Transient expression of LIM‐domain transcription factors is coincident with delayed maturation of photoreceptors in the chicken retina

Abstract

In the retina of warm-blooded vertebrates, photoreceptors are specified many days before the onset of synaptogenesis and the expression of photopigments. The factors that regulate the maturation of photoreceptors in the developing retina remain unknown. We report here that photoreceptors transiently express LIM-domain transcription factors during the development of the chicken retina. We examined the differentiation of photoreceptors through the normal course of embryonic development and at the far periphery of the postnatal retina, where the differentiation of photoreceptors is slowed and persists across a spatial gradient. In the embryonic retina, we find visinin-positive photoreceptors that transiently express Islet2 and Lim3 starting at E8 and ending around E15, but persisting in far peripheral regions of the retina through the first 2 weeks of postnatal development. During early stages of photoreceptor maturation, there is coincident and transient expression of the LIM-domain factors with axonin1, a cell surface glycoprotein that is a member of the immunoglobulin super family. Coincident with the down-regulation of Islet2 and Lim3, we find the up-regulation of calbindin, red/green opsin, rhodopsin and a synaptic marker in the OPL (dystrophin). In the periphery of the postnatal retina, photoreceptors that express Islet2, Lim3 and axonin1 do not overlap with photoreceptors that express calbindin, red/geen opsin, rhodopsin, and dystrophin. We propose that Islet2 and Lim3 may promote the expression of genes that are involved in the early stages of differentiation, but may suppress the expression of genes that are required in the mature photoreceptors.

Expression and function of the LIM-homeodomain transcription factor Islet-1 in the developing and mature vertebrate retina

“…Lim3 (Lhx3) is specifically expressed by postmitotic bipolar cells in the developing chick retina (Edqvist and Hallb€ o€ ok, 2004) and in a subset of bipolar cells in the mature mouse retina (Kim et al, 2008). Fischer et al (2008) have shown that Lim3 and Islet-2 (Isl2) are transiently expressed by differentiating photoreceptors in the developing chick retina. Isl2 is also expressed by ganglion cells in the retina (Edqvist et al, 2006) and contributes to the guidance of retinal ganglion cell axons (Pak et al, 2004).…”

“…Fischer et al, 2008 Isl1 immunoreactivity in the developing retina -Isl1 is not expressed by differentiating photoreceptors.…”

“…of Isl1 in the outer nuclear layer (ONL) during retinal development in the turtle (Francisco-Morcillo et al, 2006) and in the chick (Edqvist et al, 2006;Fischer et al, 2008).…”

Forkhead Box Protein P1 Is Dispensable for Retina but Essential for Lens Development

“…21 Although the level of Lhx3 was slightly decreased in the Foxp1-CKO lens in the microarray, Foxp1 is known to suppress Lhx3 expression and promote Hox6, 9, or 10 in motor neurons, 30 In the retina, Lhx3 promotes the expression of genes that are involved in the early stages of differentiation, but may suppress the expression of genes that are required in mature photoreceptors in chicken retina. 31 In addition, although the involvement of these particular members of Hox in retinal and lens development had not been reported, these molecules are candidates to clarify mechanisms of roles of Foxp1 in the eye.…”

Identification and Analysis of Two Novel Sites of Rat GnRH Receptor Gene Promoter Activity: The Pineal Gland and Retina

“…In particular, LIM homeodomain proteins LHX3 and ISL1 synergize with bHLH transcription factors to specify motor neuron subtype identity in the embryonic spinal cord [16]. In the chicken retina, photoreceptors transiently express LIM homeodomain proteins during development, before the onset of synaptogenesis and expression of terminal differentiation marker genes such as those encoding photopigments [17]. Besides, conditional inactivation of Isl1 in the primordium of the neural retina leads to a significant reduction in bipolar, cholinergic amacrine and ganglion cells [18].…”