SARs do not impair position-dependent expression of a kit/lacZ transgene.

We have cloned and sequenced 4.2 kb of the murine c-kit promoter region. Analysis of transgenic embryos for a kit/lacZ fusion gene showed (i) an unexpected expression in the neural retina, and (ii) an unusual sensitivity to position effects. This indicates that major c-kit tissue specific regulating elements lie outside the proximal promoter. We took advantage to the intrinsic properties of the kit/lacZ transgene to investigated the potential of scaffold attachment regions (SARs) to confer position-independence on gene regulation in an in vivo context. No SAR-dependent isolation of the kit/lacZ transgene was found in the transgenic embryos, indicating a limited capacity of SAR sequences to buffer the effect of flanking sequences on transgene expression.