Phenotypes for Etv1 MGI:3621018 MGI Mouse

abnormal golgi tendon organ morphology ( J:75311 )

• golgi tendon organ numbers are decreased in the soleus (by 77%), medial gastrocnemius (by 64%), and extensor hallucis longus (by 26%)

absent golgi tendon organ ( J:75311 )

• in some cases the soleus lacks golgi tendon organs

abnormal muscle spindle morphology ( J:75311 )

• spindle density is increased in dorsal and to a lesser extent in ventral crural muscles

• at P20-22, average spindle number is increased by 57% in the soleus, by 80% in the medial gastrocnemius, and by 26% in the extensor hallucis longus

• however, spindle numbers are decreased in proximal hindlimb muscles with dorsal muscles more severely affected than ventral muscles resulting in an overall decrease in spindle density in the hindlimbs

• about 69% of spindles contain fewer than the normal 4 intrafusal fibers and these spindles also have a shorter capsule and smaller periaxial fluid space

• the missing intrafusal fibers are generally the later forming chain fibers

abnormal innervation pattern to muscle ( J:75311 )

• myelinated nerve fibers in the soleus and medial gastrocnemius are decreased by 12-13% compared to wild-type

abnormal sensory neuron innervation pattern ( J:75311 )

• the proprioceptive branch of the soleus muscle nerve has 12% fewer myelinated fibers, innervates more spindles and fewer golgi tendon organs, and contains more group Ia afferents and fewer group Ib afferents

abnormal pacinian corpuscle morphology ( J:107207 )

• only 0.2% of 9400 neuron profiles show calbindin 2 expression compared to 5.6% of 700 neuron profiles in wild-type mice

abnormal dorsal root ganglion morphology ( J:75311 , J:107207 )

• fewer dorsal root ganglion neurons and axonal projections express calbindin 2 (J:75311)

• about a 14% and 23% decrease in neuron numbers are seen in the L4 and L3 dorsal root ganglia, respectively (J:75311)

• a 25% and 32% decrease in myelinated nerve fiber numbers are seen in the L4 and L3 dorsal root ganglia, respectively (J:75311)

• absent from the crus at P0-P1 (J:107207)

abnormal ventral spinal root morphology ( J:75311 )

• both L3 and L4 ventral spinal roots contain fewer small caliber motor axons (19% of the myelinated axon population) compared to wild-type mice (38% of the myelinated axon population)