Congratulation to co-first authors Jing Jin and Chao Chen

“Cross-species functional analyses reveal shared and separate roles for Sox11 in frog primary neurogenesis and mouse cortical neuronal differentiation.”
By Chao Chen, Jing Jin, Garrett A. Lee, Elena Silva, Maria Donoghue
May 2016

      Chao and Jing both came to Georgetown University with bachelor degrees from China.  Both had the goal to pursue a Ph.D. degree in biology and were successful.  Jing Jin worked in Dr. Elena Casey’s lab with a focus on the neural development in Xenopus laevis, while Chao worked in Dr. Donoghue’s lab on the project of SoxC genes’ role in cerebral cortex development.  Her research focuses on the roles of two SoxC genes, Sox4 and Sox11, in cerebral cortical development.

     Their article is about a cross-species functional analysis.  The process of neurogenesis – from dividing progenitor through neuronal maturation – is stereotyped across species and brain regions. Several previous studies implicate the Sox11 transcription factor in the initial step of differentiation and demonstrate pan-neuronal roles for Sox11 in different systems.  To date, however, the conservation of Sox11’s roles in neurogenesis between species has not been elucidated.

      In this study, Chao and Jing first examined expressions in mouse cortex and cortical neurons and found that Sox11 is dynamically expressed within embryonic compartments that contain differentiated neurons – activated in early embryonic days and inactivated in postnatal days. Function experiments in mouse cortical neurons also demonstrate a novel role for Sox11 to support morphological complexity of both axons and dendrites in a time dependent manner. Jing and Chao then demonstrate the Sox11 expression in frogs and found that unlike the pattern observed in mice, the expression in frog neural tissues persists throughout primary neurogenesis. The function studies in frogs support roles for Sox11 not only in promoting neuronal differentiation but also seems to unexpectedly act in the induction or maintenance of neural progenitors. Finally, they performed the gain of function studies involving the expression of one species’ Sox11 in the other species’ assay system. Surprisingly, the frog and mouse Sox11 cannot substitute for one another.  Bioinformatic data reveal that the frog Sox11 protein sequence is only 68.18% identical to the mouse’s. Thus, the functional difference likely reflected in sequence divergence.

      Their work represents the first demonstration of a role for Sox11 promoting morphological complexity of neurite in a time dependent manner and also describes an unexpected Sox11 role in the neural induction of the frog nervous system. This work also provides compelling evidence that Sox11 has shared roles but is species-specific in frog neural development and mouse corticogenesis providing insights into how Sox11 roles changed over the course of evolution.