Glypican-4, previously known as K-glypican, is a GPI-linked cell surface heparan sulfate proteoglycan of the glypican gene family, that comprises 6 members at present. Its function is only partially understood at present. However, glypican-4 seems to be involved in the control of cell growth and diffe-rentiation, especially in the development of the central nervous system and the kidney. Furthermore, glypican-4 is expressed by haematopoetic stem cells and bone marrow stromal cells. Although the antiserum was prepared against a peptide from hu man glypican-4, due to the highly conserved structure and se-quence of glypican-4, antiserum anti-peptide 1 (aa88-101) was used successfully to study brain development in the mouse.