereas HTTVNTR showed a negative result. By the contrary, Tsai et al. [28] found that the HTTRLP variant did not influence response to clozapine in Chinese patients from Taiwan. Up till now, no study on the association between 5-HTT and response to risperidone has been published. In this study, we examined whether the 5-HTT gene contributes to the therapeutic effect of risperidone in schizophrenia by investigating the potential genetic role of the HTTRLP and HTTVNTR polymorphisms in the 5-HTT gene. Haplotype analysis was also conducted to assess the association between the two markers of the 5-HTT and risperidone treatment response. One hundred and twenty-nine patients (mean age of onset 30.35 years, S.D. = 11.33, 45 male, 84 female) were recruited from the Shanghai Mental Health Center, each of whom had two (or more) of the following characteristic symptoms: delusions; hallucination; disorganized speech; grossly disorganized or catatonic behavior; negative symptoms, i.e. affective flattening, alogia, or avolition, as defined by the Diagnostic and Statistical manual of Mental Disorder, the fourth Edition (DSM IV) [6]. Most, but not all, of the subjects were first-episode patients, but in every case this was their first exposure to risperidone treatment and none have received medication for at least 1 month before this study. Patients were treated with 3–8 mg of risperidone monotherapy, given orally at bedtime. Clinical response was assessed by the brief psychiatric rating scale (BPRS) [20], which covers the core part of PANSS. BPRS ratings were conducted after 8 weeks of treatment. A reduction of 40% or more in the BPRS score at the end of the study (Week 8) was considered a response [30]. Diagnosis of each patient was made independently by two fully qualified psychiatrists, who were given no information on the genotype of the patients. This study was approved by the university ethics committee. Informed consent was obtained from each patient. DNA was extracted from peripheral blood lymphocytes following standard procedures [7]. 5HTTRLP and 5HTTVNTR
markers were genotyped on MegaBACE 1000 (Amersham Bioscience) using capillary electrophoresis technology. For HTTRLP, The sizes of fragments were 484bp (S, short), 528bp (L, long). The primers used were 5 -FAM-TCCTCCGCTTTGGCGCCTCTTCC-3 and 5 -TGGGGGTTGCAGGGGAGATCCTG-3 . For HTTVNTR, primers used were 5 -FAM-GTCAGTATCACAGGCTGCGAG-3 and 5 -TGTTCCTAGTCTTACGCCAGTG-3 . The size of fragment was 267bp (10 repeats) or 300bp (12 repeats). PCR amplification for a total 5 l reaction volume containing 10 ng genomic DNA, 0.05 l Hotstar DNA polymerase (Qiagen), 0.8 l dNTPs, 0.3 l of each primer, 0.5 l buffer was performed on Gene Amp 9700 therm cycler (PE applied Biosystems, Perkin-Elmer). Allele frequencies were calculated using the Excel software for windows. Hardy-Weinberg equilibrium analysis was performed on the online calculator (http://www.kursus.kvl. dk/shares/vetgen/ Popgen/genetik/applets/kitest.htm). The program CLUMP 2.2 [24] was used to compare genotype and allele frequencies. Haplotype frequencies were estimated using the expectation-maximization algorithm implemented in the PM program [31]. Differences in haplotype frequency distribution between non-responder group and responder group were assessed using the CLUMP program version 2.2. Odds ratios with 95% confidence interval were estimated for the effects of high-risk haplotype and calculated by Epi info 2002 software (http://www.cdc.gov/epiinfo/). After 8 weeks of therapy, 129 patients completed the assessments and were eligible for data analysis. Seventy-two patients responded to risperidone, while 57 patients did not. There were no differences between the responder group and non-responder group as regards gender, age, and blood level of risperidone at 8 weeks. The genotype and allele frequencies of two markers are shown in Table 1. Genotypes of the markers did not deviate from Hardy-Weinberg equilibrium in either the responder or non-responder group. The l allele of HTTRLP showed a significant higher frequency in the patients who showed much more improvement in BPRS score (P = 0.025). However, for HTTVNTR, no significant difference in both allele and genotype was observed in responder and non-responder group. Haplotypes with frequency >3% are shown in Table 2. We observed that the overall frequency of the haplotype was significantly different between responder and non-responder groups (P = 0.025). Especially, the L-12 haplotype were 25.7% and 11.7% in responder and non-responder group, respectively. This haplotype is sig-
Table 1 Allele and genotype frequencies for the HTTLRP and HTTVNTR polymorphisms in responder and non-responder group Polymorphism and study group
Genotype
HTTRLP Responder (n = 72) Non-responder (n = 57) HTTVNTR Responder (n = 72) Non-responder (n = 57)
SS 39 (0.54) 40 (0.70) 12/12 64 (0.89) 45 (0.79)
SL 25 (0.35) 15 (0.26) 12/10 8 (0.11) 11 (0.19)
LL 8 (0.11) 2 (0.04) 10/10 0 1 (0.02)
P
Allele
0.11
S 104 (0.71) 93 (0.83) 12 130 (0.94) 101 (0.89)
0.21
P L 36 (0.29) 19 (0.17) 10 8 (0.06) 13 (0.11)
0.025
0.09
P-value showed the difference of frequency of genotype or allele between responder group and non-responder group; values in parentheses stand for the frequency; significant P-value (<0.05) are in boldface.
