Recombinant Xenopus laevis UPF0694 transmembrane protein C14orf109 homolog A

What is UPF0694 transmembrane protein C14orf109 homolog A and why is it studied in Xenopus laevis?

UPF0694 transmembrane protein C14orf109 homolog A (TMEM251-A) is a 131-amino acid transmembrane protein encoded by the tmem251-a gene in Xenopus laevis. This protein belongs to the uncharacterized protein family UPF0694, which contains members whose functions remain largely undefined. Xenopus laevis serves as an excellent model organism for studying this protein due to its well-characterized developmental stages and the ability to express heterologous proteins in its oocytes. The large size of Xenopus oocytes makes them particularly advantageous for electrophysiological studies of membrane proteins. Xenopus laevis oocytes are fully equipped with translational machinery that can efficiently translate and correctly localize exogenous, microinjected RNAs, making them ideal for studying transmembrane proteins like TMEM251-A .

How does Xenopus laevis serve as a model system for studying transmembrane proteins?

Xenopus laevis oocytes have become a gold standard in membrane protein research for several key reasons. First, they possess robust translational machinery capable of processing exogenous mRNAs into properly folded and post-translationally modified proteins. Second, the large size of oocytes (approximately 1mm in diameter) facilitates microinjection and subsequent electrophysiological recordings. Third, Xenopus oocytes have relatively low background expression of most ion channels and transporters, allowing for clear detection of heterologously expressed proteins .

For TMEM251-A research specifically, Xenopus provides a system where the protein can be studied in a vertebrate cellular environment while maintaining experimental control. The oocytes can correctly express different subunits of multiprotein complexes, making them ideal for studying potential interaction partners of TMEM251-A. Additionally, the ability to generate large numbers of embryos synchronously through in vitro fertilization allows for developmental studies of this protein across various stages .

What expression systems are optimal for recombinant production of Xenopus laevis TMEM251-A?

The optimal expression system for recombinant Xenopus laevis TMEM251-A depends on research objectives. For high-yield protein production, E. coli has been successfully employed as demonstrated in the commercially available recombinant protein preparation . The bacterial expression system utilizing His-tagging allows for efficient purification through affinity chromatography.

When using E. coli for expression, the BL21(DE3) strain with T7 RNA polymerase is commonly employed with pET vector systems for controlled induction using IPTG. Inclusion of fusion partners such as thioredoxin or SUMO can improve solubility of the transmembrane protein.

What purification strategy yields the highest purity of recombinant TMEM251-A?

The most effective purification strategy for recombinant TMEM251-A utilizes a multi-step approach. The commercial preparation achieves greater than 90% purity using the following methodology :

• Affinity Chromatography: For His-tagged TMEM251-A, immobilized metal affinity chromatography (IMAC) using Ni-NTA resin is the initial purification step. Optimal binding occurs at pH 8.0, with elution performed using an imidazole gradient (20-250 mM).

• Detergent Selection: As a transmembrane protein, proper solubilization is critical. Mild detergents such as n-dodecyl-β-D-maltoside (DDM) or lauryl maltose neopentyl glycol (LMNG) at concentrations just above their critical micelle concentration (CMC) effectively extract the protein while maintaining structural integrity.

• Size Exclusion Chromatography: This secondary purification step separates aggregated protein and contaminants based on molecular size, simultaneously allowing buffer exchange to remove imidazole.

• Ion Exchange Chromatography: A final polishing step using anion or cation exchange chromatography depending on the protein's isoelectric point can achieve >95% purity.

The quality control for the purified protein should include SDS-PAGE, Western blotting, and mass spectrometry to confirm identity and purity. For functional studies, assessment of proper folding through circular dichroism spectroscopy is recommended.

How should recombinant TMEM251-A be stored to maintain optimal activity?

Proper storage of recombinant TMEM251-A is critical for maintaining structural integrity and biological activity. Based on commercial protocols, the following storage conditions are recommended :

• Short-term Storage: For working aliquots intended for use within one week, store at 4°C in an appropriate buffer system such as Tris/PBS-based buffer (pH 8.0) containing 6% trehalose as a stabilizing agent.

• Long-term Storage: For extended storage, maintain the protein at -20°C or preferably -80°C. Prior to freezing, add glycerol to a final concentration of 20-50% to prevent freeze-thaw damage to protein structure.

