RT Journal Article
SR Electronic
T1 <em>notum1</em>, acting downstream of pitx2, is essential for proper eye and craniofacial development
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 687798
DO 10.1101/687798
A1 Kathryn E. Hendee
A1 Elena A. Sorokina
A1 Sanaa S. Muheisen
A1 Ross F. Collery
A1 Elena V. Semina
YR 2019
UL http://biorxiv.org/content/early/2019/07/02/687798.abstract
AB Axenfeld-Rieger syndrome (ARS) is a rare autosomal dominant developmental disorder characterized by ocular anterior chamber anomalies with an increased risk of glaucoma and systemic defects. Mutations in the transcription factor PITX2 were the first identified genetic cause of ARS. Despite the developmental importance of PITX2 and its role in ARS, the pathways downstream of PITX2 have yet to be fully characterized. Comparative transcriptome analyses involving pitx2-enriched cell populations isolated via fluorescence activated cell sorting of tissues expressing (Tg(-2.6pitx2-CE4:GFP)) reporter in wild-type and pitx2M64* mutant zebrafish embryos identified the highly down-regulated target notum1b, an ortholog of human NOTUM encoding a secreted carboxylesterase that cleaves a necessary palmitoleate moiety from WNT proteins. Further experiments confirmed a decrease in notum1b and identified down-regulation of another NOTUM ortholog, notum1a, in the developing mutant eye. CRISPR-generated permanent double knockout zebrafish lines of notum1b and notum1a, notum1−/−, displayed defects in craniofacial and ocular development, including corneal defects, small lenses, increased sizes of the anterior and posterior chambers, and anomalies in teeth development. Analysis of head transcriptome of notum1−/− zebrafish in comparison to wild-type predicted an up-regulation of the WNT pathway. We present NOTUM/notum1 as an important factor in ocular and craniofacial development and a novel downstream member of the PITX2/pitx2 pathway.