Immunofluorescence panel shows staining for insulin (red) and glucagon (green) in the pancreatic islets of Langerhans. Nuclei are stained with blue. Inducible postnatal deletion of Dsp (desmoplakin) under the transcriptional control of the Cspg4 locus led to significant growth retardation. Insulin-producing beta cells and glucagon-producing alpha cells were normal. However, serum levels of IGF1 (insulin-like growth factor 1) was reduced in a gene-dose–dependent manner, and IGF1 was almost absent in the homozygous Dsp-deficient mice (exclusively in cells expressing CSPG4). Serum levels of insulin and glucose were also reduced, but the response to glucose loading was normal. See related article, page 1346.