Restricted expression of β1 tubulin.

Immunoblot analysis of (A) adult mouse tissues (Br, brain; Ht, heart; Lu, lung; Ki, kidney; Sp, spleen; Li, liver; Mu, muscle; BM, bone marrow) and (B) normal purified megakaryocytes and nonmegakaryocytic cells, using β1 tubulin-specific antiserum or monoclonal antibodies against GAPDH or all β tubulin isoforms (pan β tubulin). (C) Immunohistochemistry of adult mouse tissues using β1 tubulin-specific antiserum. Cellular staining in bone marrow and spleen is confined to a subset (arrowheads) of mature megakaryocytes (arrows point to unstained megakaryocytes). In lung, the signal derives from blood platelets within the abundant vasculature, occasionally detected as microthrombi (>). Background staining with the secondary antibody alone was negligible and is not shown. Scale bars: bone marrow, 300 μm; spleen and lung, 150 μm. (D) In the spleen, staining is noted both in megakaryocytes (arrow) and in particles most consistent with blood-derived platelets (arrowheads). Scale bar, 50 μm.