Divalent metal transporter 1 (DMT1) is critical to iron homeostasis in mammals (Gunshin et al., 2005) and mutants causing alternative splicing of DMT1 have been reported to cause hypochromic microcytic anemia (Beaumont et al., 2006; Mims et al., 2005). The aim of this study was to determine the affect of mutant-induced splicing on the cellular distribution of DMT1 (1B/IRE+) in polarized (WKPT-0293 Cl.2 (WKPT)) and non-polarized (HEK293) cell models. DMT1 was engineered that lacked exon 5 (delta E 5), mimicking the aberrant splice variant reported by Beaumont et al. (2006).

As reported previously, rat DMT1 localized predominantly to late endosomes and lysosomes when heterologously expressed in WKPT cells (Abouhamed et al., 2006). In contrast, delta E 5 mRFP-DMT1 localized in the nucleus and led to cell death after 16 hours post transfection. Similarly, mRFP-DMT1 expression in HEK293 cells presented a punctate pattern, whilst delta E 5 mRFP-DMT1 localized in the nucleus. We conclude that mutation-induced splicing events differentially affect sub-cellular localisation of DMT1 in polarized and non-polarized cells.