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PubMed1977

The effect of translatory and rotatory movements upon the eye. Their significance in the development of retinal detachment.

It was shown in experimental models that translational movements of a closed chamber do not induce liquid flow in the chamber, but rotational movements do induce a current. It was also demonstrated in the experiments that rotational currents are able to elevate a rubber membrane if there is a hole and that a liquid flow is then passing through the opening. These observations initiated the idea of fixation of the eye in cases of retinal detachment in order to promote a reattachment.

Humans↗
PubMed1996

Immunohistochemical characterization of developing and mature primate retinal blood vessels.

PURPOSE: To characterize developing retinal blood vessels with vascular markers and to relate the histochemical profile of maturing vessels to morphologic stages in retinal vascular development. METHODS: Vessels were examined in frozen and paraffin-embedded retinas and in wholemounts of Macaca monkeys ranging in age from fetal day 75 (F75) to adulthood. Endothelial cells were visualized immunohistochemically using antisera to von Willebrand's factor and CD31 with lectins Ulex europaeus, Bandeiraea simplicifolia, peanut agglutinin, Ricinis communis, and wheat germ agglutinin, and by ATPase and ADPase enzymatic histochemistry. Antibodies to vascular basement membrane and matrix markers laminin, fibronectin, and collagen types I and VIII, and antisera recognizing cell cycle-specific nuclear proteins (cyclin, Ki-67, Mib-1) also were used. RESULTS: Newly formed and mature vessels were reactive with reagents specific for CD31, von Willebrand's factor, types I and VIII collagens, laminin, fibronectin, U. europaeus, R. communis, and peanut agglutinin. Wheat germ agglutinin labeled vessels only after pretreatment with neuraminidase. All vascular markers appeared simultaneously, but some were distributed differentially between capillaries and larger vessels, along the central-peripheral extent of a vascular plexus, and among different vascular laminae. Markers of vessels failed to label spindle-shaped presumed vascular precursor cells lying peripheral to the advancing vessels during development. Spindle cells exhibited cyclin, Ki-67, and Mib-1 immunoreactivity. CONCLUSIONS: Immature and mature vitread and sclerad vessels displayed histochemical profiles that were qualitatively similar but that had subtle quantitative differences. Results do not support identification of spindle-shaped cells as vascular precursors in the developing monkey retina and are discussed in relation to mechanisms of retinal vascularization.

Aging↗
PubMed2002

Localization of VEGF receptor-2 (KDR/Flk-1) and effects of blocking it in oxygen-induced retinopathy.

PURPOSE: Vascular endothelial cell growth factor (VEGF) has been implicated in vascular development and in proliferative retinopathies. The goal of this study was to examine the immunohistochemical localization and relative levels of VEGF receptor-2 (KDR) in canine retina during postnatal vasculogenesis and during angiogenesis in oxygen-induced retinopathy (OIR) and to investigate the effects of neutralizing KDR on these processes. METHODS: Eyes from normal dogs ranging from 1 to 22 days of age and age-matched oxygen-treated animals were snap frozen for immunohistochemical analysis with antibodies against human KDR. To examine the effects of blocking KDR, 6-day-old air-reared control and oxygen-treated animals were surgically implanted with slow release polymer pellets containing control IgG or anti-KDR. Material eluted from pellets was assessed using a binding assay (measures binding to soluble KDR) to determine the kinetics of anti-KDR release and endothelial cell proliferation to measure bioactivity. Animals were killed at 22 days of age and tissues examined with adenosine diphosphatase (ADPase) histochemical staining of blood vessels. RESULTS: KDR immunoreactivity was only weakly associated with developing retinal vessels and was not observed in angioblasts throughout normal postnatal development. Immunoreactivity was very strong in reforming retinal vessels and intravitreal neovascularization in oxygen-treated animals. Anti-KDR had no effect on vessel morphology or growth in air-reared control animals. In oxygen-treated animals, anti-KDR significantly inhibited revascularization of the retina (P = 0.005) and formation of intravitreal neovascularization compared with control IgG pellet eyes (P < 0.04). CONCLUSIONS: KDR/Flk-1 was only weakly associated with normal developing primary retinal vessels but was strongly expressed by proliferating endothelial cells in reforming retinal vessels and intravitreal neovascularization after hyperoxic insult. Anti-KDR antibody delivered by slow-release pellets had no effect on normal vasculogenesis, but it inhibited the formation of intravitreal neovascularization and retinal vessel development in OIR. The study suggests that blocking KDR may be beneficial for treating pathologic angiogenesis in adult tissue.

