Two nonsense GLI3 variants are associated with polydactyly and syndactyly in two families by affecting the sonic hedgehog signaling pathway

Background: Polydactyly and syndactyly arc congenital limb deformities, segregating in an autosomal-dominant fashion. The variants in the G1,13 gene are closely related to congenital limb malformations. However, the causes underlying polydactyly and syndactyly are not well understood. Methods: We conducted a whole-exome sequencing on two four-generation Chinese families with polydactyly and syndactyly. Then c.2374C>T and c.1728C>A mutant plasmids were transfected to HEK293T cells and mice limb bud cells to explore the functional consequences of these variants. Western blot and real-time quantitative PCR were used to analyze the expression of GLI3 and Shh. Results: In these two families, the known GLI3 variant (NM_000168.6:c.2374C>T) and the novel GLI3 variant (NM_000168.6:c.1728C>A) contributed to polydactyly and syndactyly. Additionally, the GLI3 c.2374C>T mutant plasmid led to truncated GLI3 protein, and the GIB c.1728C>A mutant plasmid led to degraded GLI3 protein. Simultaneously, we demonstrated that the GLI3-mutant plasmids led to decreased Shh expression in mice limb bud cells. Conclusion: We demonstrated that the novel GLI3 variant (c.1728C>A) and known GL13 variant (c.2374C>T) contributed to the malformations in two four-generation pedigrees with polydactyly and syndactyly by affecting SHH signaling.