Table 2.
Animal models for mCa2+ handling proteins of the inner mitochondrial membrane
| Reference | Model | Major Phenotype(s) |
|---|---|---|
| Pan et al. (119) | Mcu gene trap mouse (Mcu-null) | Ablation of rapid mCa2+ uptake; reduced skeletal muscle PDH activity; impaired capacity for treadmill running; reduced grip strength. Loss of Ca2+-induced PT, but cells are not protected from death with other stimuli. No protection from cardiac I/R injury. |
| Holmstrom et al. (122) | Mcu gene trap mouse (Mcu-null) | Impaired Ca2+-induced respiration but no cardiac functional defects basally; no change in heart’s response to chronic pressure overload or acute isoproterenol stress |
| Wu et al. (124) | αMHC-DN-MCU mice [constitutive expression of dominant-negative mutant (DIME→QIMQ) MCU in cardiomyocytes] | Impaired chronotropic response to isoproterenol; aberrant cellular Ca2+ handling related to impaired ATP production |
| Rasmussen et al. (125) | αMHC-DN-MCU mice [constitutive expression of dominant-negative mutant (DIME→QIMQ) MCU in cardiomyocytes] | Increased basal oxygen consumption, impaired inotropic and lusitropic contractile responses to increased cardiac pacing frequency; no protection against cardiac I/R injury |
| Luongo et al. (126) | Mcuflfl × αMHC-MCM mice; tamoxifen-inducible deletion of Mcu in adult cardiomyocytes | Reduced mPTP activation upon acute Ca2+; stress protection from cardiac I/R injury; diminished contractile response to acute β-adrenergic stimulation |
| Kwong et al. (127) | Mcuflfl × αMHC-MCM mice; tamoxifen-inducible deletion of Mcu in adult cardiomyocytes | No basal cardiac phenotype out to 1 yr of age, diminished NCLX expression and activity; reduced mPTP activation upon acute Ca2+, stress protection from cardiac I/R injury; diminished contractile response to acute β-adrenergic stimulation; impaired treadmill running that could be overcome with an exercise warm-up period; no protection from chronic pressure overload |
| Mammucari et al. (128) | 8-wk AAV-mediated MCU overexpression in mouse hindlimb skeletal muscle | Increased skeletal muscle fiber size; increased mitochondrial content; increased PGC-1α4 and IGF1-Akt/PKB signaling |
| Mammucari et al. (128) | 8-wk AAV-mediated MCU knockdown in mouse hindlimb skeletal muscle | Decreased skeletal muscle fiber size; decreased mitochondrial content; attenuated PGC-1α4 and IGF1-Akt/PKB signaling |
| Altamimi et al. (130) | Mcuflfl × αMHC-MCM mice; tamoxifen-inducible deletion of Mcu in adult cardiomyocytes | Increased fatty acid oxidation supporting increased contractility at baseline and after isoproterenol |
| Kwong et al. (129) | Mcuflfl × MyoD-Cre mice; constitutive deletion of Mcu in skeletal muscle | Impaired mCa2+ uptake an attenuation of Ca2+-stimulated mitochondrial respiration; impaired treadmill running capacity that could be overcome with a warm-up period; impaired glucose oxidation and impaired entry of carbon substrates into the TCA cycle; increased capacity for fatty acid metabolism. |
| Kwong et al. (129) | Mcuflfl × skeletal muscle α actin-MCM mice; tamoxifen-inducible deletion of MCU in adult skeletal muscle | Impaired mCa2+ uptake but no effect on skeletal muscle growth |
| Flicker et al. (132) | Mcuflfl × UCP1-Cre mice; constitutive deletion of Mcu in brown adipose tissue | Little effect on cold tolerance, diet-induced obesity, or transcriptional responses to cold exposure, despite effective ablation of acute mCa2+ uptake |
| Drago and Davis (134) | Drosophila with RNAi-mediated silencing of MCU homolog (GC18769) in mushroom body neurons | Defects in memory, but not learning, in adult flies. This effect was caused by silencing of MCU specifically during pupal development, which led to altered structure of mushroom body neurons. |
| Drago and Davis (134) | Drosophila with RNAi-mediated global silencing of MCU homolog (GC18769) | Developmentally lethal |
