Cell Biochem Biophys (2011) 60:69–75
DOI 10.1007/s12013-011-9177-5

ORIGINAL PAPER

KF-1 Ubiquitin Ligase: Anxiety Suppressor Model
Tamotsu Hashimoto-Gotoh • Naoyuki Iwabe •Atsushi Tsujimura • Masanori Nakagawa •Yoshinori Marunaka

Published online: 1 April 2011
Ó Springer Science+Business Media, LLC 2011

Abstract Anxiety disorders are the most popular psychiatric disease in any human societies irrespective of nation,
culture, religion, economics or politics. Anxiety expression
mediated by the amygdala may be suppressed by signals
transmitted from the prefrontal cortex and hippocampus.
KF-1 is an endoplasmic reticulum (ER)-based E3-ubiquitin(Ub) ligase with a RING-H2 finger motif at the C-terminus.
The kf-1 gene expression is up-regulated in the frontal cortex
and hippocampus in rats after anti-depressant treatments.
The kf-1 null mice show no apparent abnormalities, but
exhibit selectively pronounced anxiety-like behaviors or
increased timidity-like responses. The kf-1 orthologous
genes had been generated after the Poriferan emergence, andare found widely in all animals except insects, arachnids andthreadworms such as Drosophila, Ixodes and Caenorhabditis, respectively. This suggests that the kf-1 gene may be
relevant to some biological functions characteristic to animals. Based on these observations, the Anxiety Suppressor
T. Hashimoto-Gotoh (&)  Y. Marunaka
Department of Molecular Cell Physiology,
Graduate School of Medical Science, Kyoto Prefectural
University of Medicine, 465 Kajii-cho, Kawaramachi-Hirokoji,
Kamigyo-ku, Kyoto 602-8566, Japane-mail: thg@koto.kpu-m.ac.jp
N. Iwabe
Department of Biophysics, Graduate School of Science,
Kyoto University, Kyoto, Japan
A. Tsujimura
Department of Biochemistry and Molecular Genetics,
Research Institute for Neurological Disease and Geriatrics,
Kyoto Prefectural University of Medicine, Kyoto, Japan
M. Nakagawa
Department of Neurology, Graduate School of Medical Science,
Kyoto Prefectural University of Medicine, Kyoto, Japan

Model has been proposed, which assumes that KF-1 Ubligase may suppress the amygdala-mediated anxiety bydegrading some anxiety promoting protein(s), such as aneurotransmitter receptor, through the ER-associated degradation pathway in the frontal cortex and hippocampus.
According to this model, the emotional sensitivity to environmental stresses may be regulated by the cellular protein
level of KF-1 relative to that of the putative anxiety promoter. The kf-1 null mice should be useful in elucidating themolecular mechanisms of the anxiety regulation and forscreening novel anxiolytic compounds, which may block theputative anxiety promoter.
Keywords Anxiety  Timidity  Emotional control 
Frontal cortex  Hippocampus  Amygdala

Introduction
Anxiety, or learned fear, may be an instinct acquired during
the animal evolution to promote adaptive survival byevading unnecessary danger. Anxiety disorders may beascribed to enhanced sensitivity against the environmental
stresses, which bring about heterogeneous phenotypes suchas obsessive–compulsive disorders, panic disorder, adaptive
disorder, post-traumatic stress disorder, social withdrawal(hikikomori) disorder, various phobias, and so on. Furthermore, anxiety can be a basic symptom of other psychiatric diseases, including depression and schizophrenia.
Patients with anxiety disorders interpret circumstantial
incidences such as episodes, comments, expressions, relations to others and social and physical positions in a negative way. Such interpretations may well lead individuals topronounced capture or delusions and cause emotional disruption. Under the evolutionary constraint, it is likely that

