Of the four PKP2-related genes DAG1, DAB2IP, and CTBP2 in Fam1 are associated with PKP2 through the GO BP process “negative regulation of cell migration”, while TCF25 is associated with PKP2 through the GO BP process “heart development”. The variants in all four genes are predicted neutral by PROVEAN, and all but the one in CTBP2 are rare. The highest ranking PKP2-related gene in Fam1 is DAG1, which encodes for dystroglycan, a central component of the dystrophin–glycoprotein complex (DGC). Dystroglycan is post-translationally cleaved into α- and β-dystroglycan subunits . α-dystroglycan is an extracellular protein involved in the interactions between DGC and extracellular matrix components, while β-dystroglycan contains a single transmembrane domain and a C-terminal cytoplasmic tail. The DAG1 candidate substitution ENSP00000312435.2:p.Leu86Phe is located in the α-dystroglycan N-terminal region, where the leucine side chain is solvent exposed on the side of a Ig-like domain . The position is in close proximity to Thr63, identified as a O-glycosylation  (see Additional file 1: Fig. S1). The variant was predicted to stabilize protein structure by MAESTROweb (ΔΔG = −0.231, confidence = 0.9). For the other three candidate genes, no protein structure was available in PDB, so predictions with MAESTROweb could not be computed.