Northern blots. (a) The mahoganoid 3.9 kb transcript is expressed in all tissues tested. A 5.2 kb transcript is also seen in brain, kidneys, and liver. Only kidney showed a faint transcript of 1.9 kb. (b) The retrovirus insertion in md and md2J produces several aberrantly sized transcripts: 5.9 kb/5.5 kb/4.1 kb/2.2 kb in md and 12.0 kb/3.6 kb in md2J. Skel. Mus., skeletal muscle.