A Pitx3-deficient developmental mouse model for fine motor, olfactory, and gastrointestinal symptoms of Parkinson's disease.

Parkinson's disease (PD) is characterized by the selective death of substantia nigra pars compacta (SNpc) dopaminergic neurons and includes both motor and non-motor symptoms. While numerous models exist for the study of typical PD motor deficits, fewer exist for non-motor symptoms. Previous studies have shown that a Pitx3-/- mouse model (aphakia or ak mouse) has specific developmental failure of the dopaminergic neuron population in the SNpc and that it can be used for the study of PD-related gross motor dysfunction as well as cognitive functional deficits. It remains unclear whether the aphakia mouse, both male and female, might also be used to model fine motor deficits and for additional studies of non-motor deficits associated with PD. Here, using an extensive battery of behavioral tests, we demonstrate that the aphakia mouse shows both gross and fine motor functional deficits compared with control mice. Furthermore, aphakia mice show deficits of olfactory function in buried pellet, odor discrimination and odor habituation/dishabituation tests. We also found that aphakia mice suffer from gastrointestinal dysfunction (e.g., longer whole gut transit time and colon motility deficits), suggesting that the mutation also affects function of the gut-brain axis in this animal model. Moreover, our data demonstrate that in the aphakia mouse, L-DOPA, the gold standard PD medication, can rescue both gross and fine motor function deficits but neither olfactory nor gastrointestinal symptoms, a pattern much like that seen in PD patients. Altogether, this suggests that the aphakia mouse is a suitable model for fine motor, olfactory and gastrointestinal behavioral studies of PD as well as for the development of novel disease-modifying therapeutics. SIGNIFICANCE STATEMENT: While several animal models are available to study the major motor symptoms of PD, there are fewer that replicate non-motor symptoms, which constitute a major source of morbidity for patients. Moreover, available models often require manipulations resulting in sudden massive cell loss and inflammation, both of which may interfere with understanding of the direct effects of dopaminergic neuronal loss in the SNpc. We describe a model of congenital SNpc cell deficiency in a Pitx3-/- mouse and characterize it with a battery of behavioral tests suggesting that it closely mimics non-motor as well as motor symptoms of PD, providing a useful insight into the effects of the nigrostriatal dopamine deficit. Taken together, these data suggest that the ak mouse represents a useful model to study dopaminergic system function for both motor and non-motor symptoms of PD.

Novel prenatally diagnosed compound heterozygous PXDN variants in fetal congenital primary aphakia and blepharophimosis.

OBJECTIVE: To precision survey a fetal congenital primary aphakia molecular etiology. CASE REPORT: A case of 42 years old pregnancy woman prenatal diagnostic examination by amniocentesis conducted at 17 weeks' gestation and demonstrated a normal female karyotype. Trio studies based on chromosome microarray analysis (CMA) and Sanger's genetic analysis did not detect a pathologic variant of the FOXE3 gene. Fetal congenital primary aphakia accompanied with microphthalmia detected by sonography in the second trimester (22 weeks). MRI indicated bilateral absence of the lenses, consistent with primary congenital aphakia. Due to the poor prognosis of congenital aphakia, the parents decided to terminate the fetus and provided consent for an autopsy. Pathological analysis revealed dysplasia of the anterior segment of both eyes. However, post fetal mortem extended trio whole exon sequencing (WES) and Sanger's genetic analysis identified compound heterozygous variants in the chromosomal location 2p25.3 in the PXDN gene. CONCLUSION: Extended whole exon sequencing is an important tool to study primary congenital aphakia.

Congenital primary aphakia.

