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WDR62 mutations that result in protein loss, truncation or single amino-acid substitutions are causative for human microcephaly, indicating critical roles in cell expansion required for brain development. WDR62 missense mutations that retain protein expression represent partial loss-of-function mutants that may therefore provide specific insights into radial glial cell processes critical for brain growth. Here we utilized CRISPR/Cas9 approaches to generate three strains of WDR62 mutant mice; WDR62 V66M/V66M and WDR62R439H/R439H mice recapitulate conserved missense mutations found in humans with microcephaly, with the third strain being a null allele (WDR62stop/stop). Each of these mutations resulted in embryonic lethality to varying degrees and gross morphological defects consistent with ciliopathies (dwarfism, anophthalmia and microcephaly). We find that WDR62 mutant proteins (V66M and R439H) localize to the basal body but fail to recruit CPAP. As a consequence, we observe deficient recruitment of IFT88, a protein that is required for cilia formation. This underpins the maintenance of radial glia as WDR62 mutations caused premature differentiation of radial glia resulting in reduced generation of neurons and cortical thinning. These findings highlight the important role of the primary cilium in neocortical expansion and implicate ciliary dysfunction as underlying the pathology of MCPH2 patients., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

A multitude of signalling pathways are involved in the process of forming an eye. Here we demonstrate that β-catenin is essential for eye development as inactivation of β-catenin prior to cellular specification in the optic vesicle caused anophthalmia in mice. By achieving this early and tissue-specific β-catenin inactivation we find that retinal pigment epithelium (RPE) commitment was blocked and eye development was arrested prior to optic cup formation due to a loss of canonical Wnt signalling in the dorsal optic vesicle. Thus, these results show that Wnt/β-catenin signalling is required earlier and play a more central role in eye development than previous studies have indicated. In our genetic model system a few RPE cells could escape β-catenin inactivation leading to the formation of a small optic rudiment. The optic rudiment contained several neural retinal cell classes surrounded by an RPE. Unlike the RPE cells, the neural retinal cells could be β-catenin-negative revealing that differentiation of the neural retinal cell classes is β-catenin-independent. Moreover, although dorsoventral patterning is initiated in the mutant optic vesicle, the neural retinal cells in the optic rudiment displayed almost exclusively ventral identity. Thus, β-catenin is required for optic cup formation, commitment to RPE cells and maintenance of dorsal identity of the retina.

Embryonic exposure to ethanol leads to malformations such as cyclopia. Cyclopic embryos present fused eyes and lack of the ventral specification of the brain, with physiological and morphological defects in the visual system, which provides a useful model for teratology and neurotoxicity assessments. We analysed the differentiation of the visual areas in the ethanol-induced cyclopic animals. For this purpose we exposed zebrafish embryos to 1.5% ethanol from 4 hours post-fertilisation (hpf) to 24 hpf in order to get cyclopic embryos. We monitored cytoarchitecture and quantified both the proliferation rate and cell differentiation from 2 days post-fertilisation (dpf) onwards, focusing on the main components of the visual system (retina, optic nerve and optic tectum) of normal and cyclopic zebrafish embryos. The visual system of the zebrafish embryos is affected by exposure to ethanol; two optic nerves that fuse before leaving the eyes are present in cyclopic specimens but an optic chiasm is not evident. Cell differentiation is severely delayed throughout the visual system at 2 dpf. At 5 dpf, lamination in the cyclopic retina and optic tectum is completed, but they are filled with pyknotic nuclei demonstrating cell death. At this stage the proliferation rate and expression patterns are unaltered and glial and neuronal neurochemical differentiations are similar to untreated animals. We found that the alterations produced by exposure to ethanol are not only cell-selective, but also tissue-selective. Cyclopia is the most severe phenotype induced by ethanol, although cell differentiation and proliferation can reach normal patterns after a certain period of time, which points to a neural plasticity process. Zebrafish embryos may possess a compensation mechanism against the ethanol effect, which would account for their use for pharmacogenetic and chemical screenings in the analysis of new molecules that could improve visual problems., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Purpose of Review: To summarize recent breakthroughs regarding the genes known to play a role in normal ocular development in humans and to elucidate the role mutations in these genes play in anophthalmia and microphthalmia., Recent Findings: The main themes discussed within this article are the various documented genetic advances in identifying the various causes of anophthalmia and microphthalmia. In addition, the complex interplay of these genes during critical embryonic development will be addressed., Summary: The recent identification of many eye development genes has changed the ability to identify a cause of anophthalmia and microphthalmia in many individuals. Syndrome identification and the availability of genetic testing underscores the desirability of evaluation by a geneticist for all individuals with anophthalmia and microphthalmia in order to provide appropriate management, long-term guidance, and genetic counseling.

