Table 2.
Published literature for animal models available for pre-synaptic CMS genes
| Gene | Animal | Technology Used | Model | Phenotype | Strength | Weakness | References |
| SLC5A7 | Mouse | Homologous recombination deletion (exon 2 to intron 4) | CHT(-/-) | Paralysis at birth, only spontaneous quantal release of ACh. Crossing with HB9-Cre increased survivability to 24hrs | ACh quantal release deficiency | Not viable; paralysis at birth | [16, 22–29] |
| CHT(-/+) | Improved survivability, cardiac involvement | Improved survival in heterozygotes, | Cardiac involvement noted in model, not observed, or studied in CMS patients | ||||
| CRISPR/Cas9 | CHTI89V | Developmental and behavioural defects, reduced ACh release and choline clearance | Diminished ACh release in cortex and striatum; neurological deficit observed | Impact on muscle morphology unknown | |||
| C. elegans | Cas9-sgRNA | Cho-1 | Viable, reduced ACh release, worsening phenotype when stressed | Reduced ACh release, stressing the model worsens phenotype | Impact on muscle morphology unknown | ||
| CHAT | Mouse | Injection of J1 Embryonic Stem Cell in C57BL/6 blastocyst with loss of Exon 11, 12 and 13 | ChAT(-/-) | Not viable at birth, paralysis, absent spontaneous and induced neurotransmission | Severe phenotype, absent neurotransmission | Not viable; paralysis at birth | [42–46] |
| ChAT(-/+) | Developmental impairment and behavioural defects, reduced lifespan, reduced muscle strength, motor function decreased | Viable, severe phenotype | Further work required to examine NMJs structure and muscle morphology | ||||
| D. renio | Point mutation (A to C) to the splice acceptor site of ChAT intron 2 | Bajan | Tail bend, behavioural defects, no evoked touch response, decreased spontaneous synaptic responses | Viable, CMS-like phenotype | NMJ structure and muscle morphology not investigated | ||
| Missense mutation S102R | Chata | Viable, CMS-like phenotype | NMJ structure and muscle morphology not investigated | ||||
| Canine | None (Spontaneous Mutation) | Exon 6 | Reduced run distance, stride length and recovery after exercise, decremental response at 3Hz | Exercise-induced muscle fatigue observed with decremental response | Spontaneous mutation, reproducibility challenging | ||
| SLC18A3 | Mouse | Homologous recombination Neo/tk knockdown of VAChT | VAChT(-/-) | Reduced spontaneous and induced ACh release, behavioural defects, loss of muscle strength | Knockdown of SLC18A3; Impaired ACh release, and loss of muscle strength; CMS-like phenotype | No major weakness detected; due to CMS-like phenotype | [52–58, 60–65] |
| VAChT(-/+) | Slight impairment in spontaneous ACh release, reduced memory output (maze test) and olfactory function | Impaired ACh release, and loss of muscle strength; CMS-like phenotype | Phenotype is mild, not consistent with human CMS patients | ||||
| Cre/LoxP creation of VAChT(six3 - Crefl/l) created and crossed with above line | VAChT(-/-) | Not viable at birth, paralysis, respiratory insufficiencies, cardiac development delay between parasympathetic and sympathetic tone | Severe phenotype observed | Not viable; paralysis at birth, cardiac dysfunction not documented in CMS patients | |||
| Motor neuron specific Cre/LoxP ablation of VAChT | VAChT(-/-) | Smaller motor neurons, decreased strength, hypoactive, impaired NMJ function and formation, atrophic muscle, kyphosis | Motor neuron specific, Severe phenotype, with impaired NMJ function, improved lifespan from other VAChT models | Motor neuron specific | |||
| D. melanogaster | Deletion of Cha, VAChT present in 1st exon of Cha | Cha(-/-) | Lethal phenotype at larval stage | Severe phenotype, NMJ development not studied | Not viable | ||
| C. elegans | Mutational screen revealed 19 independent unc-17 mutants | VAChTG347R | Reduced growth, poor coordination; other mutations reveal lethality that ablated gene function | Phenotype in some unc-17 mutants | Lethality in some mutations, viable mutations NMJ structure and function not studied | ||
