Wnt7a is up‐regulated in mice with heritable misexpression of Six2 associated with frontonasal dysplasia

Wnts are secreted glycoproteins involved in an array of developmental processes. In facial morphogenesis, Wnts appear to mediate development of the midface and fusion of the upper lip. We have previously described the Br mutant mouse displaying heritable frontonasal dysplasia (FND). Linkage analysis mapped the Br mutation near the homeobox transcription factor Six2 , normally expressed in the facial mesenchyme during embryonic development. The purpose of this study is to determine possible upstream and downstream events of Six2 , notably in the Wnt signaling pathway, leading to FND. Frontal nasal prominences (FNP) of E11.5 embryos were dissected and RNA extracted via Qiagen's RNeasy Mini Kit. Total RNA was reverse transcribed using Bio‐Rad's iScript cDNA Synthesis Kit. qRT‐PCR reactions were performed with SYBR Green Supermix and novel primers for Six2 and SABiosciences RT² Profiler PCR Array for Wnt signaling pathway molecules. The MyiQ iCycler thermocycler and single color real‐time PCR detection system (Bio‐Rad) were also used. Results suggest Six2 is expressed in a haploinsufficient pattern in the FNP. Additional data indicates Wnt7a expression is up‐regulated three‐fold in the Br/Br mutant. These data suggest Six2 may down‐regulate Wnt7a in the face and in the absence of suppression, Wnt7a may prevent further differentiation of midfacial structures resulting in FND. Further work will be necessary to determine specific downstream targets of Six2. Supported by R0‐1 DK064752 (SL). Grant Funding Source NIH