Animals↗
PubMed2000

Retinal cell addition and rod production depend on early stages of ocular melanin synthesis.

Retinal mitosis is regulated by dopa, a melanin precursor present in the developing retinal pigment epithelium. Its absence results in retinal deficits including a failure of approximately 30% of the rod population to develop. Here, (3)H-thymidine labelling is used to analyse patterns of cell addition spanning the main period of retinal development in rat litters containing both pigmented and albino phenotypes. Many more thymidine-labelled cells are found in each cellular layer at maturity in albinos than in their pigmented littermates. Normal spatial patterns of photoreceptor addition are seen in albinos during cone production and for most of the subsequent period of rod addition. However, abnormal spatial patterns of cell addition occur across the retinal when rod production peaks. A delay in the centre to periphery gradient of cell addition is apparent in both nuclear layers. These data are related to deficits in the mature architecture of the albino retina. The results are consistent with there being significant cell cycle and/or exit point irregularities in hypopigmented retinae. It is probable that reduced dopa levels in albinos result in the cell cycle rate not slowing appropriately with development, which may lead to cells missing their exit points. This produces abnormal patterns of cell addition at key stages and delays in the gradient of retinal maturation along with a large cell loss at critical stages of rod production.

Aging↗
PubMed2002

Slit1 and Slit2 cooperate to prevent premature midline crossing of retinal axons in the mouse visual system.

During development, retinal ganglion cell (RGC) axons either cross or avoid the midline at the optic chiasm. In Drosophila, the Slit protein regulates midline axon crossing through repulsion. To determine the role of Slit proteins in RGC axon guidance, we disrupted Slit1 and Slit2, two of three known mouse Slit genes. Mice defective in either gene alone exhibited few RGC axon guidance defects, but in double mutant mice a large additional chiasm developed anterior to the true chiasm, many retinal axons projected into the contralateral optic nerve, and some extended ectopically-dorsal and lateral to the chiasm. Our results indicate that Slit proteins repel retinal axons in vivo and cooperate to establish a corridor through which the axons are channeled, thereby helping define the site in the ventral diencephalon where the optic chiasm forms.

Animals↗
PubMed2006

c-kit marks late retinal progenitor cells and regulates their differentiation in developing mouse retina.

Retinal progenitor cells are believed to display altered proliferation and differentiation during retinal development, suggesting that retinal progenitor cell populations are not homogeneous. However, the composition of progenitor cell populations is not known, due in part to the lack of known surface markers identifying distinct stages of retinal progenitor cells. We found a dramatic change in the expression profile of the cell surface antigens c-kit and stage-specific embryonic antigen-1 (SSEA-1) in retinal progenitor cells during development. While SSEA-1 was expressed early in development, c-kit expression peaked in late stage progenitor cells. The identification of these developmental markers enabled us to characterize distinct sub-populations of retinal progenitor cells. Progenitor cell subpopulations expressing either SSEA-1, c-kit, or both showed different proliferation and differentiation abilities. Although SSEA-1-positive cells were augmented by beta-catenin signaling, c-kit-positive cells were positively regulated by Notch signaling. Taken together, our data suggest that c-kit and SSEA-1 can be used to spatiotemporally differentiate retinal progenitor populations that have intrinsically distinct characteristics. Prolonged expression of c-kit by a retrovirus resulted in the promotion of proliferation and the appearance of nestin-positive cells in the presence of the c-kit ligand, stem cell factor (SCF). This suggests a role for c-kit, Notch, and the beta-catenin signaling network in retinal development.

Animals↗
PubMed1996

Lens-specific expression of PDGF-A in transgenic mice results in retinal astrocytic hamartomas.