This article discusses the embryologic development of the eye and orbital structures. Among the defects presented are anophthalmia and microphthalmia, coloboma, persistent hyperplastic primary vitreous, Coats disease, vascular malformations, encephalocele and nasolacrimal mucocele. Clinical and imaging features of the diseases are presented, along with radiographic images., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Anophthalmia and microphthalmia describe, respectively, the absence of an eye and the presence of a small eye within the orbit. The combined birth prevalence of these conditions is up to 30 per 100,000 population, with microphthalmia reported in up to 11% of blind children. High-resolution cranial imaging, post-mortem examination and genetic studies suggest that these conditions represent a phenotypic continuum. Both anophthalmia and microphthalmia may occur in isolation or as part of a syndrome, as in one-third of cases. Anophthalmia/microphthalmia have complex aetiology with chromosomal, monogenic and environmental causes identified. Chromosomal duplications, deletions and translocations are implicated. Of monogenic causes only SOX2 has been identified as a major causative gene. Other linked genes include PAX6, OTX2, CHX10 and RAX. SOX2 and PAX6 mutations may act through causing lens induction failure. FOXE3 mutations, associated with lens agenesis, have been observed in a few microphthalmic patients. OTX2, CHX10 and RAX have retinal expression and may result in anophthalmia/microphthalmia through failure of retinal differentiation. Environmental factors also play a contributory role. The strongest evidence appears to be with gestational-acquired infections, but may also include maternal vitamin A deficiency, exposure to X-rays, solvent misuse and thalidomide exposure. Diagnosis can be made pre- and post-natally using a combination of clinical features, imaging (ultrasonography and CT/MR scanning) and genetic analysis. Genetic counselling can be challenging due to the extensive range of genes responsible and wide variation in phenotypic expression. Appropriate counselling is indicated if the mode of inheritance can be identified. Differential diagnoses include cryptophthalmos, cyclopia and synophthalmia, and congenital cystic eye. Patients are often managed within multi-disciplinary teams consisting of ophthalmologists, paediatricians and/or clinical geneticists, especially for syndromic cases. Treatment is directed towards maximising existing vision and improving cosmesis through simultaneous stimulation of both soft tissue and bony orbital growth. Mild to moderate microphthalmia is managed conservatively with conformers. Severe microphthalmia and anophthalmia rely upon additional remodelling strategies of endo-orbital volume replacement (with implants, expanders and dermis-fat grafts) and soft tissue reconstruction. The potential for visual development in microphthalmic patients is dependent upon retinal development and other ocular characteristics.

Sox2, which encodes an SRY-like HMG box transcription factor, is critical for vertebrate development. Sox2 mediates its transcriptional effects through the formation of complexes with specific co-factors, many of which are unknown. In this report, we identify Oct-1, encoded by the Pou2f1 gene, as a co-factor for Sox2 in the context of mouse lens and nasal placode induction. Oct-1, Sox2, and Pax6 are co-expressed during lens and nasal placode induction and during subsequent developmental stages. Genetic combination of Sox2 and Pou2f1 mutant alleles results in impaired induction of the lens placode, an ocular phenotype that includes anophthalmia, and a complete failure of nasal placode induction. These ocular and nasal phenotypes closely resemble those observed in Pax6 null embryos. Moreover, we identify DNA-binding sites that support the cooperative formation of a complex between Sox2 and Oct-1 and mediate Sox2/Oct-1-dependent transactivation of the Pax6 lens ectoderm enhancer in vitro. We demonstrate that the same Sox- and Octamer-binding sites are essential for Pax6 enhancer activity in the lens placode and its derivatives in transgenic mouse embryos. Collectively, these results indicate that Pou2f1, Sox2 and Pax6 are interdependent components of a molecular pathway utilized in both lens and nasal placode induction.