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complex regulation of emotional expression has developedin animals. This is most apparent in highly socialized
mammals like humans [1]. The amygdala may primarily be
responsible for the expression of anxiety or fear, and theprefrontal cortex and hippocampus may play an importantrole in fear extinction by suppressing the amygdala-mediated fear expression [2, 3]. Nevertheless, the molecularmechanisms involved in the regulation of anxiety expression are not clear and remain largely unknown. However, it
has been demonstrated, using genetic mouse models, thatthe serotonin receptor and transporter and Disc1 protein are
involved in the onset of depression and schizophrenia [4–6].
Although some genes have been reported to affect behavioral anxiety and despair [4, 7–14], anxiety- and despairlike behaviors are often confused or complicated and it may
not even be clear whether or not anxiety and depressive
disorders are distinguishable at the molecular levels in the
animal models. As far as the authors are aware, until
recently there were no reports of specific genes being
responsible for anxiety- or timidity-like behaviors, and not
being implicated in other abnormalities.

KF-1 Ubiquitin (Ub) Ligase
Ubiquitylation plays an essential role in regulating criticaleukaryotic cellular processes. Proteasomal degradation
through the endoplasmic reticulum-associated degradation(ERAD) pathway is no exception. These processes are
involved in a variety of human somatic diseases such as
cancer, viral infection, hypertension, diabetes, inflammation, muscle wastage, and neurodegenerative disorders
such as Alzheimer’s and Parkinson’s diseases [15, 16].
However, no ubiquitin ligases have been reported until
recently as being involved selectively in mental disorders
or emotional sensitivity to environmental stresses. KF-1
facilitates E2-dependent ubiquitylation and thus is anE3-ubiquitin Ub ligase [17]. KF-1 may be the first example
of such Ub ligases, which may be responsible for suppressing the anxiety response without affecting otherbehavioral features [18, 19]. KF-1 was originally identified
as a gene whose transcripts were found more frequently inthe frontal cortex of human Alzheimer’s disease (AD)patients compared to normal subjects [20]. The kf-1 gene islocated on the human chromosome 2p11.2, and expressedat the basal levels in many tissues but prominently in brain
tissue, particularly in the cerebellum and hippocampus[20]. Interestingly, the nucleotide sequence of kf-1 mRNA
is highly conserved between mouse and human not onlyin the coding region (94% homologous) but also in the
30 -untranslated region (91.3%), the latter of which may
form a stable twofold-sheet structure [20]. Consequently,
the mRNA half-life may be strictly controlled to stabilize

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Cell Biochem Biophys (2011) 60:69–75

kf-1 transcripts for the steady synthesis of KF-1 protein,suggesting that the basal cellular concentration of KF-1
protein may be important. The human KF-1 protein consists of 685 amino acid (aa) residues and contains a possible leader sequence and a RING-H2 finger motif at theN- and C-termini, respectively, with two closely locatedmembrane-spanning domains in the middle of the moleculewith 3 aa residues apart from each other (Fig. 1). kf-1 gene
expression is up-regulated in the frontal cortex and hippocampus of rats after anti-depressant treatments such as
chronic administration of serotonin selective re-uptake
inhibitor (SSRI) [21], electroconvulsive therapy [22], andrepetitive transcranial magnetic stimulation [23]. Theseobservations suggest that the elevated kf-1 transcription isassociated with some physiological responses to the antidepressant pathway but not merely with chemical reactions
to SSRIs. However, it is not clear which anti-depressantpathways this up-regulation is associated with, anxiolytic
or anti-despair pathway, or both. In co-transfected cells,
KF-1 molecules are co-localized with Presenilins, responsible for familial AD, located on the endoplasmic reticulum[19]. Therefore, KF-1 Ub ligase may be involved in ERAD
pathway for degrading some membrane proteins such as
Presenilins, neurotransmitter receptors, and so on.