PURPOSE: To investigate the possibility that platelet-derived growth factor (PDGF) might regulate aspects of mouse retinal development in vivo. METHODS: In situ hybridization was used to study the expression patterns of PDGF-A and PDGF-B and their receptors during normal mouse eye development. Transgenic mice that express human PDGF-A in the lens under the control of alpha A-crystallin promoter were generated by pronuclear microinjection. The effects of PDGF overexpression on eye development were analyzed by ocular histology, immunohistochemistry and in situ hybridizations. RESULTS: The PDGF genes are expressed by cells in close contact with retinal astrocytes. The PDGF-A messenger RNA is upregulated in the retinal ganglion neurons after birth, and PDGF-B is expressed by the blood vessel cells in the hyaloid vasculature. The authors found that lens-specific expression of PDGF-A in the eye can induce hyperplasia of retinal astrocytes, which express PDGF-alpha receptor (PDGF-alpha R) during development. The retinal alterations in the PDGF-A transgenic mice closely resemble the retinal astrocytic hamartomas found in human tuberous sclerosis (TSC) disease. CONCLUSIONS: These findings suggest that proliferation of retinal astrocytes is regulated by PDGF during normal eye development. The authors speculate that proliferation of retinal astrocytes is mediated through a PDGF signaling pathway, which may involve the TSC gene product.

Animals↗
PubMed2003

Developmental expression of heteromeric nicotinic receptor subtypes in chick retina.

Acting through nicotinic acetylcholine receptors (nAChRs), acetylcholine plays an important role in retinal development and the formation of retinal connections to target tissues, but very little is known about the nAChR subtypes expressed in vertebrate retina during neuronal development. We used immunoprecipitation and [3H]epibatidine binding to study the expression of chick retina alpha-bungarotoxin-insensitive heteromeric nAChRs during development and adulthood, and found that it is strictly developmentally regulated, reaching a peak on postnatal day 1. The increase in [3H]epibatidine receptors is caused mainly by an increase in the receptors containing the alpha2, alpha6, beta3, and beta4 subunits. The contribution of beta subunits to [3H]epibatidine receptors significantly changes during development: the beta2 subunit is contained in the majority (84%) of receptors on embryonic day (E) 7 but in only 32% on postnatal day (P) 1, whereas the beta4-containing receptors increase from 22% to 78% during the same period. Using a sequential immunodepletion procedure, we purified the beta2- and beta4-containing subtypes and found that they coassemble with alpha4 and/or alpha3 on E11, and also with the alpha2, alpha6, and beta3 on P1. After the immunodepletion of alpha6-containing receptors, the beta2- and beta4-containing receptors have a very similar pharmacological profile on P1. Parallel immunoprecipitation experiments in other brain areas showed that the developmentally regulated receptors in optic lobe are those containing the alpha2, alpha5, and beta2 subunits and those containing the alpha4 and beta2 subunits, whereas the receptors in forebrain-cerebellum contain the alpha4 and beta2 subunits with or without the alpha5 subunit. These results indicate that there is an increase in receptor heterogeneity and complexity in chick retina during development that is also maintained in adulthood.

Animals↗
PubMed2000

Effect of highly active antiretroviral therapy on the incidence of HIV-related cytomegalovirus retinitis and retinal detachment.

Cytomegalovirus retinitis (CMVR) is the most common intraocular infection encountered in ophthalmic practices. To assess the impact of highly active antiretroviral therapy (HAART) on the incidence of CMVR and subsequent retinal detachments, a retrospective review of the HIV+ patients seen at a single university and community-based practice between 1992-1993 (group 1), before the advent of protease inhibitors, was compared with the data obtained from October 1996 to October 1997 (group 2) and October 1997-1998 (group 3), after the widespread use of HAART. The incidence of CMVR and retinal detachment rates for each group was calculated and compared. Twenty five (2.6%) of 974 HIV+ patients in group 1 developed CMVR. Of these, four patients developed retinal detachment (16%). Group 2 had a total of 1084 HIV+ patients, 18 (1.7%) of whom developed CMVR, which indicates a 35% decline of the incidence of CMV retinitis at our institution (p = 0.052, Odds ratio = 0.533, Confidence interval 0.28-1.01) and three patients (20%) developed retinal detachment. Only 1 patient (0.07%) of 1274 patients in group 3 developed CMVR, which represents a 99% reduction since 1993 (p = 0.0000000456). We conclude that the incidence of CMVR at this institution has decreased significantly with the recent use of HAART therapy. This effect may be related to the aggressive use of HAART and associated immune recovery in this population of AIDS patients. In this small series, however, the rate of retinal detachment appeared unchanged, but was only observed in those individuals who were not on HAART or who had just recently started.

AIDS-Related Opportunistic Infections↗
PubMed2002

Claudin 5 is transiently expressed during the development of the retinal pigment epithelium.

