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Researchers Identify New Rare Genetic Disorder RPN1-CDG Linked to Glycosylation Process

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Scientists Identify New Rare Genetic Disease: RPN1-CDG

A team of scientists has identified a new rare genetic disease, termed RPN1-CDG, caused by a mutation in the RPN1 gene. The discovery, published on April 3, 2026, expands the understanding of congenital disorders of glycosylation and may aid in diagnosing patients with rare diseases.

Publication and Research Team

The findings were published in the peer-reviewed journal Human Genetics and Genomics Advances on April 3, 2026. The research was conducted by scientists from the Sanford Burnham Prebys Medical Discovery Institute in collaboration with international partners.

Discovery and Methodology

The study focused on two siblings presenting with an unfamiliar neurodevelopmental disorder. Using whole exome sequencing, researchers identified a specific mutation in the RPN1 gene.

This mutation was present in both affected siblings but was not found in three of their unaffected siblings. The genetic variant had not been previously reported in major public genetic databases.

Biochemical tests conducted on the patients confirmed abnormal patterns of glycosylation, consistent with the characteristics of congenital disorders of glycosylation (CDGs).

Biological Mechanism and Classification

The newly identified disorder has been classified as a congenital disorder of glycosylation (CDG), a category encompassing over 190 distinct disorders.

  • Gene and Protein Function: The RPN1 gene provides instructions for making the protein ribophorin I.
  • Cellular Role: Ribophorin I is an essential component of the oligosaccharyltransferase (OST) complex. This cellular structure is responsible for attaching sugar chains, known as glycans, to proteins—a process called glycosylation.
  • Effect of the Mutation: The identified mutation causes a truncation, or shortening, of the ribophorin I protein. This leads to instability within the OST complex.
  • Specific Subtype Affected: The structural defect specifically impairs the function of the OST-A subtype of the complex. This reduces the complex's ability to attach sugars to the proteins it normally glycosylates.

Scientific Context and Significance

  • Glycosylation Importance: Glycosylation is a fundamental cellular process where sugar chains are attached to proteins to form glycoproteins. These glycans are crucial for protein stability, proper folding, and biological function. Impairment can lead to malfunctions in various organ systems.
  • Developmental Impact: Hudson Freeze, PhD, director of the Sanford Children's Health Research Center at Sanford Burnham Prebys, stated that the glycosylation test results reflected patterns observed in other CDGs.

Freeze noted that because the OST complex is involved in numerous developmental processes, disorders affecting it typically present with a range of neurodevelopmental and other developmental issues.

  • Expanded Genetic Knowledge: The discovery of RPN1-CDG brings the total number of genes associated with diseases of the OST complex to eight.

Potential Impact

The researchers indicate that defining this new disorder contributes to a broader understanding of all CDGs. This advancement may help provide definitive diagnoses for a greater number of patients with rare, undiagnosed diseases.