Robust genetic analysis of the X-linked anophthalmic (Ie) mouse

Brianda Areli Hernandez-Moran, Andrew Papanastasiou, Dave Parry, Alison M Meynert, Phillipe Gautier, Graeme R Grimes, Ian R Adams, Violeta Trejo-Reveles, Hemant Bengani, Margaret Keighren, Ian J Jackson, David J Adams, David R FitzPatrick, Joe Rainger

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Anophthalmia (missing eye) describes a failure of early embryonic ocular development. Mutations in a relatively small set of genes account for 75% of bilateral anophthalmia cases, yet 25% of families currently are left without a molecular diagnosis. Here we report our experimental work that aimed to uncover the developmental and genetic basis of the anophthalmia characterising the X-linked Ie (eye-ear reduction) X-ray induced allele in mouse that was first identified in 1947.
Histological analysis of the embryonic phenotype showed failure of normal eye development after the optic vesicle stage with particularly severe malformation of the ventral retina. Linkage analysis mapped this mutation to a ~ 6Mb region on the X chromosome. Short and long read whole-genome sequencing (WGS) of affected and unaffected male littermates confirmed the Ie linkage but identified no plausible causative variants or structural rearrangements. These analyses did reduce the critical candidate interval and revealed evidence of multiple variants within the ancestral DNA, although none were found that altered coding sequences or that were unique to Ie. To investigate early embryonic events at a genetic level, we then generated mouse ES cells derived from male Ie embryos and wild type littermates. RNA-seq and accessible chromatin sequencing (ATAC-seq) data generated from cultured optic vesicle organoids did not reveal any large differences in gene expression or accessibility of putative cis-regulatory elements between Ie and wild type. However, an unbiased TF-footprinting analysis of accessible chromatin regions did provide evidence of a genome wide reduction in binding of transcription factors associated with ventral eye development in Ie, and evidence of an increase in binding of the Zic-family of transcription factors, including Zic3, which is located within the Ie-refined critical interval.
We conclude that the refined Ie critical region at chrX: 56,145,000-58,385,000 contains multiple genetic variants that may be linked to altered cis regulation but does not contain a convincing causative mutation. Changes in the binding of key
transcription factors to chromatin causing altered gene expression during development, possibly through a subtle mis-regulation of Zic3, presents a plausible cause for the anophthalmia phenotype observed in Ie, but further work is required to determine the precise causative allele and its genetic mechanism.
Original languageEnglish
Article number1797
Pages (from-to)1-14
Number of pages14
JournalGenes
Volume13
Issue number10
Early online date5 Oct 2022
DOIs
Publication statusPublished - 5 Oct 2022

Keywords / Materials (for Non-textual outputs)

  • Anophthalmia
  • X-chromosome
  • X-ray induced allele
  • linkage analysis
  • Zic3
  • genome wide analysis
  • eye development

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