Phylogenetic Studies on KF-1
The kf-1 orthologous genes have been found in many animals, but not in any species of other eukaryotes such as plants
and fungi, and prokaryotes (Fig. 2). Tablet animals such as
Trichoplax adhaerens [24] possess the kf-1 gene, but sponges
such as Amphimedon queenslandica [25] and choanoflagellates such as Monosiga brevicollis do not [26], the latter ofwhich belong to Protista and are believed to be unicellularorigins of the Animalia (Fig. 2). This implies that the kf-1
gene may have been generated between the poriferan andplacozoan emergences (Fig. 2). Interestingly, the kf-1 genes
are found in blood flukes (Schistosoma mansoni), but not
Insecta (Drosophila melanogaster), Arachnida (Ixodes
scapularis) or Nematoda (Caenorhabditis elegans). Nevertheless, it is likely that waterfleas (Daphnia pulex) may
possess a KF-1 protein, although its deduced structure
corresponds to only a half of the protein proximal to the
C-terminus probably due to the incomplete determination of
genome sequences. Therefore, it can be concluded, if thepresent phylotaxonomy is correct as in Fig. 2, that the kf-1
gene was lost independently three times in the lineages
leading up to D. melanogaster, I. scapularis, and C. elegans,respectively (Fig. 2). In any case, it is clear that Drosophila
cannot be an animal model for human diseases due to KF-1
deficiency, if any, unlike Parkinson’s disease model in
D. melanogaster lacking the gene for Parkin Ub ligase.

Cell Biochem Biophys (2011) 60:69–75

Fig. 1 Critical domains and SNP positions in human KF-1 Ub ligase.
Solid, dashed, and double underlines indicate a possible leader
sequences, membrane-spanning regions and RING-H2 finger motif
domain, respectively. Bold letters indicated consensus amino acidresidues conserved in animals. Note that kf-1 genes are not found in71

D. melanogaster, I. scapularis and C. elegans. Four boxed letters
indicate amino acid residues, in which critical SNPs are found in theircodons according to the NIH databases, at T180 (frame shift), S251 (S to
P substitution), P502 (P to H substitution), and E626 (termination) as
rs35921467, rs17857046, rs17853383, and rs11695337, respectively

Fig. 2 Presence, absence,
generation, and transmission of
kf-1 gene on the evolutionary
tree. The tree is as presented
previously with modifications
and corrections [19, 29]. An
open star, open arrows, andthree open crosses in the tree
branches indicate thegeneration, transmission, andtermination of the kf-1 gene,
respectively. The genomic
information of waterflea(Daphnia pulex) was obtained at\http://genome.jgi-psf.org/
Dappu1/Dappu1.home.html[.
Circles, two triangles or crosses
in front of the names fororganisms indicate the presence,probable presence or absence,
respectively, of kf-1 as confirmed in the GenBank databaseon 24 September 2010 andSUPERFAMILY databaserelease 1.73 \http://supfam.
cs.bris.ac.uk/
SUPERFAMILY_1.73/
index.html[ [30, 31] ‘etc’ for‘Insecta’, ‘Nematoda’, ‘Domain
Archaebacteria’, and ‘Domain
Eubacteria’ means that theabsence of the kf-1 gene wasconfirmed in more than 11, 6,
11, and 50 species, respectively

kf-1 Null MiceTo elucidate the biological functions of KF-1, the kf-1 nullmice should be a useful tool for future studies. In fact, kf-1

knockout mice have been generated by the gene-targeting
procedure using Cre–loxP recombination system [18]. The
resulting kf-1 null mice showed no apparent abnormalities
in anatomy, pathology, physiology, neuroethology or in

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Table 1 Behavioral test battery
conducted between kf-1-/- andkf-1?/? littermate mice

The details of these experiments
have been described in
Tsujimura et al. [18], and partly
in the section, kf-1 null mice.
Arrows, ‘:’ and ‘;’, indicate
significant increase anddecrease, respectively, in kf1-/- mice compared to kf-1?/?
littermate mice. ‘=’ indicates nosignificant differences between
kf-1-/- and kf-1?/? mice

Cell Biochem Biophys (2011) 60:69–75

Tests

Measurements

Phenotypes

General health examination

Whisker, coat, reflexes=

Physical test

Body weight=

Body temperature=

Wire hanging time:

Grip strength=

Auditory capability=

Light/dark transition test

Anxiety-like behaviors:

