title: Altered IMPA2 gene expression and calcium homeostasis in bipolar disorder.
abstract: Reduced inositol monophosphatase (IMPase) activity and elevated basal intracellular calcium levels ([Ca(2+)](B)) have been reported in B lymphoblast cell lines (BLCLs) from bipolar I affective disorder (BD-I) patients, which may reflect cellular endophenotypes of this disorder. As the PI cycle couples to intracellular Ca(2+) mobilization, these two putative endophenotypes may be related. Using an RT-PCR assay, mRNA levels were estimated for IMPA1 and 2 genes encoding human IMPase 1 and 2, respectively, in BLCLs phenotyped on [Ca(2+)](B), from patients with a DSM-IV diagnosis of BD-I (n = 12 per phenotype) and from age- and sex-matched healthy subjects (n = 12). IMPA2 mRNA levels were significantly lower in BLCLs from male BD-I patients with high [Ca(2+)](B) (n = 6) compared with healthy male subjects (n = 5) (-52%, P = 0.013), male BD-I patients with normal BLCL [Ca(2+)](B) (n = 8) (-42%, P = 0.003) and female BD-I patients with high [Ca(2+)](B) (n = 6) (-59%, P = 0.0004). A significant negative correlation was observed between IMPA2 mRNA levels and [Ca(2+)](B) in BLCLs from male (P = 0.046), but not female BD-I patients. Sex-dependent differences were also evident in postmortem temporal cortex IMPA2 mRNA levels which, in contrast to BLCLs, were significantly higher in male BD-I subjects compared with male controls (P = 0.025, n = 4/group). Collectively, these observations suggest a potential sex-dependent link between abnormalities in IMPA2 expression and calcium homeostasis in the pathophysiology of BD.
authors.affiliation: Section of Biochemical Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, Canada, M5T 1R8.
authors.forename: I S
authors.initials: IS
authors.lastname: Yoon
authors.forename: P P
authors.initials: PP
authors.lastname: Li
authors.forename: K P
authors.initials: KP
authors.lastname: Siu
authors.forename: J L
authors.initials: JL
authors.lastname: Kennedy
authors.forename: R G
authors.initials: RG
authors.lastname: Cooke
authors.forename: S V
authors.initials: SV
authors.lastname: Parikh
authors.forename: J J
authors.initials: JJ
authors.lastname: Warsh
mesh_terms: D000328:Adult; D001402:B-Lymphocytes / Q000378:metabolism; D001714:Bipolar Disorder / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D006706:Homeostasis / Q000235:genetics; D006801:Humans; D008094:Lithium / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction / Q000235:genetics; D013702:Temporal Lobe / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D008094:Lithium; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase; D002118:Calcium