EFHC2 SNP rs7055196 is not associated with fear recognition in 45 X Turner syndrome.код для вставкиСкачать
American Journal of Medical Genetics Part B (Neuropsychiatric Genetics) 147B:507 –509 (2008) Brief Research Communication EFHC2 SNP rs7055196 Is Not Associated With Fear Recognition in 45,X Turner Syndrome Andrew R. Zinn,1* Harvey Kushner,2 and Judith L. Ross3 1 Department of Internal Medicine and McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, Texas 2 Biomedical Computer Research Institute, Philadelphia, Pennsylvania 3 Department of Pediatrics, Thomas Jefferson University, Philadelphia, Pennsylvania The neurocognitive phenotype of Turner syndrome (TS) includes deficits in social cognitive skills such as recognition of the facial affect expressing fear. A TS social cognition locus was previously mapped to a 5 megabase interval of Xp11.3-p11.4 by Good et al. . A recent study by these same workers found evidence for association of a SNP in the EFHC2 gene, rs7055196, within this interval with fear recognition in 45,X TS. As EFHC2 was not a biological candidate gene for this phenotype a priori, we sought to replicate their finding in an independent cohort of 45,X TS subjects, using the same instrument to measure facial affect fear recognition. In contrast to the previous results, we find no evidence of an association between rs7055196 genotype and fear recognition. Other variations in EFHC2 and other candidate genes should be tested for association with social cognition in 45,X TS. ß 2007 Wiley-Liss, Inc. KEY WORDS: Turner syndrome; affect recognition; EFHC2 Please cite this article as follows: Zinn AR, Kushner H, Ross JL. 2008. EFHC2 SNP rs7055196 Is Not Associated With Fear Recognition in 45,X Turner Syndrome. Am J Med Genet Part B 147B:507–509. INTRODUCTION Turner syndrome (TS; 45,X, monosomy X) in adolescents and adults is associated with deficits in the recognition of faces and the identification of a ‘‘fearful’’ facial expression [Romans et al., 1998; Ross et al., 2002, 2004; Lawrence et al., 2003], which may be related to impaired social function and increased risk of autism [Skuse 2005]. Skuse and co-workers mapped a locus for TS social cognitive ability to a 5 megabase (Mb) critical region of the X chromosome short arm, Xp11.3-p11.4, by deletion mapping [Good et al., 2003]. Women with overlapping This article contains supplementary material, which may be viewed at the American Journal of Medical Genetics website at http://www.interscience.wiley.com/jpages/1552-4841/ suppmat/index.html. Grant sponsor: NIH; Grant numbers: NS42777, NS35554. *Correspondence to: Andrew R. Zinn, 5323 Harry Hines Boulevard, Dallas, TX 75390-8591. E-mail: firstname.lastname@example.org Received 16 March 2007; Accepted 20 August 2007 DOI 10.1002/ajmg.b.30625 ß 2007 Wiley-Liss, Inc. partial X chromosome deletions that included this region had a social cognitive phenotype similar to that of 45,X women. Six genes within this region were considered as candidates for the social cognitive phenotype on the basis of escape from X inactivation and reported brain expression: MAOA, MAOB, NDP, DDX53, UTX, and USP9X [Jones et al., 1996; Lahn and Page, 1997; Carrel et al., 1999; Hartzer et al., 1999; Jansson et al., 2005]. These workers further investigated MAOB, which encodes an isoform of monoamine oxidase isoform B, and showed that MAOB platelet enzyme activity was reduced in 45,X TS versus 46,XX controls, consistent with the gene escaping X inactivation [Good et al., 2003]. They hypothesized that MAOB modulates central serotonergic activity, thereby influencing amygdala cortical functional connectivity. However, in a subsequent study they found no association between MAOB enzymatic activity and sociocognitive mentalizing skills (attributing mental states to animated objects) that are deficient in 45,X TS [Lawrence et al., 2007]. As an adjunct to human studies, the 39,X (XO) mouse has been investigated as an animal model for TS cognitive phenotypes. Isles