GT1-7 Cells

GT1-7 is a clonal subline of immortalized mouse hypothalamic neurons that synthesize and secrete gonadotropin-releasing hormone (GnRH), also known as luteinizing hormone-releasing hormone (LHRH). These cells were developed through genetically targeted tumorigenesis using a transgenic mouse model in which the SV40 large T-antigen was expressed under the control of the GnRH gene promoter. This strategy resulted in hypothalamic tumors from which several GnRH-secreting cell lines were derived, including GT1-1, GT1-3, and GT1-7. GT1-7 cells display a differentiated neuronal phenotype, including the expression of neuron-specific markers such as neurofilament proteins, neuron-specific enolase, synaptic vesicle-associated proteins (VAMP-2, SNAP-25), and chromogranin B. They do not express glial markers such as GFAP or myelin proteins, confirming their neuronal identity.

Functionally, GT1-7 cells express endogenous GnRH mRNA and secrete GnRH in an episodic pattern. They possess the full processing machinery to convert pro-GnRH into mature, bioactive GnRH, including the required endopeptidases, carboxypeptidases, and amidating enzymes. These cells also secrete GnRH-associated peptide (GAP), a by-product of pro-GnRH processing. Biochemical characterization has revealed multiple molecular forms of both pro-GnRH and mature GnRH within GT1-7 cells and in the culture medium, indicating active post-translational processing. The GnRH secreted by GT1-7 is biologically active, capable of stimulating LH release from anterior pituitary cells in vitro.

GT1-7 cells exhibit low migratory activity in vitro, contrasting with other GnRH cell lines such as GN11, which are derived from more developmentally immature, migratory GnRH neurons. GT1-7 cells are considered representative of post-migratory, hypothalamic GnRH neurons and form tightly connected, neurite-linked colonies in culture. Their lack of motility, coupled with mature neuronal traits and responsiveness to regulatory factors, makes them a powerful model for studying gene regulation, developmental control, and secretory physiology of hypothalamic GnRH neurons.