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Mutational Landscape of Primary Hyperoxaluria in Morocco: Update and Implications for Diagnosis

In plain language

Primary hyperoxaluria is a rare inherited condition that causes excessive oxalate accumulation, leading to kidney stones, renal failure, and systemic oxalosis. A study evaluating 132 Moroccan patients over ten years employed a stepwise genetic testing workflow to clarify the molecular profile of the disease. Initial targeted Sanger sequencing focusing on specific exons of the AGXT gene resolved 72 percent of cases. Incorporating a targeted multi-gene panel and whole-exome sequencing increased the cumulative diagnostic yield to 78 percent. Twelve distinct variants were identified, with the c.731T>C mutation in exon 7 of the AGXT gene occurring most frequently, suggesting a founder effect. Other recurrent mutations clustered primarily across exons 1, 2, 7, and 10. These findings demonstrate that an exon-focused, tiered screening strategy offers a practical diagnostic pathway for clinical settings with limited resources.

Key takeaways

  • Targeted Sanger sequencing of specific AGXT exons resolved 72 percent of primary hyperoxaluria cases among the 132 Moroccan patients tested.
  • Combining targeted multi-gene panels and whole-exome sequencing raised the overall diagnostic yield to 78 percent.
  • The c.731T>C mutation in exon 7 of the AGXT gene was the most common variant, indicating a regional founder effect.
  • Identified pathogenic variants clustered predominantly in exons 1, 2, 7, and 10 of the AGXT gene.
  • A tiered, exon-focused testing strategy presents an effective molecular diagnostic route for resource-limited environments.

Why it matters

Primary hyperoxaluria can lead to severe complications such as kidney stones and renal failure. Pinpointing recurrent regional genetic mutations allows clinicians to establish more accessible, cost-effective screening workflows. In regions with high consanguinity and constrained resources, a targeted diagnostic strategy helps patients receive prompt and accurate molecular confirmations without the immediate need for expensive, comprehensive genomic sequencing.

Commercialisation angle

This research provides a validated diagnostic workflow that diagnostic laboratories and clinical genetics services can directly adopt to identify primary hyperoxaluria. It establishes a rationale for low-cost, targeted testing kits or protocols focused on specific mutation hotspots in the AGXT gene. The approach represents an applied clinical method ready for implementation in routine hospital or diagnostic settings, particularly in resource-constrained environments facing similar mutational profiles.

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Abstract

Introduction: Primary hyperoxaluria (PH) is a rare autosomal recessive disease characterized by an excess of oxalate, which results in nephrolithiasis, nephrocalcinosis, and ultimately, renal failure and systemic oxalosis. There are 3 forms of PH, named types 1, 2, and 3, caused by variants in the AGXT, GRHPR, and HOGA1 genes, respectively. In Morocco, where consanguinity is common, recurrent variants, mainly affecting the AGXT gene, have been documented; however, the overall molecular profile of PH remains poorly characterized. We aim here to describe the mutational landscape of PH in Morocco and to provide an accurate diagnostic approach. Methods: We analyzed 132 patients referred over 10 years for PH using a stepwise strategy. A step 1 test involved Sanger sequencing of exon 7 of the AGXT gene, followed by sequencing of exons 1, 2, and 10 of the AGXT gene. The step 2 analysis consists of a customized gene panel targeting the three PH-associated genes. Unresolved cases underwent whole-exome sequencing as a third step. Results: First-line Sanger sequencing identified biallelic pathogenic or likely pathogenic AGXT variants in 95 of 132 patients suspected of PH, corresponding to a diagnostic yield of 72%. Additional molecular diagnoses obtained through targeted PH panel sequencing and WES increased the final cumulative diagnostic yield to 78%. Twelve distinct variants were characterized by Sanger sequencing, with the c.731T>C in exon 7 of the AGXT gene, emerging as the most prevalent variant, supporting its founder effect in this population. Other variants were predominantly located in exons 7, 10, 2, and 1, highlighting mutation hotspots in this population. In unresolved cases, next-generation sequencing (NGS), including targeted gene panels and exome sequencing, uncovered additional pathogenic variants in the AGXT gene and variants in other genes associated with PH-like phenotypes. Conclusions: These results highlight the need for a simplified, exon-focused diagnostic strategy, particularly in resource-limited settings like Morocco.

Research topics

  • Kidney Stones and Urolithiasis Treatments
  • Biomedical Research and Pathophysiology
  • Parathyroid Disorders and Treatments

Read the original research

This page summarises published work. The authoritative version sits with the publisher.

DOI: 10.3390/genes17091056

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