MECR Human

What is the MECR gene and what is its primary function in human cells?

MECR (mitochondrial trans-2-enoyl-CoA reductase) encodes an enzyme that catalyzes the NADPH-dependent reduction of enoyl-ACP (acyl carrier protein) to saturated acyl-ACP in the mitochondrial fatty acid synthesis (mtFAS) pathway . This represents the last step of the fatty acid synthesis spiral, making it crucial for mitochondrial function . The enzyme is highly conserved in higher eukaryotes, indicating its evolutionary importance .

Methodologically, to study MECR function, researchers often create genetic modifications in model organisms. These modifications can include knockout models, knock-in constructs, or transgenic overexpression to observe resulting phenotypes and deduce gene function .

How are MECR mutations identified in human patients?

MECR mutations in humans are identified through several methodological approaches:

• Next-generation sequencing (NGS): Whole exome or genome sequencing can identify variants in the MECR gene.

• Variant confirmation: Findings are typically confirmed using Sanger sequencing.

• Variant classification: Identified variants are cataloged in databases such as the Global Variome shared LOVD database, which contains comprehensive information about MECR variants .

• Functional validation: Biochemical assays measuring MECR enzyme activity and protein lipoylation in patient samples.

For researchers investigating suspected MECR-related disorders, it's essential to correlate genetic findings with clinical presentations, particularly focusing on neurological symptoms, as MECR mutations have been associated with childhood onset dystonia, optic atrophy, and basal ganglia signal abnormalities .

What is MEPAN and how is it related to MECR?

MEPAN (mitochondrial enoyl-CoA reductase protein-associated neurodegeneration) is a disorder caused by recessive mutations in the human MECR gene . This condition is characterized by:

• Childhood onset dystonia

• Optic atrophy

• Basal ganglia signal abnormalities on MRI

• Decreased MECR function

• Reduced mitochondrial protein lipoylation

For researchers investigating MEPAN, it's crucial to understand that this represents a milder phenotype compared to complete MECR knockout, which in mouse models leads to embryonic lethality . The methodological approach to studying MEPAN should include neuron-specific knockout models rather than complete organism knockouts, as the latter may not survive long enough to model the disease progression accurately .

What experimental models are most appropriate for studying MECR function and pathology?

Based on research findings, several experimental models have proven valuable for MECR studies:

• Mouse genetic models: Three primary approaches have been documented:

  • Knockout models (Mecr^tm1d): Complete gene deletion leading to embryonic lethality

  • Conditional knockout models: Using Cre-loxP systems for tissue-specific deletion

  • Transgenic overexpression models: Placing Mecr under control of specific promoters (e.g., MT-1)

• Cell culture systems: For examining MECR's role in mitochondrial function, energy metabolism, and lipid synthesis.

• Patient-derived cells: For studying the effects of specific human MECR mutations.

When designing MECR studies, researchers should consider the embryonic lethality of complete knockouts and instead utilize conditional or tissue-specific approaches. For instance, cardiac-specific or neuron-specific knockouts would better model the tissue-specific manifestations of MECR dysfunction .

How does MECR overexpression impact cardiac function, and what methodologies are best for studying this relationship?

MECR overexpression significantly impacts cardiac function in mice, providing insights into potential human cardiac pathology mechanisms. Transgenic mice overexpressing Mecr under the metallothionein-1 (MT-1) promoter exhibited:

• Focal mitochondrial clumping in myocardium

• Decreased cardiac mechanical function

• Reduced performance in endurance exercise testing

• Development of ventricular dilatation

Research methodologies for studying MECR-cardiac relationships should include:

• Cardiac-specific Mecr expression: Using cardiac-specific promoters (rather than global overexpression with MT-1)

• Histological analysis: Both light and electron microscopy to examine mitochondrial morphology and tissue architecture

• Functional assessments: Including echocardiography and exercise performance testing

• Molecular analyses: Examining expression levels of related genes in cardiac tissue

The correlation between mitochondrial dysfunction and contractile heart dysfunction makes MECR transgenic mice a valuable model for studying broader mitochondrial metabolic disorders affecting the heart .

What are the technical challenges in generating viable MECR knockout models?

Creating viable MECR knockout models presents significant technical challenges due to the essential nature of this gene. Researchers have documented several important methodological considerations:

• Embryonic lethality: Complete Mecr knockout (Mecr^tm1d) in mice results in embryonic mortality within a surprisingly wide time window, making it challenging to study postnatal effects .

