Ritscher-Schinzel syndrome can be characterized as an endosomal recyclinopathy

Area of Science:

• Genetics and Molecular Biology
• Developmental Biology
• Cell Biology

Background:

• Ritscher-Schinzel syndrome (RSS) is a congenital disorder with diverse malformations and organ dysfunction.
• The genetic underpinnings and molecular mechanisms of RSS phenotypes are not fully understood.
• Emerging evidence suggests a role for the Commander multiprotein assembly in RSS.

Purpose of the Study:

• To identify the genetic causes of Ritscher-Schinzel syndrome.
• To elucidate the molecular mechanisms underlying RSS phenotypes.
• To establish a mouse model for studying RSS.

Main Methods:

• Genetic and clinical analysis of patient cohorts.
• Interactome analysis to study protein complex assembly.
• Cell surface proteomics to identify affected membrane proteins.
• Generation and analysis of mouse models.

Main Results:

• Causative mutations in COMMD4, COMMD9, and CCDC93 (Commander complex subunits) were identified in RSS patients.
• Mutations disrupt Commander complex assembly and SNX17-dependent endosomal recycling of integral membrane proteins.
• Defective recycling impacts cell surface presentation of proteins crucial for kidney, bone, and brain development.
• Mouse models recapitulated key RSS phenotypes, including proteinuria, skeletal malformations, and neurological impairment.

Conclusions:

• Ritscher-Schinzel syndrome is characterized as a 'recyclinopathy' due to impaired Commander endosomal recycling.
• This pathway dysfunction explains the multi-tissue phenotypes observed in RSS.
• Identifying the genetic basis and molecular mechanisms provides insights into RSS pathogenesis.