Another distinct feature of BAF complexes is the existence of alternative subunits for many of the positions within the complex. Only one of the homologous subunits can be incorporated at each of the polymorphic positions, such that there are hundreds of theoretically possible assemblies of BAF. The subunits are not freely exchanged and are stably associated with the complex even in highly denaturing conditions in vitro (Zhao et al., 1998; Kadoch et al., 2013). As we will discuss, each unique composition can translate to a specific biological meaning which can be instructive for a particular cell fate. Distinct BAF assemblies have been found in a number of tissues (de la Serna et al., 2001; Ohkawa et al., 2006; Cvekl and Duncan, 2007; Xiong et al., 2013; Li et al., 2013; Yu et al., 2013; Lickert et al., 2004; Lessard et al., 2007; Olave et al., 2002) and it is possible that many more cell types have chromatin remodeling mechanisms tailored to their specific needs.
