DLL1 and spondylocostal dysostosis: Seven genes are responsible for the pathogenesis of SCDO to date, including delta-like canonical Notch ligand 3 (DLL3; SCDO1, OMIM 277300) [7,8], mesoderm posterior bHLH transcription factor 2 (MESP2; SCDO2, OMIM 608681) [9], LFNG O-fucosylpeptide 3-beta-N-acetylglucosaminyltransferase (LFNG; SCDO3, OMIM 609813) [10], HES family bHLH transcription factor 7 (HES7; SCDO4, OMIM 613686) [11], T-box transcription factor 6 (TBX6; SCDO5, OMIM 122600) [12], ripply transcriptional repressor 2 (RIPPLY2; SCDO6, OMIM 616566) [13], and delta-like canonical Notch ligand 1 (DLL1; SCDO7) [14].