Open field test

Exploratory locomotion=

Elevated plus maze test

Anxiety-like behaviors:

Hot plate test

Pain sensitivity=

Social interaction test

Social interaction=

Rotarod test

Motor coordination=

Prepulse inhibition (PPI) test

Startle amplitude in startle-stimulus-only trials;

Prepulse inhibition:

Porsol forced swim test
T-maze test

Behavioral despair (immobility time)
Spatial working memory==

Fear conditioning test

Immediate freezing during conditioning phasewith aversive footshock:

Contextual testing conducted after conditioning=

Cued test with altered context=

Behavioral despair (immobility time)=

Tail suspension test

reproductive capability, and were then used for a behavioral test battery. The detailed procedures and apparatuses
used have been described [18]. As summarized in Table 1,
kf-1 null mice exhibit selectively enhanced anxiety-likebehaviors or increased timidity-like responses. The mouseanxiety-like behaviors are determined on the bases of theirnocturnal and geotaxis natures by using the light/darktransition and elevated plus maze tests. In the light/darktransition test, the apparatus is used, which consists of acage (21 9 42 9 25 cm3) divided into two chambers,
namely light and dark boxes. Mice are individually placedin the dark box at the beginning, and allowed to movefreely between the two boxes with door open. In the elevated plus maze test, plus-shaped four arms of the same
size (25 9 5 cm2) are placed at a height of 55 cm above
the floor. The arms and central square (5 9 5 cm2) aremade of opaque and white plastic plates, and two of thefour arms at opposite sides are enclosed with 15 cm hightransparent walls (closed arms). Mice are placed individually in the crossing center to face one of the closed arms.
In both the experiments, mouse movements are automatically traced and recorded. Compared to the kf-1?/? littermates, the distance travelled and stay time in the light box
are significantly reduced in the light/dark transition test
(Fig. 3a, b), and similarly in the elevated plus maze test
(Fig. 3c, d), significantly the total distance travelled andthe number of entries into the crossing center is significantly reduced. The reduced distance travelled in these123

tests should not be ascribed to physical alteration in locomotive activities of mice, but rather to mental or emotional
alterations in the mice, because no significant differences inlocomotive activity are observed in the open field test
between kf-1-/- and kf-1?/? littermate mice (P = 0.2879,
F1,38 = 1.162) [18]. One of the striking features inthese results is that the P values are strikingly small(P = 0.0004–0.0005) compared to those usually obtained insuch tests, implying that these results must be reproducible.
Consistently, the kf-1 null mice exhibit significantly
increased timidity-like responses as observed in prolonged
wire hanging time and enhanced immediate freezing toaversive foot shock compared to kf-1?/? littermates(Table 1). These observations should also reflect mental but
not physical alterations in kf-1-/- mice, since no significant
differences existed in grip strength and body weight between
kf-1-/- and kf-1?/? mice (P = 0.4060, F1,38 = 0.706 and
P = 0.6254, F1,38 = 0.242, respectively).
Another example of timidity-like responses is observedin the startle-stimulus-only trials of the startle response/
prepulse inhibition (PPI) test, in which kf-1-/- mice show
significantly lower startle amplitudes than the kf-1?/? littermates do (Fig. 3e). This reduced startle amplitude may
be interpreted similarly to the enhanced freezing as
observed after aversive foot shock. The PPI test is usedwidely to measure deficits in information-processing abilities in schizophrenic patients [27], and can be employed inboth human and animal experiments [28]. PPI of the startle

