Microscopy of sectioned neonatal mouse ovaries established the predominance of primordial follicles in Day 3 samples and the predominance of primary follicles by Day 8. To identify genetic determinants of the primordial to primary follicle transition, the transcriptome of Day 1 or Day 3 mouse ovaries was contrasted by differential display with that of Day 8 ovaries. This manuscript examines one of the up-regulated genes, the novel Nalp14 gene, whose transcript displayed 18- and 127-fold increments from Day 1 to Days 3 and 8, respectively. First noted by in situ hybridization in oocytes encased by primary follicles, Nalp14 transcripts were continuously expressed through the preovulatory stage. The transcripts declined when meiotic maturation resumed, and they were markedly diminished by the 2-cell embryo stage. The corresponding 3281-base pair, full-length cDNA coded for a 993 residue/104.6-kDa germ cell-specific protein. A member of the multifunctional NACHT NTPase family, the NALP14 protein featured 14 iterations of the leucine-rich-repeat domain, a region implicated in protein-protein interaction. Protein BLAST analysis of the NALP14 sequence revealed 2 previously reported germ cell-specific homologs (i.e., MATER [Maternal Antigen That Embryos Require], RNH2 [RiboNuclease/Angiogenin Inhibitor 2], and NALP4c). The structural attributes, expression pattern, and cellular localization of MATER and RNH2 largely conformed to those reported for NALP14.