Investigating the Role of Tbx4 in the Female Germline in Mice1

Abstract

Normal development of germ cells is essential for fertility and mammalian reproduction. Although abnormal development of oocytes or follicles may lead to primary ovarian insufficiency (POI), a disorder that causes infertility in 1% of women less than 40 yr of age, the genes and signaling pathways activated in POI are not as yet fully elucidated. Tbx4, a member of the T-box family of transcription factors, is expressed in embryonic germ cells and postnatal oocytes at all stages of folliculogenesis. To investigate the requirement for Tbx4 in the germline, we analyzed germ cell development in the absence of Tbx4. We show that primordial germ cells (PGCs) are reduced in Tbx4 homozygous null (Tbx4(-/-)) embryos at Embryonic Day (E) 10.0. Tbx4(-/-) embryos die by E10.5; to study later time points in vitro, a tamoxifen-inducible estrogen receptor Cre recombinase was used to delete Tbx4 conditional mutant alleles. In addition, Gdf9cre and Zp3cre, two oocyte-specific Cre recombinases, were used to delete Tbx4 from postnatal primordial and primary follicles, respectively. We show that in vitro differentiation of the gonad into morphologically distinct testes and ovaries occurs normally starting at E11.5 when Tbx4 is deleted. In Gdf9cre; Tbx4(fl/-) and Zp3cre; Tbx4(fl/-) adult females, primordial, primary, secondary, and antral follicles form, ovulation occurs, corpus luteum formation is normal, and the mice are fertile without any evidence of diminished ovarian reserve. Although postnatal deletion of Tbx4 in oocytes does not obviously impair fertility, it is possible that the reduction in PGCs observed in Tbx4 homozygous null mutant embryos could affect long-term fertility in adults.

A Dynamic Role of TBX3 in the Pluripotency Circuitry

“…The TBX2 subfamily (TBX2, 3, 4, and 5) has been previously implicated in the development of the reproductive system ( Douglas et al., 2012 ), and overexpressing TBX3 with the Yamanaka factors generated iPSCs with higher capacity for germline contribution ( Han et al., 2010a ). TBX3 is only expressed in genital ducts, and deletion of TBX4, a close family member of TBX3 ( Bertolessi et al., 2015 ), led to a reduced amount of primordial germ cells but with subsequent normal fertility ( Douglas et al., 2013 ). Further studies need to clarify the precise role of TBX3 for germ cell development, particularly in light of the intimate connection between DPPA3/STELLA and TBX3 ( Douglas et al., 2013 , Waghray et al., 2015 ).…”

“…TBX3 is only expressed in genital ducts, and deletion of TBX4, a close family member of TBX3 ( Bertolessi et al., 2015 ), led to a reduced amount of primordial germ cells but with subsequent normal fertility ( Douglas et al., 2013 ). Further studies need to clarify the precise role of TBX3 for germ cell development, particularly in light of the intimate connection between DPPA3/STELLA and TBX3 ( Douglas et al., 2013 , Waghray et al., 2015 ). Thus, TBX3 supports but is not absolutely required to maintain and install pluripotency and germ cell development, probably due to an alternate pluripotency network.…”

Meiotic onset is reliant on spatial distribution but independent of germ cell number in the mouse ovary

“…Busulfan (Sigma, B2635) (Douglas et al, 2013) was injected intraperitoneally (20 mg/ml in 40 μl) in pregnant E11.5 CD1 or FVB females crossed with C57/Bl6;Oct4-GFP males. Embryos were dissected from timed matings and tails genotyped by PCR.…”

Identification and Functional Evaluation of a Novel TBX4 Mutation Underlies Small Patella Syndrome

“…In addition, TBX4 mutation can lead to childhood onset pulmonary arterial hypertension (PAH) with common clinical features including pulmonary capillary dysplasia, acinar dysplasia, respiratory failure, and in severe cases, death [9]. A large number of studies have shown that Tbx4 −/− embryos die by E10.5 and Tbx4 deficiency affects the outgrowth of hindlimb indicating a key role of Tbx4 in the formation of the hindlimb [10][11][12].…”