Fig. 1.

nanos1 is expressed in adult female germ cells. RNA in situ hybridization reveals that at 21 dpf (A and B) and 35 dpf (C and D). nos1 expression (A and C) appears to be restricted to perinuclear stage oocytes (arrows) as compared to vasa (B and D) that appears to be expressed in both perinuclear stage oocytes (p.o.) as well as germ cells that are less than 20μm in diameter (arrow in D). (E) RNA in situ hybridization of a transverse section through a 2 month old female zebrafish reveals that nos1 is expressed at high levels in early stage oocytes (oriented dorsal up). In stage Ib oocytes, nos1 transcripts are enriched in a spherical cytoplasmic structure that resembles the Balbiani body (arrow). (F) In adult ovaries, vasa expression reveals that early stage oocytes localize to a ventral zone on the ovarian surface (arrow; ovary is oriented with anterior to the left and dorsal up). (H) Higher magnification of region boxed in (F) reveals an overall organization of early stage oocytes within this ventral zone, with stage Ia oocytes located dorsal to stage Ib oocytes. Similar to nos1, vasa RNA is also enriched in spherical cytoplasmic structures within stage Ib oocytes (arrow). (G) nos1 is highly expressed in stage Ib oocytes, but is either not expressed in clusters of stage Ia oocytes that localize to the ventral zone, or is expressed at levels below our ability to detect (Compare G and H). nos1 expression can not be detected in testes by in situ hybridization (I) while vasa expression can be readily detected in developing spermatocytes (J). (K) RT-PCR analysis confirms that nos1 expression in adults is female specific. ornithine decarboxylase (odc) expression analysis is included as a positive control. (L) A confocal image of an ovary double-labeled for Vasa protein (green) and nos1 RNA (red) show that nos1 and Vasa co-localize in early stage oocytes (Ib) but not in the smallest (<20μm) Vasa-positive germ cells (arrow). Scale bars: 50 μm in A-D, L; 200 μm in E, I and J; 1 mm in F; 100 μm in E and F.