title: Agammaglobulinemia and absent B lineage cells in a patient lacking the p85α subunit of PI3K.
abstract: Whole exome sequencing was used to determine the causative gene in patients with B cell defects of unknown etiology. A homozygous premature stop codon in exon 6 of PIK3R1 was identified in a young woman with colitis and absent B cells. The mutation results in the absence of p85α but normal expression of the p50α and p55α regulatory subunits of PI3K. Bone marrow aspirates from the patient showed <0.1% CD19(+) B cells with normal percentages of TdT(+)VpreB(+)CD19(-) B cell precursors. This developmental block is earlier than that seen in patients with defects in the B cell receptor signaling pathway or in a strain of engineered mice with a similar defect in p85α. The number and function of the patient's T cells were normal. However, Western blot showed markedly decreased p110δ, as well as absent p85α, in patient T cells, neutrophils, and dendritic cells. The patient had normal growth and development and normal fasting glucose and insulin. Mice with p85α deficiency have insulin hypersensitivity, defective platelet function, and abnormal mast cell development. In contrast, the absence of p85α in the patient results in an early and severe defect in B cell development but minimal findings in other organ systems.
authors.affiliation: Department of Pediatrics, University of Tennessee College of Medicine, Memphis, TN 38163, USA. mconley@uthsc.edu
authors.forename: Mary Ellen
authors.initials: ME
authors.lastname: Conley
authors.forename: A Kerry
authors.initials: AK
authors.lastname: Dobbs
authors.forename: Anita M
authors.initials: AM
authors.lastname: Quintana
authors.forename: Amma
authors.initials: A
authors.lastname: Bosompem
authors.forename: Yong-Dong
authors.initials: YD
authors.lastname: Wang
authors.forename: Elaine
authors.initials: E
authors.lastname: Coustan-Smith
authors.forename: Amber M
authors.initials: AM
authors.lastname: Smith
authors.forename: Elena E
authors.initials: EE
authors.lastname: Perez
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Murray
mesh_terms: D000361:Agammaglobulinemia / Q000201:enzymology* / Q000235:genetics* / Q000276:immunology; D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000201:enzymology* / Q000276:immunology* / Q000473:pathology; D001483:Base Sequence; D016022:Case-Control Studies; D002454:Cell Differentiation / Q000235:genetics; D058543:Class Ia Phosphatidylinositol 3-Kinase / Q000172:deficiency* / Q000235:genetics*; D018389:Codon, Nonsense; D016207:Cytokines / Q000096:biosynthesis; D004252:DNA Mutational Analysis; D003713:Dendritic Cells / Q000276:immunology; D005091:Exons; D005260:Female; D006720:Homozygote; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D010375:Pedigree; D055815:Young Adult
chemical_list: D018389:Codon, Nonsense; D016207:Cytokines; D058543:Class Ia Phosphatidylinositol 3-Kinase