| SYB1/ VAMP1 | Mouse | Nonsense mutation truncating SYB1 and VAMP1 | VAMP1(lew/lew) | Developmental and behavioural defects, muscle wasting, reduced survival (<3 weeks), decreased ACh release and synaptic transmission | Severe phenotype, with impaired NMJ function, and delayed motor development | Reduced lifespan, joint contractures not noted in model | [71–73] |
| SNAP25 | Mouse | Cre/LoxP knockout at Exon 4 | SNAP25(-/-) | Embryonic lethal, development delay, impaired NMJ formation, with reduced ACh release | Severe phenotype, with impaired NMJ function | Not viable | [76–80] |
| SNAP25(-/+) | Viable and fertile, minimal behavioural defects observed | Viable | No significant behavioural defects observed. Severe phenotype reported in SNAP25 CMS patients | ||||
| Missense mutation I67T | Blind-Drunk Mouse | Ataxic gait, behavioural impairment consistent with a schizophrenia-like symptoms | Neurological phenotype linked to schizophrenia | CMS phenotype not observed | |||
| B-6-Snap25tm3mc2 LoxP sites flanking Exon 5a/5b | SNAP25(-/-) | Fragmented axonal projections, axonal deterioration over time, behavioural defects | Impaired axonal projections, with deterioration suggesting neurological phenotype | More studies need to be determined to link to a CMS-phenotype | |||
| Rat | rAAV2/5 Over-expression in dorsal hippocampus | Male Wistar Rats (WT) | Cognitive defects, behavioural impairments | Neurological phenotype observed | Overexpression model with AAV, not observed in patients | ||
| SYT2 | Mouse | Homologous recombination inserting LacZ/Neo marker at Exon 2 | SYT2(-/-) | Developmental defects, impaired NMJ form and function, ataxic, seizures, non-viable | Severe phenotype with impairment of NMJ form and function | Non-viable, severe neurological phenotype observed with seizures, not consistent to CMS patients | [88–92] |
| D. melanogaster | Mutation of aspartate residues in the C2B domain | SYT2null | Decrease in evoked transmitter release | Decreased neurotransmitter release | Further studies are required to investigate CMS-like phenotype | ||
| L308P mutation in C2B domain | SYT2(-/-) | Developmental and behavioural defects, homozygous insertion of L308P resulted in lethal at 3 weeks | Severe neurological phenotype | Reduced lifespan | |||
| SYT2(-/+) | Developmental and behavioural defects, increased fatigability, reduced evoked transmitter release | Moderate neurological phenotype, CMS-like | CMS like however, NMJ structure not investigated | ||||
| D. renio | Morpholino injection of splice and translation blocking sequences | MO SYT2 | Loss of synchronous transmission at NMJs, asynchronous transmission not impacted | Impaired synchronous transmission | Mosaic expression of knockdown | ||
| UNC13A | Mouse | Homologous recombination in embryonic stem cells | MUNC13-1/2/3 (-/-) | Paralysis at birth, only spontaneous quantal release of Ach, small NMJs | Severe phenotype observed, NMJ form and function impaired | Not viable | [93, 95, 96] |
| C. elegans | Single copy transgenes introduced to EC6699 strain using mos1-mediated single copy insertion | MUNC13(-/-) | Developmental defects, paralysis due to impaired synaptic transmission | Severe phenotype observed, NMJ form and function impaired | Not viable | ||
| e1091, an amber mutant obtained by ethyl methansulfonate mutagenesis | MUNC13 mutant | Developmental and behavioural defects, incoordination, impaired neurotransmission | Viable model with impaired neurotransmission | Model requires more studies to confirm CMS-like phenotype | |||
| MYO9A | D. renio | Morpholino injection of splice and translation blocking sequences | MO myo9aa and myo9ab | Developmental delay, bent tail, behavioural defects, impaired NMJ structure and function | CMS phenotype, impaired NMJ structure and function | Mosaic expression system with morpholino | [15, 97–101] |
| Mouse | Mouse Exon 2 flanked with Cre/LoxP | MYO9A(-/-) | Retarded growth, behavioural defects, severe hydrocephalus, trembling gait, impaired kidney function | Neurological phenotype observed, muscle function impairment | NMJ form and function not studied | ||
