<p>Alport syndrome is a hereditary glomerular disease driven by pathogenic variants in <i>COL4A3</i>–<i>COL4A5</i> that compromise the α3–α4–α5 type IV collagen scaffold, manifesting as persistent hematuria, proteinuria, and ultimately end-stage renal disease. Its pronounced phenotypic variability, low sensitivity of renal biopsy, and limited response to ACE inhibitors complicate accurate diagnosis and therapy. In a cohort of 40 pedigrees from southwest China, we discovered 21 novel <i>COL4A3-COL4A5</i> mutations. Notably, two families carried rare digenic <i>COL4A4</i>/<i>COL4A5</i> variants, providing strong evidence for dual-locus pathogenicity. Immunofluorescence of five mutation-positive patients revealed allele-specific depletion of α3 and α5 chains in the glomerular basement membrane, with frameshift and splice-site mutations eliciting more severe collagen loss than missense. Complementary AlphaFold modeling predicted that digenic variants induce greater destabilization of Gly-X-Y triple helices domain than monogenic lesions. Over three years, ACEI therapy achieved only sporadic partial remissions, underscoring the need for precision-guided treatment strategies. This study not only expands the genetic spectrum of Alport syndrome in China’s ethnic minority populations but also elucidates the mechanistic impact of digenic inheritance.</p>

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Novel COL4A3COL4A5 variants and digenic inheritance in pediatric Alport syndrome from Southwestern China

  • Ji-Yu Chen,
  • Xue-Mei Jiang,
  • Ya-Bin Liao,
  • Yan-Hua Zhang,
  • Mi-feng Yang,
  • Jing-Jing Cui,
  • Jing Wang,
  • Jia Zhang,
  • Hong-Ye Wang,
  • Bo Zhao

摘要

Alport syndrome is a hereditary glomerular disease driven by pathogenic variants in COL4A3COL4A5 that compromise the α3–α4–α5 type IV collagen scaffold, manifesting as persistent hematuria, proteinuria, and ultimately end-stage renal disease. Its pronounced phenotypic variability, low sensitivity of renal biopsy, and limited response to ACE inhibitors complicate accurate diagnosis and therapy. In a cohort of 40 pedigrees from southwest China, we discovered 21 novel COL4A3-COL4A5 mutations. Notably, two families carried rare digenic COL4A4/COL4A5 variants, providing strong evidence for dual-locus pathogenicity. Immunofluorescence of five mutation-positive patients revealed allele-specific depletion of α3 and α5 chains in the glomerular basement membrane, with frameshift and splice-site mutations eliciting more severe collagen loss than missense. Complementary AlphaFold modeling predicted that digenic variants induce greater destabilization of Gly-X-Y triple helices domain than monogenic lesions. Over three years, ACEI therapy achieved only sporadic partial remissions, underscoring the need for precision-guided treatment strategies. This study not only expands the genetic spectrum of Alport syndrome in China’s ethnic minority populations but also elucidates the mechanistic impact of digenic inheritance.