X-Linked Glomerulopathy Due to COL4A5 Founder Variant

Area of Science:

• Genetics
• Nephrology
• Molecular Biology

Background:

• Alport syndrome is a hereditary kidney disease caused by variants in type IV collagen genes.
• X-linked Alport syndrome, due to COL4A5 variants, is the most common form, presenting with kidney failure, hearing loss, and ocular defects.

Observation:

• Exome sequencing identified a novel COL4A5 variant (c.T665G) in males with atypical X-linked glomerulopathy.
• This variant, predicted to cause a cysteine to phenylalanine substitution, was absent in major genetic variation databases.
• Literature review revealed two additional families with the same variant and similar histopathological findings.

Findings:

• The identified COL4A5 variant leads to unique histopathological features in Alport syndrome.
• Homology modeling indicates the substitution disrupts type IV collagen trimer structure and dynamics.
• Genetic analysis across three families suggests a shared haplotype and a potential founder effect.

Implications:

• This specific COL4A5 variant may initiate a distinct pathogenic mechanism in Alport syndrome.
• Understanding this variant's impact on collagen structure is crucial for diagnosing and potentially treating Alport syndrome.
• The founder effect suggests a common ancestral origin for this variant in the studied populations.