Originally published as Genetics Published Articles Ahead of Print on October 3, 2005.

Genetics, Vol. 172, 445-456, January 2006, Copyright © 2006
doi:10.1534/genetics.105.048934

A Novel Murine Gene, Sickle tail, Linked to the Danforth's short tail Locus, Is Required for Normal Development of the Intervertebral Disc

Kei Semba^*,, Kimi Araki^*, Zhengzhe Li^*, Ken-ichirou Matsumoto^*,, Misao Suzuki, Naoki Nakagata, Katsumasa Takagi, Motohiro Takeya^**, Kumiko Yoshinobu, Masatake Araki, Kenji Imai, Kuniya Abe and Ken-ichi Yamamura^*,1

^* Division of Developmental Genetics, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto 862-0976, Japan, Department of Orthopaedic Surgery, Kumamoto University School of Medicine, Kumamoto 860-8556, Japan, Division of Transgenic Technology, Institute of Resource Development and Analysis, Kumamoto University, Kumamoto 860-0811, Japan, Division of Reproductive Engineering, Institute of Resource Development and Analysis, Kumamoto University, Kumamoto 860-0811, Japan, ^** Department of Cell Pathology, Kumamoto University School of Medicine, Kumamoto 860-8556, Japan, Division of Bioinformatics, Institute of Resource Development and Analysis, Kumamoto University, Kumamoto 860-0811, Japan, Institute of Developmental Genetics, GSF-National Research Center for Environment and Health, 85764 Neuherberg, Germany and Technology Development Team for Mammalian Cellular Dynamics, BioResource Center, RIKEN, Tsukuba, Ibaraki 305-0074 Japan

¹ Corresponding author: Division of Developmental Genetics, Institute of Molecular Embryology and Genetics, Kumamoto University, 4-24-1 Kuhonji, Kumamoto 862-0976, Japan.
E-mail: yamamura{at}gpo.kumamoto-u.ac.jp

We established the mutant mouse line, B6;CB-Skt^{GtAyu8021IMEG} (Skt^Gt), through gene-trap mutagenesis in embryonic stem cells. The novel gene identified, called Sickle tail (Skt), is composed of 19 exons and encodes a protein of 1352 amino acids. Expression of a reporter gene was detected in the notochord during embryogenesis and in the nucleus pulposus of mice. Compression of some of the nuclei pulposi in the intervertebral discs (IVDs) appeared at embryonic day (E) 17.5, resulting in a kinky-tail phenotype showing defects in the nucleus pulposus and annulus fibrosus of IVDs in Skt^Gt/Gt mice. These phenotypes were different from those in Danforth's short tail (Sd) mice in which the nucleus pulposus was totally absent and replaced by peripheral fibers similar to those seen in the annulus fibrosus in all IVDs. The Skt gene maps to the proximal part of mouse chromosome 2, near the Sd locus. The genetic distance between them was 0.95 cM. The number of vertebrae in both [Sd +/+ Skt^Gt] and [Sd Skt^Gt/+ +] compound heterozygotes was less than that of Sd heterozygotes. Furthermore, the enhancer trap locus Etl4^lacZ, which was previously reported to be an allele of Sd, was located in the third intron of the Skt gene.

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