Pax-6, Prox 1, and Chx10 homeobox gene expression correlates with phenotypic fate of retinal precursor cells.
OBJECTIVE
To study the expression patterns of the homeobox genes Pax-6, Prox 1, and Chx10 during chick retinal development in vivo and in vitro.


METHODS
Sections of paraformaldehyde-fixed, paraffin-embedded eyes were obtained at a range of developmental stages. In situ hybridization was carried out on tissue sections using digoxigenin-labeled sense and antisense RNA probes that recognize chicken Pax-6 and Prox 1 (whose sequences were already available), and chicken Chx10 (which was cloned and sequenced as part of this study). Selected developmental stages were also studied by immunocytochemistry with antibodies against Pax-6 and Prox 1, and by Northern blot analysis using 32P-labeled probes.


RESULTS
Until embryonic day (ED) 5, in situ hybridization shows widespread, diffuse distribution of all three genes. Between ED 6 and ED 8, however, they acquire distinct, topographically specific patterns of expression. The Prox 1 signal is predominantly expressed in the prospective horizontal cell layer of the neuroepithelium, decreases vitreally, and is absent from ganglion cells and the prospective photoreceptor layer. Pax-6 is strongly expressed only in the prospective ganglion-cell and amacrine-cell regions at the same stages, and is not detected in prospective photoreceptors. Chx10 expression becomes concentrated in the future bipolar-cell region of the inner nuclear layer. Similar patterns are maintained by ED 15 through ED 18, after cell differentiation has taken place. Pax-6 and Prox 1 immunoreactive materials showed nuclear localization and a pattern of laminar distribution equivalent to that seen by in situ hybridization.


CONCLUSIONS
These results suggest that the differentiated fate of retinal precursor cells may be influenced by Pax-6, Prox 1, or Chx10, this hypothesis is now being tested using dissociated chick embryo retinal cell cultures.
Belecky-Adams
T
T
Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-9257, USA.
Tomarev
S
S
Li
H S
HS
Ploder
L
L
McInnes
R R
RR
Sundin
O
O
Adler
R
R
D000595:Amino Acid Sequence; D000818:Animals; D030161:Avian Proteins; D001483:Base Sequence; D015152:Blotting, Northern; D002454:Cell Differentiation; D019070:Cell Lineage / Q000502:physiology*; D002642:Chick Embryo; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D005136:Eye Proteins; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000096:biosynthesis* / Q000235:genetics; D017403:In Situ Hybridization; D051379:Mice; D008969:Molecular Sequence Data; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D010641:Phenotype; D015347:RNA Probes; D011817:Rabbits; D012097:Repressor Proteins; D012160:Retina / Q000196:embryology / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013234:Stem Cells / Q000502:physiology; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D025521:Tumor Suppressor Proteins; D000098551:Prospero-Related Homeobox 1 Protein
D030161:Avian Proteins; D004268:DNA-Binding Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; D015347:RNA Probes; D012097:Repressor Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C088975:Vsx2 protein, mouse; D000098551:Prospero-Related Homeobox 1 Protein