- A homeobox gene, HLXB9, is the major locus for dominantly inherited sacral agenesis. Ross, A.J., Ruiz-Perez, V., Wang, Y., Hagan, D.M., Scherer, S., Lynch, S.A., Lindsay, S., Custard, E., Belloni, E., Wilson, D.I., Wadey, R., Goodman, F., Orstavik, K.H., Monclair, T., Robson, S., Reardon, W., Burn, J., Scambler, P., Strachan, T. Nat. Genet. (1998)