PURPOSE: To describe the natural history, management, and visual outcome in children with congenital primary aphakia (CPA). METHODS: This is a multicenter retrospective consecutive case series from five academic centers in England and North America. RESULTS: A total of 27 eyes of 14 patients were included (male:female, 1.7:1). Thirteen patients had bilateral CPA, and 1 patient had unilateral CPA. Mean age at diagnosis was 18 months (median, 21; range, 0.5-144). Of 11 patients who underwent genetic testing, 9 had FOXE3 pathogenic variants. In all patients, visual acuity at presentation was not better than fixing and following light. Typical findings included silvery appearance of the cornea with vascularization (96%), glaucoma (81%), iridocorneal adhesions (74%), optic nerve coloboma (55%), abnormal vitreous (33%), retinal detachment (30%), and aniridia with hypoplasia of ciliary body (19%). Surgical interventions in select patients included penetrating keratoplasty (PKP), glaucoma drainage device implantation, and cyclophotocoagulation (CPC). CONCLUSIONS: Eyes with corneal ectasia and a silvery appearance of the cornea with vascularization should alert the physician to the possibility of CPA. Glaucoma causes globe enlargement and may increase the risk of corneal perforation, but glaucoma is often refractory to medical treatment, and the threshold for surgical treatment should be low. PKP outcomes are very poor.

Acupuncture Alleviates Levodopa-Induced Dyskinesia via Melanin-Concentrating Hormone in Pitx3-Deficient aphakia and 6-Hydroxydopamine-Lesioned Mice.

Although L-3,4-dihydroxyphenylalanine (L-DOPA) is currently the most effective medication for treating Parkinson's disease (PD) motor symptoms, its prolonged administration causes several adverse effects, including dyskinesia. To identify the mechanisms underlying the effects of acupuncture on L-DOPA-induced dyskinesia (LID), antidyskinetic effects of acupuncture were investigated in two mouse models of PD. Acupuncture stimulation at GB34 alleviated abnormal involuntary movements (AIMs) in Pitx3-deficient aphakia mice (ak/ak) following L-DOPA administration and these effects were reproduced in 6-hydroxydopamine (6-OHDA)-lesioned mice with LID. A transcriptome analysis of the hypothalamus revealed pro-melanin-concentrating hormone (Pmch) gene was highly expressed in acupuncture-treated mouse from ak/ak model of LID as well as 6-OHDA model of LID. Acupuncture combined with the administration of MCH receptor antagonist did not have any beneficial effects on dyskinesia in L-DOPA-injected ak/ak mice, but the intranasal administration of MCH attenuated LID to the same degree as acupuncture in both ak/ak and 6-OHDA mice with LID. A gene expression profile with a hierarchical clustering analysis of the dyskinesia-induced ak/ak mouse brain revealed an association between the mechanisms underlying acupuncture and MCH. Additionally, altered striatal responses to L-DOPA injection were observed after prolonged acupuncture and MCH treatments, which suggests that these treatment modalities influenced the compensatory mechanisms of LID. In summary, present study demonstrated that acupuncture decreased LID via hypothalamic MCH using L-DOPA-administered ak/ak and 6-OHDA mouse models and that MCH administration resulted in novel antidyskinetic effects in these models. Thus, acupuncture and MCH might be valuable therapeutic candidates for PD patients suffering from LID.

Sclerocornea-Microphthalmia-Aphakia Complex: Description of Two Additional Cases Associated With Novel FOXE3 Mutations and Review of the Literature.

PURPOSE: To describe 2 sporadic Mexican patients having congenital bilateral, total sclerocornea, aphakia, and microphthalmia associated with novel mutations in the FOXE3 gene. METHODS: Two affected individuals with congenital bilateral, total sclerocornea, aphakia, and microphthalmia underwent detailed examinations including slit-lamp examination, visual acuity, and intraocular pressure measurements. Ocular ultrasonography and ultrasound biomicroscopy were performed. Genomic DNA was isolated from blood leukocytes in each subject, and molecular analysis of the FOXE3 gene was performed. For cosegregation analysis, presumable pathogenic variants were tested by Sanger sequencing in parental DNA. RESULTS: Molecular screening of FOXE3 was performed in 2 cases with congenital bilateral, total sclerocornea, aphakia, and microphthalmia. In patient 1, genetic analysis demonstrated a novel homozygous c.291C>G (p.Ile97Met) FOXE3 pathogenic variant. In patient 2, compound heterozygosity for the novel c.387C>G (p.Phe129Leu) transversion and for the previously reported c.244A>G (p.Met82Val) transition, was recognized. CONCLUSIONS: The sclerocornea-microphthalmia-aphakia complex is a severe malformative ocular phenotype resulting from mutations in the FOXE3 transcription factor. To date, patients from at least 14 families with this uncommon ocular disorder have been described. The identification of 2 novel pathogenic variants in our patients expands the mutational spectrum in FOXE3-related congenital eye disorders. In addition, we performed a review of the clinical and genotypic characteristics of all published patients carrying biallelic FOXE3 mutations.

