Dorsoventral patterning is established in the telencephalon of mutants lacking both Gli3 and Hedgehog signaling.
Considerable data suggest that sonic hedgehog (Shh) is both necessary and sufficient for the specification of ventral pattern throughout the nervous system, including the telencephalon. We show that the regional markers induced by Shh in the E9.0 telencephalon are dependent on the dorsoventral and anteroposterior position of ectopic Shh expression. This suggests that by this point in development regional character in the telencephalon is established. To determine whether this prepattern is dependent on earlier Shh signaling, we examined the telencephalon in mice carrying either Shh- or Gli3-null mutant alleles. This analysis revealed that the expression of a subset of ventral telencephalic markers, including Dlx2 and Gsh2, although greatly diminished, persist in Shh(-/-) mutants, and that these same markers were expanded in Gli3(-/-) mutants. To understand further the genetic interaction between Shh and Gli3, we examined Shh/Gli3 and Smoothened/Gli3 double homozygous mutants. Notably, in animals carrying either of these genetic backgrounds, genes such as Gsh2 and Dlx2, which are expressed pan-ventrally, as well as Nkx2.1, which demarcates the ventral most aspect of the telencephalon, appear to be largely restored to their wild-type patterns of expression. These results suggest that normal patterning in the telencephalon depends on the ventral repression of Gli3 function by Shh and, conversely, on the dorsal repression of Shh signaling by Gli3. In addition these results support the idea that, in addition to hedgehog signaling, a Shh-independent pathways must act during development to pattern the telencephalon.
Rallu
Murielle
M
Developmental Genetics Program and the Department of Cell Biology, The Skirball Institute of Biomolecular Medicine, New York University Medical Center, 540 First Avenue, New York 10016, USA.
Machold
Robert
R
Gaiano
Nicholas
N
Corbin
Joshua G
JG
McMahon
Andrew P
AP
Fishell
Gord
G
D000818:Animals; D019521:Body Patterning / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D005865:Gestational Age; D053823:Hedgehog Proteins; D051741:Kruppel-Like Transcription Factors; D051379:Mice; D018345:Mice, Knockout; D008959:Models, Neurological; D009419:Nerve Tissue Proteins; D010641:Phenotype; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology; D043562:Receptors, G-Protein-Coupled; D015398:Signal Transduction; D000072086:Smoothened Receptor; D013687:Telencephalon / Q000196:embryology*; D015534:Trans-Activators / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D000074290:Zinc Finger Protein Gli3
D004268:DNA-Binding Proteins; C465571:Gli3 protein, mouse; D053823:Hedgehog Proteins; D051741:Kruppel-Like Transcription Factors; D009419:Nerve Tissue Proteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C491022:Smo protein, mouse; D000072086:Smoothened Receptor; D015534:Trans-Activators; D014157:Transcription Factors; D000074290:Zinc Finger Protein Gli3