Single site polymorphisms and alternative splicing of the human CD13 gene – different splicing frequencies among patients with acute myeloid leukaemia and healthy individuals

Abstract

Summary. Within the haematopoietic system, CD13/aminopeptidase N (APN), a transmembrane glycoprotein, is expressed on the surface of early committed progenitors of granulocytes and monocytes and by all cells of these lineages as they mature. CD13 is expressed on the majority of leukaemic myeloblasts in acute myeloid leukaemia (AML), and on leukaemic lymphoblasts in a small percentage of acute lymphoid leukaemia cases. Thus, anti-CD13 monoclonal antibodies are used as diagnostic markers in leukaemia typing. By systematically amplifying overlapping reverse transcription polymerase chain reaction (RT-PCR) amplicons throughout the CD13 mRNA, we identified two splice variants in which exon 3 and exon 14 were lost. Fourteen healthy individuals and 34 patients with AML were screened for these splice variants. All healthy individuals, and the majority of AML patients, had both splice variants but they represented less than 10% of the total RT-PCR-amplified CD13 product. Increased expression of both truncated CD13 mRNA forms were observed in 6% of AML patients, whereas no detectable exon 3 or exon 14 splice variants could be generated in 26% and 9% of AML patients respectively. The different splicing frequencies may reflect altered processing of pre-mRNA or expansion of certain cell types for some AML patients, even though no correlation existed to blast percentage, FAB classification, surface antigens or cytogenetic characteristics. In addition, we identified an intron of 506 bp between exon 1 and exon 2 as well as two sites of single nucleotide polymorphism with a heterozygosity index of about 0´5, making them useful as genetic markers.

CD1c(+) myeloid dendritic cells in myeloid neoplasia

“…Similar findings were observed with two additional anti‐CD13 monoclonal antibodies. The reason for the observation is unclear but may be due to CD13 polymorphisms .…”

Aminopeptidase N (CD13) Regulates Tumor Necrosis Factor-α-induced Apoptosis in Human Neutrophils

“…The gene and promoter regions have been studied extensively, and a number of highly polymorphic regions have been identified, although the functional importance of these polymorphic sites has yet to be determined (47). Myeloid progenitor cells, differentiating granulocytes, and monocytes possess an additional extended promoter region containing the elements necessary for the expression of APN (48, 49).…”

“…CD13 expression has also been found to correlate with the growth and activation of acute myeloblastic cells and lymphoblastic leukemia cells (45,54). Single site polymorphisms and splice variants of CD13 have also been associated with acute myeloid leukemia (47). Incubation of leukemic cell lines with the APN inhibitors, actinonin or bestatin, inhibits cell proliferation and stimulates apoptosis via a caspase-dependent pathway (56,57).…”

The moonlighting enzyme CD13: old and new functions to target

“…The potential importance of endocytosis in the regulation of the functions of CD13 is underscored by the reported mutations, single site polymorphisms and differences in the splicing frequencies of the human CD13 gene in patients with hematological malignancies. Some of these mutations lead to altered trafficking of CD13 [14,15], which could have pathophysiological implications.…”