Do promoters selected in mice translate to primates and humans?

The therapeutic target may be conserved between mice and humans, but the regulatory DNA controlling gene expression often is not. This makes promoter selection much harder to translate across species than many researchers expect.

A synthetic AAV promoter library showed that only about 25% of promoters that targeted the desired cell class in mice retained that targeting in macaques and humans. In contrast, non-human primates predicted human performance much more reliably (Jüttner, Roska et al., Nature Neuroscience, 2019). The biggest translation gap is therefore rodent to primate and not primate to human.

This reflects our own experience. There is often a trade-off between tissue specificity and cross-species conservation, which is why we prefer to screen promoter libraries in non-human primates or human-relevant systems such as organoids whenever possible.

This species gap is rooted in evolutionary biology, with enhancers evolving much faster than promoters. While promoters are often conserved across mammals, enhancers are frequently gained, lost, or rewired.

Villar et al. (Cell, 2015) showed extensive enhancer turnover across mammalian species. Likewise, only 10–15% of key hepatic transcription factor binding events are shared between mouse and human, despite the transcription factors themselves being highly conserved.

When designing SuRE™ libraries for murine screening, we take this into account. Promoter-proximal regulatory elements are generally more likely to retain function across species than distal enhancers, making them better starting points when translation is important.

DNA sequence strongly influences promoter activity, but sequence alone does not determine performance. Episomal assays cannot fully reproduce the chromatin environment, three-dimensional genome organization, and epigenetic regulation that shape expression in vivo.

For this reason, selecting the right MPRA assay format is just as important as selecting the promoter itself. The assay should mimic the intended therapeutic context as closely as possible.

Whenever feasible, we prioritize human-derived sequences tested in human-relevant models over promoters that performed well only in rodents. If murine screening is necessary, we typically validate promising candidates in non-human primates before advancing to a single lead promoter.

Human-derived regulatory elements begin with transcription factor binding sites and chromatin compatibility optimized for the human genome, reducing—but not eliminating—translation risk. Well-designed synthetic promoters can achieve comparable performance, provided they are selected in the appropriate biological context.

Talk to us. If your endpoint is human, we can build a human-first selection and a translation checkpoint into the design.