Novel Mutations in the β2 Integrin Gene (ITGB2) in a Moderate Leukocyte Adhesion Defect type 1 Patient

Background: Leukocyte adhesion deficiency type 1 (LAD1) is an autosomal recessive disorder caused by reduced expression or function of CD18. It was well accepted that LAD1 resulted from mutations in the gene for the integrin β2 subunit. Methods: We reported a moderate LAD1 patient with 2 novel ITGB2 mutations, and further investigated the role of the 2 mutations on the expression and function of CD18 by gene transfection. Results: The 2 novel mutations included a frameshift deletion viz c.954G del, which was considered as a major pathogenic gene for the patient, and a missense mutation viz c.1802C>A (Cys601Phe), which caused a damaging effect on the ITGB2 protein. There was no significant difference in protein expression between 293 T cells with mutant ITGB2 p.601C>F and 293 T cells with wild type ITGB2. When investigating the cellular location of the mutant ITGB2 in HeLa cells, we found that the mutant ITGB2 (p.601C>F) protein could not locate to the cell membrane. This indicated that the mutant ITGB2 protein could not perform its function at cell membrane level. Conclusion: The 2 novel ITGB2 mutations affected the expression and function of CD18 and might be pathogenic genes for LAD1.