GRIK2 & Bipolar Disorder

1. GRIK2 & Bipolar Disorder Ashley Bateman http://scienceblogs.com/seed/upload/2007/03/lab_mouse.jpg http://www.fi.edu/learn/brain/images/mri_brain.jpg

2. Bipolar Disorder (BPD) Manic-depressive disorder Extreme and unusual shifts in mood, energy, and ability to function Damages relationships & performance Often ends in suicide Affects > 5 million Americans, 3 in 100 adults

3. Diagnosis http://beingbipolar.today.com/files/2009/04/history-of-bipolar-disorder.jpg

4. Major Depressive Episode Persistent feelings of: Sadness Anxiety Guilt Anger Isolation Hopelessness Disturbances in sleep and appetite Fatigue and loss of interest in sexual activity Irritability Lack of motivation Morbid suicidal ideation http://www.thelensflare.com/large/depression_22319.jpg

5. Manic Episode Distinct period of: Elevated, expansive, irritable mood state Racing thoughts Low attention span Easily distracted Impaired judgment Spending sprees, unusual behavior Substance abuse (esp. alcohol, stimulants) Aggressive behavior Increased sexual drive http://www.motherearthnews.com/uploadedImages/articles/issues/2008-04-01/HyperKid.jpg

6. Famous People with BPD Writers: Edgar Allen Poe Mark Twain Virginia Woolf Charles Dickens Ralph Waldo Emerson F. Scott Fitzgerald Ernest Hemingway Kurt Vonnegut Emily Dickinson T.S. Eliot Hans Christian Anderson Victor Hugo Musicians: Beethoven Mozart DMX Jimi Hendrix Axl Rose Sting Brian Wilson Kurt Cobain Ozzy Ozbourne Hollywood: Britney Spears Jim Carey Robert Downey Jr. Linda Hamilton Vivien Leigh Ben Stiller Robin Williams Richard Dreyfuss Marilyn Monroe Tim Burton Francis Ford Coppola Politicians: Winston Churchill Theodore Roosevelt Abraham Lincoln Napoleon Bonaparte

7. Scientists: Sir Isaac Newton Florence Nightingale Sigmund Freud Plato Charles Darwin! http://www.csbsny.org/images/Charles_Darwin_1881.jpg

8. Genetic Cause of BPD? Many chromosomal regions and candidate genes appear to relate to the development of BPD Inconsistent results and scattered focus, results not replicated Epigenetics & environment? Heritability = 0.71 http://z.about.com/d/multiples/1/0/G/2/blgal176.jpg

9. Part 1Understand Gene & Protein

10. GRIK2 (humans) Localized on chromosome 6 Glutamate, Receptor, Ionotropic, Kainate 2 Glutamate ligand Excitatory and inhibitor neurotransmission GluR6 subunit mutation impairs binding site Arrows indicate gluR6 mutation sites Neurological Correlates: The Neuroscience of Dysfunctional Behavior. Image retrieved on February 3rd, 2009. http://neurologicalcorrelates.com/wordpress/

11. Isoforms 2nd variant: additional exon at the 3’ end Frameshift & early translation termination Shorter with distinct C-terminus GRIK2 gene: 678026 bp GRIK2 coding mRNA: 4550 bp

12. Gene function: Ontology GO Consortium Biological process Cellular component & molecular function Glutamate signaling pathway, kainate selective glutamate receptor activity Neuronal transmission events: synaptic transmission and plasticity Cell death & apoptosis http://www.nature.com/nrn/journal/v9/n6/images/nrn2379-f1.jpg

13. GRIK2 Homologs

14. GRIK2 homologues: Phylogeny Multiple alignment using Muscle & Tcoffee Phylogeny created using Phylogeny.fr

15. Protein Motifs Identical result for every species’ sequence query Highly conserved nature of putative functional domains PFAM/SMART

16. Localization in the Cell Based on what we know about receptor function, should be localized to the plasma membrane ESLpred: nucleus ??? TargetP: secretory pathway signal peptide (SP) LOCATE: secreted protein? & type I membrane protein & multipass membrane protein pTARGET: 100% confidence = plasma membrane http://maddgraphix.com/sci1-5l/plasma-Membrane.jpg

17. Protein Networks http://www.prestoncomhaltas.org.uk/assets/images/stick_person.png http://www.bradfitzpatrick.com/store/images/products/preview/a048-cartoon-mouse-clip-art.jpg

18. Key Protein Players Interacts at postsynaptic sites, form scaffold Glutamate Receptor Interacting Protein: localized scaffold, mediation of trafficking of binding partners Protein Interacting w/ Protein Kinase C: adaptor that organizes subcellular location of membrane proteins Scaffold Protein Periplasmic Binding Protein: binds the C-terminal domains of transmembrane proteins May play a role in neuronal function Kinesin Family Member: transports NMDA vesicles Glutamate Receptor, Ionotropic, Kainate 4: excitatory neurotransmitter at synapses in CNS Protein Kinase, AMP-activated, Alpha1 subunit: cellular energy sensor conserved in all eukaryotic cells Switch Regulatory Protein, associated with apoptotic cell death Sentrin/SUMO-specific protease: covalent modification of proteins by the small ubiquitin-like protein SUMO PSD95 GRIP1 PICK1 SDCBP KLHL17 KIF17 GRIK4 PRKAA1 FOS SENP1

19. Part 2Phenotypic Studies

20. Primary Literature Very few studies done on phenotype of GRIK2 mutant, other putative genes for BPD

21. Rationale Recent human genetic studies: GRIK2 as potential BPD susceptibility gene Genetic linkage of BPD to chromosome 6 Genome-wide significant linkage est. by meta-analysis Specific haplotype associated with BPD Post-mortem studies Expression of kainate receptors in areas for mood regulation http://www.hlhl.qc.ca/documents/images/Recherche/CESH/images/cerveau.jpg

22. Study Questions • Used GluR6 KO mice in behavioral tests to elucidate role of GRIK2 receptor in regards to phenotypic patterns of BPD • Determine potential specificity of this receptor (receptor control = GluR5) • Effects of lithium on GluR6 KO mice • Biochemical tests

23. Behavioral Tests Passive-avoidance test Open-field test Monitoring home cage activity Social interaction test Elevated plus-maze test Forced swim test Resident intruder test Same tests done with amphetamine & lithium http://www.c2i.ntu.edu.sg/AI+CI/Humor/AI_Jokes/img/GraduateSchoolTest.gif

24. Lithium Results Specific biochemical mechanism of action in mania unknown Reduced spontaneous locomotor activity Decreased aggressive behavior Decreased activity in anxiety-provoking regions Effect on elevated plus maze test Reduced immobility time in forced swim test http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=11125&loc=ec_rcshttp://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=401

25. Amphetamine Results GluR6 KO mice: exhibited more spontaneous activity more responsive to amphetamine more aggressive less anxious/more risk-taking behavior less immobility in forced swim test http://1.bp.blogspot.com/_Sa_HjZFUdJ0/RxksvRXcWsI/AAAAAAAAACM/QH55l7WHlPE/s320/Strong_Little_Mouse.jpg

26. Future Directions Mice mutant KO of other putative BPD genes RNAi difficult because of neuronal tissue TAP tags for protein complexes of GRIK2 More (repeated) genetic linkage and mapping studies of bipolar families Role of lithium MORE RESEARCH!