| Choi et al. (133) | Drosophila with loss-of-function mutant of MCU homolog (GC18769) | No gross defects, but flies are protected from oxidative stress. impaired mCa2+ uptake in response to caffeine. |
| Hutto et al. (237) | Zebrafish with cone photoreceptor-specific MCU overexpression | Increased mCa2+ uptake and mitochondrial swelling, but this is tolerated through late adulthood. Compensatory downregulation of MICU3. |
| Choi et al. (133) | Drosophila with muscle-specific MCU overexpression | Lethal, but lethality could be blocked by simultaneous knockdown of IP3R; lethality not blocked by simultaneous knockdown of IP3R and Sod1 |
| Choi et al. (133) | Drosophila with eye-specific overexpression of EMRE | No defective phenotype unless combined with overexpression of MCU; combined overexpression of MCU and EMRE is lethal. |
| Choi et al. (133) | Drosophila with knockdown of EMRE | Impaired mCa2+ uptake; phenocopies deletion of MCU. |
| Liu et al. (164) | Mice with constitutive deletion of Emre | Homozygous Emre−/− mice are born less frequently than expected and are small but viable. Resistance to Ca2+-induced permeability transition but no protection from cardiac I/R injury. |
| Liu et al. (163) | Heterozygous Emre deletion rescues homozygous deletion of Micu1. | |
| Antony et al. (206) | Mice with constitutive deletion of Micu1 (Micu1flfl × germline Cre-eIIa) | Perinatal lethality, trend toward reduced neuron density in nucleus ambiguus and nucleus facialis, possible defect in respiration. MEFs show excessive mCa2+ at low bath Ca2+ concentration. |
| Antony et al. (206) | Mice with inducible deletion of Micu1 in the liver (Micu1flfl injected with AAV8-Cre under a hepatocyte-specific thyroxine-binding globulin promoter) | Tolerated at baseline, but increased susceptibility to liver injury and impaired liver regeneration following experimental stress with partial hepatectomy |
| Liu et al. (163) | Mice with CRISPR/Cas9 mediated constitutive deletion of Micu1 | Perinatal lethality, small body weight and developmental delay, brain abnormalities, ataxia, and muscle weakness. Gradual compensatory downregulation of EMRE with age is associated with partial normalization of body mass and brain histology. |
| Debattisti et al. (207) | Mice with constitutive deletion of Micu1 in skeletal muscle (Micu1flfl × Creatine kinase-Cre) | Impaired mCa2+ uptake during twitch and tetanic muscle contraction, and sarcolemmal repair defect leading to muscle weakness and wasting |
| Drago and Davis (134) | Drosophila with RNAi-mediated silencing of MICU1 homolog (CG4495) in mushroom body neurons | Defects in memory, but not learning, in adult flies |
| Drago and Davis (134) | Drosophila with RNAi-mediated global silencing of MICU1 homolog (CG4495) | Developmentally lethal |
| M’Angale and Staveley (179) | Drosophila with inducible RNAi-mediated silencing of MICU1 homolog (GC4495) in neurons | Reduced survival and early loss of locomotor function |
| Xue et al. (209) | siRNA knockdown of Micu1 via lentiviral injection in the mouse heart | Exacerbated mCa2+ overload and myocardial injury, with exacerbated cardiac dysfunction, upon myocardial I/R |
| Tufi et al. (195) | Drosophila with homozygous null mutation of MICU1 homolog | Lethal; lethality is not rescued by simultaneous knockout of MCU or EMRE, or by ubiquitous overexpression of MICU3. |
| Bick et al. (234) | Micu2 gene trap mice with constitutive, global knockout of Micu2 | Little baseline phenotype, but diastolic dysfunction leads to left atrial enlargement by 16–18 mo of age. Accelerated cardiac decompensation upon chronic angiotensin II infusion; increased susceptibility to abdominal aortic aneurysm with chronic angiotensin II infusion |
