Northern blot analysis of RNA prepared from the major murine organs. Total RNA was isolated from nine organs of adult mice and electrophoresed through a 1% agarose/formaldehyde denaturing gel. After electrophoresis, the RNA was transferred to a nitrocellulose membrane and hybridized with a radiolabeled probe of the murine GP Ibα coding sequence.19 A representative photograph of the autoradiograph obtained after hybridization and washing documents an RNA species of 2.7 kb in RNA prepared from bone marrow of a mouse femur. The size of the RNA is consistent with the predicted size of the transcript encoding mouse GP Ibα (Fig 1). No other hybridizing signals were observed after a lengthy (2 weeks) exposure to x-ray film. The migrating position of an RNA molecular weight standard is shown to the left. After obtaining the autoradiograph, the nitrocellulose membrane was stripped of radioactivity and rehybridized with a radiolabeled DNA probe from the mouse 18S rRNA gene to confirm similar amounts of RNA were loaded from the different RNA preparations (lower panel).