tretinoin and Eye-Abnormalities

Retinoic acid (RA), the active derivative of vitamin A (retinol), is an essential morphogen signaling molecule and major regulator of embryonic development. The dysregulation of RA levels during embryogenesis has been associated with numerous congenital anomalies, including craniofacial, auditory, and ocular defects. These anomalies result from disruptions in the cranial neural crest, a vertebrate-specific transient population of stem cells that contribute to the formation of diverse cell lineages and embryonic structures during development. In this review, we summarize our current knowledge of the RA-mediated regulation of cranial neural crest induction at the edge of the neural tube and the migration of these cells into the craniofacial region. Further, we discuss the role of RA in the regulation of cranial neural crest cells found within the frontonasal process, periocular mesenchyme, and pharyngeal arches, which eventually form the bones and connective tissues of the head and neck and contribute to structures in the anterior segment of the eye. We then review our understanding of the mechanisms underlying congenital craniofacial and ocular diseases caused by either the genetic or toxic disruption of RA signaling. Finally, we discuss the role of RA in maintaining neural crest-derived structures in postembryonic tissues and the implications of these studies in creating new treatments for degenerative craniofacial and ocular diseases.

Topics: Animals; Craniofacial Abnormalities; Embryonic Induction; Eye Abnormalities; Humans; Neural Crest; Signal Transduction; Tretinoin

AP-2 is a recent significant addition to the list of transcription factors that have been demonstrated by targeted gene disruption to be essential for normal development. Two recent reports of AP-2 null mutant mice indicate that AP-2 holds a key position in the network of genes and proteins controlling developmental pattern and morphogenesis, and that it is particularly important for development of the cranial region and for midline fusions.

Topics: Animals; Craniofacial Abnormalities; DNA-Binding Proteins; Eye Abnormalities; Limb Deformities, Congenital; Mice; Mice, Knockout; Mutation; Neural Crest; Phenotype; Transcription Factor AP-2; Transcription Factors; Tretinoin

The homeobox transcription factor PITX2 is a known regulator of mammalian ocular development, and human PITX2 mutations are associated with Axenfeld-Rieger syndrome (ARS). However, the treatment of patients with ARS remains mostly supportive and palliative.. The authors used molecular genetic, pharmacologic, and embryologic techniques to study the biology of ARS in a zebrafish model that uses transgenes to mark neural crest and muscle cells in the head.. The authors demonstrated in vivo that pitx2 is a key downstream target of retinoic acid (RA) in craniofacial development, and this pathway is required for coordinating neural crest, mesoderm, and ocular development. pitx2a knockdown using morpholino oligonucleotides disrupts jaw and pharyngeal arch formation and recapitulates ocular characteristics of ARS, including corneal and iris stroma maldevelopment. These phenotypes could be rescued with human PITX2A mRNA, demonstrating the specificity of the knockdown and evolutionary conservation of pitx2a function. Expression of the ARS dominant negative human PITX2A K50E allele also caused ARS-like phenotypes. Similarly, inhibition of RA synthesis in the developing eye (genetic or pharmacologic) disrupted craniofacial and ocular development, and human PITX2A mRNA partially rescued these defects.. RA regulation of pitx2 is essential for coordinating interactions among neural crest, mesoderm, and developing eye. The marked evolutionary conservation of Pitx2 function in eye and craniofacial development makes zebrafish a potentially powerful model of ARS, amenable to in vivo experimentation and development of potential therapies.

