CD146 Deletion in the Nervous System Impairs Appetite, Locomotor Activity and Spatial Learning in Mice

<div><p>Cell adhesion molecules (CAMs) are crucial effectors for the development and maintenance of the nervous system. Mutations in human CAM genes are linked to brain disorders and psychological diseases, and CAM knockout mice always exhibit similar behavioral abnormalities. CD146 is a CAM of the immunoglobulin superfamily that interacts with Neurite Outgrowth Factor and involved in neurite extension <i>in vitro</i>. However, little is known about its <i>in vivo</i> function in the nervous system. In this study, we used a murine CD146 nervous system knockout (CD146^ns-ko) model. We found that the brains of some CD146^ns-ko mice were malformed with small olfactory bulbs. CD146^ns-ko mice exhibited lower body weights and smaller food intake when compared with wild type littermates. Importantly, behavior tests revealed that CD146^ns-ko mice exhibited significant decreased locomotor activity and impaired capacity for spatial learning and memory. Our results demonstrate that CD146 is important for mammalian nervous system development and proper behavior patterns.</p></div

Generation and identification of CD146^ns-ko mice.

<p>(A) Schematic strategy for constructing CD146^{floxed/floxed} mice. Two loxP sites were inserted into the promoter and 1^st intron of the CD146 gene by targeting vector. (B–E) Sections of brains and spinal cords of WT and CD146^ns-ko mice were immunostained with anti-CD146 mAb AA4. Expression of CD146 was observed on cortical neurons (B), cerebellar Purkinje cells (C), hippocampal neurons (D) in brain and neurons in spinal cord (E). Scale bar represents 200 µm. (F) Expression of CD146 in whole brain, cerebral cortex alone and spinal cord of WT and CD146^ns-ko mice was analyzed in cDNA RT-PCR assay. Data is presented as ratio of CD146 expression level normalized with WT group (means ± SEM).</p

CD146^ns-ko mice show stochastic reduction in the size of olfactory bulbs.

<p>(A) Representative images of WT brain, CD146^ns-ko normal brain and CD146^ns-ko abnormal brain. (B) A Chi-square test was performed to compare the incidence of abnormal olfactory bulbs in WT and CD146^ns-ko groups.</p

Knockout of CD146 in the nervous system resulted in decreased locomotor activity in mice.

<p>(A) Mice at the ages of 1 month and 3 months were subjected to the Rotarod test. Falling latency was recorded with a 30 seconds cut-off time. Mice at the ages of 1 month, 3 months and 6 months were subjected to the open field test. Representative running tracks of mice at the age of 3 months were shown (B). B: begin-point. E: end-point. During the 5-min free running, distance travelled (C), maximum speed (D) and rest time (E) of WT and CD146^ns-ko mice were recorded and analyzed with a two-way ANOVA. Data is presented as means ± SEM.</p

Knockout of CD146 in the nervous system impaired spatial learning and memory in mice.

<p>(A) WT and CD146^ns-ko mice at the age of 1 month were subjected to the Morris water maze test. During the 7-day training period, time spent in finding the target of each mouse was recorded and analyzed with a repeated measures ANOVA. At the last day of probe test, distance swam (B) and time spent in each quadrant by the mice (C) were recorded and analyzed with Student’s t test. The brains of 1-month-old WT and CD146^ns-ko mice were sagittally sectioned. The hippocampal area (D) and neuron density of CA1, CA3 and DG (E) were measured after Nissl staining. Data is presented as means ± SEM.</p

Knockout of CD146 in the nervous system resulted in decreased body weight and food intake in mice.

<p>Body weight of male (A) and female (B) mice at the ages of 1 month, 3 months and 6 months were measured and analyzed with a two-way ANOVA. Daily food intake of male (C) and female (D) mice at the age of 1 month was measured once a week for 4 weeks. Data is presented as means ± SEM and analyzed by a repeated measures ANOVA.</p