Two Nonsense GLI3 Variants Are Identified in Two Chinese Families With Polydactyly.

Background: Polydactyly is a prevalent limb deformity with an autosomal dominant inheritance pattern, manifesting in both syndromic and nonsyndromic forms. It exhibits significant etiological and clinical diversity. This study aims to identify the pathogenic cause in two patients with sub-PHS (sub-Pallister-Hall Syndrome) and PAP (postaxial polydactyly), respectively, from two Chinese pedigrees.

Methods: Exome sequencing was performed on patients to screen for potential pathogenic variants. Subsequently, these variants were validated by Sanger sequencing. The c.3342dupC and c.4431dupT mutant plasmids were transfected into HEK293T cells, and the effects of GLI3 mutations on transcription and protein levels were analyzed via qRT-PCR and Western blot. Additionally, Swiss Model was utilized to predict the effects of mutations on protein tertiary structure.

Results: The mutations of GLI3 (NM_000168.6: c.3342dupC; p. A1115Rfs*14) (NM_000168.6: c.4431dupT; p. Glu1478Ter) were identified in affected individuals. These mutations were present exclusively in the patients and absent in the healthy individuals. No significant difference in transcription levels between the mutations and wild type was observed. Functional analysis revealed that the truncated variants p. A1115Rfs*14 and p. Glu1478Ter exhibited reduced molecular weight and potential functional impairment due to protein retention.

Conclusion: The mutations p. A1115Rfs*14 and p. Glu1478Ter in GLI3 may account for sub-PHS and PAP in the two patients, respectively. This finding expands the mutation and phenotype spectrum associated with GLI3, providing valuable insights for the clinical diagnosis of polysyndactyly.