Phenotypes Associated with This Genotype

Genotype
MGI:3045985

• Allelic Composition: Syn2^tm1Pggd/Syn2^tm1Pggd
• Genetic Background: Not Specified

• ♀: phenotype observed in females
• ♂: phenotype observed in males
• N: normal phenotype

nervous system

seizures ( J:202031 )

• epileptic seizures in adults

abnormal brain morphology ( J:91113 )

decreased brain weight ( J:91113 )

• at E16, brain weight was 17% lower than normal

• by E19 the brain weight reduction was only 12%

delayed CNS synapse formation ( J:91113 )

• synapse formation is delayed 2-3 days in culture

abnormal neuron morphology ( J:91113 )

• neurons in culture are arrested in an undifferentiated stage prior to axon formation

abnormal synaptic vesicle number ( J:202031 )

• the number of synaptic vesicles within the mossy fiber terminals in the hilar region of the dentate gyrate is reduced, however the total number of docked synaptic vesicles does not differ

abnormal hippocampus physiology ( J:202031 )

• pre-symptomatic mutants exhibit network impairments of the dentate gyrus, showing reduced mean amplitude of the response in the hilar region and a longer propagation time of evoked field postsynaptic potentials (fPSP), indicating decreased activity in the hilus upon stimulation of the perforant path

• hilar mossy cells of both young pre-symptomatic and older symptomatic (4-6 months) mice exhibit decreased excitability, showing a lower firing rate, an increase in the rheobase, and reduced input resistance

• however, granule cell excitability is normal

abnormal CNS synaptic transmission ( J:202031 )

• reduction in synaptic activity in dentate gyrus mossy cells of young pre-symptomatic mutants

• inhibitory output of hilar mossy cells to granule cells is reduced in both pre-symptomatic and symptomatic mutants; 40Hz tetanic stimulation results in an increase in depression at inhibitory synapses in granule neurons, however it is similar to wild-type at excitatory synapses, and the ratio between the evoked excitatory and inhibitory responses on the same granule cell is increased for the last 10 responses of the train, with a decrease of inhibitory responses

abnormal excitatory postsynaptic potential ( J:202031 )

• pre-symptomatic mutants exhibit a longer propagation time of evoked field postsynaptic potentials in the hilar region of the dentate gyrus

abnormal miniature excitatory postsynaptic currents ( J:202031 )

• hilar mossy cells of the dentate gyrus of both pre-symptomatic and symptomatic mutants show a reduction in miniature excitatory postsynaptic current (mEPSC) frequency and amplitude after blocking GABA receptors and NA+ channels with bicucalline indicating a decrease in excitatory presynaptic input on hilar mossy cells

decreased synaptic depression ( J:202031 )

• the depression induced by a train of stimuli (20 Hz for 5s) is reduced in hippocampal slices of young mutants, suggesting a reduced feedback inhibition of the granule cell layer

behavior/neurological

seizures ( J:202031 )

• epileptic seizures in adults

Mouse Models of Human Disease		DO ID	OMIM ID(s)	Ref(s)
epilepsy		DOID:1826		J:202031