Cell Biochem Biophys (2011) 60:69–75

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Fig. 3 Increased anxiety-like behaviors or timidity-like responses in
kf-1-/- mice in comparison to their kf-1?/? littermates. Significantly
reduced locomotive activities in the light but not dark (a) anddecreased stay time in the light (b) in the light/dark transition test.
Significantly reduced total distance travelled (c) and decreased

number of entries into the crossing center (d) on heights in theelevated plus maze test. Significantly reduced startle amplitude instartle-stimulus-only trials (e) and increased PPI values (f) in thestartle response/prepulse inhibition test. These data are taken fromTsujimura et al. [18]response is defined as the degree (%) to which the startle
response to a sudden noise (110 and 120 dB) is reduced
when the noise is preceded shortly by a mild and lowintensity sound (74 and 78 dB). The PPI values were significantly greater in kf-1-/- than in kf-1?/? (Fig. 3f; overall
ANOVA including all four combinations, P = 0.0023,
F1,38 = 10.676). This could be due to the reduced baseline
startle amplitudes in the kf-1-/- mice (Fig. 3e, suggestingthat reduced startle amplitudes may be similar to the
reduced immediate freezing responses in the aversive footshock. Nevertheless, if PPI is independent of the baseline
startle, one cannot rule out the possibility that increased
KF-1 activity may reduce PPI and thus could be a risk
factor of schizophrenia.
No other significantly altered behaviors have been
observed in the kf-1-/- mice compared to kf-1?/? mice,
namely exploratory locomotion, pain sensitivity, social

interaction, motor coordination, despair-like behaviors,
spatial working memory, cognitive functions. In conclusion, the KF-1 Ub ligase may function specifically as ananxiety suppressor by degrading, through the ERAD
pathway, its substrate protein(s) responsible for promoting
emotional sensitivity to environmental stresses. The putative anxiety promoter could be a neurotransmitter-related
protein, but is unlikely to be a serotonin receptor ortransporter because a lack of either protein increases
anxiety-like behaviors [4, 10, 19].

Anxiety Suppressor Model
The observations as described in the preceding section
suggest that the reduction of KF-1 activity could be a risk
factor selective to anxiety disorder, but may not be relevant

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Fig. 4 A circuitry presentation of the anxiety suppressor model by
the up-regulation of kf-1 expression. The model has been proposed
previously [19]. The anxiolytic pathway after kf-1 up-regulation isincorporated into the modelto other mental disorders such as despair and cognitive
deficit. In this context, it may be worth noting that somecritical SNPs are found in the human kf-1 coding region
according to the NCBI database. These include a frame
shift, two aa substitutions and a termination codon (Fig. 1).
On the basis of these observations, the Anxiety Suppressor
Model has been proposed, assuming that KF-1 Ub ligase
may suppress amygdala-mediated anxiety when overproduced in the frontal cortex and hippocampus by transmitting some signals to the amygdala (Fig. 4).
The kf-1 null mice may be a useful tool to study themolecular mechanisms controlling the emotional sensitivity to environmental stresses. Moreover, these mice may
also be used to identify putative anxiety promoters and forscreening novel anxiolytic compounds against them.
Acknowledgments We thank all the collaborators and colleagues
for their valuable contributions and stimulus discussions during thiswork, in particular Drs. Koji Yasojima and Toshiki Mizuno for humanbrain analysis and cloning of human and mouse kf-1 cDNAs, Drs.
Masato Matsuki and Kiyofumi Yamanishi for construction of kf-1 KO
mice, and Drs. Keizo Takao and Tsuyoshi Miyakawa for behavioral studies on kf-1 KO mice. THG thanks Callum Mitchell and
A. Hashimoto-Gotoh for their critical reading and comments on thismanuscript. The kf-1-/- mouse, named the Hicky mouse, may beobtained from Riken BioResources Center (No. 01916), Japan or from
Mutant Mouse Regional Resource Center (No. 032048-JAX), USA,for academic research purposes.

References
1. Darwin, C. (1872). The expression of the emotions in man andanimals. Chicago: University of Chicago Press. [reprinted in1965].