• Lyophilization: For maximum stability, lyophilization (freeze-drying) in the presence of cryoprotectants like trehalose can extend shelf-life substantially. Reconstitution should be performed in deionized sterile water to a concentration of 0.1-1.0 mg/mL.

• Avoiding Degradation: Repeated freeze-thaw cycles significantly reduce protein activity and should be strictly avoided. Instead, prepare small working aliquots during initial reconstitution.

For reconstitution of lyophilized protein, briefly centrifuge the vial prior to opening to bring contents to the bottom. After adding the reconstitution buffer, gentle swirling rather than vortexing prevents protein denaturation. Additionally, small aliquots of reconstituted protein with glycerol addition (20-50% final concentration) should be prepared to prevent repeated freeze-thaw cycles .

What experimental approaches are most effective for determining the membrane topology of TMEM251-A?

Determining the membrane topology of TMEM251-A requires combining multiple experimental approaches to achieve reliable results. The following methodological strategies are recommended:

• Protease Protection Assays: This approach involves treating intact membrane vesicles containing TMEM251-A with proteases that cannot penetrate the membrane. Only protein domains exposed to the extracellular space will be digested, while transmembrane and intracellular domains remain protected. Subsequent western blotting with domain-specific antibodies reveals which regions were accessible to proteases.

• Substituted Cysteine Accessibility Method (SCAM): This technique involves systematically replacing amino acids with cysteines throughout the protein sequence. Membrane-impermeable thiol-reactive reagents are then applied to identify which cysteines are accessible from the extracellular space.

• Fluorescence Labeling: N- and C-terminal GFP fusion constructs expressed in Xenopus oocytes can help determine the orientation of these termini relative to the membrane. Combinations with selective permeabilization techniques provide information about cytoplasmic versus extracellular domains.

• Glycosylation Mapping: Introduction of artificial N-glycosylation sites at various positions in the protein sequence. Only sites exposed to the lumen of the endoplasmic reticulum during biogenesis will be glycosylated, helping map the topology.

Xenopus oocytes provide an excellent system for these studies due to their large size and efficiency in correctly expressing and localizing membrane proteins . For researchers with access to advanced facilities, cryo-electron microscopy of purified protein reconstituted into lipid nanodiscs offers the most definitive structural information.

How can I design experiments to identify interaction partners of TMEM251-A in Xenopus laevis?

Identifying interaction partners of TMEM251-A requires a multi-faceted approach combining in vitro and in vivo techniques. The following methodological workflow is recommended:

• Co-immunoprecipitation (Co-IP): Express tagged TMEM251-A in Xenopus oocytes or embryos, then perform pull-down experiments followed by mass spectrometry to identify co-precipitated proteins. For transmembrane proteins like TMEM251-A, careful selection of detergents is critical—start with digitonin or CHAPS which preserve many protein-protein interactions.

• Proximity Labeling: Express TMEM251-A fused to enzymes like BioID or APEX2 in Xenopus oocytes. These enzymes biotinylate nearby proteins, which can then be purified using streptavidin and identified by mass spectrometry. This approach is particularly valuable for identifying transient interactions within the membrane environment.

• Yeast Two-Hybrid Membrane System (MYTH): This modified yeast two-hybrid system is specifically designed for membrane proteins. The bait (TMEM251-A) is fused to the C-terminal half of ubiquitin and a transcription factor, while a library of prey proteins is fused to the N-terminal half of ubiquitin. Interaction reconstitutes ubiquitin, releasing the transcription factor.

• Functional Co-expression Studies: Systematically co-express TMEM251-A with candidate interaction partners in Xenopus oocytes, then assess changes in localization or function. The large size of oocytes facilitates electrophysiological measurements if TMEM251-A influences membrane conductance .

• Cross-linking Mass Spectrometry: Chemical cross-linking of proteins in their native environment followed by mass spectrometry can capture direct protein-protein interactions, particularly valuable for membrane protein complexes.

When designing these experiments, include appropriate controls including protein-specific antibodies. The C14orf109 (I-18) antibody (sc-242031) recognizes human C14orf109 and the corresponding mouse and rat homologs, and may cross-react with Xenopus laevis TMEM251-A based on sequence homology .

What functional assays can elucidate the physiological role of TMEM251-A?