L. Wang et al. / Neuroscience Letters 414 (2007) 1–4
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Table 2 Comparison of haplotype frequency estimates and test statistics between risperidone responder and risperidone non-responder groups Haplotype
1 2 3 4
HTTRLP
L L S S
HTTVNTR
10 12 10 12
Frequency (%) Responder
Non-responder
1.8 25.7 3.8 68.7
5.0 11.7 6.1 77.2
Global
P-value
Odds ratio (95% CI)
0.157 0.005 0.399 0.14
0.35 (0.08–1.59) 2.61 (1.30–5.23) 0.61 (0.19–1.95) 0.65 (0.37–1.15)
0.025
Haplotype with frequencies >3% are shown. Significant P-value (<0.05) are in boldface.
nificantly different between responder and non-responder group (P = 0.005). After conservative Bonferroni correction, the haplotype remains significantly different between responder and non-responder (P < 0.05). In clinical therapy, 30–40% of patients with schizophrenia show no obvious improvement after antipsychotic drug treatment [9]. Recently, with the significant development of pharmacogenomics, research has been increasingly focusing on the use of individualized genetic markers to predict the efficacy of antipsychotic drug treatment. Lane et al. showed that the 102T/C polymorphism of HT2A may influence individual response to risperidone [11]. They also showed that the DRD3 Ser9Gly polymorphism could influence risperidone response for negative symptoms and social functioning in schizophrenics [12]. HTTRLP of the serotonin transporter was found to be associated with response to clozapine [1]. Zalsman et al. investigated the relationship between the dopamine D4 receptor gene exon III polymorphism and response to risperidone in adolescent Israeli schizophrenics [30]. In our study, we analyzed the association between two 5HTT gene markers: HTTRLP and HTTVNTR and response to risperidone treatment. HTTRLP has the potential to regulate the transcription activity of the associated HTT gene promoter. When fused to a luciferase reporter gene and transfected into human 5HTT expressing cell lines, the short and long HTTRLP variants differentially modulate transcriptional activity of the 5HTT gene promoter [15]. For HTTVNTR, Mackenzie and Quinn reported that transgenic mice with VNTR fused to a reporter gene demonstrated higher expression of the 12 repeat in the dorsal raphe nucleus when compared to the 10 repeat. The VNTR regions act as transcriptional regulators and have alleledependent differential enhancer-like properties within an area of the hindbrain at the stage of mice embryonic development [19]. A growing body of evidence suggests that the two markers play a role in anxiety-, depression-, aggression-related personality traits, various psychiatric disorders and response to antidepressant [13]. HTTLRP was found to be associated with response to clozapine, while for HTTVNTR, there was not a significant difference between responder group and non-responder group [1,28]. In our study, we found HTTRLP was associated with risperidone treatment response. The frequency of l was significantly lower in patients who showed much less improvement in total BPRS score (P = 0.025). It has been reported that the basal activity of the l variant was more than twice that of the s form
of the 5-HTT gene promoter. It is possible that different alleles of HTTRLP will influence 5HT concentrations at all synapses, thus, efficiency of risperidone treatment could be affected. We did not find HTTVNTR was associated with risperidone treatment response. Because our sample size was relatively small, our results may involve a type II error. Therefore, HTTVNTR would repay investigation in larger sample size. In haplotype analysis, the frequency of L-12 haplotype is much higher in responder group than in non-responder group, which implies that the haplotype may help predict clinical treatment efficiency. Overall, our study provides preliminary evidence for the potential role of the serotonin transporter in the response to risperidone. In summary, we found HTTRLP is significantly associated with risperidone treatment response. l allele of HTTRLP may help predict therapeutic response to risperidone in schizophrenia. This is the first study of the association between 5HTT and risperidone treatment response. Our analyses based on the haplotype analysis further support the hypothesis that a possible association may exist between 5-HTT and the response to