Human Molecular Genetics Advance Access originally published online on July 17, 2007
Human Molecular Genetics 2008 17(5):631-641; doi:10.1093/hmg/ddm188
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Disruption of the Flnb gene in mice phenocopies the human disease spondylocarpotarsal synostosis syndrome
1 Medical Genetics Institute, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, SSB-371, Los Angeles, CA 90048, USA 2 Center for Comparative Medicine and Mouse Biology Program and 3 Department of Pathology and Laboratory Medicine, UC Davis School of Medicine, Davis, CA 95616, USA 4 Department of Human Genetics 5 Department of Pediatrics and 6 Department of Obstetrics and Gynecology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
* To whom correspondence should be addressed. Tel: +1 3104236460; Fax: +1 3104230620; Email: deborah.krakow{at}cshs.org
Received May 26, 2007; Accepted July 12, 2007
Spondylocarpotarsal synostosis syndrome (SCT) is an autosomal recessive disease that is characterized by short stature, and fusions of the vertebrae and carpal and tarsal bones. SCT results from homozygosity or compound heterozygosity for nonsense mutations in FLNB. FLNB encodes filamin B, a multifunctional cytoplasmic protein that plays a critical role in skeletal development. Protein extracts derived from cells of SCT patients with nonsense mutations in FLNB did not contain filamin B, demonstrating that SCT results from absence of filamin B. To understand the role of filamin B in skeletal development, an Flnb–/– mouse model was generated. The Flnb–/– mice were phenotypically similar to individuals with SCT as they exhibited short stature and similar skeletal abnormalities. Newborn Flnb–/– mice had fusions between the neural arches of the vertebrae in the cervical and thoracic spine. At postnatal day 60, the vertebral fusions were more widespread and involved the vertebral bodies as well as the neural arches. In addition, fusions were seen in sternum and carpal bones. Analysis of the Flnb–/– mice phenotype showed that an absence of filamin B causes progressive vertebral fusions, which is contrary to the previous hypothesis that SCT results from failure of normal spinal segmentation. These findings suggest that spinal segmentation can occur normally in the absence of filamin B, but the protein is required for maintenance of intervertebral, carpal and sternal joints, and the joint fusion process commences antenatally.