Candidate positive targets of LHX6 and LHX8 transcription factors in the developing upper jaw.

Craniofacial development is controlled by a large number of genes, which interact with one another to form a complex gene regulatory network (GRN). Key components of GRN are signaling molecules and transcription factors. Therefore, identifying targets of core transcription factors is an important part of the overall efforts toward building a comprehensive and accurate model of GRN. LHX6 and LHX8 are transcription factors expressed in the oral mesenchyme of the first pharyngeal arch (PA1), and they are crucial regulators of palate and tooth development. Previously, we performed genome-wide transcriptional profiling and chromatin immunoprecipitation to identify target genes of LHX6 and LHX8 in PA1, and described a set of genes repressed by LHX. However, there has not been any discussion of the genes positively regulated by LHX6 and LHX8. In this paper, we revisited the above datasets to identify candidate positive targets of LHX in PA1. Focusing on those with known connections to craniofacial development, we performed RNA in situ hybridization to confirm the changes in expression in Lhx6;Lhx8 mutant. We also confirmed the binding of LHX6 to several putative enhancers near the candidate target genes. Together, we have uncovered novel connections between Lhx and other important regulators of craniofacial development, including Eya1, Barx1, Rspo2, Rspo3, and Wnt11.