We report heterozygous, loss-of-function SOX2 mutations in three unrelated individuals with Anophthalmia-Esophageal-Genital (AEG) syndrome. One previously reported case [Rogers, R.C. (1988) Unknown cases. Proceedings of the Greenwood Genetic Center. 7, 57.] has a 2.7 Mb deletion encompassing SOX2 and associated with a cryptic translocation t(3;7)(q28;p21.3). The deletion and translocation breakpoints on chromosome 3q are >8.6 Mb apart and both chromosome rearrangements have occurred de novo. Another published case [Petrackova et al. (2004) Association of oesophageal atresia, anophthalmia and renal duplex. Eur. J. Pediatr., 163, 333-334.] has a de novo nonsense mutation, Q55X. A previously unreported case with severe bilateral microphthalmia and oesophageal atresia has a de novo missense mutation, R74P, that alters a highly evolutionarily conserved residue within the high mobility group domain, which is critical for DNA-binding of SOX2. In a yeast one-hybrid assay, this mutation abolishes Sox2-induced activation of the chick delta-crystallin DC5 enhancer. Four other reported AEG syndrome cases were extensively screened and do not have detectable SOX2 mutations. Two of these cases have unilateral eye malformations. SOX2 mutations are known to cause severe bilateral eye malformations but this is the first report implicating loss of function mutations in this transcription factor in oesophageal malformations. SOX2 is expressed in the developing foregut in mouse and zebrafish embryos and an apparently normal pattern of expression is maintained in Shh-/- mouse embryos, suggesting either that Sox2 acts upstream of Shh or functions in a different pathway. Three-dimensional reconstructions of the major morphological events in the developing foregut and eye from Carnegie Stages 12 and 13 human embryos are presented and compared with the data from model organisms. SOX2, with NMYC and CHD7, is now the third transcriptional regulator known to be critical for normal oesophageal development in humans.

Heterozygous mutations in the homeobox gene, PITX2, result in ocular anterior segment defects and a high incidence of early-onset glaucoma. Pitx2 is expressed in both the neural crest and the mesoderm-derived precursors of the periocular mesenchyme. Complete loss of function in mice results in agenesis or severe disruption of periocular mesenchyme structures and extrinsic defects in early optic nerve development. However, the specific requirements for Pitx2 in neural crest versus mesoderm could not be determined using these mice, and only roles in the initial stages of eye development could be assessed due to early embryonic lethality. To determine the specific roles of Pitx2 in the neural crest precursor pool, we generated neural crest-specific Pitx2 knockout mice (Pitx2-ncko). Because Pitx2-nkco mice are viable, we also analyzed gene function in later eye development. Pitx2 is intrinsically required in neural crest for specification of corneal endothelium, corneal stroma and the sclera. Pitx2 function in neural crest is also required for normal development of ocular blood vessels. Pitx2-ncko mice exhibit a unique optic nerve phenotype in which the eyes are progressively displaced towards the midline until they are directly attached to the ventral hypothalamus. As Pitx2 is not expressed in the optic stalk, an essential function of PITX2 protein in neural crest is to regulate an extrinsic factor(s) required for development of the optic nerve. We propose a revised model of optic nerve development and new mechanisms that may underlie the etiology of glaucoma in Axenfeld-Rieger patients.

A case of a newborn with atresia of the transverse colon and right facial hemiaplasia, anophthalmia, and cerebral dysfunction is reported. Colon atresia is a rare cause of congenital bowel obstruction and often associated with other malformations such as abdominal wall defects, gastrointestinal, cardiac, urogenital, and musculosceletal lesions. Facial hemiaplasia may arise in frame of chromosomal defects or as a result of neurovascular compromise caused by congenital amniotic bands. However, the combination of colon atresia and facial hemiaplasia has not been reported before., (Copyright 2002, Elsevier Science (USA). All rights reserved.)

