We investigate the etiology of VACTERL association. 

Blood samples in patients with VACTERL association and in his parents were collected for exon sequencing and analysis. Animal and molecular experiments including the zebrafish injections and morpholino, ChIP sequencing and ChIP PCR was conducted to detect and confirm the target gene.

We identify a novel missense mutation in the MED14 gene (p. Ile550Val) located on the X chromosome in a patient and his family. Importantly, med14 knockout zebrafish embryos and neonatal mice carrying the corresponding mutation display phenotypes characteristic of VACTERL association. Further investigation reveals that the Ile-to-Val mutation in MED14, the largest subunit of the Mediator complex, impairs the interaction between the Mediator and RNA polymerase II. 

Our work identifies a critical X-linked mutation that led to the development of VACTERL-like symptoms.