Transcription Factor TFAP2C Regulates Major Programs Required for Murine Fetal Germ Cell Maintenance and Haploinsufficiency Predisposes to Teratomas in Male Mice

Abstract

Maintenance and maturation of primordial germ cells is controlled by complex genetic and epigenetic cascades, and disturbances in this network lead to either infertility or malignant aberration. Transcription factor TFAP2C has been described to be essential for primordial germ cell maintenance and to be upregulated in several human germ cell cancers. Using global gene expression profiling, we identified genes deregulated upon loss of Tfap2c in embryonic stem cells and primordial germ cell-like cells. We show that loss of Tfap2c affects many aspects of the genetic network regulating germ cell biology, such as downregulation of maturation markers and induction of markers indicative for somatic differentiation, cell cycle, epigenetic remodeling and pluripotency. Chromatin-immunoprecipitation analyses demonstrated binding of TFAP2C to regulatory regions of deregulated genes (Sfrp1, Dmrt1, Nanos3, c-Kit, Cdk6, Cdkn1a, Fgf4, Klf4, Dnmt3b and Dnmt3l) suggesting that these genes are direct transcriptional targets of TFAP2C in primordial germ cells. Since Tfap2c deficient primordial germ cell-like cells display cancer related deregulations in epigenetic remodeling, cell cycle and pluripotency control, the Tfap2c-knockout allele was bred onto 129S2/Sv genetic background. There, mice heterozygous for Tfap2c develop with high incidence germ cell cancer resembling human pediatric germ cell tumors. Precursor lesions can be observed as early as E16.5 in developing testes displaying persisting expression of pluripotency markers. We further demonstrate that mice with a heterozygous deletion of the TFAP2C target gene Nanos3 are also prone to develop teratomas. These data highlight TFAP2C as a critical and dose-sensitive regulator of germ cell fate.

Elucidating human male germ cell development by studying germ cell cancer

“…This is evident in Dazl mutants, where expression of pluripotency markers persists and the germ cells eventually initiate apoptosis (Lin & Page 2005). Interestingly some of the gonadal cells in Dmrt1 mutants, as well as in animals heterozygous for Tfap2c and Nanos3 also fail to downregulate pluripotency markers after arrival in the genital ridge in the 129 genetic background (Krentz et al 2013, Schemmer et al 2013. In these mutants, the persistence of Nanog and Oct3/4 as well as other PGC and pluripotency marker genes like Dnd1, Prdm14, Lin28, cKit and Dppa3 counteracts apoptosis leading to rapid development of a germ cell tumor equivalent to a type I GCT, an early childhood tumor (Kehler et al 2004, Western 2009, Pirouz et al 2012.…”

Tpbpa mediated deletion of Tfap2c leads to deregulation of MAPK, P21, AKT and subsequent placental growth arrest

“…To this end, we performed ChIP analysis utilizing trophoblast stem cell TS-6.5 (Kubaczka et al, 2014), differentiated for 5 days as a corollary for placenta. Information about TFAP2C binding sites in the promoter region of Cdkn1a were taken from Schemmer et al (2013) and the binding site in the Dusp6 promoter region was identified by the rVista algorithm. Both were enriched for TFAP2C (Cdkn1a, 2.3×, P=0.045; Dusp6, 1.7×, P=0.032), implicating both as direct targets of TFAP2C (Fig.…”

Reprogramming of germ cells into pluripotency

“…While forced expression of Blimp1 in ESCs reduces the expression of pluripotency genes, deletion of Blimp1 in PGCs promotes the derivation of EGCs even in the absence of bFGF [52] . In addition, heterozygous Tfap2c mutant mice develop testicular teratomas against the 129/Sv background [84] . In vitro, PGClike cells induced from homozygous Tfap2c mutant ESCs show upregulation of cell cycle regulators (Cdk6) and pluripotency genes (Eras, Klf4), but downregulation of germline genes (Dmrt1, Nanos3) [84] .…”

“…In addition, heterozygous Tfap2c mutant mice develop testicular teratomas against the 129/Sv background [84] . In vitro, PGClike cells induced from homozygous Tfap2c mutant ESCs show upregulation of cell cycle regulators (Cdk6) and pluripotency genes (Eras, Klf4), but downregulation of germline genes (Dmrt1, Nanos3) [84] . Furthermore, the susceptibility locus for human testicular germ cell cancer has been found near PRDM14 [85] .…”