Teashirt1 (Tshz1) is essential for the development, survival and function of hypoglossal and phrenic motor neurons

Abstract

Breathing and feeding are essential motor functions and rely on the activity of hypoglossal and phrenic motor neurons that innervate the tongue and diaphragm, respectively. Little is known about the genetic programs that control the development of these neuronal subtypes. The transcription factor Tshz1 is strongly and persistently expressed in developing hypoglossal and phrenic motor neurons. We used conditional mutation of Tshz1 in the progenitor zone of motor neurons (Tshz1MNΔ) to show that Tshz1 is essential for survival and function of hypoglossal and phrenic motor neurons. Hypoglossal and phrenic motor neurons are born in correct numbers, but many die between E13.5-E14.5 in Tshz1MNΔ mutant mice. In addition, innervation and electrophysiological properties of phrenic and hypoglossal motor neurons are altered. Severe feeding and breathing problems accompany this developmental deficit. While motor neuron survival can be rescued by the elimination of the pro-apoptotic factor Bax, innervation, feeding and breathing defects persist in Bax−/−;Tshz1MNΔ mutants. We conclude that Tshz1 is an essential transcription factor for the development and physiological function of phrenic and hypoglossal motor neurons.