It leads to anomalies in the structure of the mature anterior segment, associated with an increased risk of glaucoma and corneal opacity.

The emerging view is that these genes act in concert to specify a population of mesenchymal progenitor cells, mainly of neural crest origin, as they migrate anteriorly around the embryonic optic cup.

These same genes then regulate mesenchymal cell differentiation to give rise to distinct anterior segment tissues.

Development appears critically sensitive to gene dosage, and variation in the normal level of transcription factor activity causes a range of anterior segment anomalies.

Interplay between PITX2 and FOXC1 in the development of different anterior segment tissues may partly explain the phenotypic variability and the genetic heterogeneity characteristic of ASD.