Studies have reported that filopodia may undergo more than one stage of development before becoming spines, and that clustering of certain proteins such as Drebrin may be used to identify the maturity of filopodia.
This sequence motif exists in group 1 metabotrophic glutamate receptor (mGluR1 and mGluR5), Shank, transient receptor potential canonical (TRPC) family channels, drebrin, oligophrenin, dynamin3, CENTG1, and ryanodin receptor.