Advanced computational analysis of CD40LG variants in atypical X-linked hyper-IgM syndrome

X-Linked Hyper-IgM Syndrome is caused by pathogenic variants in CD40LG. Three patients with atypical clinical and immunological features were identified with variants in CD40LG requiring further characterization. Flow cytometry was used to evaluate CD40L protein expression and binding capacity to a surrogate receptor, CD40muIg. Though functional anomalies were observed, there was still a lack of clarity regarding the underlying mechanism. We developed structural models for wild-type and the three variants of CD40L protein observed in these patients (p. Lys143Asn, Leu225Ser and Met36Arg) to evaluate structural alterations by molecular mechanic calculations, and assess protein movement by molecular dynamic simulations. These studies demonstrate that functional analysis of variants of unknown significance in CD40LG can be supplemented by advanced computational analysis in atypical clinical contexts. These studies in combination identify the deleterious effects of these variants and potential mechanisms for protein dysfunction.

Automated summary

X-Linked Hyper-IgM Syndrome results from pathogenic variants in CD40LG gene. We identified three patients with atypical clinical and immunological features, harboring CD40LG variants that require further characterization. Flow cytometry was used to assess CD40L protein expression and binding capacity to CD40muIg. Despite functional anomalies, the underlying mechanism remained unclear. By developing structural models and performing molecular mechanic calculations and dynamic simulations, we demonstrated that advanced computational analysis can supplement functional analysis of variants of unknown significance in CD40LG in atypical clinical contexts. These combination studies identified deleterious effects and potential mechanisms for protein dysfunction.