risperidone. The distribution of the global haplotype is significantly different between responder and non-responder group, which implies that the serotonin transporter may play a role in response to risperidone treatment. Furthermore, it may be that the L-12 haplotype could be used as a genetic marker to help predict the efficiency of risperidone treatment. However, because of limited sample size, the results are simply indicative and need to be supported by evidence from larger sample sizes and from different ethnic groups. Moreover, the contribution of single genes to drug response is modest, whereas interaction between different genes could result in a dramatic modification of drug response. Therefore, the role played by polymorphisms of other genes and by interactions between different genes in response to risperidone also needs to be investigated. Acknowledgements We are grateful to all the participants as well as the psychiatrists and mental health workers working on this project. This work was supported in part by grants from the Chinese National Key Program for Basic Research (973), the National High Tech Program (863), the National Natural Science Foundation of China, and the Shanghai Municipal Commission for Science and Technology.
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Response of risperidone treatment may be associated with polymorphisms of HTT gene in Chinese schizophrenia patients Lei Wang a,b,1 , Lan Yu b , Guang He a,b , Jing Zhang a,b , Ai-Ping Zhang a,b , Jing Du a,b , Rui-Qi Tang a,b , Xin-Zhi Zhao a,b , Jie Ma a,b , Jie-Kun Xuan a,b , Yue Xiao a,b , Niu-Fan Gu c , Guo-Ying Feng c , Ming-Qing Xu, Qing-He Xing a,b,∗,1 , Lin He a,b,∗ b
a Bio-X center, Shanghai Jiao Tong University, Shanghai, China Institute of Nutritional Science, Shanghai Institute for Biological Sciences, Chinese Academy of Sciences, Shanghai, China c Shanghai Institute of Mental health, Shanghai, China
Received 14 June 2006; received in revised form 3 September 2006; accepted 5 September 2006
Abstract Serotonin transporter (5-HTT) is a key component of the serotonergic neurotransmitter system. Few studies have focused on polymorphisms of the serotonin transporter and antipsychotic response and, in particular, there have so far been no published studies on the association between the serotonin transporter and response to risperidone. This study examined the relationship between two polymorphisms of the serotonin transporter and the efficacy of risperidone treatment in 129 patients with schizophrenia. Our results revealed that patients with l allele of HTTRLP showed a greater improvement than those without l allele on the overall brief psychiatric rating scale (BPRS) (P = 0.025). But no such relationship was found for the HTTVNTR. In haplotype analysis, the frequency of L-12 haplotype showed a significant difference between the responder group and the non-responder group (P = 0.005). Our study has, for the first time, produced evidence that the potential for therapy in patients with schizophrenia is related to the HTTRLP polymorphism in the HTT gene and haplotype L-12 may help to predict risperidone treatment efficiency. © 2007 Published by Elsevier Ireland Ltd. Keywords: Schizophrenia; 5-HTT; Polymorphisms; Risperidone treatment response
Risperidone, a new atypical antipsychotic drug, is effective on both positive and negative symptoms of schizophrenia. In clinical therapy, some patients recover completely from severe symptoms, while a large proportion of patients show no improvement. The different responses to antipsychotic drugs is greatly influenced by genetic factors and the genetic component is highly complex, polygenic and epistatic [14]. Some pharmacogenetic studies on the response to risperidone have been published [11,12,23]. But pharmacogenetic mechanism for individual differences in response to risperidone remains unclear. Components of the serotonin system are being studied as risk factors in depression, schizophrenia, obsessive–compulsive disorder, aggression, alcoholism, and autism [18] and are seen ∗ Corresponding authors at: Shanghai Jiao Tong University, Bio-X center, P.O. Box 501, Hao Ran Building, 1954 Hua Shan Road, Shanghai 200030, China. Fax: +86 21 62822491. E-mail addresses: [email protected] (Q.-H. Xing), [email protected] (L. He). 1 These two authors contributed equally to this work.