To determine the physiological function of TMEM251-A, researchers should employ a combination of loss-of-function and gain-of-function approaches integrated with functional readouts. The following methodological strategy is recommended:

• Gene Knockdown/Knockout Studies:

  • Morpholino oligonucleotides can be injected into Xenopus embryos to knock down TMEM251-A expression

  • CRISPR/Cas9 can generate genetic knockouts in Xenopus

  • Analyze resulting phenotypes with special attention to developmental processes, membrane dynamics, and cellular physiology

• Overexpression Analysis:

  • Microinject TMEM251-A mRNA into Xenopus oocytes or embryos

  • Compare phenotypic outcomes to wild-type controls

  • Use tissue-specific or inducible promoters to control expression timing and location

• Subcellular Localization:

  • Create fluorescently-tagged TMEM251-A constructs

  • Express in Xenopus oocytes or embryonic tissues

  • Use confocal microscopy to determine precise subcellular localization

  • Co-stain with markers for various organelles (ER, Golgi, plasma membrane)

• Electrophysiological Measurements:

  • Use two-electrode voltage clamp recordings in Xenopus oocytes expressing TMEM251-A

  • Measure membrane conductance under various conditions

  • Test whether TMEM251-A functions as or modulates ion channels or transporters

• Substrate Transport Assays:

  • If TMEM251-A functions as a transporter, use radioactively or fluorescently labeled potential substrates

  • Measure uptake or efflux in TMEM251-A expressing versus control oocytes

  • Manipulate intracellular and extracellular conditions to characterize transport mechanism

Xenopus oocytes provide an excellent system for these functional studies due to their low background of endogenous channels and transporters, allowing clear detection of heterologously expressed proteins. The ability to inject substrates directly into oocytes also enables the study of reverse transport and intracellular content changes .

How does TMEM251-A in Xenopus laevis compare to its homologs in other species?

Comparative analysis of TMEM251-A across species provides valuable insights into its evolutionary conservation and functional importance. The protein, originally designated as C14orf109 in humans, has been renamed TMEM251 and has homologs across vertebrate species with varying degrees of conservation.

The most significant conservation occurs within the transmembrane domains, suggesting functional constraints on these regions. The N-terminal signal sequence shows greater variation across species, while maintaining its hydrophobic character necessary for membrane insertion.

Xenopus laevis contains two homeologs of TMEM251 (TMEM251-A and TMEM251-B) due to its pseudotetraploid genome resulting from a whole genome duplication event. These homeologs show approximately 90% sequence identity to each other with most differences occurring in non-transmembrane regions.

Functional studies indicate that human TMEM251 and its Xenopus homolog likely share conserved functions, as antibodies against human C14orf109 can also detect the corresponding mouse and rat homologs . This cross-reactivity suggests structural conservation at epitope regions, which may extend to the Xenopus protein.

What strategies can be employed to study post-translational modifications of TMEM251-A?

Post-translational modifications (PTMs) often play crucial roles in regulating membrane protein function, localization, and interactions. For TMEM251-A, the following methodological approaches are recommended for comprehensive PTM analysis:

• Mass Spectrometry-Based Approaches:

  • Enrich for phosphorylated peptides using titanium dioxide (TiO₂) or immobilized metal affinity chromatography (IMAC)

  • Employ glycopeptide enrichment using hydrazide chemistry or lectin affinity chromatography

  • Use parallel reaction monitoring (PRM) for targeted quantification of specific modified peptides

  • Apply electron transfer dissociation (ETD) fragmentation which preserves labile modifications better than collision-induced dissociation (CID)

• Site-Directed Mutagenesis:

  • Systematically mutate predicted modification sites (Ser/Thr/Tyr for phosphorylation, Asn for N-glycosylation, Lys for ubiquitination)

  • Express mutants in Xenopus oocytes and compare localization, stability, and function to wild-type protein

  • Create phosphomimetic (Ser/Thr to Asp/Glu) or phosphodeficient (Ser/Thr to Ala) mutations

• Modification-Specific Antibodies:

  • Use commercially available anti-phosphotyrosine, anti-phosphoserine, or anti-phosphothreonine antibodies

  • Apply these in western blotting or immunoprecipitation experiments to detect phosphorylated TMEM251-A

• Metabolic Labeling:

  • Incorporate radioactive orthophosphate (³²P) into oocytes expressing TMEM251-A to detect phosphorylation

  • Use azide-modified sugar analogs followed by click chemistry for detection of glycosylation

• Pharmacological Manipulation:

  • Treat TMEM251-A-expressing oocytes with kinase inhibitors or phosphatase inhibitors

  • Use tunicamycin to inhibit N-glycosylation or glycosidases to remove existing glycans

  • Observe changes in protein function, localization, or stability

When expressing TMEM251-A in Xenopus oocytes, researchers should note that these cells possess endogenous kinases, phosphatases, and glycosylation machinery that may modify the recombinant protein similarly to its native context. This makes oocytes particularly valuable for studying the functional consequences of PTMs .

