ORIGINAL RESEARCH PAPER Generation of mice with a novel conditional null allele of the Sox9 gene Sook Peng Yap • Xing Xing • Petra Kraus • V. Sivakamasundari • Hsiao Yun Chan • Thomas Lufkin Received: 14 January 2011 / Accepted: 29 March 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Sox9 is expressed in multiple tissues during mouse development and adulthood. Mutations in the Sox9 gene or changes in expression levels can be attributed to many congenital diseases. Heterozygous loss-of-function mutations in the human SOX9 gene cause Campomelic dysplasia, a semi-lethal skeletal malformation syndrome. Disruption of Sox9 by con- ventional gene targeting leads to perinatal lethality in heterozygous mice, hence hampering the feasibility to obtain the homozygous Sox9 null mice for in vivo functional studies. In this study, we generated a conditional allele of Sox9 (Sox9 tm4.Tlu ) by flanking exon 1 with loxP sites. Homozygous mice for the Sox9 tm4.Tlu allele (Sox9 flox/flox ) are viable, fertile and indistinguishable from wildtype (WT) mice, indicat- ing that the Sox9 tm4.Tlu allele is a fully functional Sox9 allele. Furthermore, we demonstrated that Cre-medi- ated recombination using a Col2a1-Cre line resulted in specific ablation of Sox9 activity in cartilage tissues. Keywords Chondro-skeletogenesis Á Conditional null allele Á Cre/loxP Á FLP/FRT Á Gene targeting Á Sox9 Introduction Sox9, a transcription factor of the Sox family, is the master regulator for chondrogenesis and the key regulator for testis development (Vidal et al. 2001). Sox9 plays important roles during the development and/or differentiation of tissues as diverse as neural crest cells, notochord, melanocytes, glial cells, heart, pancreas, pyloric sphincter, intestinal epithelium and hair follicles (Lefebvre et al. 2007; Ng et al. 1997; Wegner 2010). Patients with campomelic dysplasia (OMIM #114290) an autosomal-dominant condition caused by heterozygous mutations in and around the SOX9 gene (Foster et al. 1994), are featured by short stature, bowing and angulation of the long bones, deformed pelvis and spines, craniofacial defects, and often also show sex reversal and malformations in non-skeletal organs such as brain, kidneys and heart (Houston et al. 1983; Mansour et al. 1995; Wright et al. 1995). S. P. Yap Á X. Xing Á P. Kraus Á V. Sivakamasundari Á H. Y. Chan Á T. Lufkin (&) Stem Cell and Developmental Biology, Genome Institute of Singapore, 60 Biopolis Street, Singapore 138672, Singapore e-mail: lufkin@gis.a-star.edu.sg S. P. Yap e-mail: yaps@gis.a-star.edu.sg X. Xing e-mail: xing1@gis.a-star.edu.sg P. Kraus e-mail: petramk9@gis.a-star.edu.sg V. Sivakamasundari e-mail: vsivak@gis.a-star.edu.sg H. Y. Chan e-mail: chanh1@gis.a-star.edu.sg 123 Biotechnol Lett DOI 10.1007/s10529-011-0608-6