• Construct design complexities:

  • The "knock-out-first" approach required careful placement of FRT-flanked neo selection cassettes and loxP sites

  • For knock-in studies, complex cassettes with proper transcription terminators and selection markers are necessary

• Confirmation strategies:

  • PCR and Southern blotting for genotyping

  • RNA analysis to confirm expression levels

To overcome these challenges, researchers should consider:

• Conditional knockouts using tissue-specific Cre expression

• Inducible systems to control the timing of gene deletion

• Hypomorphic alleles that reduce but don't eliminate function

• Neuron-specific knockouts for studying MEPAN-like conditions

How do MECR studies inform our understanding of mitochondrial fatty acid synthesis in humans?

MECR research provides critical insights into mitochondrial fatty acid synthesis (mtFAS) in mammals, with methodological implications for broader mitochondrial disease research:

• Essential nature of mtFAS: The embryonic lethality of Mecr knockout demonstrates that mtFAS is absolutely required for mammalian development .

• Tissue-specific effects: The disproportionate impact on cardiac tissue when Mecr is overexpressed suggests tissue-specific roles for mtFAS products .

• Links to mitochondrial function: Research methodologies investigating MECR reveal connections between fatty acid synthesis and broader mitochondrial function, including mitochondrial enlargement observed in both yeast and mammalian models .

For researchers studying human mitochondrial diseases, MECR studies highlight the importance of considering fatty acid metabolism pathways, not just oxidative phosphorylation, when investigating mitochondrial disorders. Research methodologies should include lipidomic approaches alongside traditional mitochondrial function assays.

What methods should be employed to study the correlation between MECR variants and specific clinical phenotypes?

To effectively study correlations between MECR variants and clinical phenotypes, researchers should implement a multi-faceted methodological approach:

• Genotype-phenotype correlation studies:

  • Comprehensive clinical characterization of patients with MECR mutations

  • Comparison of clinical features across different mutation types

  • Development of severity scoring systems for MEPAN

• Functional characterization of variants:

  • In vitro enzyme activity assays for different variants

  • Measurement of lipoylation status of key mitochondrial proteins

  • Assessment of mitochondrial morphology and function in patient cells

• Model systems for variant testing:

  • Introduction of human variants into mouse models using CRISPR/Cas9

  • Development of patient-derived iPSCs and differentiation into relevant cell types

  • Tissue-specific expression of variants to assess organ-specific effects

The clinical presentation of MEPAN (with neurological features including dystonia and optic atrophy) contrasts with the cardiac phenotypes observed in mouse overexpression models, suggesting complex tissue-specific roles for MECR that require careful methodological consideration when designing experiments .

How should researchers design experiments to investigate the role of MECR in non-neurological and non-cardiac tissues?

While MECR research has focused primarily on neurological (MEPAN) and cardiac phenotypes, a complete understanding requires investigation of its role in other tissues. Methodological approaches should include:

• Tissue expression profiling:

  • Northern blot analysis shows MECR is actively expressed in kidney and liver, with moderate expression in heart and other tissues

  • Quantitative PCR to compare expression levels across tissues

  • In silico analysis using EST sources from databases like UniGene (NCBI)

• Tissue-specific knockout strategies:

  • Cre-loxP systems with tissue-specific promoters

  • Temporal control using inducible systems

  • Focus on high-expression tissues (kidney, liver) that haven't been thoroughly studied

• Metabolic impact assessment:

  • Lipidomic analysis of tissue-specific changes

  • Mitochondrial function assays in different tissues

  • Correlation of tissue-specific findings with clinical presentations

The expression pattern data shown in mouse studies indicates that MECR has differential expression across tissues, suggesting potentially diverse roles that warrant tissue-specific investigation approaches .

What are the most promising therapeutic targets based on current MECR research?

Current MECR research suggests several promising therapeutic targets and approaches:

• Substrate supplementation: Providing downstream products of the mtFAS pathway to bypass MECR deficiency.

• Enzyme enhancement strategies:

  • Chaperones to stabilize mutant MECR proteins

  • Small molecules to enhance residual enzyme activity in patients with hypomorphic mutations

• Mitochondrial support therapies:

  • Antioxidants to mitigate secondary damage

  • Metabolic cofactors to support mitochondrial function

• Gene therapy approaches:

  • AAV-mediated gene delivery to affected tissues

  • Focus on neurological tissue for MEPAN patients

Methodologically, researchers should prioritize assessing these approaches in cellular models derived from patients before advancing to animal studies. Given the embryonic lethality of complete knockouts, conditional models that more closely mimic human disease states should be used for therapeutic testing .

How can high-throughput sequencing data best be integrated with functional studies of MECR variants?

