Stomatin is mis-trafficked in the erythrocytes of overhydrated hereditary stomatocytosis, and is absent from normal primitive yolk sac-derived erythrocytes.

The 32 kD lipid-raft-associated membrane protein 'stomatin' is deficient from the erythrocyte membrane in the Na+-K+ leaky haemolytic anaemia, overhydrated hereditary stomatocytosis (OHSt). To date, no mutation in the gene coding for this protein has so far been found in OHSt. In this study, we have analysed the distribution of stomatin in both cultured erythroid cells from OHSt patients and in normal embryological and fetal erythroid development. In erythroid cell cultures from OHSt patients, stomatin-immunoreactivity (stomatin-IR) was present in progenitor cells but remained restricted to the area of the multivesicular complexes and the nucleus in the developing cells and was not seen in the plasma membrane. This could be consistent with the idea that stomatin is an innocent passenger in a more fundamental trafficking abnormality. In normal embryonic development, we found that, in extraembryonic (yolk sac) erythropoiesis, neither the nucleated red cells nor their enucleated mature derivatives displayed any stomatin-IR. In contrast, all haemangiopoietic progenitor cells of intraembryonic haematopoiesis, starting with the mesodermal precursors in the aorta-gonad-mesonephros region, exhibited strong stomatin-IR. The significance of this observation on these poorly understood cells is currently unclear.