0304-3940/$ – see front matter © 2007 Published by Elsevier Ireland Ltd. doi:10.1016/j.neulet.2006.09.014
as playing an important role in the clinical effectiveness of antipsychotic drugs [17]. The serotonin transporter (solute carrier family 6, member 4, SLC6A4, also know as 5-HTT) is a key member of the serotonin system, which mediates high-affinity 5HT transport into the presynaptic neuron and has a predominant role in the termination of the extracellular effects of 5-HT [29]. Diminished 5-HT concentration within various brain regions, as well as changes in distribution and density of 5-HT1A and 5HT2A receptors, have been observed in knock out mice lacking the serotonin transporter gene [3]. On the other hand, current studies suggest that risperidone has an important effect on the serotonin system, affecting, for instant, the 5-HT1A, 5-HT2A, 5-HT2C receptors [16,27]. Variation of function of 5-HTT may affect the response to almost any agent affecting the 5HT system. Thus, individual differences in the serotonin transporter may affect the response to risperidone in schizophrenia patients. We therefore hypothesize that polymorphisms of 5-HTT may be associated with response to risperidone. Two 5-HTT polymorphisms, one consisting of a variable number of tandem repeat elements known as HTTVNTR in the intron2 and the other is a 44
2
L. Wang et al. / Neuroscience Letters 414 (2007) 1–4
base pair insertion/deletion located upstream of the transcription start site known as HTTRLP, have been widely studied in both the context of complex traits and disorders [2,4,5,8,21,26] and of treatment response to antidepressants [10,22,25]. However, few studies have focused on polymorphisms of the serotonin transporter and response to antipsychotic drugs. Arranz et al. [1] studied the two polymorphisms of 5-HTT and found HTTRLP to be associated with response to clozapine, whereas HTTVNTR showed a negative result. By the contrary, Tsai et al. [28] found that the HTTRLP variant did not influence response to clozapine in Chinese patients from Taiwan. Up till now, no study on the association between 5-HTT and response to risperidone has been published. In this study, we examined whether the 5-HTT gene contributes to the therapeutic effect of risperidone in schizophrenia by investigating the potential genetic role of the HTTRLP and HTTVNTR polymorphisms in the 5-HTT gene. Haplotype analysis was also conducted to assess the association between the two markers of the 5-HTT and risperidone treatment response. One hundred and twenty-nine patients (mean age of onset 30.35 years, S.D. = 11.33, 45 male, 84 female) were recruited from the Shanghai Mental Health Center, each of whom had two (or more) of the following characteristic symptoms: delusions; hallucination; disorganized speech; grossly disorganized or catatonic behavior; negative symptoms, i.e. affective flattening, alogia, or avolition, as defined by the Diagnostic and Statistical manual of Mental Disorder, the fourth Edition (DSM IV) [6]. Most, but not all, of the subjects were first-episode patients, but in every case this was their first exposure to risperidone treatment and none have received medication for at least 1 month before this study. Patients were treated with 3–8 mg of risperidone monotherapy, given orally at bedtime. Clinical response was assessed by the brief psychiatric rating scale (BPRS) [20], which covers the core part of PANSS. BPRS ratings were conducted after 8 weeks of treatment. A reduction of 40% or more in the BPRS score at the end of the study (Week 8) was considered a response [30]. Diagnosis of each patient was made independently by two fully qualified psychiatrists, who were given no information on the genotype of the patients. This study was approved by the university ethics committee. Informed consent was obtained from each patient. DNA was extracted from peripheral blood lymphocytes following standard procedures [7]. 5HTTRLP and 5HTTVNTR