et al.  reported that 39,X mice show increased fear reactivity and an altered pattern of GABAA subunit expression in brain. Their data implicated haploinsufficiency of a gene outside of the mouse pseudoautosomal region as the cause of the fear reactivity difference. There are presently only four nonpseudoautosomal mouse genes known to escape inactivation: Utx, Dbx, Jarid1c, and Eif2s3 [Isles et al., 2004]. UTX and DDX3X, the human orthologs of Utx and Dbx, respectively, are situated within the 5 Mb Xp11.3-p11.4 critical region for TS sociocognitive deficits [Good et al., 2003]. UTX is ubiquitously expressed and encodes a protein of unknown function [Greenfield et al., 1998]. DDX3X encodes a predicted RNA helicase that is most highly expressed in hematopoietic cells [Chung et al., 1995]. There are also human orthologs of the other two candidate mouse genes elsewhere on Xp. JARID1C encodes a protein involved in transcriptional regulation and chromatin remodeling [Jensen et al., 2005]. Mutations in human JARID1C have been shown to cause X-linked mental retardation [Jensen et al., 2005; Santos et al., 2006]. EIF2S3 encodes the gamma subunit of eukaryotic translation initiation factor 2, a ubiquitious housekeeping protein [Ehrmann et al., 1998]. Although mouse Eif2s3 mRNA level is gene dosage-sensitive, the level of Eif2s3 protein is the same in brains of XO, XX, and XY mice [Xu et al., 2006]. Recently, Skuse and co-workers performed a SNP association analysis of the 5 Mb critical region using 242 SNPs, an initial sample of 93 adults with 45,X TS, and a replication sample of 77 subjects with 45,X TS recruited in the United Kingdom [Weiss et al., 2007]. They found no significant association with any of the six a priori candidate cognitive genes listed above. Instead, they found that EFHC2, another gene within this region, was a quantitative trait locus (QTL) for fear recognition in 45,X TS. Two SNPs less than 20 kb apart within EFHC2, rs7887763, and rs7055196, were associated 508 Zinn et al. with fear recognition (P ¼ 0.022). Because these SNPs were in perfect linkage disequilibrium, only rs7055196 was further analyzed. Although the frequency of the minor, risk allele for the most strongly associated EFHC2 SNP, rs7055196, was only 0.088, it accounted for over 13% of the variance in facial affect fear recognition. EFHC2 is a novel gene expressed in brain and elsewhere predicted to contain a calcium-binding domain and other conserved domains of unknown function. The rs7055196 SNP was in linkage disequilibrium with nearby SNPs, including a Ser430Tyr coding SNP, but because the association was somewhat weaker for these other SNPs, Weiss et al.  proposed that noncoding or untyped variation in EFHC2 is responsible for the observed association. No functional data were reported regarding variation in EFHC2 alleles, for example, expression differences. MATERIALS AND METHODS We genotyped SNP rs7055196 in 97 predominantly Caucasian subjects with 45,X TS, age >11 years, for whom we had fear recognition data. Our subjects were recruited from pediatric and adult endocrinology clinics in the United States. We used the same instrument to measure facial affect recognition [Ekman and Friesen 1976] as Weiss et al. . The test was administered according to the standard protocol provided with the test instructions. Photographs showing six frequently expressed emotions (happiness, sadness, fear, anger, disgust, and surprise) are shown for 10 sec. The answer sheet provides a choice of six emotions. The subject is asked to select the one word on the answer sheet which best describes the emotion expressed in the photograph. The results are scored according to the percent correct for each emotion. Nontransformed data were analyzed using SAS 8.2 (Cary, NC). We treated the phenotype as a continuous variable rather than an arbitrary dichotomous selection in order to maximize the statistical power to detect a genotype effect. Using the Genetic Power Calculator [Purcell et