Elsevier

Developmental Biology

Volume 380, Issue 2, 15 August 2013, Pages 172-184
Developmental Biology

Metameric pattern of intervertebral disc/vertebral body is generated independently of Mesp2/Ripply-mediated rostro-caudal patterning of somites in the mouse embryo

https://doi.org/10.1016/j.ydbio.2013.05.020Get rights and content
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Highlights

  • Process of resegmentation from somites to vertebrae was analyzed using Uncx4.1-lacZ transgene.

  • Rostro-caudal boundary does not necessarily coincide with resegmentation boundary.

  • Intervertebral disc (IVD) patterning was compared between Mesp2 KO and Ripply1/2 double KO mice.

  • Metameric pattern of IVD is generated independently of rostro-caudal patterning of somite.

Abstract

The vertebrae are derived from the sclerotome of somites. Formation of the vertebral body involves a process called resegmentation, by which the caudal half of a sclerotome is combined with the rostral half of the next sclerotome. To elucidate the relationship between resegmentation and rostro-caudal patterning of somite, we used the Uncx4.1-LacZ transgene to characterize the resegmentation process. Our observations suggested that in the thoracic and lumbar vertebrae, the Uncx4.1-expressing caudal sclerotome gave rise to the intervertebral disc (IVD) and rostral portion of the vertebral body (VB). In the cervical vertebrae, the Uncx4.1-expressing caudal sclerotome appeared to contribute to the IVD and both caudal and rostral ends of the VB. This finding suggests that the rostro-caudal gene expression boundary does not necessarily coincide with the resegmentation boundary. This conclusion was supported by analyses of Mesp2 KO and Ripply1/2 double KO embryos lacking rostral and caudal properties, respectively. Resegmentation was not observed in Mesp2 KO embryos, but both the IVD and whole VB were formed from the caudalized sclerotome. Expression analysis of IVD marker genes including Pax1 in the wild-type, Mesp2 KO, and Ripply1/2 DKO embryos also supported the idea that a metameric pattern of IVD/VB is generated independently of Mesp2/Ripply-mediated rostro-caudal patterning of somite. However, in the lumbar region, IVD differentiation appeared to be stimulated by the caudal property and suppressed by the rostral property. Therefore, we propose that rostro-caudal patterning of somites is not a prerequisite for metameric patterning of the IVD and VB, but instead required to stimulate IVD differentiation in the caudal half of the sclerotome.

Keywords

Mesp2
Ripply
Uncx4.1
Vertebra
Intervertebral disc
Resegmentation

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