SCGN and MODY: Highly expressed genes in this cluster include multiple secretogranins (SCGN, SCG3 (Fig. 6D) and SCG5) and chromogranin (CHGA); transthyretin (TTR), which has a key role in vitamin A/retinol transport; and several genes that carry mutations in maturity onset diabetes of the young (MODY) including KCNK16 (Graff et al. 2021); and the ISL1 transcription factor (Chen et al. 2013).