Clinical and Genetic Characteristics of Ocular Developmental Disorders: MAC-Spectrum, Anterior Segment Dysgenesis

Abstract

To control the development of the ocular phenotype, several coordinated steps of temporally- and spatially-organized networked triggers (inductions) are necessary. This is regulated at the level of transcription. Crucial here are the so-called master genes or DNA-binding transcription factors PAX6, FOXC1, SOX2, FOXE3, OTX2, PITX2 and PAX2. Depending on the disease phenotype, it is possible to conclude on the gestational period in which ocular development was profoundly disrupted. The so-called neural crest cells contribute significantly to the development of eye structures, especially of the anterior segment. The review first presents a brief overview of the embryologic development of ocular structures and then describes major profound developmental disorders of the eyes: phenotypic and genetic features in the MAC spectrum (microphthalmia, anophthalmia, coloboma) as well as anterior segment dysgenesis (Axenfeld-Rieger spectrum, aniridia, Peters anomaly). It also outlines the systemic involvement of these diseases. In clinical and genetic diagnostic pathways, the determining factor is the exact phenotypic characterization that must be preceded by any genetic diagnosis and the further choice of diagnostic options. "Shotgun diagnostics" on all of the described genes involved in ocular developmental disorders is costly and less effective than a phenotypically-oriented selection of the genes common to the phenotypical syndrome described, and only then should it be followed by the analysis of rarer genes in a second or third molecular genetic step.