Noise propagation and scaling in regulation of gonadotrope biosynthesis.
Reproductive physiology depends on the control of biosynthesis in the pituitary gonadotrope by hypothalamic gonadotropin-releasing hormone (GnRH). The responses to GnRH include activation of extracellular signal-regulated kinase (ERK) and induction of Egr1. Using population and single cell signaling assays, we investigated the signal and noise transmission through this signaling and gene circuit, analyzing data obtained from 43,775 individual cells in 40 experiments. After exposure to GnRH, phosphorylated ERK (pERK) is elevated in 50% of the cells at 1.7 (SD = 0.3) min. Studies of the cell-to-cell response showed that for both pERK and for Egr1 protein production the mean response (mu) and standard deviation (sigma) within individual cells were linearly related (sigma = kmu) and had similar values of k. To understand the basis for the scaling observed for noise propagation through this system, we determined the relationship between pERK and egr1 mRNA levels induced at varying concentration of GnRH. While both pERK and egr1 mRNA show a saturating sigmoidal relationship to the concentration of GnRH exposure, egr1 mRNA is linearly related to the levels of pERK. These results explain the basis for variation in cellular responses in an important mammalian signaling pathway leading to gene induction.
Ruf
Frederique
F
Department of Neurology, Mount Sinai School of Medicine, New York, New York, USA.
Hayot
Fernand
F
Park
Myung-June
MJ
Ge
Yongchao
Y
Lin
Gang
G
Roysam
Badrinath
B
Sealfon
Stuart C
SC
D000818:Animals; D002460:Cell Line; D003198:Computer Simulation; D051766:Early Growth Response Protein 1 / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology; D052681:Gonadotrophs / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D008954:Models, Biological; D015233:Models, Statistical; D015398:Signal Transduction / Q000502:physiology; D013269:Stochastic Processes; D015533:Transcriptional Activation
C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D007987:Gonadotropin-Releasing Hormone; D048049:Extracellular Signal-Regulated MAP Kinases