Tex19, a Mammalian-specific Protein with a Restricted Expression in Pluripotent Stem Cells and Germ Line

Although the properties of embryonic stem (ES) cells make these cells very attractive in the field of replacement therapy, the molecular mechanisms involved in the maintenance of their pluripotency are not fully characterized. Starting from the observation that most pluripotent markers are also expressed by spermatogonia stem cells, we identified Tex19 as a new potential pluripotency marker. We show that Tex19 is a mammalian-specific protein duplicated in mouse and rat, renamed Tex19.1 and Tex19.2, whereas only one form is found in human. In mouse, both forms are localized on chromosome 11 and transcribed in opposite directions. Tex19 proteins are well conserved, showing two highly conserved domains that do not present any similarity with any other known domains. We show that Tex19.2 is specifically detected in the male somatic gonad lineage, whereas Tex19.1 expression is very similar to that of Oct4. Transcripts are maternally inherited, and expression starts as soon as the early embryo and later is limited to the germ line. Tex19.1 transcripts were also detected in mouse pluripotent stem cells, and expression of Tex19.1, like that of Oct4, decreases after murine embryonic stem and germ cell differentiation. Human TEX19 was more closely related to murine Tex19.1 and was also detected in adult testis and in undifferentiated ES cells. By immunofluorescence, we found that Tex19.1 protein localizes to the nucleus of mouse ES and inner cell mass cells. All these results suggest that Tex19.1, as well as human TEX19, could be a new factor involved in the maintenance of self-renewal or pluripotency of stem cells.