The impact of BOR SIX1 mutations on the development of the bones of the face and skull

• Gabriel Dasilva, Biological Sciences, University of Delaware

• Andres Tavares, Biological sciences, University of Delaware

One in every 40,000 children have Branchio-oto-renal (BOR) syndrome, who present
with hearing loss, fistula (which are unnatural two-way openings) over the neck, or sometimes kidney defects. Approximately 50% BOR patients have a mutation in either SIX1, which is a transcription factor or one of its cofactors, called EYA1. However, the cause underlying the remaining 50% is still unknown. A recent clinical study showed that several mutations in SIX1 associated to BOR are also linked to an increase in the risk of premature fusion of fibrous joints (sutures) that separate the cranial bones of the skull. This is problematic because until around 24 years of age the cranial bones should not be fused together to ensure that the brain has enough space to grow. To test the impact of BOR SIX1 mutations during craniofacial development, the Tavares lab is using mice carrying the BOR Six1 mutations and cell culture of bone-forming cells. In my summer project, I helped genotype two mouse lines: a Six1 knockout line and a line carrying the p.R110W BOR Six1 mutation; and I generated two expression plasmids containing the p.R110W and the p.Q22X BOR Six1 mutations in mouse. In addition, I transfected HEK293T cells with a wild type Six1 plasmid and the two plasmids I generated (p.R110W and p.Q22X) to test their expression. The next step is to transfect bone-forming cells with these constructs to check changes in their osteogenic potential.