Given a cluster, we first selected the most highly enriched gene, which would often not be unique to that cluster, but highly selective for a small number of closely related clusters. Next, we added the most specific gene, based on trinarization with a PEP of 0.05. This gene was very often specific to a very small number of clusters, and using the first two genes together would often lead to fully specific marker combinations. However, sometimes adding more genes would be necessary.
