This issue of Seminars in Medical Genetics, American Journal of Medical Genetics 
Part C investigates the human diseases caused by mutations in the BAF complex 
(also known as the mammalian SWI/SNF complex) genes, particularly focusing on 
Coffin-Siris syndrome (CSS). CSS is a rare congenital malformation syndrome 
characterized by developmental delay or intellectual disability (ID), coarse 
facial appearance, feeding difficulties, frequent infections, and 
hypoplasia/aplasia of the fifth fingernails and fifth distal phalanges. In 2012, 
42 years after the first description of CSS in 1970, five causative genes 
(SMARCB1, SMARCE1, SMARCA4, ARID1A, ARID1B), all encoding components of the BAF 
complex, were identified as being responsible for CSS through whole exome 
sequencing and pathway-based genetic screening. The identification of two 
additional causative genes (PHF6, SOX11) followed. Mutations in another BAF 
complex gene (SMARCA2) and (TBC1D24) were found to cause clinically similar 
conditions with ID, Nicolaides-Baraitser syndrome and DOORS syndrome, 
respectively. Also, ADNP was found to be mutated in an autism/ID syndrome. 
Furthermore, there is growing evidences for germline or somatic mutations in the 
BAF complex genes to be causal for cancer/cancer predisposition syndromes. These 
discoveries have highlighted the role of the BAF complex in the human 
development and cancer formation. The biology of BAF is very complicated and 
much remains unknown. Ongoing research is required to reveal the whole picture 
of the BAF complex in human development, and will lead to the development of new 
targeted therapies for related disorders in the future.