<i>Tex 19</i> Paralogs Exhibit a Gonad and Placenta-Specific Expression in the Mouse

Abstract

Abstract.We have previously suggested that TEX19, a mammalian-specific protein of which two paralogs exist in rodents, could be implicated in stem cell self-renewal and pluripotency. We have established here the expression profiles of Tex19.1 and Tex19.2 during mouse development and adulthood. We show that both genes are coexpressed in the ectoderm and then in primordial germ cells (PGCs). They are also coexpressed in the testis from embryonic day 13.5 to adulthood, whereas only Tex19.1 transcripts are detected in the developing and adult ovary as well as in the placenta and its precursor tissue, the ectoplacental cone. The presence of both Tex19.1 and Tex19.2 in PGCs, gonocytes and spermatocytes opens the possibility that these two genes could play redundant functions in male germ cells. Furthermore, the placental expression of Tex19.1 can explain why Tex19.1 knockout mice show embryonic lethality, in addition to testis defects. T ex19 (Testis expressed gene 19) was initially identified as testis specific through a cDNA subtraction strategy [1]. Tex19 is restricted to mammals, is present as a unique gene in humans, and has been duplicated in the mouse and rat giving rise to the paralogs Tex19.1 and Tex19.2. Through protein comparison in 11 mammalian species, two highly Tex19-conserved domains named MCP and VPTEL domains have been characterized [2]. However, none of them shares homologies with known proteins, therefore preventing any functional prediction. Interestingly, an N-Ter cysteine was recently found to be bound to Ubr2, which may help Tex19 stabilization [3].Analysis of Tex19.1 knockout (KO) mice highlights a critical role for Tex19 in spermatogenesis, where it seems to act as a repressor of transposable elements. It was also reported that about half of the homozygous pups are missing, suggesting a function of Tex19.1 in survival during the perinatal period [4,5]. It was further shown that Tex19.1 is expressed by different pluripotent stem cells such as embryonic stem (ES), embryonic germ (EG) and embryonic carcinoma cells (ECC) and that the pattern of Tex19.1 expression almost parallels that of Oct4, a canonical marker of cell pluripotency. Altogether, these latter observations suggest that Tex19.1, as well as its human ortholog, could be a new factor involved in the maintenance of self-renewal or pluripotency of stem cells. Up to now, the expression patterns of Tex19.1 and Tex19.2 have been essentially analyzed by RT-PCR [2], thus limiting the amount of information on the cell types expressing these genes.With the aim of helping to evaluate Tex19.1 and Tex19.2 functions, we decided to precisely determine their expression patterns at the cellular level by in situ hybridization (ISH) of whole mounts and/or histological sections from E (embryonic day) 7.5 to adulthood. Our results indicate notably that Tex19.1 and Tex19.2 expression patterns mostly overlap in male mice and thus that functional redundancy between these two genes could attenuate the Tex19.1 KO phenotype. Materials and Methods Embryos and go...

The genome-defence gene Tex19.1 suppresses LINE-1 retrotransposons in the placenta and prevents intra-uterine growth retardation in mice

“…2D). This suggests that Tex19.1 is expressed in the hypomethylated trophectoderm-derived components of the placenta, but not in methylated extraembryonic mesoderm-derived components (25,34) and is consistent with mRNA in situ hybridization data (36). There is also considerable overlap between IAP expression (Fig.…”

“…The hypomethylated epigenetic state of placental DNA affects gene promoters in addition to retrotransposons (27); therefore, we investigated whether this cohort of hypomethylation-sensitive germline genome-defence genes is also expressed in the hypomethylated placenta. Tex19.1 has been previously reported to be expressed in extraembryonic tissues (17,36), but analysis of multiple-tissue microarray data (32) suggests that no other known member of this group of genome-defence genes is expressed in the placenta (Fig. 2A).…”

Tex19 paralogs are new members of the piRNA pathway controlling retrotransposon suppression

“…In the mouse, Tex19.1 and Tex19.2 expression is restricted to the germ line and the placenta (Celebi et al, 2012). Analyses of Tex19.1KO mice have previously highlighted a variable phenotype.…”

“…unpublished observations). Considering the overlapping profile of Tex19.1 and Tex19.2 expression (Celebi et al, 2012), we wondered whether there was any functional redundancy between the two genes in testes. We therefore generated conditional double KO mice for Tex19.1 and Tex19.2 genes, which exist as tandem duplication (Fig.…”

“…Later on, they are co-expressed from embryonic day (E)13.5 until adulthood in testes. However, only Tex19.1 transcripts are present in developing and adult ovaries as well as in the placenta (Celebi et al, 2012). Tex19.1-knockout (Tex19.1KO) mice show a variable degree of male infertility due to impaired meiosis associated with an upregulation of MMERVK10C retrotransposon expression (Öllinger et al, 2008;Tarabay et al, 2013).…”