Recombinant Ajellomyces dermatitidis Altered inheritance of mitochondria protein 31, mitochondrial (AIM31)

Advanced Research Questions

• How might AIM31 function relate to the dimorphic transition in Ajellomyces dermatitidis?

The dimorphic transition in A. dermatitidis (mold to yeast form) involves a heat-related partial uncoupling of oxidative phosphorylation, a process occurring in mitochondria . AIM31's potential role in this transition can be investigated through the following methodological approaches:

• Differential expression analysis:

  • Compare AIM31 expression levels between mold and yeast forms using RT-qPCR

  • Perform proteomics analysis of mitochondrial fractions from both morphological states

• Functional studies:

  • Generate AIM31 knockout or knockdown strains using CRISPR-Cas or RNAi techniques

  • Assess impact on:

    • Temperature-induced morphological transition (30°C vs. 37°C)

    • Mitochondrial membrane potential using fluorescent dyes (JC-1)

    • Respiratory complex integrity using blue native PAGE

    • Reactive oxygen species (ROS) levels using fluorescent probes

• Interaction analyses:

  • Perform co-immunoprecipitation to identify protein interaction partners that differ between morphological states

  • Use BioID or proximity labeling to identify proteins in close proximity to AIM31 in each form

The link between AIM31 and dimorphism is supported by findings that the transition from mycelial to yeast phase affects oxidative phosphorylation , and that the histidine kinase DRK1 regulates both dimorphism and virulence gene expression .

• What mitochondrial DNA editing technologies can be applied to study AIM31 function in pathogenic fungi?

Recent advances in mitochondrial DNA editing provide new opportunities for studying AIM31 function. Researchers can consider these methodological approaches:

• TALE-linked deaminases (TALEDs):

  • These engineered proteins allow for A-to-G editing of mitochondrial DNA

  • Recent improvements have reduced off-target effects by >99%

  • Optimized variants minimize bystander edits and off-target mtDNA mutations

  • Application: Create point mutations in AIM31 to assess the impact of specific residues on protein function

• DddA-derived cytosine base editors (DdCBEs):

  • Enable C-to-T editing in mitochondrial DNA

  • Show fewer transcriptome-wide off-target edits compared to TALEDs

  • Application: Generate stop codons or alter specific amino acids in AIM31

• Engineered bacterial toxins for mitochondrial editing:

  • New molecular editors derived from bacterial toxins can make precise C- G-to-T- A nucleotide changes

  • Recently developed at UW Medicine and Broad Institute

  • Application: Introduce specific mutations in AIM31 regulatory regions to study expression control

When implementing these technologies, researchers should:

• Design multiple guide RNAs targeting the AIM31 locus

• Include appropriate controls to assess editing efficiency

• Validate edits using deep sequencing

• Assess potential off-target effects through whole mitochondrial genome sequencing

• How can protein interaction mapping be used to identify AIM31's role in mitochondrial function?

To comprehensively identify AIM31's interaction partners and functional role, researchers should implement a multi-faceted protein interaction mapping approach:

• Affinity enrichment-mass spectrometry (AE-MS):

  • Express AIM31 with a C-terminal FLAG-tag to maintain mitochondrial localization

  • Perform pull-downs under different growth conditions (glucose vs. galactose media)

  • Analyze interaction partners using CompPASS scoring

  • This approach has successfully identified novel functions for uncharacterized mitochondrial proteins

• Proximity-dependent biotinylation (BioID):

  • Fuse AIM31 to a promiscuous biotin ligase (BirA*)

  • Identify proteins in close proximity through streptavidin purification

  • This method can capture transient interactions that might be missed by co-IP

• Conditional interactome analysis:

  • Compare AIM31 interactomes under normal and stress conditions (oxidative stress, hypoxia)

  • Identify condition-specific binding partners

• Validation studies:

  • Confirm key interactions using reciprocal co-immunoprecipitation

  • Employ CRISPR knockout models to assess the impact on AIM31 localization and function

  • Use blue native PAGE to assess effects on respiratory supercomplex assembly

Implementation example: In a study of uncharacterized mitochondrial proteins, researchers prioritized protein interactions with a stringent cutoff score that achieved 93% sensitivity for known PPIs while eliminating 95% of likely background interactions .

• What methods are optimal for studying AIM31's role in mitochondrial function and bioenergetics?

