Kell (ECE-3), a highly polymorphic
blood group glycoprotein, displays more than 30
antigens that produce allo-
antibodies and, on red blood cells (RBCs), is complexed through a single
disulfide bond with the
integral membrane protein, XK. XK is a putative
membrane transporter whose absence results in a late onset form of neuromuscular abnormalities known as the
McLeod syndrome. Although Kell
glycoprotein is known to be an endothelin-3-converting
enzyme, the full extent of its physiological function is unknown. To study the functions of Kell
glycoprotein, we undertook targeted disruption of the murine Kel gene by homologous recombination. RBCs from Kel(-/-) mice lacked Kell
glycoprotein, Kell/XK complex, and endothelin-3-converting
enzyme activity and had reduced levels of XK. XK
mRNA levels in spleen, brain, and testis were unchanged. In Kel(-/-) mice RBC Gardos channel activity was increased and the normal enhancement by
endothelin-3 was blunted. Analysis of the microvessels of
tumors produced from LL2 cells indicated that the central portion of
tumors from wild-type mice were populated with many mature blood vessels, but that vessels in
tumors from Kel(-/-) mice were fewer and smaller. The absence of Kell
glycoprotein mildly affected some motor activities identified by foot splay on the drop tests. The targeted disruption of Kel in mouse enabled us to identify phenotypes that would not be easily detected in humans lacking Kell
glycoprotein. In this regard, the Kell knockout mouse provides a good animal model for the study of normal and/or pathophysiological functions of Kell
glycoprotein.