Table 1 Key observations advanced in support of neo-oogenesis in mammals, and proposed alternative explanations.

2.(i)

BrdU-incorporation in Mvh⁺ germ cells located in the OSE

[7, 10].

Mitosis in germline stem

cells.

MtDNA synthesis, and DNA recombination and repair in tardy oocytes, in the neonatal ovary.

Mvh⁺ germ cells located in the OSE [7–9].

Existence of a germinal epithelium.

Oocytes in transit across the OSE during exfoliation [54].

2.(ii)

"Oocyte-like" phenotype of cells in OSE-derived cultures [8, 9].

De novo formation of immature and secondary ocytes from stem cells.

Nondescript cells undergoing oncosis.

Small, round cells, above and below the OSE [9].

Putative female germline stem cells.

Small immune cells in the OSE [54].

"Embryoid body-like" and "blastocyst-like" structures [9] in OSE-derived cultures.

Pathenogenetic activation of de novo oocytes.

Nondescript cellular aggregates, and vesicles of OSE.

Expression of Oct4, Sox2, Nanog and c-kit by OSE derivatives [9].

Embryonic-like, germline stem cells.

Cultures containing regenerative epithelium [58].

Cell lines producing early oocytes [11].

Female germline stem cell lines.

Mixed cultures of OSE, early oocytes and/or oogonia.

2.(iii)

BU-induced depletion of the follicle pool [7, 15] and extinction of fertility.

Destruction of replicative, female germline stem cells by BU treatment, without atresia.

Induction of oocyte atresia by BU treatment; and proof of absence of female germline stem cells.

2.(iv)

EGFP⁺ cells with germ-cell markers in ovaries of CT-treated mice following BMT or PBCT [12, 13].

De novo oocytes from bone marrow-derived precursors.

Oct4-expressing macrophages; and autofluorescent, somatic cells of the ovary.

Presence of PGC and HSC in extraembryonic regions during early post-implantation development [12].

Incorporation of oocyte precursors within the haematopoietic system.

Distinct temporal and spatial niches for the origins and migration of germinal and haematopoietic lineages.

2.(v)

Replicative, unipotent oocyte-like cells [10].

Existence of female germline stem cells.

Residual oogonia induced to proliferate by specified culture conditions, and expansion of populations of functional oogonia.

Immuno-magnetic isolation of Mvh⁺ proliferating cells from disaggregated ovaries [10].

Selective purification of stem cells via Mvh binding to anti-Mvh antibody.

Harvesting of oogonia and primary oocytes due to Mvh binding to anti-Mvh antibody, or to Fc receptors on the plasma membrane of oogonia and oocytes binding to Fc moiety of antibody.

3.

Restoration of the host follicle pool in CT-treated mice following BMT [12, 13].

Stimulation of endogeneous, de novo oogenesis.

Induction of autoimmunity to ovarian antigens by CT; and rescue of fertility via tolerance restored by haematopoietic chimaerism.