Formation of the neural tube plays a primary role in establishing the body plan of the vertebrate embryo. Here we describe the phenotype and physical mapping of a highly penetrant X-linked male-lethal murine mutation, exma (exencephaly, microphthalmia/anophthalmia), that specifically disrupts development of the rostral neural tube and eye. The mutation arose from the random insertion of a transgene into the mouse X Chromosome (Chr). Eighty-three percent of transgenic male embryos display an open, disorganized forebrain and lack optic vesicles. No transgenic males survive beyond birth. Hemizygous females show a variable phenotype, including reduced viability and occasional exencephaly and/or microphthalmia. Altered or reduced expression patterns of Otx2, Pax6, Six3, and Mrx, known markers of early forebrain and eye development, confirmed the highly disorganized structure of the forebrain and lack of eye development in affected exma male embryos. Physical mapping of the transgene by FISH localized a single insertion site to the interval between Dmd and Zfx on the X Chr. A 1-Mb contig of BAC clones was assembled by using sequences flanking the transgene and revealed that the insertion lies close to Pola1 and Arx, a gene encoding a highly conserved homeobox protein known to be expressed in the developing forebrain of the mouse. Data from Southern blots of normal and transgenic DNA demonstrated that a large segment of DNA encompassing Arx and including part of Pola1 was duplicated as a result of the transgene insertion. From the physical mapping results, we propose a model of the gross rearrangements that accompanied transgene integration and discuss its implications for evaluating candidate genes for exma.

Primary anophthalmos is a heterogeneous condition. In its nonsyndromal form, it is usually considered an autosomal recessive trait. However, other causes such as chromosomal abnormalities and prenatal insults need to be considered. We report on a unique reciprocal translocation 46,XX,t(3;11)(q27;p11.2) in a baby with isolated anophthalmos. Both Chitayat et al. [1996] and Alvarez Arratia et al. [1984] have reported on cases of terminal deletion of the long arm of chromosome 3. In each case the child had multiple anomalies including microphthalmia or anophthalmia. Because our patient appears to have no other anomalies, this break point may indicate that a genetic locus for eye formation exists at chromosome site 3q27. Published 1999 Wiley-Liss, Inc.

The Drosophila gene sine oculis (so), a nuclear homeoprotein that is required for eye development, has several homologues in vertebrates (the SIX gene family). Among them, SIX3 is considered to be the functional orthologue of so because it is strongly expressed in the developing eye. However, embryonic SIX3 expression is not limited to the eye field, and SIX3 has been found to be mutated in some patients with holoprosencephaly type 2 (HPE2), suggesting that SIX3 has wide implications in head development. We report here the cloning and characterization of SIX6, a novel human SIX gene that is the homologue of the chick Six6(Optx2) gene. SIX6 is closely related to SIX3 and is expressed in the developing and adult human retina. Data from chick and mouse suggest that the human SIX6 gene is also expressed in the hypothalamic and the pituitary regions. SIX6 spans 2567 bp of genomic DNA and is split in two exons that are transcribed into a 1393-nucleotide-long mRNA. Chromosomal mapping of SIX6 revealed that it is closely linked to SIX1 and SIX4 in human chromosome 14q22.3-q23, which provides clues about the origin and evolution of the vertebrate SIX family. Recently three independent reports have associated interstitial deletions at 14q22.3-q23 with bilateral anophthalmia and pituitary anomalies. Genomic analyses of one of these cases demonstrated SIX6 hemizygosity, strongly suggesting that SIX6 haploinsufficiency is responsible for these developmental disorders., (Copyright 1999 Academic Press.)