markers were genotyped on MegaBACE 1000 (Amersham Bioscience) using capillary electrophoresis technology. For HTTRLP, The sizes of fragments were 484bp (S, short), 528bp (L, long). The primers used were 5 -FAM-TCCTCCGCTTTGGCGCCTCTTCC-3 and 5 -TGGGGGTTGCAGGGGAGATCCTG-3 . For HTTVNTR, primers used were 5 -FAM-GTCAGTATCACAGGCTGCGAG-3 and 5 -TGTTCCTAGTCTTACGCCAGTG-3 . The size of fragment was 267bp (10 repeats) or 300bp (12 repeats). PCR amplification for a total 5 l reaction volume containing 10 ng genomic DNA, 0.05 l Hotstar DNA polymerase (Qiagen), 0.8 l dNTPs, 0.3 l of each primer, 0.5 l buffer was performed on Gene Amp 9700 therm cycler (PE applied Biosystems, Perkin-Elmer). Allele frequencies were calculated using the Excel software for windows. Hardy-Weinberg equilibrium analysis was performed on the online calculator (http://www.kursus.kvl. dk/shares/vetgen/ Popgen/genetik/applets/kitest.htm). The program CLUMP 2.2 [24] was used to compare genotype and allele frequencies. Haplotype frequencies were estimated using the expectation-maximization algorithm implemented in the PM program [31]. Differences in haplotype frequency distribution between non-responder group and responder group were assessed using the CLUMP program version 2.2. Odds ratios with 95% confidence interval were estimated for the effects of high-risk haplotype and calculated by Epi info 2002 software (http://www.cdc.gov/epiinfo/). After 8 weeks of therapy, 129 patients completed the assessments and were eligible for data analysis. Seventy-two patients responded to risperidone, while 57 patients did not. There were no differences between the responder group and non-responder group as regards gender, age, and blood level of risperidone at 8 weeks. The genotype and allele frequencies of two markers are shown in Table 1. Genotypes of the markers did not deviate from Hardy-Weinberg equilibrium in either the responder or non-responder group. The l allele of HTTRLP showed a significant higher frequency in the patients who showed much more improvement in BPRS score (P = 0.025). However, for HTTVNTR, no significant difference in both allele and genotype was observed in responder and non-responder group. Haplotypes with frequency >3% are shown in Table 2. We observed that the overall frequency of the haplotype was significantly different between responder and non-responder groups (P = 0.025). Especially, the L-12 haplotype were 25.7% and 11.7% in responder and non-responder group, respectively. This haplotype is sig-
Table 1 Allele and genotype frequencies for the HTTLRP and HTTVNTR polymorphisms in responder and non-responder group Polymorphism and study group
Genotype
HTTRLP Responder (n = 72) Non-responder (n = 57) HTTVNTR Responder (n = 72) Non-responder (n = 57)
SS 39 (0.54) 40 (0.70) 12/12 64 (0.89) 45 (0.79)
SL 25 (0.35) 15 (0.26) 12/10 8 (0.11) 11 (0.19)
LL 8 (0.11) 2 (0.04) 10/10 0 1 (0.02)
P
Allele
0.11
S 104 (0.71) 93 (0.83) 12 130 (0.94) 101 (0.89)
0.21
P L 36 (0.29) 19 (0.17) 10 8 (0.06) 13 (0.11)
0.025
0.09
P-value showed the difference of frequency of genotype or allele between responder group and non-responder group; values in parentheses stand for the frequency; significant P-value (<0.05) are in boldface.
