Aberrant Cerebellar Development in Mice Lacking Dual Oxidase Maturation Factors

Background: Thyroid hormone (TH) plays a key role in the developing brain, including the cerebellum. TH deficiency induces organizational changes of the cerebellum, causing cerebellar ataxia. However, the mechanisms causing these abnormalities are poorly understood. Various animal models have been used to study the mechanism. Lacking dual oxidase (DUOX) and its maturation factor (DUOXA) are major inducers of congenital hypothyroidism. Thus, this study examined the organizational changes of the cerebellum using knockout mice of the Duoxa gene (Duoxa?/?). Methods: The morphological, behavioral, and electrophysiological changes were analyzed in wild type (Wt) and Duoxa-deficient (Duoxa?/?) mice from postnatal day (P) 10 to P30. To detect the changes in the expression levels of presynaptic proteins, Western blot analysis was performed. Results: The proliferation and migration of granule cells was delayed after P15 in Duoxa?/? mice. However, these changes disappeared by P25. Although the cerebellar structure of Duoxa?/? mice was not significantly different from that of Wt mice at P25, motor coordination was impaired. It was also found that the amplitude of paired-pulse facilitation at parallel fiber?Purkinje cell synapses decreased in Duoxa?/? mice, particularly at P15. There were no differences between expression levels of presynaptic proteins regulating neurotransmitter release at P25. Conclusions: These results indicate that the anatomical catch-up growth of the cerebellum did not normalize its function because of the disturbance of neuronal circuits by the combined effect of hypothyroidism and functional disruption of the DUOX/DUOXA complex.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140263/1/thy.2015.0034.pd

image_1_In Utero and Postnatal Propylthiouracil-Induced Mild Hypothyroidism Impairs Maternal Behavior in Mice.EPS

<p>Thyroid hormones (THs) play crucial roles in general and brain development. Even if the hypothyroidism is mild, it may alter brain function, resulting in irreversible behavioral alterations. Although various behavioral analyses have been conducted, the effects of propylthiouracil (PTU) treatment during in utero and postnatal periods on maternal behavior have not yet been studied. The present study examined in mice whether THs insufficiency during development induce behavioral changes. Pregnant C57BL/6j mice were divided into three groups, and each group was administered different dosages of PTU (0, 5, or 50 ppm) in drinking water during in utero and postnatal periods (from gestational day 14 to postnatal day 21). First, locomotor activity and cognitive function were assessed in the offspring at 10 weeks. Next, female offspring were mated with normal mice and they and their offspring were used to assess several aspects of maternal behavior (identifying first pup, returning all pups to nest, time spent nursing, and licking pups). As expected, locomotor and cognitive functions in these mice were disrupted in a PTU dose-dependent manner. On postpartum day 2, dams who had been exposed 50 ppm PTU during in utero and postnatal periods displayed a significantly longer time identifying the first pup and returning all three pups back to the nest, less time nursing, and decreased licking behavior. The decrease in maternal behavior was significantly correlated with a decrease in cognition. These results indicate that insufficiency of THs during in utero and postnatal periods impairs maternal behavior, which may be partly induced by impaired cognitive function.</p

In Utero and Postnatal Propylthiouracil-Induced Mild Hypothyroidism Impairs Maternal Behavior in Mice

Thyroid hormones (THs) play crucial roles in general and brain development. Even if the hypothyroidism is mild, it may alter brain function, resulting in irreversible behavioral alterations. Although various behavioral analyses have been conducted, the effects of propylthiouracil (PTU) treatment during in utero and postnatal periods on maternal behavior have not yet been studied. The present study examined in mice whether THs insufficiency during development induce behavioral changes. Pregnant C57BL/6j mice were divided into three groups, and each group was administered different dosages of PTU (0, 5, or 50 ppm) in drinking water during in utero and postnatal periods (from gestational day 14 to postnatal day 21). First, locomotor activity and cognitive function were assessed in the offspring at 10 weeks. Next, female offspring were mated with normal mice and they and their offspring were used to assess several aspects of maternal behavior (identifying first pup, returning all pups to nest, time spent nursing, and licking pups). As expected, locomotor and cognitive functions in these mice were disrupted in a PTU dose-dependent manner. On postpartum day 2, dams who had been exposed 50 ppm PTU during in utero and postnatal periods displayed a significantly longer time identifying the first pup and returning all three pups back to the nest, less time nursing, and decreased licking behavior. The decrease in maternal behavior was significantly correlated with a decrease in cognition. These results indicate that insufficiency of THs during in utero and postnatal periods impairs maternal behavior, which may be partly induced by impaired cognitive function

Executive Function Deficits and Social-Behavioral Abnormality in Mice Exposed to a Low Dose of Dioxin <em>In Utero</em> and via Lactation

<div><p>An increasing prevalence of mental health problems has been partly ascribed to abnormal brain development that is induced upon exposure to environmental chemicals. However, it has been extremely difficult to detect and assess such causality particularly at low exposure levels. To address this question, we here investigated higher brain function in mice exposed to dioxin <em>in utero</em> and via lactation by using our recently developed automated behavioral flexibility test and immunohistochemistry of neuronal activation markers Arc, at the 14 brain areas. Pregnant C57BL/6 mice were given orally a low dose of 2,3,7,8-tetrachlorodibenzo-<em>p</em>-dioxin (TCDD) at a dose of either 0, 0.6 or 3.0 µg/kg on gestation day 12.5. When the pups reached adulthood, they were group-housed in IntelliCage to assess their behavior. As a result, the offspring born to dams exposed to 0.6 µg TCDD/kg were shown to have behavioral inflexibility, compulsive repetitive behavior, and dramatically lowered competitive dominance. In these mice, immunohistochemistry of Arc exhibited the signs of hypoactivation of the medial prefrontal cortex (mPFC) and hyperactivation of the amygdala. Intriguingly, mice exposed to 3.0 µg/kg were hardly affected in both the behavioral and neuronal activation indices, indicating that the robust, non-monotonic dose-response relationship. In conclusion, this study showed for the first time that perinatal exposure to a low dose of TCDD in mice develops executive function deficits and social behavioral abnormality accompanied with the signs of imbalanced mPFC-amygdala activation.</p> </div

Low competitive dominance in the low TCDD dose (TC-0.6) group.