| Tufi et al. (195) | Drosophila with CRISPR/Cas9-induced disruption of MICU3 homolog | Viable, but have a modest reduction in life span, climbing defect (interpreted as neurological defect) in both young and older flies. No effect on basal mitochondrial respiration in fly head tissue. |
| Puente et al. (236) | Mice with germline Micu3 deletion | No basal cardiac phenotype but protection from chronic isoproterenol-induced mCa2+ overload, contractile dysfunction, and left ventricular dilation; protection from ex vivo I/R injury |
| Lambert et al. (242) | CAG-CAT-MCUB transgenic × αMHC-MerCreMer mice (inducible adult cardiomyocyte-specific MCUB overexpression): | |
| • 5-day cardiac MCUB overexpression | Acute 5-day overexpression: diminished acute mCa2+ uptake; diminished baseline cardiac contractility and diminished contractile response to acute β-adrenergic stimulation; reduced mitochondrial metabolism; increased mortality during cardiac ischemia | |
| • 1-mo cardiac MCUB overexpression: | Chronic 1-mo overexpression: diminished acute mCa2+ uptake; normal cardiac contractile response to acute β-adrenergic stimulation, normal mitochondrial metabolism; reduced myocardial infarct size upon I/R | |
| Huo et al. (241) | Tetracycline-off model of cardiomyocyte MCUB overexpression (αMHC-tTA × TRE-MCUB mice, constitutively kept off DOX to allow constitutive MCUB overexpression | No detrimental effect on baseline cardiac function; protection of heart from I/R injury and mPTP activation |
| Huo et al. (241) | Mice with Mcub knockout first allele, for constitutive whole body disruption of Mcub | No detrimental effect on mCa2+ uptake, oxygen consumption, or cardiac function at baseline; exacerbated myocardial injury, cardiac remodeling, and contractile function following cardiac I/R |
| Tomar et al. (253) | Mice with constitutive, endothelial cell-specific deletion of Mcur1 (Mcur1flfl × VE-Cad-Cre) | Impaired endothelial cell mCa2+ uptake and reduced basal and agonist-induced increase in ATP; diminished cell proliferation and migration but increased autophagy. Mice are normal but have increased body heat dissipation associated with increased UCP2 expression in Mcur1-KO endothelial cells. |
| Tomar et al. (253) | Mice with constitutive, cardiomyocyte-specific deletion of Mcur1 (Mcur1flfl × αMHC-Cre) | Born at expected ratios but are small and die within 3 wk of birth; decreased cardiomyocyte mCa2+ uptake and mtCU currents, but normal cardiomyocyte mCa2+ content; increased autophagy in Mcur1-KO cardiomyocytes |
| Beutner et al. (275) | Mice with constitutive RyR1 knockout (RyR1−/−) | Lethal birth defect; animals die immediately after birth; trend toward elevated basal oxygen consumption in neonatal RyR1−/− heart homogenates; loss of Ca2+-stimulated increase in mitochondrial respiration |
| Luongo et al. (166) | Mice with tamoxifen-inducible, cardiomyocyte-specific deletion of NCLX (Slc8b1fl/fl × αMHC-MerCreMer) | Reduced cardiomyocyte mCa2+ efflux, cardiomyocyte mCa2+ overload, increased ROS production, and cardiomyocyte necrosis; left ventricular dilation and impaired contractility, cardiac hypertrophy and fibrosis; 87% lethality within 2 wk of cardiomyocyte NCLX deletion; rescued by simultaneous deletion of the mPTP component Cyclophilin D |
| Luongo et al. (166) | Mice with constitutive, cardiomyocyte-specific NCLX deletion (Slc8b1flfl × αMHC-Cre) | Normal viability but reduced mCa2+ efflux; compensatory reduction in mCa2+ uptake; normal cytosolic Ca2+ handling |
| Luongo et al. (166) | Mice with cardiomyocyte-specific, doxycycline-controlled transgenic NCLX overexpression (TRE-NCLX × αMCH-tTA) | Increased cardiomyocyte mCa2+ efflux; increased resistance to permeability transition, protection against cardiac I/R injury; protection from LV dilation, contractile dysfunction, hypertrophy, fibrosis, and inflammation after myocardial infarction |
