The identification of a conserved Eya3 signal and prolactin-releasing factors in the long day response of a seasonal mammal

• Published in: Current biology Vol. 20; no. 9; pp. 829 - 835
• Main Authors: Dupré, Sandrine M, Miedzinska, Katarzyna, Duval, Chloe V, Yu, Le, Goodman, Robert L, Lincoln, Gerald A, Davis, Julian RE, McNeilly, Alan S, Burt, David D, Loudon, Andrew SI
• Format: Journal Article
• Language: English
• Published: 29-04-2010
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2010.02.066

Seasonally breeding mammals such as sheep use photoperiod, encoded by the nocturnal secretion of the pineal hormone melatonin, as a critical cue to drive hormone rhythms and synchronise reproduction to the most optimal time of year [
1
,
2
]. Melatonin acts directly on the
pars tuberalis
(PT) of the pituitary, regulating expression of thyrotropin (TSH) which then relays messages back to the hypothalamus to control reproductive circuits [
3
,
4
]. In addition, a second local intra-pituitary circuit controls seasonal prolactin (PRL) release
via
a currently uncharacterised low molecular weight peptide(s) termed tuberalin(s) of PT origin [
5
–
7
]. Studies in birds identified the transcription factor
Eya3
as the first molecular response activated by long photoperiods (LP) [
8
]. Using arrays and
in situ
hybridization studies, we show
Eya3
as the strongest LP activated gene in sheep, revealing a common photoperiodic molecular response in birds and mammals. We also identified
TAC1
(encoding the tachykinins Substance P and Neurokinin A; NKA) to be strongly activated by LP within the sheep PT. We show that these PRL secretagogues act on primary pituitary cells, and are thus candidates for the elusive PT-expressed “tuberalin” seasonal hormone regulator.