A zebrafish model of foxe3 deficiency demonstrates lens and eye defects with dysregulation of key genes involved in cataract formation in humans.

The Forkhead box E3 (FOXE3) gene encodes a transcription factor with a forkhead/winged helix domain that is critical for development of the lens and anterior segment of the eye. Monoallelic and biallelic deleterious sequence variants in FOXE3 cause aphakia, cataracts, sclerocornea and microphthalmia in humans. We used clustered regularly interspaced short palindromic repeats/Cas9 injections to target the foxe3 transcript in zebrafish in order to create an experimental model of loss of function for this gene. Larvae that were homozygous for an indel variant, c.296_300delTGCAG, predicting p.(Val99Alafs*2), demonstrated severe eye defects, including small or absent lenses and microphthalmia. The lenses of the homozygous foxe3 indel mutants showed more intense staining with zl-1 antibody compared to control lenses, consistent with increased lens fiber cell differentiation. Whole genome transcriptome analysis (RNA-Seq) on RNA isolated from wildtype larvae and larvae with eye defects that were putative homozygotes for the foxe3 indel variant found significant dysregulation of genes expressed in the lens and eye whose orthologues are associated with cataracts in human patients, including cryba2a, cryba1l1, mipa and hsf4. Comparative analysis of this RNA-seq data with iSyTE data identified several lens-enriched genes to be down-regulated in foxe3 indel mutants. We also noted upregulation of lgsn and crygmxl2 and downregulation of fmodb and cx43.4, genes that are expressed in the zebrafish lens, but that are not yet associated with an eye phenotype in humans. These findings demonstrate that this new zebrafish foxe3 mutant model is highly relevant to the study of the gene regulatory networks conserved in vertebrate lens and eye development.

FOXE3 mutations: genotype-phenotype correlations.

Microphthalmia and anophthalmia (MA) are severe developmental eye anomalies, many of which are likely to have an underlying genetic cause. More than 30 genes have been described, each of which is responsible for a small percentage of these anomalies. Among these, is the FOXE3 gene, which was initially described in individuals with dominantly inherited anterior segment dysgenesis and, subsequently, associated with recessively inherited primary aphakia, sclerocornea and microphthalmia. In this work, we describe 8 individuals presenting with an MA phenotype. Among them, 7 are carrying biallelic recessive FOXE3 mutations and 2 of these have novel mutations: p.(Ala78Thr) and p.(Arg104Cys). The last of our patients is carrying in the heterozygous state the recessive p.(Arg90Leu) mutation in the FOXE3 gene. To further understand FOXE3 involvement in this wide spectrum of ocular anomalies with 2 different patterns of inheritance, we reviewed all individuals with ocular abnormalities described in the literature for which a FOXE3 mutation was identified. This review demonstrates that correlations exist between the mutation type, mode of inheritance and the phenotype severity. Furthermore, understanding the genetic basis of these conditions will contribute to overall understanding of eye development, improve the quality of care, genetic counseling and, in future, gene-based therapies.

Lack of FOXE3 coding mutation in a case of congenital aphakia.

PURPOSE: To report the findings in a patient with congenital primary aphakia, a rare disease known to be caused by mutations in the FOXE3 gene. METHODS: The clinical appearances and visual functions of the patient were determined from the medical records. Genetic analyses were performed to search for mutations in the FOXE3 gene by Sanger sequencing and whole exome sequencing. RESULTS: The 2-month-old male patient first presented with bilateral congenital aphakia associated with microphthalmia, corneal opacity, and dysplasia of the anterior segment. At the age of 2-years, his visual acuity in the left eye was 20/1000 at 30 cm, he was able to discriminate red, blue, and yellow light stimuli, and a b-wave was recorded by scotopic combined rod-cone electroretinograms. The right eye became blind during the follow-up period. No mutation in the FOXE3 gene was detected. CONCLUSION: Although congenital aphakia is known to be caused by mutations in the FOXE3 gene, the results of lack of coding mutation in this patient suggests a possible genetic heterogeneity of the disease.

