title: Strong evidence for a novel schizophrenia risk locus on chromosome 1p31.1 in homogeneous pedigrees from Tamil Nadu, India.
abstract: OBJECTIVE
  The study of ethnically homogeneous populations may help to identify schizophrenia risk loci. The authors conducted a genomewide linkage scan for schizophrenia in an Indian population.
  
  
  METHODS
  Participants were 441 individuals (262 affected probands and siblings) who were recruited primarily from one ethnically homogeneous group, the Tamil Brahmin caste, although individuals from other geographically proximal castes also participated. Genotyping of 124 affected sibling pair pedigrees was performed with 402 short tandem repeat polymorphisms. Linkage analyses were conducted using nonparametric exponential LOD (logarithm of the odds ratio for linkage) scores and parametric heterogeneity LOD scores. Parametric heterogeneity scores were calculated using simple dominant and recessive models, correcting for multiple statistics. The data were examined for evidence of consanguinity. Genomewide significance levels were determined using 10,000 gene dropping simulations.
  
  
  RESULTS
  These findings revealed genomewide significant linkage to chromosome 1p31.1, through the use of both exponential and heterogeneity LOD scores, incorporating correction for multiple statistics and mild consanguinity. The estimated sibling recurrence risk associated with this putative locus was 1.95. Analysis for heterogeneity LOD scores also detected suggestive linkage to chromosomes 13q22.1 and 16q12.2. Using 117 tag single nucleotide polymorphisms (SNPs), family-based association analyses of phosphodiesterase 4B (PDE4B), the closest schizophrenia candidate gene, detected no convincing evidence of association, suggesting that the chromosome 1 peak represents a novel risk locus.
  
  
  CONCLUSIONS
  This is the first study-to the authors' knowledge-to report significant linkage of schizophrenia to chromosome 1p31.1. Further investigation of this chromosome region in diverse populations is warranted to identify underlying sequence variants.
authors.affiliation: correspondence and reprint requests to Prof. Mowry; bryan_mowry@qcmhr.uq.edu.au.
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Holliday
authors.forename: Dale R
authors.initials: DR
authors.lastname: Nyholt
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Tirupati
authors.forename: Sujit
authors.initials: S
authors.lastname: John
authors.forename: Padmavati
authors.initials: P
authors.lastname: Ramachandran
authors.forename: Mangala
authors.initials: M
authors.lastname: Ramamurti
authors.forename: Ayankaran Jothi
authors.initials: AJ
authors.lastname: Ramadoss
authors.forename: Anitha
authors.initials: A
authors.lastname: Jeyagurunathan
authors.forename: Sowndari
authors.initials: S
authors.lastname: Kottiswaran
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Smith
authors.forename: Cheryl
authors.initials: C
authors.lastname: Filippich
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Nertney
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Nancarrow
authors.forename: Nicholas K
authors.initials: NK
authors.lastname: Hayward
authors.forename: W Scott
authors.initials: WS
authors.lastname: Watkins
authors.forename: Lynn B
authors.initials: LB
authors.lastname: Jorde
authors.forename: Rangaswamy
authors.initials: R
authors.lastname: Thara
authors.forename: Bryan J
authors.initials: BJ
authors.lastname: Mowry
mesh_terms: D000328:Adult; D000483:Alleles; D002874:Chromosome Mapping; D002878:Chromosomes, Human, Pair 1 / Q000235:genetics*; D003241:Consanguinity; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4 / Q000235:genetics; D005260:Female; D005838:Genotype; D006801:Humans; D007194:India; D008126:Lod Score; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D012559:Schizophrenia / Q000175:diagnosis / Q000208:ethnology / Q000235:genetics*
chemical_list: D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; C517360:PDE4B protein, human