α-Internexin expression in photoreceptor-like cells of the developing chicken pineal gland

Abstract

BackgroundIt has been reported that some pinealocytes have similar functions to retina photoreceptors in many non-mammalian vertebrates. Two types of pinealocytes, rudimentary-receptor pinealocytes and secretory pinealocytes, have been identified in the pineal gland of juvenile gull, but whether they exist in the chicken pineal gland was unknown. Hence, the purpose of this study was to investigate chicken α-internexin (chkINA) expression patterns in photoreceptor-like cells of the developing chicken pineal gland. Method In this study, we observed distribution patterns of chkINA in pineal gland at post-hatching day (P) 1, P7, P14, P21, P35, and at young adulthood chicks by using Immunocytologic analysis, and Western blot analysis. The ultrastructure changes were also observed by electron microscope. ResultsWestern blot and immunohistochemistry showed that chkINA expression was high in early developmental stages, but decreased across development. Visinin-immunoreactive cells were also detected during early development, reaching their greatest expression at post-hatching day 7, then gradually reducing over development. Further, confocal imaging revealed that chkINA and visinin were colocalized in photoreceptor-like cells of the chicken pineal gland. Ultrastructural observations revealed rudimentary-receptor pinealocyte morphology with cytoskeletal intermediate filaments in the embryonic chicken pineal gland. Therefore, we suggest that the existence of rudimentary-receptor pinealocytes might be highly relevant for photoreceptor-like cells. Conclusions We conclude that chkINA may be a useful photoreceptor-like cell marker for studying the chicken pineal gland. In particular, it could be a major cytoskeletal intermediate filament in rudimentary-receptor pinealocytes, which are homologous to photoreceptor cells in the chicken pineal gland. From an evolutionary viewpoint, we suggest that chkINA may be located not only in photoreceptor-like cells, but also in rudimentary-receptor pinealocytes.

Influence of Different Light Spectra on Melatonin Synthesis by the Pineal Gland and Influence on the Immune System in Chickens

“…According to [ 49 ], the pineal gland is populated by three main cell types: photoreceptor-like cells, pinealocytes, and supporting cells. The latter mainly consist of ependymal and astrocyte-like cells.…”

“…Another study showed that visinin in chick pinealocytes increased significantly after continuous light exposure, indicating the photosensitivity of pinealocytes and a possible role of visinin in photoreception [ 49 , 59 ]. Visinin is the specific marker of cone photoreceptor cells in the chicken retina [ 49 , 74 , 75 ]. Hao et al [ 49 ] used visinin to identify photoreceptor-like cells in the chicken pineal gland.…”

“…Visinin is the specific marker of cone photoreceptor cells in the chicken retina [ 49 , 74 , 75 ]. Hao et al [ 49 ] used visinin to identify photoreceptor-like cells in the chicken pineal gland. Following immunohistochemistry, the immunoreactivity of visinin was poorly expressed in the embryonic stage to adulthood, except at 7 days of age, when expression was high, which means that the number of photoreceptor-like cells in the chick pineal gland may be the highest in number at 1 week of age and then gradually decreases.…”

“…Following immunohistochemistry, the immunoreactivity of visinin was poorly expressed in the embryonic stage to adulthood, except at 7 days of age, when expression was high, which means that the number of photoreceptor-like cells in the chick pineal gland may be the highest in number at 1 week of age and then gradually decreases. Therefore, it is suggested that visinin-immunopositive photoreceptor-like pinealocytes in the chick pineal gland may play a role in neuroendocrine function [ 49 ].…”

Embryonic development of the chick pineal gland throughout the incubation periods

“…Since it functions like a primitive eye responsible for the perception of light, it is also called the parietal eye, primitive eye, third eye or apical eye (Altınbay, 2020; Kumar & Meshram, 2020; Tainika & Bayraktar, 2022). Birds have a very different pineal gland structure morphologically and cytologically (Hao et al., 2021; Petrusewicz‐Kosinska et al., 2019; Prusik, 2022; Ralph, 2020; Sapède & Cau, 2013). The structure of the organ shows significant changes during the incubation periods (Calvo & Boya, 1978, 1979; Jov'e et al., 1999; Möller & Möller, 1990; Ohshima & Matsuo, 1988).…”