Topics: Animals; Animals, Genetically Modified; Anterior Eye Segment; Disease Models, Animal; Eye; Eye Abnormalities; Eye Diseases, Hereditary; Facial Bones; Facial Muscles; Gene Expression Regulation, Developmental; Homeobox Protein PITX2; Homeodomain Proteins; In Situ Hybridization; Morpholinos; Polymerase Chain Reaction; RNA, Messenger; Skull; Transcription Factors; Tretinoin; Zebrafish

Retinoic acid (RA) is known to be required at various levels of eye patterning via Retinoic Acid Receptors (RAR); however the molecular and cellular mechanisms triggered by these nuclear receptors are still obscure. The genetic studies performed here enable us to present a new model to study RA action during eye development. By inactivating the three RARs, specifically in the periocular mesenchyme, we discriminate the individual contribution of each RAR during eye development and describe a new function for RARs during the formation of the optic nerve. We demonstrate that RARalpha is the only receptor that mediates RA signalling in the neurectoderm during ocular development. Surprisingly, and despite a sophisticated pattern of RA-activity in the developing retina, we observed that RA signalling is not autonomously required in this tissue for eye formation. We show that the action of RA during eye morphogenesis is occurring specifically in neural crest-derived periocular mesenchyme and is mediated by all three RARs. Furthermore, we point out that Pitx2, which encodes a homeodomain transcription factor, is a key RA-responsive gene in neural crest cells during eye development. Interestingly, we observed that RA is required in the neural crest cells for normal position of the extraocular muscle.

Topics: Animals; Body Patterning; Embryo, Mammalian; Eye; Eye Abnormalities; Homeobox Protein PITX2; Homeodomain Proteins; Mesoderm; Mice; Mice, Inbred C57BL; Morphogenesis; Muscles; Mutation; Neural Crest; Optic Nerve; Receptors, Retinoic Acid; Retina; Retinoic Acid Receptor alpha; Retinoic Acid Receptor gamma; Signal Transduction; Transcription Factors; Tretinoin

Aberrant activation of the Hedgehog (Hh) signaling pathway in different organisms has shown the importance of this family of morphogens during development. Genetic screens in zebrafish have assigned specific roles for Hh in proliferation, differentiation and patterning, but mainly as a result of a loss of its activity. We attempted to fully activate the Hh pathway by removing both receptors for the Hh proteins, called Patched1 and 2, which are functioning as negative regulators in this pathway.. Here we describe a splice-donor mutation in Ptc1, called ptc1hu1602, which in a homozygous state results in a subtle eye and somite phenotype. Since we recently positionally cloned a ptc2 mutant, a ptc1;ptc2 double mutant was generated, showing severely increased levels of ptc1, gli1 and nkx2.2a, confirming an aberrant activation of Hh signaling. As a consequence, a number of phenotypes were observed that have not been reported previously using Shh mRNA overexpression. Somites of ptc1;ptc2 double mutants do not express anteroposterior polarity markers, however initial segmentation of the somites itself is not affected. This is the first evidence that segmentation and anterior/posterior (A/P) patterning of the somites are genetically uncoupled processes. Furthermore, a novel negative function of Hh signaling is observed in the induction of the fin field, acting well before any of the previously reported function of Shh in fin formation and in a way that is different from the proposed early role of Gli3 in limb/fin bud patterning.. The generation and characterization of the ptc1;ptc2 double mutant assigned novel and unexpected functions to the Hh signaling pathway. Additionally, these mutants will provide a useful system to further investigate the consequences of constitutively activated Hh signaling during vertebrate development.

Topics: Animal Structures; Animals; Base Sequence; Body Patterning; DNA Mutational Analysis; Embryo, Nonmammalian; Eye Abnormalities; Gene Expression Regulation, Developmental; Hedgehog Proteins; Membrane Proteins; Molecular Sequence Data; Mutant Proteins; Mutation; Patched Receptors; Patched-1 Receptor; Phenotype; Receptors, Cell Surface; RNA Splice Sites; Sequence Homology, Amino Acid; Signal Transduction; Somites; Tretinoin; Veratrum Alkaloids; Zebrafish; Zebrafish Proteins