How can CRISPR/Cas9 genome editing be applied to study TMEM251-A function in Xenopus laevis?

CRISPR/Cas9 genome editing provides powerful tools for investigating TMEM251-A function through targeted genetic modifications. The following methodological workflow is recommended for Xenopus laevis:

• Guide RNA (gRNA) Design:

  • Target conserved regions of the tmem251-a gene using multiple bioinformatics tools (e.g., CHOPCHOP, CRISPOR)

  • Account for Xenopus laevis' pseudotetraploid genome by designing gRNAs that target both homeologs if desired

  • Verify specificity to avoid off-target effects

  • Include gRNAs targeting different exons to increase success probability

• Delivery Methods:

  • For F0 phenotypic analysis: microinject Cas9 protein (1-2 ng) complexed with gRNA (400-800 pg) into fertilized eggs at one-cell stage

  • For germline transmission: inject dorsal blastomeres at 4-8 cell stage to target the presumptive germ cells

  • Use a fluorescent tracer (e.g., GFP mRNA) to confirm successful injection

• Mutation Detection and Characterization:

  • Perform T7 endonuclease I assay or heteroduplex mobility assay on PCR products from targeted regions

  • Use high-resolution melt analysis for rapid screening

  • Confirm mutations through Sanger sequencing of individual clones

  • For complex edits, apply next-generation sequencing

• Phenotypic Analysis:

  • Examine developmental phenotypes in F0 mosaic embryos

  • For transmembrane proteins like TMEM251-A, focus on cell membrane integrity, morphogenesis, and tissue-specific effects

  • Use tissue-specific markers to identify affected developmental processes

  • Perform rescue experiments by co-injecting wild-type mRNA to confirm specificity

• Functional Validation:

  • Extract oocytes from F0 adults or raise F1 generation from founders

  • Perform electrophysiological measurements to assess membrane properties

  • Analyze protein localization using immunohistochemistry

  • Conduct molecular interaction studies to identify disrupted protein-protein interactions

The efficiency of CRISPR/Cas9 editing in Xenopus laevis typically ranges from 40-90% depending on the target sequence. When designing experiments, researchers should account for potential compensation by the homeologous gene (tmem251-b) by creating double knockouts if necessary .

What are common challenges in expressing and purifying TMEM251-A and how can they be overcome?

Transmembrane proteins like TMEM251-A present unique challenges during expression and purification. The following table outlines common issues and recommended solutions:

When working with recombinant TMEM251-A, researchers should note that E. coli expression systems can produce high yields but may lack important post-translational modifications. For functional studies, expression in Xenopus oocytes may provide a more native-like protein despite lower yield . The commercial recombinant preparation achieves >90% purity through optimized protocols that include lyophilization with trehalose as a stabilizing agent .

How can I optimize TMEM251-A expression in Xenopus laevis oocytes for electrophysiological studies?

Optimizing TMEM251-A expression in Xenopus laevis oocytes requires attention to several critical factors. The following methodological approach is recommended:

• mRNA Preparation:

  • Clone the tmem251-a gene into a vector containing 5' and 3' untranslated regions from Xenopus β-globin for enhanced translation efficiency

  • Use linearized DNA templates and high-fidelity RNA polymerase (T7, SP6, or T3) for in vitro transcription

  • Include 5' cap analog and 3' poly(A) tail to improve mRNA stability and translation

  • Purify mRNA using LiCl precipitation followed by ethanol precipitation to remove enzymes and unincorporated nucleotides

• Oocyte Selection and Preparation:

  • Obtain oocytes from adult female Xenopus laevis through partial ovariectomy

  • Select stage V-VI oocytes (1.0-1.2 mm diameter) with clear polarization between animal and vegetal poles

