Phenotypes for Egr3 MGI:3688874 MGI Mouse

postnatal lethality, incomplete penetrance ( J:49575 )

• born in expected numbers but 40% are dead by weaning

abnormal cholinergic neuron morphology ( J:160727 )

• at birth, mice exhibit a modest loss of all sizes of cholinergic motor neurons compared with wild-type mice

• at P5, mice exhibit increased motor neuron loss compared with wild-type mice due to loss of small diameter gamma-motor neurons

• at P10, loss of gamma-motor neurons is more complete with a 25% loss of gamma-motor neurons compared with wild-type mice

• at P20, mice exhibit a loss of small diameter cholinergic motor neurons compared with wild-type mice

decreased motor neuron number ( J:160727 )

• at birth, mice exhibit a modest loss of all sizes of cholinergic motor neurons compared with wild-type mice

• at P5, mice exhibit increased motor neuron loss compared with wild-type mice due to loss of small diameter gamma-motor neurons

• at P10, loss of gamma-motor neurons is more complete with a 25% loss of gamma-motor neurons compared with wild-type mice

• at P20, mice exhibit a loss of small diameter cholinergic motor neurons compared with wild-type mice

abnormal somatic sensory system morphology ( J:49575 )

abnormal muscle spindle morphology ( J:76256 )

• number of muscle spindles is normal at birth but progressively disassemble

• only about 1/3 of normal numbers are present at 12 days of age and those are about 50% smaller than normal

• spindle response to stimulation is defective

absent muscle spindles ( J:49575 )

• adult skeletal muscles lack muscle spindles

• normal numbers of type I extrafusal fibers

abnormal dorsal root ganglion morphology ( J:49575 )

• 75% loss of large myelinated fibers and 90% loss of small myelinated fibers from the L4 dorsal root ganglion

abnormal proprioceptive neuron morphology ( J:49575 , J:76256 )

• normal numbers of proprioceptive neurons in newborn mice but the neurons are smaller in size (J:49575)

• numbers of myelinated neurons drops to 75% of control numbers in adults (J:76256)

• neuron loss is primarily type Ia and II sensory as well as gamma motor neurons (J:76256)

• type Ib sensory neurons are unaffected (J:76256)

abnormal nervous system physiology ( J:76256 )

abnormal somatic nervous system physiology ( J:76256 )

• type Ia neurons function normally during first week of life but synaptic connection to motoneurons is lost at 2 days of age

abnormal excitatory postsynaptic potential ( J:76256 )

• loss of monosynaptic excitatory postsynaptic potential normally generated by stimulation of proprioceptive neurons of muscles

tremors ( J:49575 )

• prominent resting tremors

ataxia ( J:49575 )

abnormal limb posture ( J:49575 )

• abnormal limb position when stationary

abnormal gait ( J:49575 )

• waddling, uncoordinated gait