This study investigated the effects of dietary retinoic acid (RA) on frog hindlimb development. Xenopus laevis (African clawed frog) tadpoles were fed a diet supplemented with 0, 1, 10, or 100 microg of RA/g of food for 2 or 5 d at different stages of metamorphosis. Hindlimb deformities were induced in the group fed 100 microg of RA/g of diet for 5 d. Exposures beginning at mid-hindlimb bud development induced bilaterally bent tibiafibula (bony triangles), while exposures later in hindlimb development induced deformities of the feet, including fusion of the 1st and 2nd clawed digits and reduced length of the 4th and 5th digits (due to reduced, missing, or misplaced phalanges). There were also cases of extra phalanges in the 5th digit. The eye was another target of RA exposure. In one experiment, 58% of the tadpoles fed 10 microg of RA/g had a smaller or absent right eye. Additionally, 11% of the tadpoles fed 100 microg of RA/g of diet developed a smaller or absent left eye. Waterborne heavy metals (Zn or Cu) modified RA effects on the hindlimb and eye. Co-exposure to metals and RA resulted in cases of unilateral bony triangles and reduced rates of smaller eyes. There were also cases of extra hindlimb digits in Zn-exposed animals. Dietary RA exposure in tadpoles can cause some deformities that differ from waterborne RA exposures in previous studies. RA also induced deformities that resemble those in affected wild frog populations (bony triangles), although the patterns of other deformities and missing segments (phalanges and metatarsals) are not similar to those documented in the wild.

Topics: Abnormalities, Drug-Induced; Animals; Dose-Response Relationship, Drug; Embryo, Nonmammalian; Eye Abnormalities; Hindlimb; Metals, Heavy; Metamorphosis, Biological; Tretinoin; Xenopus laevis

We have identified a cDNA coding for a Xenopus MARCKS-like protein (XMLP) from a cDNA library prepared from activin-treated ectoderm. Using whole-mount in situ hybridization and RT-PCR, we found XMLP maternal transcripts during the cleavage stages. After MBT, the signals were restricted to the neural plate. Subsequently XMLP was expressed predominantly in the brain, somites and pronephros. Ectopic expression of XMLP resulted in eye and axis defects and in a change of the expression pattern of Krox 20, a neural marker for rhombomeres 3 and 5. Injected XMLP caused apoptosis. It was characterized by loss of intercellular adhesion contacts, transient plasma membrane ruffling at gastrula, and epithelial disruption attailbud stage. Overexpression of mutant XMLPs showed that this phenotype was correlated with its putative PSD domain and glycine at position 2. The embryos injected with a morpholino oligo complementaryto XMLPmRNA showed malformations of the anterior axis and eye defects. Extirpation experiments indicated that the phenotypes might be correlated with disturbed morphorgenetic movements rather than an inhibition of induction process. Overexpression of XCYP26 resulted in a shift of the expression pattern of XMLP. In the early tailbud stage (stage 20) the signal stripe in the XCYP26 injected half of the embryo got diffuse or even disappeared. This observation suggests that retinoic acid plays an important role in the regulation of XMLP. Our results suggest that XMLP might participate in pattern formation of the embryonic axis and the central nervous system.

Topics: Amino Acid Sequence; Animals; Base Sequence; Brain; Calmodulin-Binding Proteins; Chorionic Gonadotropin; DNA-Binding Proteins; Early Growth Response Protein 2; Eye Abnormalities; Gene Deletion; Gene Expression Regulation, Developmental; Humans; In Situ Hybridization; Lac Operon; Membrane Proteins; Microfilament Proteins; Molecular Sequence Data; Morphogenesis; Neural Tube Defects; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Transcription Factors; Tretinoin; Xenopus laevis; Zinc Fingers

To identify the critical time for developmental eye abnormalities, pregnant C 57 BL/6 NJcl mice were injected intraperitoneally once with 12.5 mg/kg of retinoic acid on days 7 (day-7 group), 8 (day-8 group), 9 (day-9 group), 10 (day-10 group), and 11 (day-11 group) of pregnancy. Each group consisted of 5 pregnant mice. The fetuses were observed grossly on day 18 of gestation, and the eyes were examined histologically in serial sections. Various gross malformations such as microphthalmos, cleft lip and palate, and central nervous system anomalies were observed in the day-7 group. However, microphthalmos was the only gross malformation found in the day-8 group, and there were no gross malformations in the other 3 groups. The histological examination indicated that the critical time for anophthalmos was day 7 of gestation or earlier because of its appearance in the day-7 group alone. The critical time for microphthalmos, faulty closure of the embryonic fissure, aphakia, and faulty separation of the lens vesicle was day 8 of gestation or earlier considering their occurrence in both day 7 and day 8 groups, and the time for goniodysgenesis was day 9 of gestation or earlier because of its appearance in the day 7, day 8, and day 9 groups.

