Although the rate of expression changes during fetal development is faster than at any other stage of life and reduces considerably after birth, this rate remains relatively high during infancy (especially the first half year of postnatal life) and childhood (Colantuoni, et al., 2011). During early postnatal life (in infancy and childhood) the gene expression changes of the developing brain have substantially larger amplitudes than later age-related changes (Somel, et al., 2010). Most of these changes occur during the first years of life (Somel, Franz, Yan, Lorenc, Guo, & Giger, 2009). At the same time, the formation of the transcription status of some genes is complete by adolescence, and is maintained throughout the rest of the life, as shown in a study of transcriptional dynamics of excitatory and inhibitory vesicular neurotransmitter transporter mRNAs (VGluT1 to VGAT) during normal human development (Fung, Webster, Weickert, 2011). Specifically, it was found that the ratio of VGluT1/ VGAT increased during early postnatal development to reach a peak at age 5–12 years, after which the balance between those mRNAs remains constant into adulthood.
