Relationship of Pax6 activity levels to the extent of eye development in the mouse, Mus musculus.
In this study we extend the mouse Pax6 mutant allelic series to include a homozygous and hemizygous viable hypomorph allele. The Pax6(132-14Neu) allele is a Phe272Ile missense mutation within the third helix of the homeodomain. The mutant Pax6 homeodomain shows greatly reduced binding activity to the P3 DNA binding target. Glucagon-promoter activation by the entire mutant Pax6 product of a reporter gene driven by the G1 paired and homeodomain DNA binding target was slightly increased. We constructed mutant Pax6 genotypes such that Pax6 activity ranged between 100 and 0% and show that the extent of eye development is progressively reduced as Pax6 activity decreased. Two apparent thresholds identify three groups in which the extent of eye development abruptly shifted from complete eye at the highest levels of Pax6 to a rudimentary eye at intermediate levels of Pax6 to very early termination of eye development at the lowest levels of Pax6. Of the two Pax6-positive regions that participate in eye development, the surface ectoderm, which develops into the lens vesicle and the cornea, is more sensitive to reduced levels of Pax6 activity than the optic vesicle, which develops into the inner and outer retinal layers.
Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, D-85764 Neuherberg, Germany. favor@helmholtz-muenchen.de
Jack
J
Favor
Christian Johannes
CJ
Gloeckner
Angelika
A
Neuhäuser-Klaus
Walter
W
Pretsch
Rodica
R
Sandulache
Simon
S
Saule
Irmgard
I
Zaus
D000818:Animals; D001947:Breeding; D002874:Chromosome Mapping; D004247:DNA / Q000378:metabolism; D005123:Eye / Q000196:embryology*; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005298:Fertility; D018507:Gene Expression Regulation, Developmental; D005838:Genotype; D005934:Glucagon / Q000235:genetics; D006579:Heterozygote; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008817:Mice, Mutant Strains; D009929:Organ Size; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*
D005136:Eye Proteins; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; C000605730:PAX6 protein, human; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; D012097:Repressor Proteins; D004247:DNA; D005934:Glucagon