2. Academic Validation
  3. Dual loss of p110δ PI3-kinase and SKAP (KNSTRN) expression leads to combined immunodeficiency and multisystem syndromic features

Dual loss of p110δ PI3-kinase and SKAP (KNSTRN) expression leads to combined immunodeficiency and multisystem syndromic features

  • J Allergy Clin Immunol. 2018 Aug;142(2):618-629. doi: 10.1016/j.jaci.2017.10.033.
Nigel Sharfe 1,  Ariana Karanxha 1,  Harjit Dadi 1,  Daniele Merico 2,  David Chitayat 3,  Jo-Anne Herbrick 4,  Spencer Freeman 5,  Sergio Grinstein 5,  Chaim M Roifman 6
Affiliations

Affiliations

  • 1 Canadian Centre for Primary Immunodeficiency, Immunogenomic Laboratory, Division of Immunology & Allergy, Department of Pediatrics, Hospital for Sick Children, Toronto, Ontario, Canada.
  • 2 Centre for Applied Genomics, Hospital for Sick Children, Toronto, Ontario, Canada; Deep Genomics, Inc, Toronto, Ontario, Canada.
  • 3 Clinical and Metabolic Genetics, Hospital for Sick Children, Toronto, Ontario, Canada.
  • 4 Centre for Applied Genomics, Hospital for Sick Children, Toronto, Ontario, Canada.
  • 5 The Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada.
  • 6 Canadian Centre for Primary Immunodeficiency, Immunogenomic Laboratory, Division of Immunology & Allergy, Department of Pediatrics, Hospital for Sick Children, Toronto, Ontario, Canada. Electronic address: [email protected].
PMID: 29180244 DOI: 10.1016/j.jaci.2017.10.033
Abstract

Background: We previously reported a novel syndrome characterized by combined immunodeficiency associated with severe developmental defects-subsequently known as Roifman-Chitayat syndrome (RCS; OMIM 613328). Linkage analysis identified 2 disease-associated loci.

Objectives: We sought to identify the genetic defect in these patients and characterize their immunologic cellular abnormalities.

Methods: Genetic, immunologic, protein, and cellular functional analyses were used to identify and characterize patient genetic deficiencies and aberrant patient cell behavior.

Results: Deleterious variants were found at both loci identified by linkage analysis: a homozygous stop codon in PI3-kinase p110δ (PIK3CD) and a homozygous frame shift mutation in SKAP (KNSTRN), both ablating protein expression. Patients with RCS display aberrant B-cell development, similar to p110δ-deficient mice, but also aberrant T-cell spreading, cell-cell interaction, and migration. Patients also display significant developmental abnormalities not seen in p110δ knockouts (eg, optic nerve atrophy and skeletal anomalies) that we ascribe to loss of SKAP. Aberrant SKAP expression can prolong anaphase and this may contribute to developmental defects. However, we also identified microtubule-associated protein 4 microtubule-binding protein as a novel SKAP-binding partner and show that it undergoes relocalization in patient T cells, with associated areas of aberrant microtubule hyperstabilization, likely contributing not only to the altered properties of RCS lymphoid cells but also to developmental defects.

Conclusions: The complex RCS presentation, with combined developmental and immunologic defects, is associated with a combined deficiency of 2 genes products, PI3-kinase p110δ and SKAP, both of which appear to play a significant role in the disease.

Keywords

KNSTRN; MAP4; PI3-kinase; PIK3CD; SKAP; immunodeficiency; lymphocyte; microtubule; syndromic.

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