<p>(A, B, C) Time-course of visit frequency in the first session of the day (21:50–22:40). The gray-colored period indicates the first five minutes (22:00–22:05) of the task. Vertical dotted lines indicate a peak in the group-averaged number of visits. (A, B, C) Time-course of visit frequency at the beginning of the session (21:50–22:40). Colored lines indicate the averaged visit frequency across all the sessions of each mouse, and the black thick lines indicate the average of each group: (A) Control, (B) TC-0.6, and (C) TC-3.0. (D) Visit frequency in the first five minutes throughout the sessions for each group (mean ± S.E.M., n = 8/group). (E, F) Average number of visits and duration of licking per session are shown as indices of daily water consumption. Error bars indicate ± S.E.M., n = 8/group. (G) A diagram of the competition task, in which the Control and TC-0.6 groups of mice (littermates of the mice used in the behavioral flexibility task) were subjected to the same water deprivation schedule as in the behavioral flexibility task. From days 1 to 4, all of the mice (a total of 14 mice, comprised of the Control and TC-0.6 groups) were housed in the same IntelliCage apparatus (a highly competitive condition). From days 5 to 8, each group of mice was housed separately in two different IntelliCage apparatuses (a less competitive condition). From days 9 to 12, all the mice were again housed in the same IntelliCage apparatus (a highly competitive condition). (H) Visit frequency in the first five minutes in the competition task. * and † indicate a significant difference from the Control group in the identical time period and from the TC-0.6 group on days 5 to 8, respectively. Error bars indicate ± S.E.M., n = 7/group.</p

Impaired behavioral flexibility in TCDD-exposed mice (inter-session analysis).

<p>(A) Overview of IntelliCage apparatus. (B) Group composition of mice housed and tested in each IntelliCage apparatus. (C) Behavioral sequencing task. Mice were allowed to obtain water reward for 4 seconds when they visited an “active” rewarded corner (blue circle). The location of the active rewarded corner was alternately switched between the two diagonally positioned corners each time the mouse received a reward. Thus, the mice had to acquire the behavioral sequence of alternating between the two rewarded corners to continuously obtain rewards. A visit to the never-rewarded corners (gray circles with a diagonal line) was counted as a discrimination error. (D) Serial reversal task. For each mouse, the assigned spatial patterns of the rewarded corners (seq. 1 or seq. 2) were reversed 11 times every 7 or 4 sessions. (E) Time-line of the experiment for each day. (F, G) Learning performance on the behavioral flexibility test. For the purpose of readability, data from the TC-0.6 and TC-3.0 groups of mice were separately plotted in F and G, respectively, whereas the data from the Control group are shown in F and G. Discrimination error rates (the number of discrimination errors in the first 100 corner visits in the session) are indicated as the means ± S.E.M. (n = 8/group). For each session, the individual mouse's discrimination error rate was transformed into a z-score calculated among all the mice. The bars in the insets in F and G indicate the averaged z-scores for each group in the first sessions of all the Revs (early stage of reversal learning) and in the second to fourth sessions of all Revs (late stage of reversal learning). * indicates a significant difference from the Control group (<i>P</i><0.05, ANOVA followed by Tukey's post hoc test).</p

Impaired behavioral flexibility in TCDD-exposed mice (intra-session analysis).

<p>(A) The curves of cumulative error visit (mean ± S.E.M., n = 8/group) in the first sessions of Rev. 1, 2, and 11 (Rev.1-1, Rev.2-1, and Rev.11-1, respectively) of each group are shown. * represents a significantly lower cumulative error visit than chance in the Control group within a range of 80th–100th total visit (<i>P</i><0.05, repeated ANOVA). (B) Error rates per 20-visit block in Rev. 1-1, Rev. 2-1, and Rev. 11-1 (mean ± S.E.M., n = 8/group). The first 100 corner visits in each session were divided into five blocks (block 1 to 5) and analyzed using factorial ANOVA. The black, red and green bars indicate the data from the Control, TC-0.6, and TC-3.0 groups, respectively. † and * indicate a significantly higher or lower difference from chance (50%, gray line), respectively.</p

Compulsive repetitive nose poking in mice exposed to a low TCDD dose (TC-0.6).

<p>(A, B, C) The number of nose pokes per rewarded visit (open triangle) and non-rewarded visit (closed circle): (A) Control, (B) TC-0.6, (C) TC-3.0. Each plotted point indicates the average number of nose pokes per visit made by an individual mouse in a session. (D) Group-averaged numbers of nose pokes throughout the sessions per rewarded visit or non-rewarded visit. Error bars indicate ± S.E.M., n = 8/group. * indicates a significant difference from the Control and TC-3.0 groups (<i>P</i><0.05, ANOVA, followed by Tukey's post hoc test).</p