123

Cell Biochem Biophys (2011) 60:69–75
2. Sotres-Bayon, F., Cain, C. K., & LeDoux, J. E. (2006). Brainmechanisms of fear extinction: Historical perspectives on thecontribution of prefrontal cortex. Biological Psychiatry, 60,
329–336.
3. Bishop, S. J. (2007). Neurocognitive mechanisms of anxiety: An
integrative account. Trends in Cognitive Sciences, 11, 307–316.
4. Heisler, L. K., Chu, H.-M., Brennan, T. J., Danao, J. A., Bajwa,
P., Parsons, L. H., et al. (1998). Elevated anxiety and antidepressant-like responses in serotonin 5-HT1A receptor mutant
mice. Proceedings of the National Academy of Sciences of theUnited States of America, 95, 15049–15054.
5. Holmes, A., Yang, R. J., Murphy, D. L., & Crawley, J. N. (2003).
Evaluation of antidepressant-related behavioral responses in micelacking the serotonin transporter. Neuropsychopharmacology, 27,
914–923.
6. Clapcote, J. S., Lipina, V. T., Millar, J. K., Mackie, S., Christie,S., Ogawa, et al. (2007). Behavioral phenotypes of Disc1 missense mutations in mice. Neuron, 54, 387–402.
7. Chen, Y. J., Johnson, M. A., Lieberman, M. D., Goodchild, R. E.,
Schobel, S., Lewandowski, N., et al. (2008). Type III neuregulin1 is required for normal sensorimotor gating, memory-related
behaviors, and corticostriatal circuit components. Journal of
Neuroscience, 28, 6872–6883.
8. Gogos, J. A., Morgan, M., Luine, V., Santha, M., Ogawa, S.,
Pfaff, D., et al. (1998). Catechol-O-methyltransferase-deficient
mice exhibit sexually dimorphic changes in catecholamine levels
and behavior. Proceedings of the National Academy of Sciencesof the United States of America, 95, 9991–9996.
9. Holmes, A., Kinney, J. W., Wrenn, C. C., Li, Q., Yang, R. J., Ma,
L., et al. (2003). Galanin GAL-R1 receptor null mutant micedisplay increased anxiety-like behavior specific to the elevatedplus-maze. Neuropsychopharmacology, 28, 1031–1044.
10. Holmes, A., Yang, R. J., Lesch, K.-P., Crawley, J. N., & Murphy,
D. L. (2003). Mice lacking the serotonin transporter exhibit
5-HT1A receptor-mediated abnormalities in tests for anxiety-likebehavior. Neuropsychopharmacology, 28, 2077–2088.
11. Miyakawa, T., Yagi, T., Watanabe, S., & Niki, H. (1994).
Increased fearfulness of Fyn tyrosine kinase deficient mice. Brain
Research. Molecular Brain Research, 27, 179–182.
12. Miyakawa, T., Leiter, L. M., Gerber, D. J., Gainetdinov, R. R.,
Sotnikova, T. D., Zeng, H., et al. (2003). Conditional calcineurinknockout mice exhibit multiple abnormal behaviors related toschizophrenia. Proceedings of the National Academy of Sciencesof the United States of America, 100, 8987–8992.
13. Nakajima, R., Takao, K., Huang, S. M., Takano, J., Iwata, N.,
Miyakawa, T., et al. (2008). Comprehensive behavioral phenotyping of calpastatin-knockout mice. Molecular Brain, 1, 7.
14. Yamasaki, N., Maekawa, M., Kobayashi, K., Kajii, Y., Maeda, J.,
Soma, M., et al. (2008). a-CaMKII deficiency causes immaturedentate gyrus, a novel candidate endophenotype of psychiatricdisorders. Molecular Brain, 1, 6.
15. Kostova, Z., Tsai, Y. C., & Weissman, A. M. (2007). Ubiquitin
ligases, critical mediators of endoplasmic reticulumassociateddegradation. Seminars in cell and developmental biology, 18,
770–779.
16. Petroski, M. D. (2008). The ubiquitin system, disease, and drug
discovery. BMC Biochemistry, 9, S7. Available at http://www.
pubmedcentral.nih.gov/picrender.fcgi?artid=2582801&blobtype=pdf.
17. Lorick, K. L., Jensen, J. P., Fang, S., Ong, A. M., Hatakeyama, S.,& Weissman, A. M. (1999). RING fingers mediate ubiquitinconjugating enzyme (E2)-dependent ubiquitination. Proceedingsof the National Academy of Sciences of the United States ofAmerica, 96, 11364–11369.
18. Tsujimura, A., Matsuki, M., Takao, K., Yamanishi, K., Miyakawa, T., & Hashimoto-Gotoh, T. (2008). Mice lacking the kf-1

