Disclosed are transgenic cells trasfected with pituitary tumor transfer gene (PTTG)-­containing expression vectors and uses therefor. The nucleic acids may be operatively linked to a vector, optionally provided with control and expression sequences and/or being carried by a host cell. In one embodiment, the host cell is a thyroid stimulating hormone (TSH)-sensitive cell transfected with an expression vector comprising a DNA segment encoding functional PTTG, wherein the cell overexpresses PTTG in response to TSH. Also disclosed is an in vitro cell model for the study of genetic regulation mediated by PTTG in a mammalian cell wherein PTTG expression can be modulated by exposing the cell to TSH or estrogen. In one embodiment, the cell model is used to study the effect of PTTG expression on NIS expression or to modulate NIS expression.