To determine the role of retinal axons in the development of the corticocollicular projection in mice, the lipophilic fluorescent dye, DiI, was used to compare the development of the cortical projections in phenotypically normal (C57BL/6J) mice to that of anophthalmic 129SV/CPorJ mice. Cortical axons in anophthalmic mice found their targets and established a laminar specificity similar to those of cortical axons in normal mice despite the absence of the retinal projection. Cortical axons in normal mice reached the superior colliculus before those in anophthalmic mice and also had a faster rate of growth within the colliculus. Unlike cortical axons in normal mice in early postnatal ages, those in anophthalmic mice formed a disperse bundle in the stratum opticum. Axons labeled by focal applications of DiI into area 17 terminated in a larger and more medial area in anophthalmic mice than in normal mice. Thus, retinal axons are not essential for cortical axons to reach the superior colliculus, but they may have a role in organizing the growth of later-arriving cortical axons. Furthermore, cortical axons can terminate in the superior colliculus with a coarse topography when retinal axons are absent, but they cannot form a topographically refined projection., (Copyright 1999 Published by Elsevier Science B.V.)

Clinical Anophthalmos is a very rare condition and this is illustrated in Benin City, Nigeria where the two cases described are the only cases that have been seen at the University of Benin Teaching Hospital over a period of twenty years. The two cases were unilateral anophthalmos. The first case is a case of primary anophthalmos while the second case is the consecutive or degenerative type of anophthalmos.

The eyes absent (eya) gene plays an essential role in the events that lead to formation of the Drosophila eye; without expression of eya in retinal progenitor cells, they undergo programmed cell death just prior to the morphogenetic furrow, leading to an eyeless or reduced eye phenotype. The eya gene has recently been found to be highly conserved to humans, defining a new gene family. Insights into the gene's function in the fly, therefore, are likely to be relevant to the role of its homologs in vertebrates. Detailed studies at the subcellular level indicate that the Eya protein is localized to the nucleoplasm, suggesting a role in control of nuclear events. The eya gene shows expression and roles in tissues other than the eye, including subsets of cells of the adult visual system, brain, and ovary, as well as an elaborate expression pattern in the embryo. Various mutations in the eya gene cause loss of ocelli, female sterility, or lethality. Analysis of the embryonic lethal phenotype indicates that mutant alleles show defects in head morphogenesis. These data indicate that eya has critical roles in morphogenesis of a number of tissues in the animal, in addition to its role in early eye formation. Despite multiple roles at multiple stages of development of the fly, both the type I and type II forms of the protein, when expressed ectopically during larval development, can direct eye formation., (Copyright 1998 Academic Press.)

Developmental mechanisms that regulate the areal and laminar distribution of various macromolecules, including neurotransmitter receptors in the cerebral cortex, are not known. In the present study, we examined the development of monoaminergic receptors in the rhesus monkey striate and peristriate visual cortex in the absence of input from the retina. Binocular enucleation was performed between embryonic days E60 and E81, prior to the ingrowth of geniculocortical fibers into the cortical plate and before genesis of the granular and supragranular layers of the visual cortex. The animals were delivered at term (E165) and sacrificed at 2 or 12 months of age, and their brains frozen and the occipital lobes cut at 20 microns in the coronal plane. Cortical binding of 3H-clonidine, 125I-pindolol, 3H-5-HT, 3H-ketanserin, 3H-spiperone, 3H-SCH23390, and 3H-prazosin that label various monoamine receptors were autoradiographically visualized and quantified using a computer imaging system. All radioligands displayed specific laminar patterns in the striate and prestriate areas in both groups of animals. The areal and laminar distribution in the anophthalmic monkeys was similar to that in the controls. Significantly, in all enucleated animals, just as in the controls, a particularly high density of 3H-clonidine and 3H-prazosin was observed in the sublayers of layer IV involved in color vision. The present results show that the monoamine receptors in primate visual cortex can establish and maintain distinct laminar and areal patterns in the absence of activity or molecular cues originated from the retina, and provide new insight into the cortical consequences of secondary congenital anophthalmia.

