Novel dedicator of cytokinesis 8 mutations identified by multiplex ligation-dependent probe amplification

Dedicator of cytokinesis 8 (DOCK8) deficiency is an innate error of adaptive immunity characterized by recurrent infections with viruses, bacteria and fungi, very high serum IgE concentrations, and a progressive deterioration of T- and B-cell-mediated immunity. We studied the genetic and immunological features of two sisters (aged 11 and 6 yr). Mutational analysis of genomic DNA and cDNA from the patients and their parents, by a combination of PCR and bidirectional targeted sequencing, failed to localize the mutation site. However, a multiplex ligation-dependent probe amplification (MLPA) assay revealed two novel large deletions, del1-14 exons and del8-18 exons, of DOCK8 in both patients. Immunoblot analysis demonstrated that DOCK8 protein was absent from the peripheral blood lymphocytes of both patients. These data suggest that compound heterozygous del1-14 exons and del8-18 exons mutations result in a loss of function of DOCK8 protein and a typical DOCK8 deficiency phenotype.