During the development of chick retinal pigment epithelium (RPE), the permeability and selectivity of the epithelium's tight junctions are continuously modulated. Overall paracellular permeability decreases, but selectivity increases. Because the claudin family of transmembrane proteins appears to provide the structural basis for selectivity, we examined the expression of claudins as a function of development in chick RPE. Degenerate primers were used with the reverse transcriptase-polymerase chain reaction (RT-PCR) to obtain complete sequences of chick claudins 3 and 5. Northern blotting and semi-quantitative RT-PCR demonstrated that claudin 5 was expressed in RPE, but claudin 3 was expressed only in the choroid layer of the eye. Northern blotting, semiquantitative RT-PCR and immunoblotting demonstrated that the expression of claudin 5 was transient, with peak levels of expression between embryonic days 10 and 14. Primary cultures were used to demonstrate that factors secreted by the neural retina induced the expression of claudin 5 nearly 3-fold if RPE was isolated from embryonic day 7 embryos. There was little effect if RPE was isolated from embryonic day 14. The upregulation of claudin 5 correlates with permeability changes that occur during the intermediate stage of RPE development. Interestingly, claudin 5 must be replaced during the late stage of development when the number and complexity of tight junctional strands increases. This would imply more changes in selectivity.

Amino Acid Sequence↗
PubMed2000

Treatment of cytomegalovirus retinitis with an intraocular sustained-release ganciclovir implant.

The objective of this prospective study was to evaluate the efficacy and complications of the use of an intraocular sustained-release ganciclovir implant for the treatment of active cytomegalovirus (CMV) retinitis in AIDS patients. Thirty-nine eyes of 26 patients were submitted to ocular surgery. All patients underwent complete ocular examination before and after surgery. The surgical procedure was always done under local anesthesia using the same technique. The mean time for the surgical procedure was 20 min (range, 15 to 30 min). The average follow-up period was 3.7 months. Of all patient, only 4 presented recurrence of retinitis after 8, 8, 9 and 2 months, respectively. Three of them received a successful second implant. All 39 eyes of the 26 patients presented healing of retinitis as shown by clinical improvement evaluated by indirect binocular ophthalmoscopy and retinography. Retinitis healed within a period of 4 to 6 weeks in all patients, with clinical regression signs from the third week on. Six (15.4%) eyes developed retinal detachment. None of the patients developed CMV retinitis in the contralateral eye. The intraocular implant proved to be effective in controlling the progression of retinitis for a period of up to 8 months even in patients for whom systemic therapy with either ganciclovir or foscarnet or both had failed. The intraocular sustained-release ganciclovir implant proved to be a safe new procedure for the treatment of CMV retinitis, avoiding the systemic side effects caused by the intravenous medications and improving the quality of life of the patients.

AIDS-Related Opportunistic Infections↗
PubMed1999

Retinal detachment in myopic eyes after laser in situ keratomileusis.

PURPOSE: To analyze the incidence and characteristics of retinal detachment in myopic patients treated by laser-assisted in situ keratomileusis. METHODS: We retrospectively studied the retinal detachments observed in 1,554 consecutive eyes (878 patients) undergoing laser-assisted in situ keratomileusis for the correction of myopia (follow-up, 30.34+/-10.27 months; range, 16 to 54). Mean patient age was 33.09+/-8.6 years (range, 20 to 60). Before treatment with laser-assisted in situ keratomileusis, all patients had a comprehensive examination, and detected lesions predisposing to retinal detachment were treated before performing the laser-assisted in situ keratomileusis procedure. RESULTS: Retinal detachment occurred in four (0.25%) of 1,554 eyes of four (0.45%) of 878 patients. All four patients who developed retinal detachment in one eye were women. Degree of preoperative myopia was -13.52+/-3.38 diopters (range, -8.00 to -27.50). The time interval between refractive surgery and retinal detachment was 11.25+/-8.53 months (range, 2 to 19 months). In all cases retinal detachment was spontaneous. In all eyes the retina was reattached successfully at the first retinal detachment surgery. Mean best-corrected visual acuity after laser-assisted in situ keratomileusis and before retinal detachment development was 20/43 (range, 20/50 to 20/30). After retinal detachment repair, best-corrected visual acuity was 20/45 (range, 20/50 to 20/32). Differences between best-corrected visual acuity before and after reattachment were not statistically significant (P = .21, paired Student t test). A myopic shift was induced in three eyes that had retinal detachment repaired by scleral buckling, from -0.58+/-0.72 diopter (range, +0.25 to -1.00) before retinal detachment and -2.25+/-1.14 diopters (range, -1.00 to -3.25) after retinal detachment surgery (P = .03, paired Student t test). CONCLUSIONS: Laser-assisted in situ keratomileusis for correction of myopia is followed by a low incidence of retinal detachment. Conventional scleral buckling surgery was successful in most cases and did not cause significant changes in the final best-corrected visual acuity. A significant increase in the myopic spherical equivalent was observed after scleral buckling in these patients.