Cell Biochem Biophys (2011) 60:69–75
gene exhibit increased anxiety- but not despair-like behavior.
Frontiers in Behavioral Neuroscience, 2, 4. doi:10.3389/neuro.
08.004.2008.
19. Hashimoto-Gotoh, T., Iwabe, N., Tsujimura, A., Takao, K., &Miyakawa, T. (2009). KF-1 ubiquitin ligase: An anxiety suppressor. Frontiers in Neuroscience, 3, 15–24. doi:10.3389/neuro.
01.004.2009.
20. Yasojima, K., Tsujimura, A., Mizuno, T., Shigeyoshi, Y., Inazawa, J., Kikuno, R., et al. (1997). Cloning of human and mouse
cDNAs encoding novel zinc finger proteins expressed in cerebellum and hippocampus. Biochemical and Biophysical ResearchCommunications, 231, 481–487.
21. Yamada, M., Yamada, M., Yamazaki, S., Takahashi, K.,
Nishioka, G., Kudo, K., et al. (2000). Identification of a novel
gene with RING-H2 finger motif induced after chronic antidepressant treatment in rat brain. Biochemical and BiophysicalResearch Communications, 278, 150–157.
22. Nishioka, G., Yamada, M., Kudo, K., Takahashi, K., Kiuchi, Y.,
Higuchi, T., et al. (2003). Induction of kf-1 after repeated electroconvulsive treatment and chronic antidepressant treatment in
rat frontal cortex and hippocampus. Journal of Neural Transmission, 110, 277–285.
23. Kudo, K., Yamada, M., Takahashi, K., Nishioka, G., Tanaka, S.,
Hashiguchi, T., et al. (2005). Repetitive transcranial magnetic
stimulation induces kf-1 expression in the rat brain. Life Sciences,76, 2421–2429.
24. Srivastava, M., Begovic, E., Chapman, J., Putnam, N. H.,
Hellsten, U., Kawashima, T., et al. (2008). The Trichoplax genome and the nature of placozoans. Nature, 454, 955–960.

75
25. Srivastava, M., Simakov, O., Chapman, J., Fahey, B., Gauthier,M. E., Mitros, T., et al. (2010). The Amphimedon queenslandica
genome and the evolution of animal complexity. Nature, 466,
720–727.
26. King, N., Westbrook, M. J., Young, S. L., Kuo, A., Abedin, M.,
Chapman, J., et al. (2008). The genome of the choanoflagellate
Monosiga brevicollis and the origin of metazoans. Nature, 451,
783–788.
27. Geyer, M. A., & Ellenbroek, B. (2003). Animal behavior modelsof the mechanisms underlying antipsychotic atypicality. Progress
in Neuro-Psychopharmacology and Biological Psychiatry, 27,
1071–1079.
28. Arguello, P. A., & Gogos, J. A. (2006). Modeling madness in
mice: One piece at a time. Neuron, 52, 179–196.
29. Hashimoto-Gotoh, T., Tsujimura, A., Watanabe, Y., Iwabe, N.,
Miyata, T., & Tabira, T. (2003). A unifying model for functional
difference and redundancy of presenilin-1 and -2 in cell apoptosis
and differentiation. Gene, 323, 115–123.
30. Gough, J., Karplus, K., Hughey, R., & Chothia, C. (2001).
Assignment of homology to genome sequences using a library of
hidden Markov models that represent all proteins of known
structure. Journal of Molecular Biology, 313, 903–919.
31. Wilson, D., Pethica, R., Zhou, Y., Talbot, C., Vogel, C., Madera,M., et al. (2009). SUPERFAMILY—comparative genomics, data
mining and sophisticated visualization. Nucleic Acids Research,
37, D380–D386.

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