MVD

MVD encodes mevalonate diphosphate decarboxylase, a conserved enzyme of the mevalonate/sterol biosynthesis pathway whose fungal orthologs functionally complement yeast MVD-deficient mutants and are required for ergosterol production (PMID:12073030, PMID:31156588). Beyond its metabolic role, MVD physically interacts with mortalin (GRP75); mortalin overexpression lowers Ras and phosphorylated ERK2, an effect rescued by co-expressed MVD, linking MVD to Ras-ERK signaling control of proliferation (PMID:12646231). In human skin, biallelic loss of MVD function in keratinocytes is sufficient to cause porokeratosis: affected individuals carry a germline heterozygous MVD mutation and acquire a distinct somatic second-hit (frameshift, transition, or loss of heterozygosity) in each lesion, so that clonal expansion of an MVD-deficient keratinocyte precursor generates each lesion through a Knudson two-hit mechanism across multiple porokeratosis subtypes (PMID:30942823, PMID:31207227, PMID:33491095). A knock-in mouse carrying a porokeratosis-equivalent Mvd variant shows reduced cutaneous Mvd protein and, upon inflammatory challenge, attenuated skin inflammation with activated autophagy and no significant change in cholesterol-regulatory genes (PMID:37227548). A homozygous missense MVD variant co-segregates with autosomal recessive nonsyndromic sensorineural hearing impairment, with MVD protein localized to cochlear spiral ganglion cells (PMID:34135477).

1. 2002 Medium

   Establishing that the MVD gene product is a bona fide mevalonate diphosphate decarboxylase required showing its enzymatic function is conserved and physiologically regulated.

   Evidence Heterologous complementation of a yeast erg19(ts) mutant by Candida albicans MVD, with protein expression and Northern analysis of regulation

   PMID:12073030

   Open questions at the time

   • Does not characterize the human MVD enzyme directly
   • Catalytic residues and kinetics not defined here
2. 2003 Medium

   Whether MVD has roles beyond metabolism was addressed by identifying a protein partner that connects it to growth-control signaling.

   Evidence Yeast and mammalian two-hybrid plus Co-IP identifying mortalin/GRP75 binding, with overexpression rescue of mortalin-induced Ras/pERK2 suppression

   PMID:12646231

   Open questions at the time

   • Mechanism linking the enzyme to Ras-ERK is not defined
   • Single lab; physiological relevance in vivo untested
3. 2009 Low

   The structural basis for substrate, ATP, and inhibitor binding was probed to rationalize the catalytic mechanism of decarboxylation.

   Evidence Molecular docking and short MD simulation of S. cerevisiae MVD predicting substrate/ATP/inhibitor-contacting residues and a water-bridge deprotonation model

   PMID:19653015

   Open questions at the time

   • Purely computational; no experimental mutagenesis or crystal structure validation
   • Predictions are for the yeast enzyme, not human MVD
4. 2019 High

   The disease relevance of MVD was established by showing biallelic keratinocyte inactivation causes porokeratosis via combined germline and somatic mutations.

   Evidence Paired whole-exome sequencing of lesional skin versus blood in linear porokeratosis identifying germline splice plus somatic frameshift hits; targeted per-lesion sequencing in DSAP showing distinct second hits per lesion

   PMID:30942823 PMID:31207227

   Open questions at the time

   • Downstream metabolic consequence of MVD loss in keratinocytes not mechanistically traced
   • How biallelic loss drives clonal expansion at the pathway level unresolved
5. 2019 Medium

   Whether the vacuolar/sterol-pathway role of MVD is conserved and feedback-regulated was tested in a filamentous fungus.

   Evidence Subcellular localization, RNAi, overexpression, and sterol quantification of the Aspergillus oryzae ortholog AoErg19

   PMID:31156588

   Open questions at the time

   • Fungal ortholog; mammalian localization not addressed
   • Feedback regulation of human MVD pathway not established
6. 2021 Medium

   The two-hit model was extended across porokeratosis subtypes and connected to immune dysregulation in patients.

   Evidence Mutation and loss-of-heterozygosity analysis in porokeratosis plantaris/palmaris families; flow cytometry of patient PBMCs showing altered CD8+/Vd9Vd2 T-cell frequencies and cytokines

   PMID:33491095 PMID:35665211

   Open questions at the time

   • Causal link between MVD loss and T-cell changes not demonstrated
   • Immune findings rest on a single small cohort with one method
7. 2021 Low

   A second disease association was proposed, linking MVD to hearing through spiral ganglion expression.

   Evidence Exome and linkage analysis in a consanguineous family with recessive hearing impairment plus mouse cochlear immunohistochemistry

   PMID:34135477

   Open questions at the time

   • No functional or enzymatic rescue; single family
   • Causal mechanism in auditory neurons untested
8. 2023 Medium

   An in vivo model defined the cellular consequences of partial MVD loss, separating inflammatory and autophagy effects from cholesterol regulation.

   Evidence CRISPR/Cas9 MvdF250S/+ knock-in mouse with imiquimod challenge, assessed by Western blot, immunofluorescence, and qPCR

   PMID:37227548

   Open questions at the time

   • Mechanism linking MVD loss to autophagy activation not defined
   • Heterozygous model does not reproduce biallelic keratinocyte loss seen in lesions

• How biallelic MVD enzymatic deficiency mechanistically drives keratinocyte clonal expansion, autophagy, and inflammation — and whether the mortalin/Ras-ERK interaction operates in these contexts — remains unresolved.
• No defined metabolic intermediate linking MVD loss to lesion phenotype
• Mortalin-MVD signaling not tested in skin or hearing models
• No structural validation of human enzyme catalytic mechanism