Novel growth factor supporting survival of murine primordial germ cells: Evidence from conditioned medium of ter fetal gonadal somatic cells

The ter (teratoma, chromosome 18) mutation causes a deficiency of primordia l germ cells (PGCs) in ter/ter embryos from the ter congenic mouse strain a t 8.0 days post coitum (dpc). In order to analyse the function of the ter g ene, here we examined effects of conditioned medium (CM) from 14.5 dpc test icular and ovarian somatic cells of +/+, +/ter, or ter/ter genotype on mous e PGCs "mixed-cultured" with own somatic cells on feeder cells. The results showed that +/+ and +/ter CM supported survival in 9.5 and 11.5 dpc ICR PG Cs but ter/ter CM did not rescue TUNEL (terminal deoxynucleotidyl transfera se-mediated dUTP nick-end labeling)-positive apoptosis in the PGCs though i t did not affect 5-bromo-2-deoxyuridine incorporation in PGCs. This support ive substance in +/+ CM, not ter/ter CM, was characterized as soluble, heat labile, and larger than 30 kDa. We also found that several known growth fa ctors for PGCs and their receptors were expressed in ter/ter testes as well as +/+ testes, suggesting the ter function is independent. Thus, it was co ncluded that fetal gonadal somatic cells express a novel PGC growth factor (designated as TER Factor) supporting survival of PGCs not somatic cells an d that the PGC deficiency in ter/ter testes is caused by a loss of this fac tor. (C) 2001 Wiley-Liss, Inc.