Effective integration of sequencing and functional data requires sophisticated methodological approaches:

• Variant prioritization pipeline:

  • Classification of variants based on conservation, structural predictions, and population frequency

  • Prioritization of variants for functional testing based on bioinformatic predictions

  • Integration with clinical data from databases like Global Variome shared LOVD

• High-throughput functional assays:

  • Development of cell-based reporter systems for MECR function

  • CRISPR-based screens to assess variant impacts

  • Metabolomic signatures as readouts for MECR activity

• Data integration frameworks:

  • Machine learning approaches to correlate sequencing and functional data

  • Network analyses to place MECR in broader mitochondrial pathways

  • Development of prediction algorithms for variant pathogenicity

• Validation in patient samples:

  • Correlation of in silico and in vitro findings with patient biomarkers

  • Development of accessible biomarkers for MECR function

This integrated approach allows researchers to move beyond simple variant identification to meaningful functional characterization of MECR variants identified through sequencing projects.

What methodological considerations should be made when developing biomarkers for MECR-related disorders?

Developing effective biomarkers for MECR-related disorders requires careful methodological planning:

• Direct enzyme activity measurement:

  • Development of accessible tissues or surrogate markers for MECR activity

  • Standardization of assays across laboratories

• Downstream pathway markers:

  • Lipoylation status of mitochondrial proteins as a functional readout

  • Metabolomic profiling focusing on fatty acid intermediates

• Tissue-specific considerations:

  • Neurological markers (CSF, neuroimaging) for MEPAN

  • Cardiac markers for potential cardiac involvement

  • Consideration of tissue accessibility for routine clinical monitoring

• Validation methodology:

  • Initial discovery in well-characterized patient cohorts

  • Validation in independent patient populations

  • Correlation with disease severity and progression

• Application in clinical trials:

  • Selection of biomarkers that can serve as meaningful endpoints

  • Focus on markers that reflect clinically relevant outcomes

Researchers should be particularly attentive to the neurological manifestations of MECR deficiency when developing biomarkers for MEPAN, while also considering the potential cardiac involvement suggested by animal models .

What databases and resources are available for researchers studying MECR variants?

Researchers investigating MECR have several specialized resources available:

• Variant databases:

  • Global Variome shared LOVD contains comprehensive information about MECR variants

  • ClinVar and other general variant databases may contain additional entries

• Expression databases:

  • UniGene (NCBI) provides EST-based expression data across tissues

  • GTEx for human tissue-specific expression patterns

• Model organism resources:

  • European Mouse Mutant Archive (EMMA) provides cryopreserved embryos of mutant mice

  • Mouse repositories for specialized Mecr mutant lines

• Research literature:

  • PubMed and other literature databases for MECR-related publications

  • Reference to seminal papers on MECR function and disease associations

Methodologically, researchers should cross-reference findings across multiple databases and validate computer predictions with experimental data whenever possible.

What experimental protocols have been validated for studying MECR function in different tissue contexts?

Several experimental protocols have been validated for studying MECR across different tissue contexts:

• Genotyping protocols:

  • PCR-based methods using specific primer sets (e.g., 5′-CAGGGCTGACCCAGAGTTTC-3′ and 5′-GACCCTGCTCTCATGAGCTGTCC-3′)

  • Southern blotting for transgene integration analysis

• Expression analysis:

  • Northern blotting for tissue expression patterns

  • RT-PCR and qPCR for quantitative expression analysis

• Histological analysis:

  • Haematoxylin-eosin staining for tissue morphology

  • Electron microscopy for mitochondrial structure examination

• Functional assessments:

  • Exercise performance testing in animal models

  • Cardiac function evaluation protocols

These validated protocols provide a foundation for researchers to build upon when designing new experiments to investigate MECR function in various tissues and disease contexts.

How can interdisciplinary approaches enhance MECR research outcomes?

MECR research benefits significantly from interdisciplinary approaches that integrate diverse expertise:

• Collaboration between basic scientists and clinicians:

  • Connecting molecular findings with clinical manifestations

  • Translating laboratory discoveries to clinical applications

  • Identifying clinically relevant research questions

• Integration of diverse methodologies:

  • Combining genetic, biochemical, and physiological approaches

  • Utilizing advanced imaging techniques alongside molecular studies

  • Incorporating systems biology approaches

• Cross-species investigation:

  • Leveraging evolutionary conservation of MECR across species

  • Comparative studies between yeast, mouse, and human systems

  • Translation of findings between model organisms and humans

• Technology integration:

  • Application of CRISPR/Cas9 for precise genetic modifications

  • Implementation of multi-omics approaches (genomics, proteomics, metabolomics)

  • Development of computational models of MECR function

The complex nature of MECR's role in mitochondrial function and disease necessitates these interdisciplinary approaches to fully understand its biology and develop effective interventions for MECR-related disorders.