RARE LYN AND BLK VARIANTS ACT IN EPISTASIS TO CAUSE HUMAN AUTOIMMUNITY.
Ms Sonia Nambadan1, Dr Tom Lea- Henry1, Dr Vicki Athanasopoulos1, Dr Morgan Downes1, Ms Jean Cappello1, Ms Isabella Bales1, Ms Bridie Moy1, Ms Thuy Nguyen Huynh1, Ms Joanne Chow1, Mrs Alamelu Vengatasalam1, Ms Jiaxi Huang1, Ms Gemma Hart1, Ms Somasundhari Shanmuganandam1, Ms Abbey Curran1, Dr Kathleen Morrisroe4, Dr Giles Walters2, Dr Richard Kitching3, Dr Simon H Jiang1
1Department of Immunology and Infectious Disease, John Curtin School of Medical Research, Australian National University, Canberra, Australia, 2Department of Renal Medicine, The Canberra Hospital, Canberra , Australia, 3Centre for Inflammatory Diseases, Monash University, Melbourne , Australia, 4Department of Rheumatology, The Canberra Hospital, Canberra , Australia
Aim: To determine the individual and epistatic effects of novel LYN and rare BLK variants in a family with complex autoimmunity.
Background: Systemic lupus erythematosus and related autoimmune diseases have a strong genetic risk. The Src B family members LYN and BLK are frequently associated with autoimmune disease. Rare gain of function (GoF) mutations in LYN are described to cause human SLE, although loss of function (LoF) BLK mutations have unclear effects on immune response. Indeed, BLK is thought to be immunologically redundant. We identify a family with complex autoimmunity with both a novel LYN and a rare BLK mutation potentially acting in epistasis.
Methods: Overexpression assays with Interferon-β (IFN-β) to detect gene activity, immunoprecipitation (IP) & western blot to assess transcriptional activity, CRISPR models of both alleles were crossed and underwent immunophenotyping, calcium flux experiments by flow cytometry, ELISA, and Hep-2 for autoantibody detection.
Results: Luciferase reporter assay identified LYN-var as a GoF variant and BLK-var as a LoF variant. We replicated orthologous mutations creating Lyn-var and Blk-var mouse strains which were then intercrossed. Lyn-var/var mice, develop antinuclear antibodies by 36 weeks. The marginal zone and marginal zone precursor cells showed significant differences in the intercrossed mice compared to that of the independent variant strains and wildtype. Lyn-var/var B cells had an increased B cell receptor calcium flux, although it was markedly reduced in the presence of Blk-var/var.
Conclusion: Here we identify novel and rare mutations in Src B family members LYN and BLK, demonstrating disturbed immune disruption from these individual alleles in mice bearing orthologous mutations. Further, we demonstrate novel pathogenic interactions between Src B family kinase members.
Presentation Slides PDF – Click here
Biography:
Sonia Nambadan is an M.Phil student in the Jiang group at the John Curtin School of Medical Research, Australian National University. She has completed a Master of Science degree in Microbiology.