Topics: Animals; Dose-Response Relationship, Drug; Eye Abnormalities; Female; Fetal Diseases; Injections, Intraperitoneal; Mice; Mice, Inbred C57BL; Pregnancy; Time Factors; Tretinoin

To clarify the relationship between neural crest cells and ocular anomalies, pregnant mice were treated intraperitoneally with 12.5 mg/kg retinoic acid suspended in corn oil on day 7 of pregnancy (RA group). Control mice were given an equal volume of corn oil (control group). Each group consisted of 5 mother mice, and the offsprings were removed on day 18 of gestation. The fetal mortality was 46.3% in the RA group and 2.2% in the control group. Twenty-two live fetuses of the RA group and 45 of the control group were grossly observed, and the eyes were examined histologically. In the RA group, gross malformations such as microphthalmos (95.5%), cleft lip and palate (36.4%), and central nervous system anomalies (31.8%) were observed, and in the control group, malformations such as microphthalmos (6.7%), central nervous system anomalies (2.2%), and low set ears (2.2%) were seen. Histological examination revealed microphthalmos (47.7%), anophthalmos (38.6%), faulty closure of the embryonic fissure (36.4%), developmental abnormalities of the vitreous (34.1%), aphakia (22.7%), goniodysgenesis (18.2%), and faulty separation of the lens vesicle (15.9%) in the RA group. These anomalies arose from abnormal neural crest cell migration induced by retinoic acid. They were detected in only 3.3, 1.1, 3.3, 8.9, 1.1, 2.2 and 2.2%, respectively of the control group.

Topics: Animals; Eye Abnormalities; Fetus; Mice; Mice, Inbred C57BL; Microphthalmos; Neural Crest; Teratogens; Tretinoin

The growth and differentiation factor transforming growth factor-beta2 (TGFbeta2) is thought to play important roles in multiple developmental processes. Targeted disruption of the TGFbeta2 gene was undertaken to determine its essential role in vivo. TGFbeta2-null mice exhibit perinatal mortality and a wide range of developmental defects for a single gene disruption. These include cardiac, lung, craniofacial, limb, spinal column, eye, inner ear and urogenital defects. The developmental processes most commonly involved in the affected tissues include epithelial-mesenchymal interactions, cell growth, extracellular matrix production and tissue remodeling. In addition, many affected tissues have neural crest-derived components and simulate neural crest deficiencies. There is no phenotypic overlap with TGFbeta1- and TGFbeta3-null mice indicating numerous non-compensated functions between the TGFbeta isoforms.

Topics: Abnormalities, Multiple; Animals; Bone and Bones; Cleft Palate; Craniofacial Abnormalities; Cyanosis; Ear, Inner; Embryonic Induction; Epithelium; Eye Abnormalities; Genes, Homeobox; Heart Defects, Congenital; Mesoderm; Mice; Mice, Inbred C57BL; Mice, Knockout; Phenotype; Transforming Growth Factor beta; Tretinoin; Urogenital Abnormalities

