Abstract
Purpose:
To investigate the dynamic changes of isoform-specific protein expression and phosphorylation of synapsins in visual cortex of the postnatal mice with monocular deprivation (MD).
Methods:
Forty-two clean neonatal C57BL/6J mice were divided into seven groups randomly and six for each group. The mice were sacrificed to obtain the tissue samples at postnatal 7, 14, 21, 28, 35, 42, 60 days respectively. Similarly, Thirty neonatal healthy C57BL/6J mice were divided into five groups randomly (Monocular Deprivation groups, MD groups) and six for each group. The right eyelids of MD groups were sutured at postnatal 14, 21, 28, 35, 60 days respectively, and sacrificed after 7 days to obtain the tissue samples. Western blot were applied to quantitatively analyze the level of Synapsin phosphorylation and protein expression in the visual cortex.
Results:
The results showed that the total (T-) protein levels of synapsins including the isoform of Ia/b, IIa/b and IIIa were about 21-26% of adult level in visual cortex of mice at postnatal 7 days (P7), and then the T-synapsin Ia/b and IIb could quickly reach adult level at P35. However, the T-synapsin IIa and IIIa increased more slowly (71-74% at P35), and then kept increasing in the visual cortex of mice at P60. Unlike to the changes of T-synapsins, the level of phosphorylated (P-) synapsin Ia/b (not IIa/b and IIIa) at site 1 increased with development to the highest level (286.0±16.7%) at P21, and then decreased rapidly to a low level in visual cortex of mice at P35-60. In addition, we found that the levels of P-synapsin Ia/b increased significantly (p<0.05, n=6 per group) in left visual cortex of P28 and P35 (not P21 and P42) mice with one-week MD of right eye; and no significant changes of T-synapsins were observed in both left and right sides of visual cortex in P21-42 mice with MD treatment.
Conclusions:
These results suggested that the isoform-specific protein expression and site-1 phosphorylation of synapsins might play a different role in the synaptic plasticity of visual cortex, and monocular deprivation delays the dynamic changes of phosphorylated synapsin Ia/b at site-1 in contralateral visual cortex of juvenile mice.