The mouse Small eye (Sey) locus is situated on chromosome 2. Molecular analyses have shown that SeyNeu represents a point mutation leading to a splice site error and loss of the functional gene product. The Sey locus has been shown to be identical with the paired box (Pax)-6 gene, which contains paired-like and homoeobox domains and is a developmental control gene. Pax-6 expression occurs in many parts of the central nervous system during embryogenesis. Therefore, we may expect the Sey mutation to result in abnormal development of the central nervous system. The present study shows that Pax-6 mutation has a bimodal effect upon neurogenesis in mouse: it causes a delay of premigratory neurons in a stage-, region-, and gene-dose-dependent manner. Additionally, Sey mutation impairs axonal growth and differentiation. Neurons of the cortical plate cease differentiation on approximately day 16 of gestation and appear to have increased cohesion: their cytoplasm is swollen and vacuolated. These changes coincide both with reduced formation of axons and with the onset of vacuolar degeneration in existing axons, glial cells and radial glial fibers. Consequently, there is an impairment of the peripheral migration of putative neurons so that the neonatal lesion pattern of the neocortical roof becomes dominated by a broad spectrum of neuronal migration disorders.

Knowledge of human brain development biology has increased rapidly over the last decade due to fundamental acquisitions in the fields of organogenesis, fetal development, and post-natal growth. The role of the neural crests during cephalic organogenesis, recently studied by Mme Nicole Le Douarin, has given new biological dimensions to the head : it is an organic complex, globally neural in character, and of encephalofacial territorialization. The cervicocephalic region derives this original segmentation from the migratory property of this contingent of the neural crests. In this perspective, the nasofrontal bud is therefore an embryonic cephalic segment, in which appears the pro-encephalon, the eyes, the olfactory bulb, and the median facial zones (bone, cartilage, teeth). Any morphogenetic anomaly in this original craniofacial segment creates associated malformation of the brain, the base of the skull, and the face (eyes and olfactory bulbs) : the neurocristopathies. In this respect, and from the semiological point of view, the face is the "predicate" of the brain. A new classification of these malformations is proposed, based on the clinical study of the ethmoid, a cartilaginous median organ which is accessible clinically. Epigenesis lasts for 18 months in this organ, which forms a part of the face and the neurocranium, and which is known to play a "motor" morphogenetic role on the osteomembranous face : the ethmoidal syndromes (hypo- and hyper-septoethmoidism). Future reports will discuss the neurocristopathies of the branchial arches.

An otherwise normal adult Charles River rat (CD strain) was observed to have no recognizable eyes. Breeding and morphological studies were undertaken to determine the nature of the ocular defect, as well as its cause and pathogenesis. The anomaly was found to be inherited as an autosomal recessive trait with variable expressivity. It was characterized by unilateral or bilateral congenital microphthalmia with multiple associated ocular abnormalities including a neuroepithelial cyst, optic nerve aplasia, and cataract. In several elderly rats, no eye was found histologically in the orbit, suggesting reabsorption of malformed tissues as the basis of the anophthalmia. Study of the prenatal morphogenesis of the microphthalmia suggested that the primary disorder reflects a disturbance of the neuroepithelium of the retinal anlage and results in defective early formation of the optic cup. The abnormalities in other ocular structures, particularly in the lens, are considered secondary. This ocular malformation emphasizes the early interactions and interdependence of the lens and retina in normal morphogenesis and provides an animal model for study of lens-retinal relationships in abnormal morphogenesis. It is particularly relevant in understanding the pathogenesis of microphthalmia with cysts in the human eye.

Small eyes (Sey) is a semidominant, homozygous lethal mutation in the mouse (Roberts, 1967). It is allelic with SeyH, a radiation-induced homozygous prenatal lethal which has been mapped on chromosome 2. The effect of the Sey mutation is apparently limited to the growth and differentiation of the presumptive lens and nasal placodes. Homozygous Sey/Sey embryos can be distinguished as early as 10.5 days post coitum (p.c.); the optic vesicles grow out, but the ectoderm does not give rise to a lens and nasal pits never form. Immunohistochemical studies show that the distribution of the extracellular matrix glycoprotein laminin is not significantly different in the cephalic region of Sey/Sey versus Sey/+ or +/+ embryos. Sey/Sey embryos develop to term but without eyes or nose, and die soon after birth. Further analysis of Sey/Sey embryos may throw light on the mechanisms underlying morphogenesis of craniofacial structures in mammals.

