Motor-Coordination-Dependent Learning, More than Others, Is Impaired in Transgenic Mice Expressing Pseudorabies Virus Immediate-Early Protein IE180

The cerebellum in transgenic mice expressing pseudorabies virus immediate-early protein IE180 (TgIE96) was substantially diminished in size, and its histoarchitecture was severely disorganized, resulting in severe ataxia. TgIE96 mice can therefore be used as an experimental model to study the involvement of cerebellar circuits in different learning tasks. The performance of three-month-old TgIE96 mice was studied in various behavioral tests, including associative learning (classical eyeblink conditioning), object recognition, spatial orientation (water maze), startle response and prepulse inhibition, and passive avoidance, and compared with that of wild-type mice. Wild-type and TgIE96 mice presented similar reflexively evoked eyeblinks, and acquired classical conditioned eyelid responses with similar learning curves for both trace and delay conditioning paradigms. The two groups of mice also had similar performances during the object recognition test. However, they showed significant differences for the other three tests included in this study. Although both groups of animals were capable of swimming, TgIE96 mice failed to learn the water maze task during the allowed time. The startle response to a severe tone was similar in both control and TgIE96 mice, but the latter were unable to produce a significant prepulse inhibition. TgIE96 mice also presented evident deficits for the proper accomplishment of a passive avoidance test. These results suggest that the cerebellum is not indispensable for the performance of classical eyeblink conditioning and for object recognition tasks, but seems to be necessary for the proper performance of water maze, prepulse inhibition, and passive avoidance tests

A soluble form of human nectin-2 impairs exocrine secretion of pancreas and formation of zymogen granules in transgenic mice

Transgenic mouse lines expressing a soluble form of human nectin-2 (hNectin-2Ig Tg) exhibited distinctive elevation of amylase and lipase levels in the sera. In this study, we aimed to clarify the histopathology and to propose the transgenic mouse lines as new animal model for characteristic pancreatic exocrine defects. The significant increase of amylase and lipase levels in sera of the transgenic lines approximately peaked at 8 weeks old and thereafter, plateaued or gradually decreased. The histopathology in transgenic acinar cells was characterized by intracytoplasmic accumulation of abnormal proteins with decrease of normal zymogen granules. The hNectin-2Ig expression was observed in the cytoplasm of pancreatic acinar cells, which was consistent with zymogen granules. However, signals of hNectin-2Ig were very weak in the transgenic acinar cells with the abnormal cytoplasmic accumulaion. The PCNA-positive cells increased in the transgenic pancreas, which suggested the affected acinar cells were regenerated. Acinar cells of hNectin-2Ig Tg had markedly small number of zymogen granules with remarkable dilation of the endoplasmic reticulum (ER) lumen containing abundant abnormal proteins. In conclusion, hNectin-2Ig Tg is proposed as a new animal model for characteristic pancreatic exocrine defects, which are due to the ER stress induced by expression of mutated cell adhesion molecule that is a soluble form of human nectin-2

Prepulse inhibition task.

<p>Graphical representation of the indexes related to response latency (Resp Lat), maximum peak latency (Peak Lat), maximum peak value (Max Peak), and area (Resp Area) of the responses shown by wild-type (WT) and TgIE96 (TG) groups during a prepulse inhibition task. Values are mean ± SEM of the obtained indexes ([(startle/prepulse ratio) ×100]/baseline value). *, Statistical differences between groups <i>P</i><0.05; **, <i>P</i><0.01 (<i>Post hoc</i> one-way ANOVA).</p

Experimental model used for the classical conditioning of eyelid responses.

<p>(<i>A</i>) Animals were implanted with bipolar EMG recording electrodes in the left orbicularis oculi (OO) muscle and with stimulating electrodes on the supraorbital nerve. For trace and delay eyeblink conditioning, a tone was used as a CS, lasting 20 ms or 250 ms, respectively. The tone was evoked from a loudspeaker located 30 cm in front of the animal's head. Both CSs were followed 250 ms from their onset by a US consisting of an electrical shock presented to the ipsilateral supraorbital nerve. (<i>B</i>, <i>C</i>) Superimposed (n = 20) EMG recordings collected from the 1st conditioning session corresponding to a representative animal of the control and TgIE96 groups, respectively. R1 and R2 indicate the presence of the two characteristic EMG components of the blink response evoked by the electrical stimulation (Stim.) of the supraorbital nerve.</p

Learning curves collected from the two groups of animals during classical eyeblink conditioning paradigms.

<p>(<i>A, B</i>) Schematic representation of the trace (<i>A</i>) and delay (<i>B</i>) conditioning paradigms, illustrating CS and US stimuli presentations and examples of EMG recording obtained during the 1st (for trace) and 5th (for delay) conditioning sessions of representative TgIE96 animals. The arrow in B points to a short-latency alpha response. (<i>C, D</i>) Learning curves corresponding to habituation (H1, H2), conditioning (C1–C5), and extinction (E1–E4) sessions obtained during trace (<i>C</i>) and delay (<i>D</i>) conditioning paradigms, respectively. Data are mean ± SEM of the percentage of CRs from wild-type (WT) and TgIE96 (TG) groups. Two-way ANOVA followed by a <i>post hoc</i> analysis showed statistical differences between conditioning and the two habituation sessions of each experimental group, displayed by its own symbols (black circle for WT, and white triangle for TG): one, <i>P</i><0.05; two, <i>P</i><0.01; three, <i>P</i><0.001. In addition, no differences were found between groups for the two different conditioning paradigms.</p

Object recognition task.

<p>Representation of the attention devoted to a familiar (Fam) or a novel (New) object exhibited by wild-type (WT) and TgIE96 (TG) groups, during an object recognition task, for the training (0 h) session, and 1, 24, and 72 h afterwards. The object presentation sequence is schematized at the bottom. Values are mean ± SEM of the percentage of the total attention exhibited in each session (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012123#s2" target="_blank">Material and Methods</a> section). *, Statistical differences between percentages of attention, <i>P</i><0.05; **, <i>P</i><0.01; ***, <i>P</i><0.001 (<i>Post hoc</i> one-way ANOVA).</p

Passive avoidance task.

<p>Time spent by wild-type (WT) and TgIE96 (TG) groups to enter the dark area for the Acquisition session, and 24 and 48 h afterwards, during a passive avoidance task. Values are mean ± SEM of the percentage of the time limit (5 min) employed. *, Statistical differences between groups, <i>P</i><0.05 (<i>Post hoc</i> one-way ANOVA).</p

Water maze task.

<p>Representation of the time spent by wild-type (WT) and TgIE96 (TG) groups to reach a submerged platform in a water maze task during the three sessions of the experiment. Data represent mean percentage ± SEM of the time limit (60 s = 100%) for each group. **, Statistical differences between groups in a session, <i>P</i><0.01; ***, <i>P</i><0.001 (<i>Post hoc</i> one-way ANOVA).</p