Temporal difference in frequency of the ON, OFF, and ON/OFF fibers of wild-type and <i>mCry1^−/−mCry2^−/−</i> mice.

<p>The actual number and proportion (%) of types of the optic fiber during daytime and nighttime are shown. The mean firing rates of each responding cell are exhibited in the bottom of each column described as before/during/after light stimulation. n.d.; not determined.</p

Temporal difference in frequency of the response types in the SCN of wild-type and <i>mCry1^−/−mCry2^−/−</i> mice.

<p>The actual number and proportion (%) of responding cells in mouse SCN during daytime and nighttime are shown. The mean firing rates of each responding cell are exhibited in the bottom of each column described as before/during/after light stimulation.</p><p>*<i>P<0.001</i>, when compared with daytime group of wild-type mice and <i>mCry1^−/−mCry2^−/−</i> mice (Dunn's test). n.d.; not determined.</p

Reduced light response of neuronal firing activity in the optic nerve fibers of <i>mCry1^−/− mCry2^−/−</i> mice.

<p><b>A</b>, <b>B</b>, and <b>C</b>, Peristimulus time histograms of three distinct response patterns were recorded: ON fibers, which respond to light onset (A), OFF fibers, which respond to light offset (B), and ON/OFF fibers, which respond to both light onset and offset (C). The mean firing rate per second (Hz) is plotted every 5 min in the histogram. Light intensity was 1.0×10¹⁵ photons·cm⁻²·s⁻¹ for 60 sec. The timing of the light pulse is indicated in the step diagram above the records. <b>D</b>, The magnitude of change in the discharge rate for retinal illumination recorded in the ON fiber. Histograms depict data as mean ± SEM; the number of animals is shown in parentheses. **<i>P</i><0.01 vs. others, Tukey's test.</p

Behavioral Characteristics of Ubiquitin-Specific Peptidase 46-Deficient Mice

<div><p>We have previously identified <i>Usp46,</i> which encodes for ubiquitin-specific peptidase 46, as a quantitative trait gene affecting the immobility time of mice in the tail suspension test (TST) and forced swimming test. The mutation that we identified was a 3-bp deletion coding for lysine (Lys 92), and mice with this mutation (MT mice), as well as <i>Usp46</i> KO mice exhibited shorter TST immobility times. Behavioral pharmacology suggests that the gamma aminobutyric acid A (GABA_A) receptor is involved in regulating TST immobility time. In order to understand how far <i>Usp46</i> controls behavioral phenotypes, which could be related to mental disorders in humans, we subjected <i>Usp46</i> MT and KO mice to multiple behavioral tests, including the open field test, ethanol preference test, ethanol-induced loss of righting reflex test, sucrose preference test, novelty-suppressed feeding test, marble burying test, and novel object recognition test. Although behavioral phenotypes of the <i>Usp46</i> MT and KO mice were not always identical, deficiency of <i>Usp46</i> significantly affected performance in all these tests. In the open field test, activity levels were lower in <i>Usp46</i> KO mice than wild type (WT) or MT mice. Both MT and KO mice showed lower ethanol preference and shorter recovery times after ethanol administration. Compared to WT mice, <i>Usp46</i> MT and KO mice exhibited decreased sucrose preference, took longer latency periods to bite pellets, and buried more marbles in the sucrose preference test, novelty-suppressed feeding test, and marble burying test, respectively. In the novel object recognition test, neither MT nor KO mice showed an increase in exploration of a new object 24 hours after training. These findings indicate that <i>Usp46</i> regulates a wide range of behavioral phenotypes that might be related to human mental disorders and provides insight into the function of USP46 deubiquitinating enzyme in the neural system.</p> </div

Open field test.

<p>Total distance of movement (A), number of climbing and rearing events (B), time spent in the outer zone (C), and resting time in the outer zone (D) of an open field for 5 min. <i>Usp46</i> KO mice showed significantly lower values than WT and MT mice for the total distance of movement and the number of climbing and rearing events. Nonmoving time in the outer zone was significantly higher for KO mice. The number of mice used is shown within parentheses. One-way ANOVA with Fisher's PLSD test; *<i>P</i><0.05, **<i>P</i><0.01.</p

Novel object recognition test.

<p>(A) Number of explorations of the 2 objects on the training day. Compared to WT mice, <i>Usp46</i> KO mice showed significantly lower numbers of explorations for each object. The number of explorations for object B made by KO mice was also significantly lower than that by MT mice. (B) A familiar object was substituted by a novel object at 24 hours after the training. The number of explorations for the novel object was significantly increased for the WT mice, but not for <i>Usp46</i> MT and KO mice. (C) Total number of explorations for the objects on the training day and 24 hours after the training. The number of explorations made by KO mice was significantly lower than those by WT or MT mice. The number of mice used is shown within parentheses. One-way ANOVA with Fisher's PLSD test; *<i>P</i><0.05, **<i>P</i><0.01. Student's <i>t</i> test; ^#<i>P</i><0.05.</p

Novelty-suppressed feeding test.

<p>(A) <i>Usp46</i> MT and KO mice showed an increased latency time to bite pellets in a test box. (B) Feeding time in the test box for 10 min. KO mice exhibited significantly lower feeding times. (C) Feeding time in the home cage for 5 min. The KO mice showed significantly longer feeding times. (D) Total food consumption (in the test box for 10 min, and the home cage for 5 min) was not significantly different between the MT, KO, and WT mice. The number of mice used is shown within parentheses. One-way ANOVA with Fisher's PLSD test; *<i>P</i><0.05, **<i>P</i><0.01.</p

Maternal behaviors post parturition.

<p>Maternal behaviors (arched-back nursing, nursing in prone position and licking/grooming) were observed for 3 days following parturition. The ratio of occurrence of these behaviors is shown as the percent of total observation time. The number of mice used is shown within parentheses. *<i>p</i> < 0.05, Mann-Whitney U test.</p

Outline of fostering experiments. B6-CO: B6 mice fostered by their biological mother.

<p>B6-IF: B6 mice fostered by a different B6 mother. B6-CF: B6 mice fostered by an MT mother. MT-CO: MT mice fostered by their biological mother. MT-IF: MT mice fostered by a different MT mother. MT-CF: MT mice fostered by a B6 mother. Offspring were tested at 8–12 weeks of age.</p

Fostering effects on maternal behavior in MT mice.

<p>MT-CF showed significant improvements in time spent nursing, rearing and latency to retrieve 1^st pup. The number of mice used is shown within parentheses. *<i>p</i> < 0.05, one-way ANOVA with Tukey’s <i>post hoc</i> test.</p