VIP blockade leads to microcephaly in mice via disruption of Mcph1-Chk1 signaling
Sandrine Passemard, … , Pierre Gressens, Vincent Lelièvre
Sandrine Passemard, … , Pierre Gressens, Vincent Lelièvre
Published July 1, 2011
Citation Information: J Clin Invest. 2011;121(8):3072-3087. https://doi.org/10.1172/JCI43824.
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Research Article Neuroscience

VIP blockade leads to microcephaly in mice via disruption of Mcph1-Chk1 signaling

Abstract

Autosomal recessive primary microcephaly (MCPH) is a genetic disorder that causes a reduction of cortical outgrowth without severe interference with cortical patterning. It is associated with mutations in a number of genes encoding protein involved in mitotic spindle formation and centrosomal activities or cell cycle control. We have shown previously that blocking vasoactive intestinal peptide (VIP) during gestation in mice by using a VIP antagonist (VA) results in microcephaly. Here, we have shown that the cortical abnormalities caused by prenatal VA administration mimic the phenotype described in MCPH patients and that VIP blockade during neurogenesis specifically disrupts Mcph1 signaling. VA administration reduced neuroepithelial progenitor proliferation by increasing cell cycle length and promoting cell cycle exit and premature neuronal differentiation. Quantitative RT-PCR and Western blot showed that VA downregulated Mcph1. Inhibition of Mcph1 expression led to downregulation of Chk1 and reduction of Chk1 kinase activity. The inhibition of Mcph1 and Chk1 affected the expression of a specific subset of cell cycle–controlling genes and turned off neural stem cell proliferation in neurospheres. Furthermore, in vitro silencing of either Mcph1 or Chk1 in neurospheres mimicked VA-induced inhibition of cell proliferation. These results demonstrate that VIP blockade induces microcephaly through Mcph1 signaling and suggest that VIP/Mcph1/Chk1 signaling is key for normal cortical development.

Authors

Sandrine Passemard, Vincent El Ghouzzi, Hala Nasser, Catherine Verney, Guilan Vodjdani, Adrien Lacaud, Sophie Lebon, Marc Laburthe, Patrick Robberecht, Jeannette Nardelli, Shyamala Mani, Alain Verloes, Pierre Gressens, Vincent Lelièvre

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Figure 3

VA-induced microcephaly triggers cell cycle exit and early differentiation of cortical progenitors in embryos.

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VA-induced microcephaly triggers cell cycle exit and early differentiati...
(A and B) Immunofluorescent staining for p27kip1 on coronal E11.5 sections in dorsal telencephalon of VA-treated embryos compared with controls. Scale bars: 20 μm. The labeling index (number of p27kip1-positive cells over the total number of nuclei stained by DAPI) is increased in VA-treated embryos as compared with controls (n = 7 per group, unpaired t test, **P < 0.01). (C) Immunofluorescent staining for Dcx on coronal E12.5 sections in dorsal telencephalon of VA-treated embryos compared with controls. Postmitotic Dcx-positive neurons are observed in VA-treated embryos in LGE and in the dorsal, medial, and lateral preplate, while positive staining remained almost absent in controls at E12.5. Scale bars: 200 μm). Lower panel shows high-magnification photographs of Dcx-immunoreactive cells in boxes 1 and 2. Scale bars: 50 μm. (D) Calretinin immunoreactivity at the same level as mentioned above. Note the intense labeling in LGE (box 2) and in the dorsal (box 1), medial, and lateral preplates, which are undetectable in controls. Scale bars: 200 μm. Lower panel shows high-magnification photographs of calretinin-immunoreactive cells in boxes 1 and 2.