Tissue distribution of different 5′-UTR isoforms of AC133 mRNA.AC133 isoforms were amplified by PCR and separated on a 2% agarose gel stained with ethidium bromide. Panels Aiv and Biii show expression of AC133 by RT-PCR with primers located in the 3′ distal exons common to all known AC133 isoforms in indicated tissues or cell lines. (A) Expression of exon 1A, exon 1B, and exon 1D containing isoforms of AC133 mRNA in human adult tissues is represented in panels Ai and Aii. (B) Expression of exon 1A–, exon 1B–, and exon 1D–containing isoforms of AC133 mRNA in human brain, kidney, bone marrow, fetal liver, CD34⁺ cord blood cells, and cell lines Caco-2 and NT-2 are represented in panels Bi and Bii. Results are consistent in at least 3 independent PCR reactions. (C) Northern blot analysis of total RNA isolated from Caco-2, WERI-Rb-1, and NT-2 cell lines. Equal amounts of RNA (20 μg) were loaded in each lane. Blot was hybridized with a ³²P-labeled probe for human AC133 mRNA. Size positions of RNA ladder are indicated on the right side. A ³²P-labeled probe for human glyceraldehyde 3–phosphate dehydrogenase (G3PDH) was included as an internal control for loading and is shown in the bottom line.