A single nucleotide deletion of 293delT in SEDL gene causing spondyloepiphyseal dysplasia tarda in a four-generation Chinese family

Spondyloepiphyseal Dysplasia Tarda (SEDT; MIM 313400) is a rare genetically heterogeneous disorder of vertebral and epiphyseal growth resulting in disproportionally short-trunked short stature, barrel-shaped chest, and dysplasia of the large joints. It is caused by the mutations of SEDL gene. The distinctive radiological signs and the X-linked mode of inheritance make it easy to diagnose. Here a four-generation Chinese SEDT family has been analyzed and the disease-causing mutation has been found. After polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) analysis and DNA sequencing, a previously unreported deletion of T in exon 5 of SEDL gene (i.e. 293delT) was observed and seven individuals in the family carried the mutation. It results in frameshift and a putative truncated protein with the 97 N-terminal amino acids, and 9 changed amino acids. Therefore, loss of function of the gene could be predicted. However, this mutation has not been detected in 50 age and sex matched unrelated controls.