  • Defolliculate oocytes using collagenase treatment (2 mg/ml in Ca²⁺-free OR2 solution) for 1-1.5 hours

  • Allow oocytes to recover for 24 hours in modified Barth's solution containing antibiotics

• Microinjection Parameters:

  • Inject 50-100 ng of mRNA in 50 nl volume into the cytoplasm near the border of animal and vegetal hemispheres

  • Use pulled glass micropipettes with tip diameter of 10-20 μm

  • For co-expression studies with potential interacting proteins, adjust mRNA ratios to achieve desired expression levels

  • Include negative controls (water-injected) and positive controls (known channel/transporter)

• Incubation Conditions:

  • Maintain injected oocytes at 16-18°C in modified Barth's solution

  • Replace solution daily to prevent bacterial growth

  • Allow 2-5 days for optimal protein expression before electrophysiological recordings

  • Monitor health of oocytes and discard any showing signs of deterioration

• Electrophysiological Recording Optimization:

  • Use two-electrode voltage clamp technique with electrodes filled with 3M KCl

  • Optimize holding potential based on expected function (start with -60 mV)

  • Perform recordings in appropriate bath solutions based on hypothesized function

  • Apply potential substrates or modulators to characterize transport or channel properties

The large size of Xenopus oocytes makes them ideal for electrophysiological characterization of membrane proteins like TMEM251-A. Additionally, oocytes have relatively low background conductances, allowing clear detection of heterologously expressed proteins . If TMEM251-A does not exhibit intrinsic channel or transport activity, consider co-expression with potential interacting partners to reveal modulatory functions.

What quality control methods should be employed to verify the identity and activity of recombinant TMEM251-A?

Comprehensive quality control is essential to ensure the identity, purity, and functional integrity of recombinant TMEM251-A. Researchers should implement the following methodological workflow:

• Identity Verification:

  • Mass Spectrometry Analysis: Perform peptide mass fingerprinting after tryptic digestion to confirm protein identity against theoretical digest patterns

  • Western Blotting: Use specific antibodies like C14orf109 (I-18) that may cross-react with Xenopus laevis TMEM251-A

  • N-terminal Sequencing: Verify the first 5-10 amino acids through Edman degradation

  • Intact Mass Analysis: Compare observed molecular weight with theoretical prediction, accounting for post-translational modifications

• Purity Assessment:

  • SDS-PAGE: Evaluate purity through Coomassie or silver staining (commercial preparation achieves >90% purity)

  • Size Exclusion Chromatography: Analyze peak homogeneity and retention time

  • Dynamic Light Scattering: Assess sample monodispersity and detect aggregation

  • Analytical Ultracentrifugation: Determine sedimentation coefficient and homogeneity

• Structural Integrity:

  • Circular Dichroism Spectroscopy: Evaluate secondary structure composition, particularly alpha-helical content expected in transmembrane domains

  • Fluorescence Spectroscopy: Measure intrinsic tryptophan fluorescence as an indicator of native folding

  • Limited Proteolysis: Compare digestion patterns between batches to ensure consistent folding

  • Thermal Shift Assays: Determine protein stability and the effects of various buffer conditions

• Functional Validation:

  • Ligand Binding Assays: If ligands are known or predicted, assess binding through techniques like surface plasmon resonance

  • Reconstitution into Liposomes: Evaluate membrane insertion and orientation

  • Electrophysiological Studies: If expressed in Xenopus oocytes, measure membrane conductance changes in response to stimuli

  • Protein-Protein Interaction Assays: Verify interactions with known binding partners through pull-down assays

• Batch Consistency:

  • Certificate of Analysis: Document key parameters including concentration, purity, pH, and endotoxin levels

  • Stability Testing: Monitor protein integrity under storage conditions (4°C, -20°C, -80°C) over time

  • Lot-to-Lot Comparison: Perform side-by-side testing of critical parameters between production batches

For storage and handling, best practices include aliquoting to avoid freeze-thaw cycles, maintaining protein in Tris/PBS-based buffer with 6% trehalose (pH 8.0), and adding glycerol (20-50%) for freezing . When reconstituting lyophilized protein, gentle mixing rather than vortexing prevents denaturation.

What emerging technologies could advance our understanding of TMEM251-A function?

