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

Abstract

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 1/1 Skt Gt ] and [Sd Skt Gt /1 1] 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. T HE notochord is an integral component of the axial structure of vertebrates, functions as a signaling center during embryogenesis, and plays essential roles in patterning of both somites and the neural tube (Ang and Rossant 1994; Wilson et al.1995; Chiang et al.1996). In addition, the notochord has major roles in vertebral column formation. In the mouse, the notochord is a continuous rod of constant diameter extending from the hypophysis to almost the tip of the tail at embryonic day (E) 9.5. At E10.5-E11.5, signals from the notochord induce the migration, proliferation, and fusion of the sclerotome to form a continuous and unsegmented perichordal tube around the notochord and neural tube. At 12.5, mesenchyme acquires a characteristic metameric pattern of densely packed areas caudally and loosely packed areas cranially. Some densely packed cells move cranially and give rise to the annulus fibrosus of the future intervertebral disc (IVD). The remaining densely packed cells fuse with the immediately caudal loosely packed cells to form the cartilaginous primordia of the vertebral bodies. Notochord cells located in the vertebral body of cranial regions start to relocate into intervertebral regions (Paavola et al. 1980;Rufai et al. 1995;Aszodi et al. 1998). At E13.5, the vertebral regions are enlarged and chondrified. The notochord proliferates and undergoes hypertrophy to form the gelatinous center of the intervertebral disc, called the nucleus pulposus. This nucleus is surrounded by the circularly arranged fibers of the annulus fibrosus. These two structures together constitute the IVD (Langman 1969;Theiler 1988 intervertebral regions. Failures in somite, neural tube, and notochord formation are closely correlated with vertebral malformations. However, the mechanisms that underlie the formatio...

Effect of cell number on mesenchymal stem cell transplantation in a canine disc degeneration model

“…Beagles are sometimes being used to study IVD degeneration since their disc cells share similarities with human discs. [33][34][35][36][37] . Degeneration is produced by nucleotomy in the model used in the present study, and thus may have differences from naturally occurring IVD degeneration in humans.…”

Lasp1 misexpression influences chondrocyte differentiation in the vertebral column

“…However, the"wavy tail mouse mutant did not develop any of these characteristics, as only the tail was deformed and only during postnatal development. Other mouse models developed defects in the lumbal region or tail already around midgestation, like in the wavy tail mutant these malformation were restricted to the vertebral column but not muscular development (flaky tail (Rothnagel et al, 1994), TgN(Imunsd)379Rpw (Schrick et al, 1995), Sickle tail (Semba et al, 2006), Jun (Behrens et al, 2003), Delta-like I (Teppner et al, 2007), or Tgfbr2 (Baffi et al, 2006)). …”

Retinoic acid receptor regulation of epimorphic and homeostatic regeneration in the axolotl

“…This might be due to the fact that many RA synthesis genes are upregulated after LE135 treatment. Many cluster 2/3 genes (n=101) are expressed in proximal developing limb buds in other limbed vertebrates or required for proper limb development [cluster 2 expressed in proximal limb: Meis1 (Mercader et al, 2000(Mercader et al, , 2005, Meis2 (Mercader et al, 2000(Mercader et al, , 2005, Pbx1 (Selleri et al, 2001), Arid5b (Ristevski et al, 2001); cluster 2 expressed in limb bud: Mia3 (Bosserhoff et al, 2004), Rac1 (Bell et al, 2004;Suzuki et al, 2013), Asph (Patel et al, 2014), Neo1 (Hong et al, 2012), Cyp26B1 (MacLean et al, 2001), Flrt2 (Haines et al, 2006), Rarγ (Pennimpede et al, 2010), Rbp1 (Gustafson et al, 1993), KIAA1217 (Semba et al, 2006); cluster 3 (Table S1) expressed in proximal limb: Fibin (Taher et al, 2011;Wakahara et al, 2007), Epha7 (Araujo et al, 1998), Nrip1 (Smith et al, 2014), Rnd3 (Bell et al, 2004); cluster 3 expressed in limb bud: Apcdd1 (Jukkola et al, 2004), Zfn638 (Bell et al, 2004), Stat3 (Gray et al, 2004), Tsh2 (Caubit et al, 2000;Erkner et al, 1999)]. The association of these genes with limb patterning in other vertebrates supports the idea that RA reprograms the distal cells to resemble a proximal limb cell fate.…”