Adult↗
PubMed1988

Murine glutamine synthetase: cloning, developmental regulation, and glucocorticoid inducibility.

We have cloned the murine glutamine synthetase (GS) gene and measured GS enzyme activity and mRNA in five tissues (retina, brain, liver, kidney, and skeletal muscle) during perinatal development. Retinal GS enzyme activity increases 200-fold between Day 1 and Day 21 and is accompanied by an increase in the level of GS mRNA; developmental regulation in other tissues is much less dramatic. Based on Southern blotting analysis, a single GS gene gives rise to the tissue-specific patterns of GS mRNA expression. The increase in murine retinal GS observed during perinatal development is similar in magnitude to that observed in the chicken retina just prior to hatching. In the embryonic chicken retina, glucocorticoid hormones mediate a large increase in the level of GS mRNA. However, although glucocorticoids induce a 12-fold increase in GS mRNA in murine skeletal muscle, expression of the retinal enzyme and mRNA is only modestly glucocorticoid-inducible in the mouse. Therefore, despite the hormonal responsiveness of the murine GS gene, it is not likely that glucocorticoids are important physiological modulators of the developmental rise in murine retinal GS.

Age Factors↗
PubMedDate not supplied

Treatment of intravitreal and prepapillary neovascularization following branch retinal vein occlusion.

Ten eyes which had developed retinitis proliferans following branch retinal vein occlusion were treated with xenon photocoagulation utilizing an ablative technique limited to the effected retinal quadrants. In eight of the ten eyes, complete regression of the vessels was obtained, as evidenced by nonfilling on subsequent fluorescein angiography. The remaining two eyes showed significant but incomplete closure. There were no postoperative vitreous hemorrhages, no significant permanent complications, and the visual acuity remained at or better than pretreatment levels in all cases. In conclusion, we wish to reemphasize the limited scope of this report. The series, though consecutive, is small and the follow-up period relatively short. On the basis of the cases presented here, we believe that continued investigation using this mode of treatment is warranted, and that this method may prove to be of significant value in the management of complicated retinal branch vein occlusion.

Adult↗
PubMed1984

Ectopic photoreceptor cells and cell death in the developing rat retina.

To confirm the identity of presumed photoreceptor-like neurones displaced from their normal location in the developing retina we have examined their morphology and extent of occurrence in the Long-Evans hooded rat aged one to six weeks postnatally. Displaced photoreceptor cells (PR) in the inner nuclear layer showed changing nuclear chromatin patterns during retinal development akin to those occurring in PR cells in the outer nuclear layer. PR cell cytoplasmic specializations included outer segments in various stages of formation and presynaptic terminal features including synaptic ribbons and vesicles. Processes abutting on PR cell terminals did not have postsynaptic specializations. Displaced PR cells may have arisen from PR progenitors which failed to retain a foothold at the retina's ventricular surface. The incidence of displaced PR cells determined from quantification of their planimetric densities decreased from 18% of the INL cell population at day 9 postnatally to less than 2% at day 15. A few such cells remained even at 36 days. Their fate appeared to be migration to the ONL and, or, in situ degeneration. Counts of necrotic cells carried out at ages preceding, during, and following the period during which ectopic PR cells were most numerous indicated that the decline in numbers of displaced PR cells coincided temporally with the period during which cell degeneration in the INL was most prominent. Degeneration of cells in the INL, including ectopic PR cells, was sufficient to account for a considerable proportion of the retinal thinning that occurred during development. Results suggest that future studies of retinal development in genetically or experimentally manipulated animals should consider abnormalities in cell migration and death.

Animals↗
PubMed2006

Development of the human retina in the absence of ganglion cells.