The association of unilateral mandibulofacial dysostosis and anophthalmos at the same side is reported. The proband presented at the age of six months with: right anophthalmos and hypoplasia of the orbit at the same side, hypoplasia of the right mandible and maxilla, right external ear deformity, cyanotic heart disease, hemivertebrae, cataract and corneal opacity in the left eye. This case shows the maximal effect of the abnormal development of the first branchial arch (the mandible, maxilla, and ears) on the globe and the orbit. The other end of the spectrum in which the minimal effect on the globe was present (unilateral absence of choriocapillaris and retinal pigment epithelium inferiorly) was reported by Cotlier & Alghadyan in 1981. This supports the concept that abnormal development of the mandible may influence the development of the orbit and the globe. The extent of the influence of the abnormal developing first branchial arch on the eye is discussed.

Extirpation of cranial neural crest cells in presomite to 5 somite chick embryos produces monsters which in all essential respects are identical to human cyclopias. The primary lesion involves damage to the forebrain and consequently the inhibition of the nasal placode and nasal organ development as well as the destruction of the anterior neural crest cells, with the resultant absence of the nasal and interobital septa and of the facial dermal skeleton.

The authors analyze 8 cases of congenital anophthalmia (CA). In all the cases this condition has been a component of multiple congenital developmental abnormalities; in 4 cases the defect has been nosologically diagnosed. Developmental defects of the central nervous system have been revealed in all the cases. Histologic studies have made it possible to single out, with due consideration for the normal embryogenesis of the eye, the following variants of CA: (1) complete anophthalmia, (2) partial anophthalmia--(a) purely neuroectodermal, (b) mixed mesodermal/ectodermal, (3) anophthalmia with cysts, (4) anophthalmia with intracranial synophthalmus. The possible mechanisms of teratogenesis acting in every case of CA are discussed.

Immunofluorescence with anti-crystallin antisera was done on the eye rudiments of mouse embryos of a congenitally anophthalmic strain. In a few of the embryos a lens vesicle formed, which, although much smaller than in controls and delayed in development, appeared morphologically normal. alpha-Crystallin could be identified in the cells of the rudiments. In addition the cells looked cytologically similar to those of the normal lens vesicle; they were elongated and the nuclei displayed interkinetic nuclear migration. Therefore, the surface ectoderm of the anophthalmia mouse can differentiate into a lens vesicle that appears biochemically and cytologically normal. This indicates that the optic vesicle in this mutant is capable of inducing a lens, while the surface ectoderm can respond to the stimulus in a normal fashion.

A certain percentage of congenitally anophthalmic mouse embryos have the ability to generate small lens vesicles that have previously been shown to produce alpha crystallin at 13-day gestation. Further immunohistological analysis of 13- and 15-day-gestation anophthalmia embryos indicates that beta crystallin is present in those 13-day embryos which have lens vesicles with lens-fiber formation. Also, 15-day embryos with lenses demonstrating fiber elongation can produce both beta and gamma crystallins. The conclusion is drawn that the genetic potential to produce at least three characteristic biochemical markers of normal lens differentiation is present in the anophthalmia mutant. The spatial distribution patterns of the crystallins in normal and anophthalmia embryos were similar. However, there appeared to be a transposition in the temporal appearance of beta and gamma crystallins in the anophthalmia mutant. Optic cups and associated lenses in 15-day anophthalmia specimens were much smaller than those in controls. The optic and lens rudiments in these anophthalmia embryos were fairly proportional in size, which indicates that some degree of allometric growth compensation had occurred during the course of development. This ability for differential growth compensation in the mouse eye appears to be restricted to the predifferentiative stages of eye formation.

