Expression of Islet transcription factor paralogues during pineal development in vertebrates

CHASELON, DOMINIQUE; CAMARANO, ADRIANA C; CERVINO, AILEN; CIRIO, MARIA CECILIA; J DE SOUSA, FLAVIO S

Congreso; LASDB Meeting 2019 Xth Meeting of the Latin American Society for Developmental Biology; 2019

The pineal gland originates from the dorsal diencephalon of the vertebrate brain. In mammals, the main function of the pineal is the secretion of melatonin during night time by a specialised neuron, the pinealocyte. Studies in model organisms have allowed for the identification of a few genes necessary for pineal development. In fish, amphibians and avian embryos, the expression of paralogues of the Islet subfamily of LIM-HD transcription factors have been identified in the developing pineal gland, but not in mammals, leading us to study the expression of these factors during mouse development. By immunofluorescence, we observed that Islet expression is present in the pineal already at E14.5, when the evagination of the pineal anlage is well under way. Expression of Islet protein increases at later stages of development and, at birth, it is present in the outer pineal and in rosettes of developing pinealocytes. Importantly, Islet protein colocalises with the enzyme tryptophan hydroxylase (TPH), a marker of melatonin-producing cells, showing that Islet is a marker of differentiated pinealocytes. Data from genomic databases suggest that it is the Isl2 paralogue, but not Isl1, that is expressed in the pineal gland of mammals. To better characterise the evolution of these factors, we are also studying Isl1 and Isl2 expression during pineal development of the frog, Xenopus laevis. Our results establish Islet genes as potential regulators of pineal development in vertebrates.