| MYO9A(-/+) | Behavioural defects, impaired hippocampal synapse formation, memory and learning impairment | Neurological phenotype observed | NMJ form and function not studied | ||||
| PREPL | Mouse | Cre/LoxP targeting Exon 10 of PREPL | PREPL(-/-) | Reduced body weight, behavioural defects, impaired mitochondrial function, hypotonia | Viable, Muscle morphology dysfunction, with behavioural changes | Mitochondrial deficits not confirmed in patients | [110, 111] |
| LAMA5 | D. renio | Morpholino injection of splice and translation blocking sequences | MO LAMA5 | Muscle and nerve structural abnormalities, developmental delay, behavioural and developmental defects | CMS phenotype, impaired NMJ structure and function | Mosaic expression system with morpholino | [113–118] |
| Mouse | CRISPR/Cas9 creation of R291 L mutant | LAMApm | Die at birth, severe developmental defects, impaired kidney, and lung function | Severe phenotype with developmental defects | Not viable, NMJs not studied | ||
| Inducible Cre/LoxP (SP-Clama5fl/-) with doxycycline | SP-CLama5(fl/-) | Lethal shortly after birth, hypoxic, impaired epithelial differentiation and lung development | Severe phenotype, with developmental delay, respiratory issues consistent with patients | Early lethality, more studies required to examine NMJs of this model | |||
| Chimeric transgene Mr51 and Mr5G2H | LAMA(-/-) | Embryonic lethal, impaired lung and limb development; Mr5G2 H mice were viable but have reduced body size, and kidney function. | Mr5G2 H are viable and have impaired development | Not viable; Mr5G2 H viable but CMS phenotype not studied, lacks severe CMS phenotype seen in LAMA5-CMS patients | |||
| RPH3A | Mouse | Neomycin cassette flanking between exons of Rph3a, electroporated into ES cells | Rph3atm1Sud/J | Fertile, Enhanced axonal regeneration; rescues behavioural deficits after spinal cord injury. | Neuronal phenotype observed, mice are fertile | NMJs specifically not investigated, more information is needed to confirm CMS phenotype | [142–146] |
| Mouse | αsyn-PFF injected into C57Bl6 with AAV9-Rph3A overexpression | hSyn-GFP-Rph3a-WPRE-AAV9 | αsyn-PFF reduced Rph3A interaction with GluN2a-contiaing NMDRs, inducing neurological behavioural dysfunction, rescued with AAV9-Rph3a. | Neuronal phenotype observed, impacting Rph3A | NMJ phenotype not observed, not linked to CMS phenotype | ||
| Rat | RNAi knockdown in Middle cerebral artery occulusion (MCAO) model | LV-Rph3A-RNAi | Exacerbates cerebral infarction and neuronal death leading to neurological behavioural dysfunction | Neurological phenotype observed | MCAO model investigated, effect on NMJ unknown | ||
| C. elegans | Null mutation - 1500bp deletion including the promoter and 3 exons | Rbf-1 | Appeared lethargic, no impact on NMJ morphology, defecation, pharyngeal pumping and mating | Lethargic model, appears weak. | Did not alter NMJ morphology, | ||
| SLC25A1 | D. renio | Morpholino injection of splice and translation blocking sequences | MO SLC25A1 | Motor impairment, altered tail morphology, decreased swim and touch-evoked response, stunted motor neuron branching, with incomplete synapses | Neuromuscular phenotype observed, viable | Mosaic expression system with morpholino | [123, 126, 127] |
| Mouse | SLC25A1 overexpression | TRE-SLC25A1 nTg | Autistic-like phenotype (aberrant behaviours and repetitive jumping), altered synaptic structure and white matter content | Neurological phenotype observed, limited to brain involvement | SLC25A1 overexpression not observed in patients | ||
| SLC25A1 liver-restricted knockout (SLC25A1tm1a (EUCOMM) Wtsi +tg (Alb - cre) 21Mgn | SLC25A1-/- | Viable, normal liver histology, body weight and liver fat content, protected from steatosis, improved blood glucose clearance | Model restricted to liver assessment | NMJ phenotype not observed, not linked to CMS phenotype | |||
| D. melanogaster | Mutation to seaEP(reduced expression) | I(3)EP3364 | Increased chromosome aberrations, no functional characteristics noted | Viable model, more studies need to examine impact on NMJ neurotransmission | No phenotype observed |