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Bidirectional signaling between oocytes and granulosa cells is required for normal folliculogenesis. Oocyte-secreted members of the transforming growth factor beta (TGFB) family, growth differentiation factor 9 (GDF9), and bone morphogenetic protein 15 (BMP15) are well-known mediators of granulosa cell function. Deletion in granulosa cells of Smad4, the common SMAD mediating all canonical TGFB-related protein signals, results in infertility. Reciprocal signaling by granulosa cell-expressed TGFB family ligands, such as activin, to the oocyte during follicle development has been proposed but not tested in vivo using conditional knockout mice. Therefore, we generated two oocyte-specific conditional knockout models for the common SMAD, Smad4, using cre recombinase expression from either the zona pellucida 3 (Zp3) or Gdf9 promoter. Cre expression from the Gdf9 promoter occurs at a slightly earlier time point in follicle development than from Zp3. Deletion of Smad4 using Zp3cre had no effect on fertility, while deletion of Smad4 with Gdf9icre resulted in a slight, but significant, reduction in litter size. These mouse models suggest a novel, although minor, role for Smad4 in the oocyte restricted to the primordial follicle stage.

Novel pathways in polycystic ovary syndrome (PCOS) are being identified in gene expression studies in PCOS tissues; such pathways may contain key genes in disease etiology. Previous expression studies identified both dickkopf homolog 1 (DKK1) and DnaJ (Hsp40) homolog, subfamily B, member 1 (DNAJB1) as differentially expressed in PCOS tissue, implicating them as candidates for PCOS susceptibility. To test this, we genotyped a discovery cohort of 335 PCOS cases and 198 healthy controls for three DKK1 single nucleotide polymorphisms (SNPs) and four DNAJB1 SNPs and a replication cohort of 396 PCOS cases and 306 healthy controls for 1 DKK1 SNP and 1 DNAJB1 SNP. SNPs and haplotypes were determined and tested for association with PCOS and component phenotypes. We found that no single nucleotide polymorphisms were associated with PCOS risk; however, the major allele of rs1569198 from DKK1 was associated with increased total testosterone (discovery cohort P = 0.0035) and dehydroepiandrosterone sulfate (replication cohort P = 0.05). Minor allele carriers at rs3962158 from DNAJB1 had increased fasting insulin (discovery cohort P = 0.003), increased HOMA-IR (discovery cohort P = 0.006; replication cohort P = 0.036), and increased HOMA-%B (discovery cohort P = 0.004). Carriers of haplotype 2 at DNAJB1 also had increased fasting insulin, HOMA-IR, and HOMA-%B. These findings suggest that genetic variation in DKK1 and DNAJB1 may have a role in the hyperandrogenic and metabolic dysfunction of PCOS, respectively. Our results also demonstrate the utility of gene expression data as a source of novel candidate genes in PCOS, a complex and still incompletely defined disease, for which alternative methods of gene identification are needed.