Table 2.

RNA Binding Proteins and Transcription Factors recently implicated in Primordial Follicle Formation

Protein	Location	Known Function	Findings	Reference
DAZL	Oocytes	RBP essential for meiosis entry and progression	Mutants have impaired germ cell nest breakdown Translational regulation of Tex14 is DAZL dependent	[48]
DDX6	Oocytes	RNA Helicase	DDX6 deletion disturbs primordial follicle formation and impairs P-body like granule assembly Deletion activates the PI3K pathway causing abnormal enlargement of oocytes	[49]
ELAVL2	Oocytes	RBP, targets DDX6	Associates with mRNAs encoding components of processing bodies (P-bodies). Promotes translation of DDX6 in oocytes in nests Directs P-body like granule assembly through DDX6	[49]
FIGLA	Oocytes	Transcription Factor	Figla depletion impedes meiotic progression, causes DNA damage resulting in an increase in oocyte apoptosis. RNA seq reveals high overlap of affected genes in Figla, Lhx8, and Sohlhl null mice. FIGLA, LHX8, and SOHLH1 cooperate by direct interaction forming a nuclear complex. This network is necessary for oocyte maintenance and differentiation.	[43]
IRX3	Somatic Cells- during nest stage Oocytes- nest breakdown becomes oocyte specific post follicle formation	Transcription Factor	Extending IRX3 expression in somatic cells post nest breakdown does not affect fertility Loss of Irx3 alone causes a reduction follicle number and infertility	[45, 46]
IRX5	Somatic Cells- during nest stage and post follicle formation, extinguishes before onset of puberty Oocytes- during nest breakdown	Transcription Factor	A single knockout Irx5 resulted in no significant difference in ovarian phenotype mice displayed sub-fertility later in life	[45, 46]
LHX8	Oocytes	Transcription Factor	RNA seq reveals high overlap of affected genes in Figla, Lhx8, and Sohlh1 null mice. FIGLA, LHX8, and SOHLH1 cooperate by direct interaction forming a nuclear complex. This network is necessary for oocyte maintenance and differentiation.	[43]
SOHLH1	Oocytes	Transcription Factor	RNA seq reveals high overlap of affected genes in Figla, Lhx8, and Sohlhl null mice. FIGLA, LHX8, and SOHLH1 cooperate by direct interaction forming a nuclear complex. This network is necessary for oocyte maintenance and differentiation.	[43]
SP1	Oocytes and Somatic Cells	Transcription Factor	Crucial for pregranulosa cell development and primordial follicle formation. Knockdown suppressed nest breakdown, oocyte apoptosis and primordial follicle formation, but by puberty oocytes in nests underwent cell death. SP1 governs and recruits Foxl2+ pregranulosa cells mainly by binding directly to the Notch2 gene promoter.	[47]