IDENTIFICATION OF A CHICKEN HOMOLOG IN THE BRN-3 SUBFAMILY OF POU-TRANSCRIPTION FACTORS

Among the many transcription factors thus far identified several are f ound to be expressed almost exclusively in the nervous system. The Brn -3 subfamily of POU-transcription factors constitutes a highly conserv ed group of such factors showing expression predominantly in sensory n eurons, We now describe the nucleotide sequence and proposed amino aci d sequence of a chicken homologue to the murine and human Brn-3 genes. Furthermore we characterise the early embryonic expression pattern of this chicken Brn-3 gene and show it to be expressed in peripheral sen sory ganglia as well as in retinal ganglion cells. Based on these find ings we conclude that the chicken homologue to the murine and human Br n-3a genes has been cloned. We have begun to examine possible regulato ry pathways of Brn-3a by stimulating chick embryonic peripheral gangli a with trophic factors and assaying resulting levels of Brn-3a with a quantitative PCR approach. Trigeminal and dorsal root ganglia stimulat ed in culture by NGF and NT-3 embryonic day 9 (E9) produce neurites wi thout raising the Brn-3a mRNA levels.