Skax23^m1Jus mice grow poorly and exhibit a kinky tail defect caused by delayed endochondral ossification. (A) The Skax23^m1Jus mouse mutant was generated and identified as part of the chromosome 11 balancer mutagenesis screening at the Mouse Mutagenesis and Phenotyping Center for Developmental Defects at Baylor College of Medicine in Houston (http://www.mouse-genome.bcm.tmc.edu). Skax23^m1Jus was identified as a dominant mutant with a kinky tail phenotype and poor growth. (B) Mutant adult mice (n = 7) were significantly smaller than WT (n = 7) ****P < .0001, WT vs Skax23^m1Jus mice. (C) Radiographic analyses of adult mice show abnormal fusion and hypertrophy of tail bone joints in Skax23^m1Jus mice when compared with WT littermates (low-power view, 1.5-2×; high-power view, 3×). (D) Wholemount staining of newborn mice using Alcian blue (for cartilage) or Alizarin red (for bone) was performed. Skax23^m1Jus newborn mice had kinky tails (arrowhead) with delayed endochondral ossification (asterisk).