Retinal development was studied in eyes from fetal and neonatal human anencephalic (AnC) and normal age-matched infants to determine the time of retinal ganglion cell (GC) loss and its effect on the development of other retinal neurons. At fetal week (Fwk) 14, GC loss was evident in central retina and by Fwk 19-20 almost all GC were absent, although immunocytochemical labeling for GC markers brain 3, neurofilament M and parvalbumin detected a few GC in the AnC far periphery at older ages. The inner nuclear and inner plexiform (IPL) layers showed variable amounts of thinning but all normal bipolar (BP) and horizontal cell markers were still present. The amacrine (AM) labels calbindin and calretinin were markedly reduced. Lamination for these markers in the IPL was less organized than in normal retinas, with BP and AM markers extending into the degenerated GC layer. Cone and rod photoreceptors had normal morphology and topography in AnC retina and each expressed normal phototransduction and synaptic markers. The prospective fovea was identified in AnC neonatal retina by cone packing and the absence of immunolabeled rod photoreceptors. In one AnC neonatal retina, blood vessels and astrocytes extended across the inner retina in the putative fovea and there was no evidence of a pit. In another AnC neonatal retina, blood vessels and astrocytes formed a foveal avascular zone in the inner retina and a shallow pit was present within this zone. However, both foveas showed evidence for the onset of cone elongation and packing. These findings support the model of Springer and Hendrickson [2005; Vis. Neurosci. 22, 171] in which the foveal avascular zone is critical for pit formation, but suggest that mechanisms inherent to the outer retina may be involved in early stages of foveal cone packing.

Anencephaly↗
PubMed2003

Expression of neuropeptides and their receptors in the developing retina of mammals.

The present review examines various aspects of the developmental expression of neuropeptides and of their receptors in mammalian retinas, emphasizing their possible roles in retinal maturation. Different peptidergic systems have been investigated with some detail during retinal development, including substance P (SP), somatostatin (SRIF), vasoactive intestinal polypeptide (VIP), pituitary adenylate cyclase-activating polypeptide (PACAP), neuropeptide Y (NPY), opioid peptides and corticotrophin-releasing factor (CRF). Overall, the developmental expression of most peptides is characterized by early appearance, transient features and achievement of the mature pattern at the time of eye opening. Concerning possible developmental actions of neuropeptides, recent studies imply a role of SP in the modulation of cholinergic neurotransmission in early postnatal rabbit retinas, when cholinergic cells participate in the retinal spontaneous waves of activity. In addition, the presence of transient SRIF expressing ganglion cells and recent observations in SRIF receptor knock-out mice indicate variegated roles of this peptide in the development of the retina and of retinofugal projections. Furthermore, VIP and PACAP exert protective and growth-promoting actions that may sustain retinal neurons during their development, and opioid peptides may control cell proliferation in the developing retina. Finally, a peak in the expression of certain peptides, including VIP, NPY and CRF, is present around the time of eye opening, when the retina begins the analysis of structured visual information, suggesting important roles of these peptides during this delicate phase of retinal development. In summary, although the physiological actions of peptides during retinal development are far from being clarified, the data reviewed herein indicate promising perspectives in this field of study.

Animals↗
PubMed2000

p57(Kip2) regulates progenitor cell proliferation and amacrine interneuron development in the mouse retina.

A precise balance between proliferation and differentiation must be maintained during retinal development to obtain the correct proportion of each of the seven cell types found in the adult tissue. Cyclin kinase inhibitors can regulate cell cycle exit coincident with induction of differentiation programs during development. We have found that the p57(Kip2) cyclin kinase inhibitor is upregulated during G(1)/G(0) in a subset of retinal progenitor cells exiting the cell cycle between embryonic day 14.5 and 16.5 of mouse development. Retroviral mediated overexpression of p57(Kip2) in embryonic retinal progenitor cells led to premature cell cycle exit. Retinae from mice lacking p57(Kip2) exhibited inappropriate S-phase entry and apoptotic nuclei were found in the region where p57(Kip2) is normally expressed. Apoptosis precisely compensated for the inappropriate proliferation in the p57(Kip2)-deficient retinae to preserve the correct proportion of the major retinal cell types. Postnatally, p57(Kip2) was found to be expressed in a novel subpopulation of amacrine interneurons. At this stage, p57(Kip2 )did not regulate proliferation. However, perhaps reflecting its role during this late stage of development, animals lacking p57(Kip2) showed an alteration in amacrine subpopulations. p57(Kip2) is the first gene to be implicated as a regulator of amacrine subtype/subpopulation development. Consequently, we propose that p57(Kip2) has two roles during retinal development, acting first as a cyclin kinase inhibitor in mitotic progenitor cells, and then playing a distinct role in neuronal differentiation.

Animals↗