al., 2003] with QTL variance 0.13, minor (risk) allele frequency 0.088, sample size 97, and alpha ¼ 0.05, our power to detect an association was 96% if rs7055196 is in complete linkage disequilibrium with the causal EFHC2 variation (D0 ¼ 1) and 83% if D0 ¼ 0.8 (Table 1). We had 80% power to detect an effect size of 8% of the total QTL variance if D0 ¼ 1 and 12% if D0 ¼ 0.8. We used a pre-designed Applied Biosystems (ABI) TaqMan1 allelic discrimination (AD) assay (ABI Part Number 4351379, Assay ID: C__29047262_10) according to the manufacturer’s protocol. RESULTS Eighty-six subjects had the common A allele, and 11 had the minor G allele, giving a minor allele frequency (MAF) of 0.113, not significantly different from that of 0.088 reported by Weiss et al.  (P ¼ 0.53, Fisher’s exact test). The mean TABLE I. Power Calculations Total QTL variance 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 Power, MAF ¼ 0.088, D0 ¼ 1 Power, MAF ¼ 0.088, D0 ¼ 0.8 0.61 0.69 0.76 0.81 0.86 0.89 0.92 0.94 0.96 0.43 0.50 0.56 0.62 0.67 0.72 0.76 0.80 0.83 MAF, minor allele frequency. Fig. 1. Mean Facial Affect Fear Recognition score (% correct) of 45,X TS subjects according to rs7055196 genotype. Data shown are mean þ SD. Facial Affect Fear Recognition scores (percent recognition) for our 45,X subjects who carried the different rs7055196 alleles showed no significant difference: 49.8 26.5 (n ¼ 86) versus 46.2 26.1 (n ¼ 11), P ¼ 0.67, t-test (Fig. 1). The study by Weiss et al.  included only adult women with TS, whereas our study population included both adults and adolescents. However, this cognitive phenotype has been shown to be present and stable in TS females across a wide age range [Ross et al., 1995, 2002; Romans et al., 1998]. To test whether age differences could explain the lack of association in our study, we performed ANCOVA with rs7055196 genotype and age as covariates. The overall R squared was only 0.005613. The overall F-ratio with age and SNP genotype was 0.17 (overall P-value 0.7675). The P-value for SNP genotype was 0.6846, and the P-value for age was 0.5535. The measure of skewness was 0.054 and the measure of kurtosis was 1.04, so neither affected the results. The complete battery of nonparametric tests available in SAS 8.2 were also run, and none showed a significant difference in mean facial affect recognition score between SNP genotype groups (data not shown). DISCUSSION Our results do not support the contention that fear recognition as measured by recognition of facial affect is associated with genetic variation in EFHC2 SNP rs7055196, at least not in a typical North American 45,X TS cohort. Possible reasons for the lack of replication include differences in ethnic/ racial makeup, IQ, visuospatial ability, or behavioral status of the study groups, but this information was not given in the previous study. In addition, there could be differences in overall facial processing ability, which we did not measure. Given possible genetic differences in the populations, other SNPs in EFHC2 should be tested for association with fear recognition in 45,X TS, followed by SNPs in other genes in the Xp11.4-p11.3 interval, and in candidate genes elsewhere on the X chromosome such as JARID1C. ACKNOWLEDGMENTS The authors thank Purita Ramos and the UT Southwestern Human Genetic Variation core laboratory for genotyping. The study was supported by NIH grants NS42777, NS32531 (JLR) and NS35554 (ARZ). REFERENCES Carrel L, Cottle AA, Goglin KC, Willard HF. 1999. A first-generation X-inactivation profile of the human X chromosome. Proc Natl Acad Sci U S A 96(25):14440–14444. Chung J, Lee SG, Song K. 1995. Identification of a human homolog of a putative RNA helicase gene (mDEAD3) expressed in mouse erythroid cells. Korean J Biochem 27:193–197. Fear Recognition in 45,X Turner Syndrome Ehrmann IE, Ellis PS, Mazeyrat S, Duthie S, Brockdorff N, Mattei MG, Gavin MA, Affara NA, Brown GM, Simpson E, et al. 1998. 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