Dynamic Expression of Genes Encoding Ubiquitin Conjugating Enzymes (E2s) During Neuronal Differentiation and Maturation: Implications for Neurodevelopmental Disorders and Neurodegenerative Diseases

<b>Background:</b> The ubiquitination process plays a crucial role in neuronal differentiation and function. Numerous studies have focused on the expression and functions of E3 ligases during these different stages, far fewer on E2 conjugating enzymes. In mice, as in humans, these E2s belong to 17 conjugating enzyme families. <b>Objectives:</b> We analyzed by real-time PCR the expression dynamics of all known E2 genes during an in vitro differentiation of mouse hippocampal neuronal cultures, and after, we analyzed their stimulation with N-methyl-D-aspartate (NMDA). <b>Results:</b> We found that 36 of the 38 E2 genes were expressed in hippocampal neurons. Many were up-regulated during neuritogenesis and/or synaptogenesis stages, such as <i>Ube2h</i>, <i>Ube2b</i>, and <i>Aktip</i>. Rapid and delayed responses to NMDA stimulation were associated with the increased expression of several E2 genes, such as <i>Ube2i</i>, the SUMO-conjugating E2 enzyme. We also observed similar expression profiles within the same E2 gene family, consistent with the presence of similar transcription factor binding sites in their respective promoter sequences. <b>Conclusions:</b> Our study indicates that specific expression profiles of E2 genes are correlated with changes in neuronal differentiation and activity. A better understanding of the regulation and function of E2s is needed to better understand the role played by the ubiquitination process in physiological mechanisms and pathophysiological alterations involved in neurodevelopmental or neurodegenerative diseases.