OBJECTIVETo further investigate the genetic basis of hereditary X-linked spondyloepiphyseal dysplasia tarda (SEDL) and provide useful information for the prevention and treatment of the disease.

METHODSRT-PCR and cDNA sequencing were used to test mRNA expression of SEDL gene in a patient with 13 bp deletion of SEDL gene involving the acceptor splice site of intron 5.

RESULTSOf two different sizes of mRNA products identified in the patient, the 393 bp product was created due to the activation of cryptic splice site within exon 6; the 433 bp product was completely consistent with the part of genomic sequence on chromosome 8.

CONCLUSIONThe intragenic deletion that occurred in the acceptor splice site of the 3'region of intron 5 and the 5' coding region of exon 6 results in the activation of a cryptic splice site within exon 6, which causes 47 bp deletion of the resulting mRNA followed by a frameshift that would add two missense amino acids and then be followed by a termination codon (D109-S123del; S124fsX126). In addition, the mutation may activate the transcription of pseudogene SEDLP2 on chromosome 8 to partly complement the function of SEDL protein.