Mechanistic dissection of Vps45's function(s) using mutations underpinning Severe Congenital Neutropenia

Severe congenital neutropenia (SCN) is a rare haematological disorder defined by a reduction in neutrophils, the white blood cells that fight infection. SCN patients are susceptible to opportunistic bacterial infections that become life-threatening. In 2013, Stepensky and colleagues identified the first mutation in the VPS45 gene associated with SCN V, these patients displayed an increase in apoptosis (programmed cell death) in their neutrophils and resistance to treatment. Most SCN patients have regular granulocyte-colony stimulating factor (G-CSF) treatment to manage symptoms, however patients with SCN V are subject to much more invasive bone marrow transplants to treat their condition. In addition to this SCN causing VPS45 mutation, 4 more have since been identified. Until this point Vps45 had been well-characterised as a membrane trafficking protein in yeast and more recently has been implicated in autophagy, whether these functions are related to SCN is unknown.
In this project I investigated how Vps45 is involved in increased apoptosis in cells using the model organism, Saccharomyces cerevisiae (budding yeast) by characterising the different roles of Vps45. Using yeast strains with VPS45 mutations analogous to the mutations identified in SCN V patients, I used three physiological assays to investigate the role of Vps45 in membrane trafficking, autophagy and apoptosis. By dissecting the roles of Vps45 in different processes in the cell I have identified a potential model for Vps45’s role in protection from apoptosis, characterising this role of Vps45 and its known interactors in different mechanisms will eventually lead to a more suitable treatment for SCN V patients.