Expression of Notch ligands in primary mouse stromal cell cultures. RT-PCR analysis of Delta 1 (D1), Jagged 1 (J1), and Jagged 2 (J2) mRNAs in primary murine stromal cell culture. RT-PCR was performed on cultures that contained no visible hematopoietic elements (top panel) and on day 13.5 mouse embryo RNA (bottom panel), with (+) or without (−) reverse transcription. Products were analyzed on a 2% agarose gel. Lane M contains a pBR322 HaeIII marker (Sigma), the visible fragment sizes are 587, 540, 504, 458, 434, 267, 234, 213, 192, and 184 bp. All RT-PCR products were of the predicted size and their identity was further confirmed by sequencing.