• mice exhibit no obvious phenotype

• fails to form, on six sides out of eight, in four embryos

• missing, on five sides out of six, in three embryos

• 1 week after birth, few mice are still alive

• mice exhibit abnormal development of facial neuron precursors that do not migrate into r6 unlike in wild-type mice

• mice exhibit impaired development of retrotapezoid nucleus neurons compared with wild-type mice

• the parafacial area e-pF oscillator exhibits only occasional motor activity bursts with reduced frequency compared to in wild-type mice

• rhythmic phrenic discharges are less frequent than in wild-type mice

• mice fail to exhibit an accelerated respiratory-like rhythm phrenic discharge in response to low pH challenge unlike similarly treated wild-type mice

• surviving mice are smaller than wild-type mice

• mice exhibit abnormal development of facial neuron precursors that do not migrate into r6 unlike in wild-type mice

• mice exhibit impaired development of retrotapezoid nucleus neurons compared with wild-type mice

• mice die at E13.5

• mice exhibit phenotypic defects observed in Phox2b^tm1Jbr homozygotes

• 1 week after birth, mice are dead

• mice exhibit impaired development of retrotapezoid nucleus neurons compared with wild-type mice

• the parafacial area e-pF oscillator exhibits only occasional motor activity bursts with reduced frequency compared to in wild-type mice

• rhythmic phrenic discharges are less frequent than in wild-type mice

• mice fail to exhibit an accelerated respiratory-like rhythm phrenic discharge in response to low pH challenge unlike similarly treated wild-type mice

• mice exhibit impaired development of retrotapezoid nucleus neurons compared with wild-type mice

• absence of all head parasympathetic ganglia

• despite the absence of visceral or branchial motoneurons, the main trunk of the facial nerve is present (J:157532)

• visceromotor neurons are not produced

• absence of visceral or branchial motoneurons