Expression Of Hippo Pathway Core Protein YAP At Different Time Points Of Postnatal Brain Development In Mice

Objective: In order to explore the role of the core protein of Hippo pathway in postnatal brain development of mice,and understand whether Hippo pathway plays a role in postnatal brain development and how to play a role.Methods: The growth and development of brain tissue in C57BL/6 mice were detected by measuring brain weight and brain diameter at postnatal(P)3days,6 days,9 days,3 weeks and 8 weeks;.Western blot was used to detect the expression of Hippo pathway core protein in mouse brain.Four color multiple fluorescent immunohistochemical staining was used to detect the changes of microglia and neurons in the cortex,hippocampus and striatum of mice at five different time points,as well as the expression of YAP in microglia and neurons.In this study,the measurement data were expressed by means ± standard deviation(mean ± SD),and the analysis method was single factor analysis of variance(ANOVA).When P<0.05,it means that there is statistical significance.Results:(1)The results of brain weight and brain diameter showed that with the increase of mice age,the brain weight increased from 0.10 g to 0.40 g,meanwhile the brain diameter increased from 0.70 cm to 1.01 cm,and finally stabilized.(2)The western blot results showed that the expression of LATS1 and MST1 decreased with the increase of mice age.Compared with P3d group,the protein levels of YAP and P-YAP-S127 in P3w group and P8w group were significantly lower.(3)The results of four color immunofluorescence showed that with the increase of age,the percentage of microglia in the cortex increased from 0.77% to 8.40%,while the percentage of neuron decreased from 76.73% to25.08%.At the same time,YAP gradually accumulated into the nucleus in both cells,and Hippo pathway was not activated.In the hippocampus,the percentage of microglia increased from 3.73% to 16.76% with the age of mice,but there was no significant change from P9d to P3w.And the percentage of neurons decreased from 85.35% to 39.18%,but there was no significant change between P6d and P9d.Meanwhile,YAP also accumulated into the nucleus gradually in both cells,and Hippo pathway was not activated.The change of microglia in striatum was the same as that in cortex.With the increase of mice age,the percentage increased from 1.66% to 12.90% and YAP accumulated into the nucleus.From birth to P3w,the percentage of neurons in striatum decreased from 62.03% to 21.43% but there was no significant change between P3w and P8w.Between P3d group and P6d group,there was no significant change in the expression of YAP.From P6d to P3w,YAP accumulated into the nucleus.However,the expression of YAP outside the nucleus increased from P3w to P8w.Conclusions:(1)Hippo pathway may ensure normal brain development by limiting excessive brain growth;(2)Hippo pathway may regulate the number of microglia by affecting the regrowth of microglia.