GnRH Pulse Frequency Control of Fshb Gene Expression Is Mediated via ERK1/2 Regulation of ICER
Authors: Thompson, Iain R.; Ciccone, Nick A.; Zhou, Qiongjie; Xu, Shuyun; Khogeer, Ahmad; Carroll, Rona S.; Kaiser, Ursula B.
The pulsatile release of GnRH regulates the synthesis and secretion of pituitary FSH and LH. Two transcription factors, cAMP-response element-binding protein (CREB) and inducible cAMP early repressor (ICER), have been implicated in the regulation of rat Fshb gene expression. We previously showed that the protein kinase A pathway mediates GnRH-stimulated CREB activation. We hypothesized that CREB and ICER are activated by distinct signaling pathways in response to pulsatile GnRH to modulate Fshb gene expression, which is preferentially stimulated at low vs high pulse frequencies. In the L beta T2 gonadotrope-derived cell line, GnRH stimulation increased ICER mRNA and protein. Blockade of ERK activation with mitogen-activated protein kinase kinase I/II (MEKI/II) inhibitors significantly attenuated GnRH induction of ICER mRNA and protein, whereas protein kinase C, calcium/calmodulin-dependent protein kinase II, and protein kinase A inhibitors had minimal effects. GnRH also stimulated ICER in primary mouse pituitary cultures, attenuated similarly by a MEKI/II inhibitor. In a perifusion paradigm, MEKI/II inhibition in L beta T2 cells stimulated with pulsatile GnRH abrogated ICER induction at high GnRH pulse frequencies, with minimal effect at low frequencies. MEKI/II inhibition reduced GnRH stimulation of Fshb at high and low pulse frequencies, suggesting that the ERK pathway has additional effects on GnRH regulation of Fshb, beyond those mediated by ICER. Indeed, induction of the activating protein 1 proteins, cFos and cJun, positive modulators of Fshb transcription, by pulsatile GnRH was also abrogated by inhibition of the MEK/ERK signaling pathway. Collectively, these studies indicate that the signaling pathways mediating GnRH activation of CREB and ICER are distinct, contributing to the decoding of the pulsatile GnRH to regulate FSH beta expression.
ERBB4 Confers Risk for Polycystic Ovary Syndrome in Han Chinese
Authors: Peng, Yingqian; Zhang, Wei; Yang, Ping; Tian, Ye; Su, Shizhen; Zhang, Changming; Chen, Zi-Jiang; Zhao, Han
A recent genome-wide association study (GWAS) of polycystic ovary syndrome (PCOS) in European cohorts has identified six susceptibility loci mapping to 11q22.1 (YAP1), 2p21 (THADA), 11p14.1 (FSHB), 2q34 (ERBB4), 12q21.2 (KRR1), and 5q31.1 (RAD50). The loci of 11q22.1, 2p21 and 11p14.1 have been confirmed to be associated with PCOS in Chinese; whereas the other three new loci (2q34, 12q21.2, and 5q31.1) still need to be evaluated in Chinese. This study was aimed to determine if the three new loci identified in European PCOS also confer risks for PCOS in Han Chinese. We performed a case-control genetic association study comprising 1500 PCOS cases and 1220 age-matched control subjects. Marker SNPs rs1351592 (2q34, ERBB4), rs1275468 (12q21.2, KRR1) and rs13164856 (5q31.1, RAD50) were genotyped using TaqMan-MGB probe assay. Genotyping analysis showed the allele frequency of rs1351592 in gene ERBB4 was significantly different (P = 1.05E-03) between PCOS cases and control group, and remained significant even after BMI adjustment (P-adjusted = 2.09E-04). However, the allele frequencies of the other two risk variants, rs1275468 (12q21.2, KRR1) and rs13164856 (5q31.1, RAD50), were not significantly different in the replication cohort. Our results demonstrate that ERBB4, with the strongest association in European PCOS, also confers risk for PCOS in Han Chinese.