Early onset leprosy reveals a joint effect of LRRK2 and NOD2 variants

Leprosy, caused by Mycobacterium leprae, has a long incubation period and cases with age-of-onset <5 years are rare. Here, we studied a three-generational multiplex leprosy family which included monozygotic twins age <24 months suffering from paucibacillary leprosy. Whole genome sequencing identified a homozygous double mutation in the LRRK2 gene (N551K, R1398H) and a heterozygous mutation in NOD2 (R702W) as candidate variants underlying the early onset phenotype in the twins. The same amino acid substitutions had previously been identified as shared risk-modulating factors for Crohn's disease and Parkinson's disease. To evaluate the functional impact of the LRRK2 mutations, we employed genome editing in RAW264.7 cells. Cells expressing the LRRK2 variants displayed reduced respiratory burst and apoptosis following mycobacterial challenge. Moreover, the BCG-induced respiratory burst was significantly lower in LRRK2 wild-type-expressing cells transfected with NOD2 R702W compared with NOD2 wild-type constructs. Employing co-immunoprecipitation, we showed that LRRK2 and NOD2 wild-type proteins interact in RAW cells. This interaction was independent of the LRRK2 variants but strongly reduced for NOD2 R702W. However, N-glycolyl MDP-triggered RIP2 phosphorylation and NF-kB activation were additively reduced by both LRRK2 and NOD2 mutations. Finally, we observed a joint effect of LRRK2 and NOD2 variants on cytokine/chemokine secretion with the most significant reduction of secretion observed for the mutant genotypes carried by the twins. These data demonstrated the pleiotropic effects of LRRK2 and NOD2 in response to mycobacterial infection consistent with a role of the identified mutations in the development of early onset leprosy.