STRUCTURAL ORGANIZATION OF THE GENE FOR CD40 LIGAND - MOLECULAR ANALYSIS FOR DIAGNOSIS OF X-LINKED HYPER-IGM SYNDROME

CD40 ligand (CD40L) on activated T cells plays a crucial role for Ig h eavy-chain class switching and the mutation of the gene for this ligan d in the X-chromosome causes immunodeficiency with hyper-IgM (X-HIM). We isolated and characterized the human genomic clone for CD40 L to ob tain information about the transcriptional regulatory regions of the g ene and to develop a molecular diagnostic method for X-HIM patients. T he genomic DNA isolated was over 12 kb long containing 5 exons that co ver fun sequence of mRNA for the ligand. DNA motif analysis based on t ranscription factor database revealed the presence of a GATA 1 box at around -265 bp. The typical TATA box, CAT site or GC rich region was n ot found in the 5' flanking region. However, two possible TATA like se quences were found at around -27 and -136 bp. Using the oligonucleotid e primers corresponding to the introns, we performed a PCR-SSCP analys is of each exon from a patient with X-HIM syndrome and detected abnorm ality in exon 5. When sequenced, dinucleotide deletion in this exon wa s found in the patient and in one X allele of his mother as the only d ifferent sequence from that of the control gene. This procedure is sim ple and could be used for diagnosis of the X-HIM syndrome.