Abstract
Purpose :
Mutations in collagen type IV alpha 1 (COL4A1) and alpha 2 (COL4A2) cause a multisystem disorder characterized by variable cerebrovascular, ocular, renal and neuromuscular manifestations. The affected tissues are mainly derived from two distinct embryonic origins: the neural crest cells (NCCs) and the mesoderm germ layer. Approximately one-third of patients with COL4A1 and COL4A2 mutations have ocular anterior segment dysgenesis (ASD), including congenital glaucoma resulting from dysgenesis of structures derived from the periocular mesenchyme. Defects in NCC biology have long been proposed to contribute to ASD. Because vascular defects are common in patients with COL4A1 and COL4A2 mutations and can influence NCC survival and migration, we hypothesize that primary vascular defects may alter NCC biology underlying ASD.
Methods :
Whole-mount immunofluorescence, confocal microscopy, and 3D reconstruction were performed on control and Col4a1 mutant mouse embryos at embryonic day (E) 9.5 and E10.5 using antibodies against CD31 to label vascular endothelial cells, and SOX10 to label migratory NCCs.
Results :
Gross morphology and quantitative analysis of E9.5 Col4a1 mutant embryos showed abnormal cerebral vasculature remodeling compared to controls, revealing an early onset of cerebral angiogenesis defects. SOX10 and cleaved Caspase 3 labeling, respectively, revealed that Col4a1 mutant and control embryos had similar numbers of migrating cranial NCCs and a similar degree of cell death at both E9.5 and E10.5. However, compared to control littermates, cranial NCCs moving towards the eye region in E9.5 mutants showed abnormal migration, forming a less cohesive migratory stream. On the other hand, within the periocular mesenchyme of E9.5 and E10.5 Col4a1 mutant embryos, NCCs clustered more together and interacted more closely with the vasculature.
Conclusions :
In agreement with our hypothesis, our results show for the first time that Col4a1 mutations lead to cranial NCC migratory defects in the context of early-onset defective angiogenesis. However, NCC number and survival are not affected by Col4a1 mutations. Further examinations are needed to understand both the molecular causes and consequences of the uncovered NCC migratory phenotype. Future work will also analyze the mesodermal contribution to ASD in Col4a1 mutants.
This is a 2021 ARVO Annual Meeting abstract.