Schematic diagram of the mechanism for regulating rib number. a) The genome-wide association result shows that there are two significant loci on chromosomes 1 and 7 for rib number. b) The protein-protein interaction network around genes mapped to the chromosomes 1 and 7 loci (yellow nodes). The DAB2-DAB2IP and TGFB3 subnetworks overlap and are enriched for genes (red nodes) in the Wnt signaling pathway (fold enrichment = 20, Fisher’s Exact Test p-value= 9.99 × 10−16, EASE score = 2.1 × 10−14). c) Schematic graph showing somite formation (adapted from ). Vertebrae form during somitogenesis. The Wnt signaling pathway is critical for maintaining and stopping clock oscillation. d) Hypothetically, the chromosome 1 and 7 loci affect the number of ribs through an interaction between DAB2IP-DAB2-TGFB3 and the Wnt signaling pathway.