To comprehensively evaluate AIM31's impact on mitochondrial function, researchers should employ the following methodological approaches:

• Genetic manipulation strategies:

  • Generate knockout/knockdown models using CRISPR-Cas9 or RNAi

  • Create point mutations in conserved domains

  • Develop rescue experiments with wild-type and mutant constructs

• Mitochondrial functional assays:

  • Measure mitochondrial membrane potential using JC-1 or TMRM dyes

  • Quantify reactive oxygen species (ROS) using MitoSOX or DCF-DA

  • Assess citrate synthase activity as a marker of mitochondrial mass

  • Perform respirometry using Seahorse XF analyzer to measure:

    • Oxygen consumption rate (OCR)

    • Extracellular acidification rate (ECAR)

    • ATP production rate

• Structural and morphological analyses:

  • Examine mitochondrial network morphology using fluorescence microscopy

  • Assess cristae ultrastructure via transmission electron microscopy

In SMA carrier fibroblast studies, researchers observed reduced citrate synthase activity, depolarized mitochondrial membrane potential, and increased ROS levels . Similar approaches could be applied to study AIM31's impact on mitochondrial function in Ajellomyces dermatitidis.

• How does AIM31 contribute to respiratory chain function and what techniques can confirm this role?

AIM31 in Ajellomyces dermatitidis likely functions as a respiratory supercomplex factor similar to its homologs in other fungi. To investigate this role, researchers should employ:

• Respiratory complex assembly analysis:

  • Isolate mitochondria from wild-type and AIM31-deficient strains

  • Perform blue native PAGE to visualize intact respiratory complexes and supercomplexes

  • Conduct in-gel activity assays for specific complexes (particularly Complex I and IV)

  • Use 2D BN/SDS-PAGE to identify subunit composition changes

• Functional respiratory measurements:

  • Measure complex-specific activities using spectrophotometric assays:

    • Complex I (NADH:ubiquinone oxidoreductase)

    • Complex II (succinate dehydrogenase)

    • Complex III (ubiquinol:cytochrome c oxidoreductase)

    • Complex IV (cytochrome c oxidase)

    • ATP synthase activity

  • Perform high-resolution respirometry on isolated mitochondria

• Coenzyme Q (CoQ) analysis:

  • Quantify CoQ levels using HPLC with electrochemical detection

  • Assess electron transfer through the CoQ pool

• Genetic interaction studies:

  • Perform synthetic genetic array analysis with known respiratory complex components

  • Create double mutants with genes involved in respiratory complex assembly

This functional characterization approach was successfully applied to identify the role of PYURF as a SAM-dependent methyltransferase chaperone supporting both complex I assembly and coenzyme Q biosynthesis , and a similar strategy could elucidate AIM31's specific contributions to respiratory function.

• What are the methodological challenges in using real-time PCR to detect and quantify AIM31 expression in Ajellomyces dermatitidis during infection?

Researchers studying AIM31 expression during A. dermatitidis infection face several methodological challenges that require specific strategies to overcome:

• Sample preparation challenges:

  • Low abundance of fungal RNA in host tissues

  • Difficulty distinguishing fungal from host RNA

  • Solution: Use laser capture microdissection to isolate fungal cells from infected tissues or develop highly specific primers targeting fungal sequences

• Primer and probe design considerations:

  • Design primers specific to A. dermatitidis AIM31 (BDCG_03143/BDBG_02412)

  • Target regions with minimal sequence similarity to host genes

  • Validate specificity against host genomic DNA

  • Example primer approach based on successful B. dermatitidis detection :

  Target	Primer/Probe	Sequence (5' to 3')
  AIM31 forward	AIM31-F	[Sequence specific to A. dermatitidis AIM31]
  AIM31 reverse	AIM31-R	[Sequence specific to A. dermatitidis AIM31]
  AIM31 probe	AIM31-P	[Fluorescently labeled probe sequence]

• Analytical sensitivity and specificity optimization:

  • Develop positive control plasmids containing the AIM31 gene

  • Determine limit of detection (aim for ~100 copies/μl as achieved for B. dermatitidis detection)

  • Include internal amplification controls to identify PCR inhibition

  • Perform spiking experiments with known quantities of A. dermatitidis cells to assess recovery efficiency

• Reference gene selection for normalization:

  • Identify stable reference genes in A. dermatitidis under infection conditions

  • Validate reference gene stability across different morphological forms (yeast vs. mycelial)

  • Consider using multiple reference genes for more reliable normalization

A real-time PCR assay for B. dermatitidis detection achieved 100% specificity and 86% sensitivity compared to culture methods , providing a methodological framework that could be adapted for AIM31 expression studies.