Expression of the insulin-like growth factor II gene in the choroid plexus and the leptomeninges of the adult rat central nervous system.

The rat insulin-like growth factor II gene, encoding a fetal somatomedin, expresses a multitranscript family in embryonic/fetal tissues and in the adult brain and spinal cord. By performing in situ hybridization on tissue sections of adult brain and spinal cord, we have found that these transcripts are not expressed in neural or glial cells but are expressed in the epithelium of the choroid plexus of each cerebral ventricle and in the leptomeninges. We propose that the choroidal epithelial cells synthesize and secrete insulin-like growth factor II into the cerebrospinal fluid.