Figure 2. Genetic testing and pathogenicity analysis of the proband.

A: Pedigree of the family: The GUCY2D gene variant c.2512C>T: p.Arg838Cys is co-segregated between patient and normal phenotypic members in the family; B: Sanger sequencing diagram: Such a variant was not detected in both parents of the proband and was presumed to be the de novo one or the presence of germline mosaicism in one of the parents accordingly. Such a variant was detected in the proband's son (III-2); C: Conservation analysis: The GUCY2D gene variant c.2512C>T was highly conserved across species; D: Wild-type and mutant-type structure modeling of GUCY2D p.Arg838Cys. Analysis of 3D image of the protein structure revealed that amino acid No.838 changed from polar positively charged arginine mutated to polar uncharged cysteine, resulting in significant changes in the spatial structure of proteins.