A novel loss-of-function variant in STAT1 causes Mendelian susceptibility to mycobacterial disease
Kunlun Lv1, Zhuoqing Gong1,2, Yiting Fu1
1Dermatology Hospital, Southern Medical University, Guangzhou, China.
Introduction:
Mendelian Susceptibility to mycobacterial disease (MSMD) is a rare inherited immunodeficiency disorder characterized by increased susceptibility to atypical mycobacterial infections induced by defective IFN-γ pathway.
Methods:
We report three patients from a family presenting with multiple osteolytic lesions and cutaneous granulomas due to Mycobacterium marinum infections. Functional studies, including Western blotting and immunofluorescence, assessed phosphorylation and nuclear translocation of the mutant STAT1-Ile707Thr in eukaryotic overexpression systems. A luciferase reporter assay evaluated its transcriptional activity. Additionally, structural analysis using AlphaFold3 predicted the variant's functional impact.
Results:
A novel STAT1 variant (c.2120T>C, p.Ile707Thr) was identified. The STAT1-Ile707Thr mutant exhibited reduced phosphorylation and impaired nuclear translocation compared to wild-type STAT1. The luciferase assay confirmed decreased transcriptional activity. AlphaFold3-based cluster analysis supported a loss-of-function effect of the mutant.
Discussion:
This study expands the spectrum of STAT1 variants and microbial pathogens associated with MSMD.
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