Ectopic expression of lipid homeostasis genes in rare cells of the teleost pituitary gland

Abstract

AbstractDirecting both organismal homeostasis and physiological adaptation, the pituitary is a key endocrine gland in all vertebrates. It communicates the needs of the organism to different organs by secreting hormones into the bloodstream. Here, we have used the model fish medaka to investigate the developmental dynamics in the pituitary using a comprehensive RNA-seq time series. Using expression trend analyses we show that one of the most prominent changes during sexual maturation is the strong decrease of transcripts encoding secreted lipid transport proteins, which are typically only produced by the liver. By integrating developmental trends with single-cell transcriptomics, we demonstrate that rare, previously uncharacterized cells are responsible for this expression pattern. With levels as high as for established peptide hormone-encoding genes, this ectopic expression exposes a major new mechanism in the juvenile teleost pituitary. In addition, it implies the existence of unexpected connections between endocrine communication, sexual maturation, and lipid homeostasis.