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Dynamic and differential Oct-1 expression during early Xenopus embryogenesis: persistence of Oct-1 protein following down-regulation of the RNA.
Veenstra GJ
,
Beumer TL
,
Peterson-Maduro J
,
Stegeman BI
,
Karg HA
,
van der Vliet PC
,
Destrée OH
.
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As a first step towards the elucidation of the role of the transcription factor Oct-1 in development, we prepared a monoclonal antibody to study the spatio-temporal distribution of Oct-1 protein in vivo. Here we report differential expression of the Oct-1 gene in the Xenopus embryo both at the RNA and the protein level. Transcripts and protein are detected in ectodermal and mesodermal cell lineages, in which the expression exhibits a pattern of progressive spatial restriction in the course of development. The Oct-1 expression as reported here is not correlated with cell density or cell proliferation in the embryo. Our results suggest a role of Oct-1 in the specification and differentiation of neuronal and neural crest cells. In many other cells, the developmental decision to down regulate Oct-1 is delayed, probably due to a high stability of the protein.
pou2f1 (POU class 2 homeobox 1) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage13, lateral view, dorsal up
pou2f1 (POU class 2 homeobox 1) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 22, lateral view, anteriorright, dorsal up.
pou2f1 (POU class 2 homeobox 1) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 43, dorsal view, anteriorright.
pou2f1 (POU class 2 homeobox 1) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 17, lateral view, dorsal up.
Fig. 3. Localization of Oct-I transcripts in Xenopus embryos as-established by whole mount in situ hybridization. Unless indicated otherwise, photographs show lateral views of embryos oriented with the anterior side to the right. See Table 1 for a key to the capital-indicated embryonic structures. (A) Animal view of an early blastula stage (stage 6.5) embryo. (B) Stage 17 embryo (neurula stage). (C) Embryo of stage 24. (D) Tailbud stage (stage 28) embryo. (E) Stage 32 embryo (tailbud stage). (F) Tadpole stage (stage 41) embryo. The eye is pigmented; barely any transcripts are detected at this stage. (G) Dorsal view of the stage 28 brain. Compare Fig. 4E. (H) Dorsal view of the stage 36 brain.
Fig. 4. Localization of Oct-I (pou2f1) protein in Xenopus embryos as determined by whole mount immunohistochemistry using MAb 12F11 (pou2f1 Ab1). Unless indicated otherwise, all panels represent complete maximum projections of embryos that are oriented with the anterior side to the right. See Table I for a key to the capital-indicated embryonic structures. (A) Lateral view of a gastrula stage embryo (stage 13).Arrow head points to the dorsal blastopore lip. (B) Lateral view of a neurula stage embryo (stage 17). (C) Stage 22 embryo (neural tube stage), lateral view. (D) Dorsal view of stage 32 (tailbud stage) embryo. (E) Embryo of stage 36, dorsal view. Compare Fig. 3G. A specific staining is observed in the lens. (F and H) Projections of, respectively, dorsal and ventral halves of the stage 43 embryo. A complete projection is presented in the Figs. 2C and 7A. Aspecific staining is observed in the lens. The fluorescence observed posteriorly in the embryo represents an artefact. (G) Projection showing a lateral view of the stage 45 brain. Wedge shows the pseudo color settings used.
Fig. 5. Spatial restriction of Oct-I expression in the neural plate. (A) Dorsal view of stage 17 embryo showing transcripts hybridizing laterally in the neural plate (arrow heads). The anterior side of the embryo is oriented to the right. (B) Anterior view of the same embryo showing that the stripes of expression (arrowheads) are connected medially at the level of the eye anlagen. Dorsal side is on the left. (C and D) Transversal sections showing Oct-l RNA and W-1 protein laterally in the posterior neural plate (arrow heads). Lower levels of Oct-I protein are observed medially in the neural plate and in the neural crest and the ectoderm (panel D).
Fig. 6. Details of Ott-I expression. (A) Parasagittal optical section of a stage 24 embryo showing the presence of W-l protein in the somites. The anterior side of the embryo is on the right. (B) Transversal section of a stage 28 embryo showing the Ocr-I transcripts being spatially restricted in the hindbrain. Furthermore, Ott-1 RNA is detected in the otic vesicle. (C-F) Frontal optical sections of the stage 43 embryo. The anterior side of the embryo is on the right. (C) Oct-1 protein is detected in the infundibulum (neurohypophysis) and the chiasmatic ridge. (D) Section more ventral in comparison with the section shown in panel C, showing Ott-I protein being present in the adenohypophysis. (E) Spatial restriction of Ocr-I expression in mid- and hindbrain. The highest levels of Dct-I protein are observed in the midbrain at the border with the hindbrain. (F) Maximum projection of frontal sections containing the otic vesicle and the cranial sensory ganglia. Roman numbers refer to the numbers of the cephalic nerves that relay in the Dct-I positive ganglia. The ganglia of the facial nerve (VII) contain relatively low levels of the protein at this stage of development. Note that the other sensory relay centers of the cephalic nerves, i.e., the olfactory bulb and the retina, also contain relatively high levels of Ott-I protein at least at some stage of development (compare Fig. 4D-G).
