A Novel Mutation in Cse1l Disrupts Brain and Eye Development with Specific Effects on Pax6 Expression

Abstract

Forward genetics in the mouse continues to be a useful and unbiased approach to identifying new genes and alleles with previously unappreciated roles in mammalian development and disease. Here, we report a new mouse allele of Cse1l that was recovered from an ENU mutagenesis screen. Embryos homozygous for the anteater allele of Cse1l display a number of variable phenotypes, with craniofacial and ocular malformations being the most obvious. We provide evidence that Cse1l is the causal gene through complementation with a novel null allele of Cse1l generated by CRISPR-Cas9 editing. While the variability in the anteater phenotype was high enough to preclude a detailed molecular analysis, we demonstrate a very penetrant reduction in Pax6 levels in the developing eye along with significant ocular developmental phenotypes. The eye gene discovery tool iSyTE shows Cse1l to be significantly expressed in the lens from early eye development stages in embryos through adulthood. Cse1l has not previously been shown to be required for organogenesis as homozygosity for a null allele results in very early lethality. Future detailed studies of Cse1l function in craniofacial and neural development will be best served with a conditional allele to circumvent the variable phenotypes we report here. We suggest that human next-generation (whole genome or exome) sequencing studies yielding variants of unknown significance in CSE1L could consider these findings as part of variant analysis.

Advances in Understanding the Pathogenesis of Craniofacial Birth Defects

“…Cranial neural crest cells also contribute to the cornea, iris, sclera, ciliary body, trabecular meshwork, and aqueous outflow tracts; defects in their migration and differentiation can cause numerous anomalies in these ocular structures, such as Axenfeld-Reiger Syndroma and Peters Anomaly. Another study in this Special Issue used the forward-genetics approach of ENU mutagenesis in mouse to identify a new player in ocular development [ 3 ]; Blizzard et al discovered a new, hypomorphic allele of Cse1l , whose wildtype protein functions in several cellular processes including nuclear transport, cell cycle, and apoptosis. The previously reported Cse1l -null mutant is early embryonic lethal, whereas the hypomorphic Cse1l mutants described in this report survive to organogenesis stages, presenting with a number of variable craniofacial and ocular phenotypes including microphthalmia and coloboma.…”