Localization of <i>Tfap2β</i>, <i>Casq2</i>, <i>Penk</i>, <i>Zic1</i>, and <i>Zic3</i> Expression in the Developing Retina, Muscle, and Sclera of the Embryonic Mouse Eye

Optic development involves sequential interactions between several different tissue types, including the overlying ectoderm, adjacent mesoderm, and neural crest mesenchyme and the neuroectoderm. In an ongoing expression screen, we identified that <i>Tfap2β</i>, <i>Casq2</i>, <i>Penk</i>, <i>Zic1</i>, and <i>Zic3</i> are expressed in unique cell types in and around the developing eye. <i>Tfap2β</i>, <i>Zic1</i>, and <i>Zic3</i> are transcription factors, <i>Casq2</i> is a calcium binding protein and <i>Penk</i> is a neurotransmitter. <i>Tfap2β</i>, <i>Zic1</i>, and <i>Zic3</i> have reported roles in brain and craniofacial development, while <i>Casq2</i> and <i>Penk</i> have unknown roles. These five genes are expressed in the major tissue types in the eye, including the muscles, nerves, cornea, and sclera. <i>Penk</i> expression is found in the sclera and perichondrium. At E12.5 and E15.5, the extra-ocular muscles express <i>Casq2</i>, the entire neural retina expresses <i>Zic1</i>, and <i>Zic3</i> is expressed in the optic disk and lip of the optic cup. The expression of <i>Tfap2β</i> expanded from corneal epithelium to the neural retina between E12.5 to E15.5. These genes are expressed in similar domains as Hedgehog (<i>Gli1</i>, and <i>Ptch1</i>) and the Wnt (<i>Lef1</i>) pathways. The expression patterns of these five genes warrant further study to determine their role in eye morphogenesis.