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

Lauren E Blizzard,Ronald R Waclaw,Rolf W Stottmann,Chelsea Menke,Shaili D Patel,Salil A Lachke

doi:10.3390/jdb9030027

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.

Highlights

Chromosome segregation 1-like (S. cerevisiae) (Cse1l; known as cellular apoptosis susceptibility gene CAS or exportin-2) has been linked to nuclear transport, cell cycle maintenance, cell proliferation, apoptosis, and many other cellular functions [1,2]
CSE1L functions in nuclear transport as a re-exporter of importin-α, and it has been implicated in a wide range of cellular processes including cell cycle control, chromosome stability, apoptosis, and even direct gene regulation
While Cse1l has been shown to be critical for embryonic development, further study in organogenesis has proved elusive due to the early embryonic lethality [21]

Summary

Introduction

Chromosome segregation 1-like (S. cerevisiae) (Cse1l; known as cellular apoptosis susceptibility gene CAS or exportin-2) has been linked to nuclear transport, cell cycle maintenance, cell proliferation, apoptosis, and many other cellular functions [1,2]. Under a variety of cellular stress conditions, importin-α can be imported into the nucleus in the absence of RAN and importin-β In these conditions, the consequent disturbance in the Ran gradient results in the loss of CSE1L-mediated export of importin-α which initiates a blockage of nuclear import and accumulation of importin-α in the nucleus [8]. The consequent disturbance in the Ran gradient results in the loss of CSE1L-mediated export of importin-α which initiates a blockage of nuclear import and accumulation of importin-α in the nucleus [8] This accumulation has been implicated in the expression of factors inducing non-apoptotic cell death [9]. It has been shown that the nuclear transport mechanism requiring CSE1L demonstrates distinct cargo specificity, and this selectivity may indirectly contribute to some epigenetic control within the cell [16,17]

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