Cis-regulatory control of corticospinal system development and evolution


The co-emergence of a six-layered cerebral neocortex and its corticospinal output system is one of the evolutionary hallmarks of mammals. However, the genetic programs that underlie their development and evolution remain poorly understood. Here we identify a conserved non-exonic element (E4) that acts as a cortex-specific enhancer for the nearby gene Fezf2 (also known as Fezl and Zfp312), which is required for the specification of corticospinal neuron identity and connectivity. We find that SOX4 and SOX11 functionally compete with the repressor SOX5 in the transactivation of E4. Cortex-specific double deletion of Sox4 and Sox11 leads to the loss of Fezf2 expression, failed specification of corticospinal neurons and, independent of Fezf2, a reeler-like inversion of layers. We show evidence supporting the emergence of functional SOX-binding sites in E4 during tetrapod evolution, and their subsequent stabilization in mammals and possibly amniotes. These findings reveal that SOX transcription factors converge onto a cis-acting element of Fezf2 and form critical components of a regulatory network controlling the identity and connectivity of corticospinal neurons.

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Figure 1: Identification of a cortex-specific Fezf2 enhancer.
Figure 2: Loss of neocortical Fezf2 expression and CS axons in E4-knockout mice.
Figure 3: SOX4 and SOX11 bind to and activate E4 via competition with SOX5.
Figure 4: Sox4 and Sox11 are required for Fezf2 expression and CS tract formation.
Figure 5: Functional analysis of species differences in E4 sequence.


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We thank W. Han, Y. Imamura Kawasawa, D. Liu and T. Nottoli for technical help; A. Giraldez and A. M. M. Sousa for reagents; and the Sestan laboratory for discussions. This work was supported by the National Institutes of Health (NS054273, MH081896, AR54153), the March of Dimes Foundation and a McDonnell Scholar Award (N.S.).

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S.S., K.Y.K. and N.S. designed the research; S.S. performed the experiments; S.S. and K.Y.K. performed the confocal imaging, M.L. analysed coexpression and deep sequencing data; S.S., K.Y.K. and N.S. analysed the other data; V.L. generated mice with floxed Sox4 and Sox11 alleles; N.S. conceived the study; and S.S., K.Y.K. and N.S. wrote the manuscript. All authors discussed and commented on the data.

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Correspondence to Nenad Šestan.

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Shim, S., Kwan, K., Li, M. et al. Cis-regulatory control of corticospinal system development and evolution. Nature 486, 74–79 (2012).

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