| Jadiya et al. (323) | Neuronal-specific, constitutive deletion of NCLX in 3xTg-AD Alzheimer’s disease mouse model (3xTg-AD × Slc8b1fl/fl × Camk2a-Cre) | Accelerated impairment in spatial working memory, contextual recall, and cued recall; increased amyloid burden and tau pathology |
| Jadiya et al. (323) | Neuronal-specific, doxycycline-controlled overexpression of NCLX in 3xTg-AD Alzheimer’s disease mouse model (3xTg-AD × TRE-NCLX × Camk2a-tTA) | Protection against age-related cognitive decline, reduced amyloid plaque burden and tau pathology; reduced susceptibility to permeability transition; reduced Alzheimer’s disease-associated increase in brain superoxide production and lipid peroxidation |
| Pathak et al. (325) | Mice with constitutive, global CRISPR/Cas9-meditated disruption of NCLX (Slc8b1−/−) | Viable and develop fewer and smaller tumors when subjected to the colitis-associated colorectal cancer model |
| Sharma et al. (326) | C. elegans with null mutation in the NCLX-like gene ncx-9 | Developmental defects in the left/right projection patterning of the GABAergic motor neuron circuit |
| Hasegawa and van der Bliek (343) | C. elegans with null mutation in letm-1 | Homozygous animals arrest in L3 larval stage and are small and infertile. Heterozygous animals are normal. |
| Hasegawa and van der Bliek (343) | C. elegans with RNAi-mediated knockdown of letm-1 | Delayed development and small body size at adulthood; swollen and disorganized mitochondria |
| Hasegawa and van der Bliek (343) | C. elegans with transgenic expression of LETM-1 under the control of the myo-3 promoter | Crimping of the mitochondrial matrix, swelling of outer mitochondrial membrane, occasional detachment of outer membrane from the inner mitochondrial membrane and matrix |
| McQuibban et al. (353) | Drosophila with ubiquitous LETM1 (CG4589) knockdown using the tub-GAL4 driver, the da-GAL4 driver, or the act-GAL4 driver | Lethal during development |
| McQuibban et al. (353) | Drosophila with muscle-specific LETM1 (CG4589) knockdown using the mef2-GAL4 driver | Larvae are small and have reduced physical activity; most flies arrest growth in the pupal stage. Flies that progress to adulthood are small, weak, and unable to fly. |
| McQuibban et al. (353) | Drosophila with eye-specific LETM1 (CG4589) knockdown using the ey-GAL4 driver | Small eye facets surrounded by scar tissue; ommatidia exhibit swollen mitochondria. |
| McQuibban et al. (353) | Drosophila with nervous system-specific LETM1 (CG4589) knockdown using the elav-GAL4 driver or s-nyb-GAL4 driver | Reduced speed of locomotion and increased time spent immobile; reduced neurotransmitter release following nerve stimulation |
| Jiang et al. (372) | Mice with homozygous deletion of Letm1 via gene trap | Lethal by day 6.5 of embryogenesis |
| Jiang et al. (372) | Mice with heterozygous deletion of Letm1 via gene trap | ∼50% die by day E13.5. Surviving mice are relatively normal and have normal mitochondrial morphology, but have impaired brain ATP concentration and reduced PDH activity. Have increased seizures in response to kainic acid. |
| Zhang et al. (377) | Rats with lentiviral knockdown of LETM1 in the hippocampus and dentate gyrus | Mitochondrial swelling and reduced mitochondrial gene expression; increased susceptibility to seizures in a pilocarpine-induced epilepsy model. Increased seizure susceptibility is not corrected by treatment with the K+/H+ ionophore nigericin. |
| Elrod et al. (414) | Mice with constitutive, global ablation of Cyclophilin D (Ppif−/−) | Loss of mPTP activity; impaired cardiac mCa2+ efflux; increased cardiac TCA cycle flux and shift toward glucose rather than fatty acid metabolism; impaired cardiac contractility in response to acute isoproterenol infusion; exaggerated pressure overload-induced cardiac dysfunction and hypertrophy; exaggerated cardiac dysfunction and death upon chronic exercise |
See glossary for abbreviations.