Identification of Eight Novel Alternative Splicing Forms of CD72 and Their Differential Expression in a Mouse Model of SLE / 生物化学与生物物理进展

ABSTRACT

CD72 is a B cell specific receptor that exists in multiple alternative splicing forms. Eight novel alternative splicing forms of CD72 were identified from the spleenocytes of BALB/C mice. Two very unique intron sequences were found in those alternative splicing forms. One kind of splicing variants retained the intron1 in the mRNA. This intron can be translated into 32 amino acid residues without changing the reading frame of the whole proteins. Another kind of splicing variants used an alternative 3' splice site in intron 3(3'AS) which led to premature termination of its encoded protein. The differential expression of the CD72 splicing variants were compared in BALB/C and NZB/W mice that were at different stage of systematic lupus erythematosis(SLE) disease development. It was found that 1) splicing forms containing 3'AS was rare in all samples examinated; 2) splicing forms containing two ITIM domains and transmembrane domains were more abundant in BALB/C mice than in NZB/W mice, even in some cases the two ITIM domains were separated by the intron 1; 3) a shorter splicing form with both exon2 and exon3 missing was expressed highly in terminally diseased NZB/W mice.These results suggested an important role of CD72 alternative splicing forms in B cell receptor signaling and in SLE.