Despite a common understanding that Gli TFs are utilized to reiterate a Hh morphogen gradient, genetic analyses suggest craniofacial development does not completely fit this paradigm. Using the mouse model (Mus musculus), we demonstrated that rather than being driven by a Hh threshold, robust Gli3 transcriptional activity during skeletal and glossal development required interaction with the basic helix-loop-helix TF Hand2. Not only did genetic and expression data support a co-factorial relationship, but genomic analysis revealed that Gli3 and Hand2 were enriched at regulatory elements for genes essential for mandibular patterning and development. Interestingly, motif analysis at sites co-occupied by Gli3 and Hand2 uncovered mandibular-specific, low-affinity, 'divergent' Gli binding motifs (<strong>d</strong>GBMs). Functional validation revealed these <strong>d</strong>GBMs conveyed synergistic activation of Gli targets essential for mandibular patterning and development. In summary, this work elucidates a novel, sequence-dependent mechanism for Gli transcriptional activity within the craniofacial complex that is independent of a graded Hh signal.
Sequencing data have been deposited in GEO under accession codes GSE141431, GSE141173.ChIP data have been deposited in GEO under accession code GSE146961All data generated or analyzed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 1,5,8,9, Figure 1-figure supplement 1, Figure 8-figure supplement 2, and Figure 9-figure supplement 1
bulk RNA-seq of wild-type, Gli2f/f;Gli3f/f;Wnt1-Cre, and Hand2f/f;Wnt1-Cre mouse e10.5 dissection mandibular prominencesNCBI Gene Expression Omnibus, GSE141431.
Single cell sequencing of dissected mouse mandibular prominence at embryonic day e11.5 and e13.5NCBI Gene Expression Omnibus, GSE141173.
Gli3 and Hand2 ChIP-sequencing of developing face and mandibular prominenceNCBI Gene Expression Omnibus, GSE146961.
Genome-wide candidate HAND2 target regions in mouse embryonic tissuesNCBI Gene Expression Omnibus, GSE55707.
- Samantha A Brugmann
- Kevin A Peterson
- Kelsey H Elliott
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All of the animals were handled according to approved institutional animal care and use committee (IACUC) protocols (IACUC2017-0063) of Cincinnati Children's Hospital Medical Center.
- Kathryn Song Eng Cheah, The University of Hong Kong, Hong Kong
© 2020, Elliott et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.