Autoregulation of canonical Wnt signaling controls midbrain development.
After the primary anterior-posterior patterning of the neural plate, a subset of wnt signaling molecules including Xwnt-1, Xwnt-2b, Xwnt-3A, Xwnt-8b are still expressed in the developing brain in a region spanning from the posterior part of the diencephalon to the mesencephalon/metencephalon boundary. In this expression field, they are colocalized with the HMG-box transcription factor XTcf-4. Using antisense morpholino loss-of-function strategies, we demonstrate that the expression of this transcription factor depends on Xwnt-2b, which itself is under the control of XTcf-4. Marker gene analyses reveal that this autoregulatory loop is important for proper development of the midbrain and the isthmus. Staining for NCAM reveals a lack of dorsal neural tissue in this area. This reduction is caused by a reduced proliferation rate as shown by staining for PhosphoH3 positive nuclei. In rescue experiments, we demonstrate that individual isoforms of XTcf-4 control the development of different parts of the brain. XTcf-4A restored the expression of the mesencephalon marker genes pax-6 and wnt-2b but not the isthmus marker gene en-2. XTcf-4C, in contrast, restored en-2, but had only weak effects on pax-6 and wnt-2b. Thus, autoregulation of canonical Wnt signaling and alternative expression of different isoforms of XTcf-4 is essential for specifying the developing CNS.
Zoologisches Institut II, Universität Karlsruhe (TH), 76131 Karlsruhe, Germany.
Martin
M
Kunz
Michael
M
Herrmann
Doris
D
Wedlich
Dietmar
D
Gradl
D000818:Animals; D001483:Base Sequence; D019521:Body Patterning; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006706:Homeostasis; D008636:Mesencephalon / Q000196:embryology* / Q000378:metabolism*; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D051820:TCF Transcription Factors; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D051153:Wnt Proteins; D014981:Xenopus / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins
D020319:Oligodeoxyribonucleotides, Antisense; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D051820:TCF Transcription Factors; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; D051153:Wnt Proteins; D029867:Xenopus Proteins; C544896:tcf7l2 protein, Xenopus