Islet-1 (Isl1) is a member of the LIM/homeodomain family of transcription factors. It binds and regulates the promoters of the insulin, glucagon and somatostatin genes, and may play an important role in regulating insulin gene expression. It is central to the embryogenesis of pancreatic islets of Langerhans and is involved in the specification of motor neurons. It is expressed in subsets of neurons of the adrenal medulla and dorsal root ganglion, and in inner nuclear and ganglion cell layers in the retina.
Isl1 is essential for heart development, as its expression defines cardiac progenitor cell populations and is required for normal cardiac development and asymmetry.
Mutations in this gene have been associated with maturity-onset diabetes of the young.