Several cutting-edge technologies hold promise for elucidating the function and molecular mechanisms of TMEM251-A. Researchers should consider these methodological approaches for future studies:

• Cryo-Electron Microscopy (Cryo-EM):

  • Determine high-resolution structure of TMEM251-A in lipid nanodiscs or detergent micelles

  • Visualize conformational changes upon interaction with potential binding partners

  • Map functional domains and potential ligand binding sites with near-atomic resolution

  • Combine with molecular dynamics simulations to understand protein dynamics

• Genome-Wide CRISPR Screens:

  • Identify genetic interactions with tmem251-a through systematic knockout or activation screens

  • Use synthetic lethality approaches to uncover functionally related genes

  • Apply in Xenopus cell lines or embryos using high-throughput phenotyping

  • Correlate phenotypes with molecular pathways to infer function

• Single-Cell Transcriptomics and Proteomics:

  • Map expression patterns of TMEM251-A across different cell types in developing Xenopus embryos

  • Identify co-expressed gene modules that suggest functional associations

  • Track changes in expression during key developmental transitions or in response to perturbations

  • Integrate with spatial transcriptomics to understand tissue-specific roles

• Optogenetic and Chemogenetic Tools:

  • Engineer light-sensitive domains into TMEM251-A to allow temporal control of activity

  • Develop small-molecule modulators of TMEM251-A function for precise manipulation

  • Combine with electrophysiology in Xenopus oocytes for real-time functional analysis

  • Apply in developing embryos to understand tissue-specific functions

• Integrative Multi-Omics Approaches:

  • Combine transcriptomics, proteomics, metabolomics, and interactomics data

  • Create comprehensive models of TMEM251-A function within cellular networks

  • Use systems biology approaches to predict phenotypic outcomes of perturbations

  • Validate predictions through targeted experiments in Xenopus model system

These technologies, particularly when applied in combination, could significantly advance our understanding of TMEM251-A beyond current knowledge limitations. The Xenopus model system continues to be valuable for these studies due to its experimental tractability and the sophisticated tools available for genetic manipulation .

How might comparative studies across species contribute to our understanding of TMEM251-A function?

Comparative analysis across species represents a powerful approach to uncover conserved functions and species-specific adaptations of TMEM251-A. The following methodological strategy can maximize insights from evolutionary comparisons:

• Phylogenetic Analysis and Evolutionary Rate Studies:

  • Construct comprehensive phylogenetic trees of TMEM251 homologs across vertebrate and invertebrate species

  • Calculate evolutionary rates for different protein domains to identify functionally constrained regions

  • Map known mutations or variants onto phylogenetic trees to correlate with functional divergence

  • Perform synteny analysis to identify conserved genomic neighborhoods suggesting functional associations

• Structure-Function Correlation Across Species:

  • Align amino acid sequences from diverse species to identify invariant residues likely critical for function

  • Create homology models based on structures from different species if available

  • Perform site-directed mutagenesis of conserved residues in Xenopus TMEM251-A to validate functional importance

  • Express homologs from different species in Xenopus oocytes to compare functional properties

• Expression Pattern Comparison:

  • Compare tissue-specific and developmental expression patterns of TMEM251 across species

  • Identify conserved regulatory elements in promoter regions that drive expression

  • Correlate expression patterns with physiological processes to infer potential functions

  • Use cross-species transcriptomics data to identify co-expressed gene modules conserved across evolution

• Functional Complementation Studies:

  • Test whether TMEM251 homologs from different species can rescue phenotypes in Xenopus knockouts

  • Create chimeric proteins combining domains from different species to map functional regions

  • Express human TMEM251 in Xenopus oocytes alongside native TMEM251-A to compare properties

  • Evaluate conservation of protein-protein interactions across species

• Phenotypic Analysis Following Genetic Manipulation:

  • Compare phenotypes resulting from TMEM251 knockout or overexpression across model organisms

  • Focus on developmental processes, particularly those involving membrane dynamics or cellular communication

  • Correlate phenotypic differences with sequence divergence to identify functionally important regions

  • Assess conservation of genetic interactions across species

The pseudotetraploid genome of Xenopus laevis provides a unique opportunity to study sub-functionalization between the two homeologs (TMEM251-A and TMEM251-B) as a model for functional divergence after gene duplication . This natural experiment in genome evolution can provide insights into how TMEM251 function may have specialized in different contexts.