The presence of the NXNL1 and five photoreceptor specific genes (ABCA4, RDH12, CNGB1, SAG and CUCA1C), whose mutations cause inherited retinal degenerations, in the list of 156 down-regulated probesets with high MI suggests that MI identifies events linked to photoreceptor dysfunction or degeneration. The gene discussed is ABCA4; the disease is retinal degeneration.