Development
Author: Ricardo Daniel Romero Marin | Email: naft.rromero@gmail.com
Ricardo Daniel Romero Marin1°, Ángeles Amette Estrada1°, M. Cecilia Cirio1°, Flávio S J de Souza1°
1° Instituto de Fisiología, Biología Molecular y Neurociencias, CONICET
The pineal gland, a small cerebral structure responsible for nocturnal melatonin secretion,
exhibits remarkable morphological and cellular diversity among different vertebrates. While
the pineal is a fairly simple neuroendocrine structure in mammals, in anuran amphibians the
pineal complex includes the frontal organ, a structure derived from the pineal primordium that
exhibits photoreceptor capabilities. Transcription factors involved in mouse pineal
development include Pax6, Otx2, Crx and Lhx9, but the function of the Islet (Isl) transcription
factors in the pineal remains unexplored. This family, composed of Isl1 and Isl2, is present in
all vertebrates and encodes highly similar LIM-homeodomain proteins. In the present study,
we have characterised Islet expression in the pineal of developing mouse embryos and in
early and late stage Xenopus laevis larvae by immunofluorescence. We found that Islet is
expressed in differentiating pinealocites in both species, where is colocalises with
developmental factors like Pax6 as well as markers of melatonin synthesis, like serotonin and
tryptophan hydroxylase. Remarkably, Islet is also expressed in the frontal organ of the late
frog larva, suggesting that Islet factors might be involved in the development of photoreceptor,
as well as neuroendocrine, functions of the vertebrate pineal complex.