The Lhx-7 gene in the oral mesenchyme

A frontal section of a stage 24 chick embryo head showing the distribution of transcripts of the Lhx-7 gene. This has been visualised by in situ hybridisation with an RNA probe labelled with 35S. This binds to the Lhx-7 mRNA and its presence is detected as silver grains after autoradiography. These grains appear as white dots under darkfield illumination and can be seen in the oral mesenchyme of the first branchial arch in regions where the teeth will develop. The developing eyes can be seen at the top of the picture.