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A Non-random Mouse Model for Pharmacological Reactivation of Mecp2 on the Inactive X Chromosome
Published on: May 22, 2019
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Axenfeld-Rieger syndrome associated with a megabase-scale inversion separating PITX2 from a conserved enhancer locus
Lucas A Mitchell1,2, Joshua Schmidt1,3, Emmanuelle Souzeau3
1Genomics and Inherited Disease Program, Garvan Institute of Medical Research, Sydney, New South Wales, Australia.
Medrxiv : the Preprint Server for Health Sciences
|June 12, 2025
Summary
Structural variants disrupting enhancer elements near the PITX2 gene cause Axenfeld-Rieger Syndrome (ARS). This finding expands genetic mechanisms for ARS and aids in diagnosing undiagnosed cases.
Area of Science:
- Genetics
- Developmental Biology
- Ophthalmology
Background:
- Axenfeld-Rieger Syndrome (ARS) is an autosomal dominant disorder affecting ocular and non-ocular features.
- Genetic causes are primarily coding variants in PITX2 or FOXC1, but many ARS cases remain undiagnosed.
Purpose of the Study:
- To identify genetic variants underlying undiagnosed Axenfeld-Rieger Syndrome.
- To investigate non-coding structural variants impacting PITX2 gene regulation.
Main Methods:
- Whole-genome sequencing was employed to detect structural variants.
- Analysis focused on non-coding regions and their regulatory interactions with PITX2.
Main Results:
- Two distinct non-coding structural variants were identified in patients with typical ARS presentation.
- A large deletion (450 kb) and an inversion (12.5 Mb) were found to remove or displace enhancer elements critical for PITX2 regulation.
- These variants disrupt enhancer-PITX2 interactions without altering the PITX2 coding sequence.
Conclusions:
- Non-coding structural variants, specifically enhancer-disrupting inversions, represent a novel genetic mechanism for Axenfeld-Rieger Syndrome.
- These findings highlight the importance of considering non-coding regulatory elements in genetic diagnostics for ARS and similar conditions.
- This expands the understanding of genetic underpinnings for complex developmental disorders.
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