In melanocytes, melanosomes (vesicles containing the pigment melanin) are transported on microtubules. They are then bound by Rab27A which recruits Slac2-a and myosin Va. This complex then transfers the melanosomes from the microtubules to actin filaments. This transfer is necessary for the transport of melanosomes from the perinuclear area to the cell periphery. The loss of any one of these proteins interrupts melanosome transport and results in the hypopigmentation. However, these three proteins do not work together in other cells and RAB27A effectors may be 'mix and match.' For example, the knockout of Rab27 causes the hypopigmentation but also immunodeficiency due to deficiencies in cytotoxic killing activity in cytotoxic T cells (something that also depends on vesicle transport). While, the knockout of myosin Va does not cause immunodeficiency, but it does cause neural defects. Though some neural problems (i.e. brain damage) can be seen in Rab27A deficient children, this is thought to be a secondary effect of the immune problems, and not directly due to the lack of Rab27A. Munc13-4 has also drawn attention based on its involvement in causing bleeding manifestations in<unk> .Munc13-4 through its interactions with Rab27a appears to be important for the dense granule release from platelets. The mutated Rab27a interaction with Munc13-4 is the cause of bleeding in type 2<unk> .
Griscelli syndrome
Maroteaux–Lamy syndrome
Gianotti–Crosti syndrome
Mungan syndrome
Sugarman syndrome
Fraser syndrome
Rosselli–Gulienetti syndrome
MORM syndrome