Figure 1.

Generation of transgenic mice expressing the ALV receptor. (A) A schematic of the transgene cassette used to express TVA indicates the positions of the 5′ (−2738) and 3′ (+330) ends of the GP-Ibα regulatory sequence ligated to 950 bp of tv-a cDNA. Numbering is assigned relative to “0” for the native GP-Ibα transcription start site. The 330-bp of untranslated GP-Ibα sequence includes the first exon and part of the second exon (░⃞) separated by the first intron (■). The horizontal arrow indicates the transcribed message. Translation begins with a methionine at the 5′ end of the tv-a cDNA. Arrowheads indicate the positions of primers used for RT-PCR. (B) A founder mouse positive for the transgene by Southern blot analysis, no. 9562, was bred with nontransgenic littermates. RNA was isolated from the bone marrow of a transgene-containing offspring (9562 “+”) and a nontransgenic littermate (9562 “−”) and was subjected to RT-PCR without (−) and with (+) reverse transcriptase in the reaction. The 420-bp band indicative of TVA mRNA (arrow) is seen in lane 2. The 420-bp signal (lane 2) is absent when reverse transcriptase is not included in the RT-PCR reaction (lane 1). Bone marrow from mice lacking the transgene do not express TVA mRNA (lanes 3 and 4). DNA size markers (bp) are indicated on the left.