The optic anlage of the anophthalmic murine strain ZRDCT/an has been studied. In this strain, 70% of the adults are anophthalmic, 30% are one-eyed. The eye primordium appears and starts to differentiate at day 9 of gestation, then it degenerates. At 13 days of gestation, it has practically disappeared. When isolated and cultured in vitro, the 10-day anophthalmic anlage develops in the same way as a control optic-cup culture from a Swiss or C57B16 mouse. When grafted in the back of a 15--17 day Swiss foetus, this 10-day anophthalmic anlage also develops: retina and lens differentiate, the structures which grow are very similar to those obtained when C57B16 optic cups are grafted in the same conditions. It appears from these results that the eye regression of the mutant in situ is not a process intrinsic to the anlage. If withdrawn from its local environmental influences, the eye primordium is able to express its aptitude for differentiation.

Two infants were found to have bilateral anophthalmos and other congenital anomalies. Secondary anophthalmia was diagnosed in one patient who showed malformations of the brain and an absence of ocular tissues including the optic nerves. The other patient had degenerative (consecutive) anophthalmos; fragments of ocular tissues including the optic nerves were found in the orbits.

Prospective anterolateral neural fold was grafted from normal axolotls into the posterior neural fold region (statocyst area) of eyeless mutant hosts. These unilateral anteroposterior grafts stimulated bilateral eye formation in the eyeless mutant at a rate of 79%. Replacing the statocyst area of mutants with the statocyst area from normals stimulated bilateral eye formation in 49% of the cases. Grafting of prospective anterolateral neural fold between normals and mutants or excising the statocyst region of mutants, had no effect. The results are interpreted on the basis of a hypothetical anteroposterior morphogenetic system that might be out of balance in the mutant.

The following malformations were observed in a human embryo of 28 mm crown-rump length obtained at operation for tubal rupture in a case of extrauterine pregnancy: 1. Secondary anophthalmia with dysplasia and in part aplasia of the diencephalon. Rudiments of both eyes and eyestalklike proliferations within the diencephalon. No lenses and on the left side only a palpebral fissure. Hypoplasia of the right telencephalic hemisphere and of the right side of diencephalon, mesencephalon and proximal parts of the medulla oblongata. Pseudotumorous proliferations in the diencephalon, in the alar plate of the medulla oblongata (protruding into the fourth ventricle) and in the arachnoid. Hypoplasia of the right internal, middle, and external ear. Dysplasia and in part aplasia of facial osseous elements (cebocephalia). 2. Proximal esophageal atresia with distal tracheoesophageal fistula. 3. A Fallot's tetralogy with right-sided aortic arch and regressive right-sided ductus arteriosus, tricuspid atresia, hypoplasia of the right ventricle with excessive hypertrophy of its wall, and hypoplasia of the pulmonary trunk. Single left superior vena cava and abnormal, semicircular course of the stems of both coronary arteries.

Anophthalmic white (Wh) of the Syrian hamster is a highly pleiotropic dominant spotting color mutation causing homozygotes to be deaf, blind, and white. An ultrastructural analysis of embryonic tissue reveals that Wh causes the retention of cilia by cells of opposing layers of the embryonic retina and by the lens fiber cells. Previous ultrastructural analyses indicate that Wh also causes the retention of cilia by secretory cells of the anterior lobe of adult pituitaries. We propose that the primary ultrastructural defects caused by Wh is the retention of cilia by embryonic cells. These retained cilia are hypothesized to interfere with normal cell-cell interactions and subsequent cell differentiation.

Nine patients with aberrations in development and placement of the eyes and periocular structures who also had serious defects in central nervous system development were evaluated in order to better understand normal ocular development. Included were an incompletely developed twin stillborn infant who lacked both eyes and the nose, a stillborn infant with cyclopia hypognathia, 6 spontaneous abortuses with varying degrees of holoprosencephaly, and a 17-year-old male with a serious defect in central nervous system development whose right eye was positioned laterally above the right ear. In all cases, evidence indicates that orbital and periocular structures are determined by the underlying optic vesicle rather than independently derived as has been suggested by previous studies.

The picture presented by congenital anophthalmus is presented and its primary, secondary and degenerative forms are distinguished. The frequency of this rare abnormality is discussed with reference to the literature data, both clinical and experimental, and the possible part played by various physical, chemical, infectious and genetic factors is explained. Some considerations are expressed concerning the qualitative and chronological mechanisms of action and the harmful factors responsible for this embryopathy.