Both retinoid receptor null mutants and classic nutritional deficiency studies have demonstrated that retinoids are essential for the normal development of diverse embryonic structures (e.g. eye, heart, nervous system, urogenital tract). Detailed analysis of retinoid-modulated events is hampered by several limitations of these models, including that deficiency or null mutation is present throughout gestation, making it difficult to isolate primary effects, and preventing analysis beyond embryolethality. We developed a mammalian model in which retinoid-dependent events are documented during distinct targeted windows of embryogenesis. This was accomplished through the production of vitamin A-depleted (VAD) female rats maintained on sufficient oral retinoic acid (RA) for growth and fertility. After mating to normal males, these RA-sufficient/VAD females were given oral RA doses which allowed for gestation in an RA-sufficient state; embryogenesis proceeded normally until retinoids were withdrawn dietarily to produce a sudden, acute retinoid deficiency during a selected gestational window. In this trial, final RA doses were administered on E11.5, vehicle at E12.5, and embryos analyzed on E13.5; during this 48 hour window, the last RA dose was metabolized and embryos progressed in a retinoid-deficient state. RA-sufficient embryos were normal. Retinoid-depleted embryos exhibited specific malformations of the face, neural crest, eyes, heart, and nervous system. Some defects were phenocopies of those seen in null mutant mice for RXR alpha(-/-), RXR alpha(-/-)/RAR alpha(-/-), and RAR alpha(-/-)/RAR gamma(-/-), confirming that RA transactivation of its nuclear receptors is essential for normal embryogenesis. Other defects were unique to this deficiency model, showing that complete ligand 'knock-out' is required to see those retinoid-dependent events previously concealed by receptor functional redundancy, and reinforcing that retinoid receptors have separate yet overlapping contributions in the embryo. This model allows for precise targeting of retinoid form and deficiency to specific developmental windows, and will facilitate studies of distinct temporal events.

Topics: Abnormalities, Multiple; Animals; Diet; Embryo Implantation; Embryonic and Fetal Development; Eye Abnormalities; Female; Liver; Nervous System; Nervous System Malformations; Neural Crest; Pregnancy; Rats; Rats, Mutant Strains; Rats, Sprague-Dawley; Receptors, Retinoic Acid; Retinoids; Tretinoin; Vitamin A Deficiency

The eye is the organ whose development is the most frequently altered in response to maternal vitamin A deficiency [VAD; Warkany, J. and Schraffenberger, S. (1946). Archs Ophthalmol. 35, 150-169]. With the exception of prenatal retinal dysplasia, all the ocular abnormalities of the fetal VAD syndrome are recapitulated in mouse mutants lacking either RARalpha and RARbeta2, RARalpha and RARgamma, RARgamma and RARbeta2, or RXRalpha [Lohnes, D., Mark, M., Mendelsohn, C., Dolle, P., Dierich, A., Gorry, P., Gansmuller, A. and Chambon, P. (1994) Development 120, 2723-2748; Mendelsohn, C., Lohnes, D., Décimo, D., Lufkin, T., LeMeur, M., Chambon, P. and Mark, M. (1994) Development 120, 2749-2771; Kastner, P., Grondona, J. Mark, M., Gansmuller, A., LeMeur, M., Décimo, D., Vonesch, J.L., Dollé, P. and Chambon, P. (1994) Cell 78, 987-1003], thus demonstrating that retinoic acid (RA) is the active vitamin A metabolite during prenatal eye morphogenesis. Whether retinoids are also involved in postnatal eye development could not be investigated, as VAD newborns are not viable and the above RAR double null mutants and RXRalpha null mutants died in utero or at birth. We report here the generation of viable RARbeta2/RARgamma2 double null mutant mice, which exhibit several eye defects. The neural retina of newborn RARbeta2gamma2 mutants is thinner than normal due to a reduced rate of cell proliferation, and from day 4 shows multiple foci of disorganization of its layers. These RARbeta2gamma2 mutants represent the first genetically characterized model of retinal dysplasia and their phenotype demonstrates that RARs, and therefore RA, are required for retinal histogenesis. The RARbeta2gamma2 retinal pigment epithelium (RPE) cells display histological and/or ultrastructural alterations and/or fail to express cellular retinol binding protein I (CRBPI). Taken altogether, the early onset of the RPE histological defects and their striking colocalisation with areas of the neural retina displaying a faulty laminar organization, a reduced neuroblastic proliferation, and a lack of photoreceptor differentiation and/or increased apoptosis, make the RPE a likely target tissue of the RARbeta2gamma2 double null mutation. A degeneration of the adult neural retina, which may similarly be secondary to a defective RPE, is also observed in these mutants, thus demonstrating an essential role of RA in the survival of retinal cells. Moreover, all RARbeta2gamma2 mutants display defects in structures

