Download Overexpression of the Transcription Factor Sp8 Induced Ectopic

Overexpression of the transcription factor Sp8 induces ectopic
motor neurons in the p3 domain of chick spinal cord
Xiaosu Li1, Chao Lin1, Sijing Song2, and Zhengang Yang1*
1Institutes
of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University,
Shanghai 200032, China
2College of Life Science and Technology, Hua Zhong Agricultural University, Wuhan 436700,
China
*
Corresponding author
Email: [email protected]
Abstract During the period of neurogenesis in the spinal cord, particular types of neurons are
generated from specific progenitor cells located in different dorsoventral (DV) regions of the
ventricular zone. The graded morphogens along the DV axis of the neural tube confer positional
information to the progenitor cells. Morphogens achieve through induction or inhibition of a set of
transcription factors expression in a concentration dependent manner. By combinatorial expression
of distinct transcription factors, the DV axis of the neural tube can be divided into multiple
domains and cross-repressive interactions between complementary pairs of transcription factors
further refine and sharpen the boundaries between adjacent domains. The action of these
transcription factors directs different progenitor populations to generate particular subtypes of
neurons. Sp8 is a zinc finger transcription factors belonging to specificity protein (Sp) family and
expression of Sp8 in the basal plate of spinal cord has been reported. However there is no study
addressing the function role of Sp8 during spinal cord development. In the present study, we first
confirmed Sp8 expression in the spinal cord using immunohistochemistry. During neurogenesis in
the spinal cord, Sp8 expression shares the same ventral limit with Olig2 and is complementary to
Nkx2.2. Olig2+ domain and Nkx2.2+ domain are neighboring with each other, and give rise to
Isl1+ motor neurons and Sim1+ V3 interneurons respectively. When mouse Sp8 was
overexpressed in the chick spinal cord using either retrovirus or in ovo electroporation, we found
that ectopic motor neurons were induced in the Nkx2.2+ p3 domain. Meanwhile, Nkx2.2
expression was cell-autonomously repressed by Sp8 expression. This suggests that Sp8
participates in patterning the ventral spinal cord.
Key word: Sp8, motor neuron, Nkx2.2, dorsoventral patterning, spinal cord