Bromodomain; WDR9 repeat I_like subfamily. WDR9 is a human gene located in the Down Syndrome critical region-2 of chromosome 21. It encodes for a nuclear protein containing WD40 repeats and two bromodomains, which may function as a transcriptional regulator involved in chromatin remodeling and play a role in embryonic development. Bromodomains are 110 amino acid long domains, that are found in many chromatin associated proteins. Bromodomains can interact specifically with acetylated lysine.