PRX

Periaxin (PRX) is a PDZ-domain-containing protein required for the maintenance of peripheral nerve myelin, where biallelic loss-of-function mutations cause early-onset demyelinating Charcot-Marie-Tooth type 4F and Dejerine-Sottas neuropathy with prominent sensory and motor involvement and focally folded myelin on nerve biopsy (PMID:21741241, PMID:25628743). Truncations that remove the C-terminal region of the long isoform (L-PRX) abolish normal myelin architecture, establishing that this domain is essential for peripheral nerve function (PMID:16534116, PMID:18504680). The PRX locus produces distinct isoforms with separable functions: in human cerebral endothelial cells PRX localizes predominantly to the nucleus, where its PDZ domain is necessary and sufficient to strengthen endothelial barrier integrity and suppress Type I interferon-response inflammatory genes (PMID:29968755). Isoform-specific splicing defects in the final intron of L-PRX—causing intron retention that switches expression to the PDZ-only S-PRX isoform or small in-frame deletions—disrupt lens cortex adherens junction organization and cause dominant congenital cataract through a mechanism distinct from the recessive neurological phenotype (PMID:41230902). Beyond these genetic and barrier-function findings, the molecular partners and biochemical activity of periaxin have not been characterized in the available corpus.

1. 2006 Low

   Established that the C-terminal region of periaxin is required for peripheral nerve myelin maintenance by linking a frameshift truncation to demyelinating neuropathy.

   Evidence Genetic sequencing and protein-level truncation analysis in a CMT4F patient

   PMID:16534116

   Open questions at the time

   • Single patient without functional reconstitution
   • No mechanistic dissection of how C-terminal loss disrupts myelin
   • Molecular partners of the C-terminal domain unidentified
2. 2008 Low

   Extended periaxin's required role to sensory as well as motor peripheral nerve myelin, showing the deficit is not motor-restricted.

   Evidence Genetic sequencing of a homozygous frameshift variant in a consanguineous early-onset CMT family

   PMID:18504680

   Open questions at the time

   • Genotype-phenotype linkage only, no molecular experiment
   • Mechanism of sensory fiber vulnerability unknown
3. 2011 Low

   Broadened the clinical spectrum of PRX loss to late-onset benign neuropathy and tied PRX deficiency to focally folded myelin architecture on biopsy.

   Evidence Genetic sequencing and nerve biopsy histopathology of a homozygous nonsense variant

   PMID:21741241

   Open questions at the time

   • No molecular mechanistic experiment
   • Basis for variable onset/severity unexplained
4. 2014 Low

   Demonstrated that biallelic loss-of-function of periaxin is sufficient to cause severe Dejerine-Sottas demyelinating neuropathy, consolidating the recessive loss-of-function model.

   Evidence Whole-exome and capillary sequencing with co-segregation analysis of compound heterozygous nonsense variants

   PMID:25628743

   Open questions at the time

   • No biochemical or cell-biological mechanism
   • Downstream effectors in Schwann cell myelination unidentified
5. 2018 Medium

   Revealed a non-neural function for PRX: nuclear localization in human cerebral endothelial cells where its PDZ domain enhances barrier integrity and suppresses interferon-response inflammation.

   Evidence Transcriptomics, transendothelial resistance and permeability assays, and PDZ-only (S-PRX) domain dissection by overexpression in mouse endothelial cells

   PMID:29968755

   Open questions at the time

   • Single lab, no independent replication
   • Nuclear mechanism by which a PDZ domain strengthens barrier function unresolved
   • Direct interaction partners and target transcription circuit unidentified
6. 2025 Medium

   Distinguished isoform-specific pathology: disruption of L-PRX splicing (intron retention favoring S-PRX or in-frame deletions) causes dominant congenital cataract via lens adherens junction disorganization, mechanistically separate from recessive neuropathy.

   Evidence Exome/genome and RNA sequencing confirming aberrant splicing across four cataract families

   PMID:41230902

   Open questions at the time

   • No functional reconstitution of the dominant-negative/gain-of-function mechanism
   • Molecular basis of L-PRX's role at lens adherens junctions undefined
   • Single study

• The direct molecular partners, biochemical activity, and the structural basis by which the PDZ and C-terminal domains organize junctions and myelin remain undefined.
• No identified direct physical interactors
• No structural model linking domain function to junction or myelin organization
• Mechanism reconciling nuclear endothelial role with junctional/myelin roles unknown