Topics: Animals; Animals, Newborn; Cell Division; DNA; Eye Abnormalities; Female; Immunohistochemistry; In Situ Hybridization; Male; Mice; Mice, Mutant Strains; Microscopy, Electron; Receptors, Retinoic Acid; Retina; Retinal Degeneration; Retinal Diseases; Retinal Dysplasia; Rod Opsins; Tretinoin

Exogenously applied retinoic acid is known to cause teratogenic effects in a variety of animal systems. We examined whether the formation of teratogenic effects may be influenced by the electrical charge of retinoic acid. The pKa of retinoic acid ranges from 6 to 8, indicating that it is electrically neutral in a pH5 medium and is negatively charged in a pH9 medium. With this idea in mind, embryos of the pond snail Lymnaea stagnalis were pulse-treated with retinoic acid and cultured in media of different pH. The percentage of embryos with retinoic acid-induced eye defects was 6-fold lower in the pH9 medium as compared to the pH5 medium. In contrast, the apical plate defects induced by retinoic acid were not pH-dependent. The observation that high pH prevents eye defects but not apical plate defects can be explained by taking into account an electrophoretic redistribution of retinoic acid resulting from the voltage gradients that are generated by the Lymnaea embryo.

Topics: Animals; Culture Techniques; Electrochemistry; Eye; Eye Abnormalities; Hydrogen-Ion Concentration; Lymnaea; Teratogens; Tretinoin

Numerous congenital malformations have been observed in fetuses of vitamin A-deficient (VAD) dams [Wilson, J. G., Roth, C. B., Warkany, J., (1953), Am. J. Anat. 92, 189-217]. Previous studies of retinoic acid receptor (RAR) mutant mice have not revealed any of these malformations [Li, E., Sucov, H. M., Lee, K.-F., Evans, R. M., Jaenisch, R. (1993) Proc. Natl. Acad. Sci. USA 90, 1590-1594; Lohnes, D., Kastner, P., Dierich, A., Mark, M., LeMeur, M., Chambon, P. (1993) Cell 73, 643-658; Lufkin, T., Lohnes, D., Mark, M., Dierich, A., Gorry, P., Gaub, M. P., Lemeur, M., Chambon, P. (1993) Proc. Natl. Acad. Sci. USA 90, 7225-7229; Mendelsohn, C., Mark, M., Dollé, P., Dierich, A., Gaub, M.P., Krust, A., Lampron, C., Chambon, P. (1994a) Dev. Biol. in press], suggesting either that there is a considerable functional redundancy among members of the RAR family during ontogenesis or that the RARs are not essential transducers of the retinoid signal in vivo. In order to discriminate between these possibilities, we have generated a series of RAR compound null mutants. These RAR double mutants invariably died either in utero or shortly after birth and presented a number of congenital abnormalities, which are reported in this and in the accompanying study. We describe here multiple eye abnormalities which are found in various RAR double mutant fetuses and are similar to those previously seen in VAD fetuses. Interestingly, we found further abnormalities not previously reported in VAD fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Abnormalities, Multiple; Animals; Bone and Bones; Brain; Extremities; Eye; Eye Abnormalities; Facial Bones; Genotype; Limb Deformities, Congenital; Mice; Mice, Mutant Strains; Morphogenesis; Phenotype; Receptors, Retinoic Acid; Skull; Tretinoin

Topics: Abnormalities, Drug-Induced; Animals; Brain; Dose-Response Relationship, Drug; Eye Abnormalities; Female; Gestational Age; Mice; Mice, Inbred C3H; Pregnancy; Tretinoin