L. Wang et al. / Neuroscience Letters 414 (2007) 1–4
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Table 2 Comparison of haplotype frequency estimates and test statistics between risperidone responder and risperidone non-responder groups Haplotype
1 2 3 4
HTTRLP
L L S S
HTTVNTR
10 12 10 12
Frequency (%) Responder
Non-responder
1.8 25.7 3.8 68.7
5.0 11.7 6.1 77.2
Global
P-value
Odds ratio (95% CI)
0.157 0.005 0.399 0.14
0.35 (0.08–1.59) 2.61 (1.30–5.23) 0.61 (0.19–1.95) 0.65 (0.37–1.15)
0.025
Haplotype with frequencies >3% are shown. Significant P-value (<0.05) are in boldface.
nificantly different between responder and non-responder group (P = 0.005). After conservative Bonferroni correction, the haplotype remains significantly different between responder and non-responder (P < 0.05). In clinical therapy, 30–40% of patients with schizophrenia show no obvious improvement after antipsychotic drug treatment [9]. Recently, with the significant development of pharmacogenomics, research has been increasingly focusing on the use of individualized genetic markers to predict the efficacy of antipsychotic drug treatment. Lane et al. showed that the 102T/C polymorphism of HT2A may influence individual response to risperidone [11]. They also showed that the DRD3 Ser9Gly polymorphism could influence risperidone response for negative symptoms and social functioning in schizophrenics [12]. HTTRLP of the serotonin transporter was found to be associated with response to clozapine [1]. Zalsman et al. investigated the relationship between the dopamine D4 receptor gene exon III polymorphism and response to risperidone in adolescent Israeli schizophrenics [30]. In our study, we analyzed the association between two 5HTT gene markers: HTTRLP and HTTVNTR and response to risperidone treatment. HTTRLP has the potential to regulate the transcription activity of the associated HTT gene promoter. When fused to a luciferase reporter gene and transfected into human 5HTT expressing cell lines, the short and long HTTRLP variants differentially modulate transcriptional activity of the 5HTT gene promoter [15]. For HTTVNTR, Mackenzie and Quinn reported that transgenic mice with VNTR fused to a reporter gene demonstrated higher expression of the 12 repeat in the dorsal raphe nucleus when compared to the 10 repeat. The VNTR regions act as transcriptional regulators and have alleledependent differential enhancer-like properties within an area of the hindbrain at the stage of mice embryonic development [19]. A growing body of evidence suggests that the two markers play a role in anxiety-, depression-, aggression-related personality traits, various psychiatric disorders and response to antidepressant [13]. HTTLRP was found to be associated with response to clozapine, while for HTTVNTR, there was not a significant difference between responder group and non-responder group [1,28]. In our study, we found HTTRLP was associated with risperidone treatment response. The frequency of l was significantly lower in patients who showed much less improvement in total BPRS score (P = 0.025). It has been reported that the basal activity of the l variant was more than twice that of the s form
of the 5-HTT gene promoter. It is possible that different alleles of HTTRLP will influence 5HT concentrations at all synapses, thus, efficiency of risperidone treatment could be affected. We did not find HTTVNTR was associated with risperidone treatment response. Because our sample size was relatively small, our results may involve a type II error. Therefore, HTTVNTR would repay investigation in larger sample size. In haplotype analysis, the frequency of L-12 haplotype is much higher in responder group than in non-responder group, which implies that the haplotype may help predict clinical treatment efficiency. Overall, our study provides preliminary evidence for the potential role of the serotonin transporter in the response to risperidone. In summary, we found HTTRLP is significantly associated with risperidone treatment response. l allele of HTTRLP may help predict therapeutic response to risperidone in schizophrenia. This is the first study of the association between 5HTT and risperidone treatment response. Our analyses based on the haplotype analysis further support the hypothesis that a possible association may exist between 5-HTT and the response to risperidone. The distribution of the global haplotype is significantly different between responder and non-responder group, which implies that the serotonin transporter may play a role in response to risperidone treatment. Furthermore, it may be that the L-12 haplotype could be used as a genetic marker to help predict the efficiency of risperidone treatment. However, because of limited sample size, the results are simply indicative and need to be supported by evidence from larger sample sizes and from different ethnic groups. Moreover, the contribution of single genes to drug response is modest, whereas interaction between different genes could result in a dramatic modification of drug response. Therefore, the role played by polymorphisms of other genes and by interactions between different genes in response to risperidone also needs to be investigated. Acknowledgements We are grateful to all the participants as well as the psychiatrists and mental health workers working on this project. This work was supported in part by grants from the Chinese National Key Program for Basic Research (973), the National High Tech Program (863), the National Natural Science Foundation of China, and the Shanghai Municipal Commission for Science and Technology.
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