DES

Desmin (DES) is a muscle intermediate filament protein whose network integrity is essential for normal cardiomyocyte structure, and whose disruption underlies a spectrum of cardiomyopathies and cardiac conduction disease (PMID:33478057, PMID:22215463). Multiple disease-causing lesions converge on a common loss-of-normal-filament-network mechanism: the missense variant p.A337P forms cytoplasmic aggregates in SW-13 cells and iPSC-derived cardiomyocytes, linking aggregation to left-ventricular non-compaction cardiomyopathy (PMID:33478057), and an exon-3 splice variant (c.735G>C) producing an in-frame deletion of residues p.D214–E245 likewise yields abnormal cytoplasmic aggregates, whereas the corresponding simple missense change does not, pinpointing the deleted segment as required for proper assembly (PMID:34680517). Desmin function is additionally modulated by phosphorylation of its N-terminal domain: the p.S13F mutation disrupts a phosphorylation site, and impaired PKA/PDE4D compartmentalization caused by a PDE4DIP variant reduces PKA phosphorylation of desmin following isoproterenol stimulation, placing desmin downstream of the PKA/PDE4D signaling axis as a penetrance modifier (PMID:34289528). Founder mutations p.S13F and p.N342D produce fully penetrant cardiac conduction disease and cardiomyopathy with right ventricular involvement (PMID:22215463). Beyond these filament-assembly and phosphorylation findings, no further mechanistic detail has been characterized in the available corpus.

1. 2004 Medium

   Established whether DES sequence variation segregates with inherited dilated cardiomyopathy in a canine model, testing the gene's causal contribution outside human pedigrees.

   Evidence BAC cloning, FISH mapping, SNP/microsatellite genotyping and haplotype association in a Dobermann DCM family

   PMID:15475165

   Open questions at the time

   • Negative result in one breed does not exclude DES involvement in other models or species
   • No functional or molecular characterization of desmin protein performed
   • Does not address mechanism of any pathogenic variant
2. 2012 Low

   Demonstrated that specific DES founder mutations cause a fully penetrant clinical syndrome combining cardiac conduction disease and cardiomyopathy with right ventricular involvement, defining the disease phenotype.

   Evidence Clinical phenotyping of p.S13F and p.N342D carriers with genealogy and haplotype analysis

   PMID:22215463

   Open questions at the time

   • Clinical/haplotype study only — no in vitro biochemistry establishing the molecular consequence of either mutation
   • Does not distinguish whether the mutations act through filament disruption, phosphorylation, or another mechanism
   • Penetrance modifiers not identified
3. 2018 Medium

   Showed that a DES point mutation causes aggregation rather than normal filament formation, establishing a loss-of-normal-network mechanism for LVNC cardiomyopathy.

   Evidence Transfection of desmin-p.A337P into SW-13 cells and iPSC-derived cardiomyocytes with confocal microscopy

   PMID:33478057

   Open questions at the time

   • Single lab; does not quantify dominant-negative versus haploinsufficient contribution
   • No structural model of how p.A337P perturbs assembly
   • Downstream cellular consequences of aggregation not defined
4. 2021 Medium

   Placed desmin phosphorylation downstream of the PKA/PDE4D signaling axis and identified PDE4DIP as a penetrance modifier, connecting a structural protein defect to a signaling compartment.

   Evidence Whole exome sequencing of kindreds plus in vitro assays showing reduced PDE4DIP/PDE4D colocalization, elevated cAMP/PKA, and decreased PKA phosphorylation of desmin after isoproterenol

   PMID:34289528

   Open questions at the time

   • Functional consequence of altered desmin phosphorylation on filament behavior not directly measured
   • Single lab; epistasis based on one PDE4DIP variant
   • PKC site disruption by p.S13F not functionally dissected from PKA effects
5. 2021 Medium

   Demonstrated that an in-frame exon-3 deletion, but not a corresponding missense change, drives aggregation, mapping a specific desmin segment required for proper network assembly.

   Evidence Nanopore amplicon sequencing of explanted myocardium, Western blot, and transfection with confocal microscopy comparing truncated desmin to p.E245D

   PMID:34680517

   Open questions at the time

   • Single lab; aggregation assessed in cell culture rather than patient cardiomyocytes
   • Mechanism by which residues p.D214–E245 stabilize assembly not resolved at structural level
   • Heterozygous dominant effect on wild-type desmin not quantified

• How desmin filament disruption mechanistically produces cardiac conduction disease and the distinct cardiomyopathy subtypes, and how phosphorylation state controls assembly in vivo, remain unresolved.
• No structural model linking specific mutations to filament assembly defects
• Causal chain from aggregation to conduction disease and contractile failure not established
• In vivo role of PKA/PDE4D-regulated desmin phosphorylation not demonstrated