Lens status influences the association between CFH polymorphisms and age-related macular degeneration: findings from two population-based studies in Singapore.

AIMS: To determine the differential effects of genetic polymorphism in CFH and ARMS2 on risk of age-related macular degeneration (AMD) between phakic vs. pseudophakic/aphakic eyes. METHODS: 9,529 eyes of 4,918 participants from the Singapore Malay Eye Study and Singapore Indian Eye Study were analyzed. Participants had detailed eye examinations, including slit-lamp examinations and dilated fundus photography. AMD grading was performed according to the Wisconsin age-related maculopathy grading system. Lens status was defined. Single nucleotide polymorphisms (SNPs) rs10801555 (Y402H) within CFH and rs3750847 in ARMS2 were assessed. The main outcome measure was early AMD or any AMD. RESULTS: No significant associations between the CFH Y402H genotypes and early AMD were found in phakic individuals. In contrast, among pseudophakic/aphakic individuals, the CFH Y402H risk genotypes were significantly associated with higher odds of early AMD, with an OR of 1.57 (95% CI: 1.07-2.29) for GA genotype and 2.40 (95% CI: 1.25-4.61) for AA genotype, compared to those with GG genotype. There was significant interaction between pseudophakic/aphakic status and CFH Y402H variant on risk of early AMD (p = 0.037), adjusting for age, gender, and the first 5 genetic principal components. No significant interaction was found between lens status and ARMS2 rs3750847. CONCLUSIONS: CFH genetic polymorphism and pseudophakic/aphakic status may have a potential synergistic effect on early AMD, suggesting roles for the complement system and related pathways in the pathogenesis of AMD in eyes after cataract surgery.

Expression of truncated PITX3 in the developing lens leads to microphthalmia and aphakia in mice.

Microphthalmia is a severe ocular disorder, and this condition is typically caused by mutations in transcription factors that are involved in eye development. Mice carrying mutations in these transcription factors would be useful tools for defining the mechanisms underlying developmental eye disorders. We discovered a new spontaneous recessive microphthalmos mouse mutant in the Japanese wild-derived inbred strain KOR1/Stm. The homozygous mutant mice were histologically characterized as microphthalmic by the absence of crystallin in the lens, a condition referred to as aphakia. By positional cloning, we identified the nonsense mutation c.444C>A outside the genomic region that encodes the homeodomain of the paired-like homeodomain transcription factor 3 gene (Pitx3) as the mutation responsible for the microphthalmia and aphakia. We examined Pitx3 mRNA expression of mutant mice during embryonic stages using RT-PCR and found that the expression levels are higher than in wild-type mice. Pitx3 over-expression in the lens during developmental stages was also confirmed at the protein level in the microphthalmos mutants via immunohistochemical analyses. Although lens fiber differentiation was not observed in the mutants, strong PITX3 protein signals were observed in the lens vesicles of the mutant lens. Thus, we speculated that abnormal PITX3, which lacks the C-terminus (including the OAR domain) as a result of the nonsense mutation, is expressed in mutant lenses. We showed that the expression of the downstream genes Foxe3, Prox1, and Mip was altered because of the Pitx3 mutation, with large reductions in the lens vesicles in the mutants. Similar profiles were observed by immunohistochemical analysis of these proteins. The expression profiles of crystallins were also altered in the mutants. Therefore, we speculated that the microphthalmos/aphakia in this mutant is caused by the expression of truncated PITX3, resulting in the abnormal expression of downstream targets and lens fiber proteins.

Pitx3 directly regulates Foxe3 during early lens development.

Pitx3 is a bicoid-related homeodomain transcription factor critical for the development of the ocular lens, mesencephalic dopaminergic neurons and skeletal muscle. In humans, mutations in PITX3 are responsible for cataracts and anterior segment abnormalities of varying degree; polymorphisms are associated with Parkinson’s disease. In aphakia (ak) mice, two deletions in the promoter region of Pitx3 cause abnormal lens development. Here, we investigated systematically the role of Pitx3 in lens development including its molecular targets responsible for the ak phenotype. We have shown that ak lenses exhibit reduced proliferation and aberrant fiber cell differentiation. This was associated with loss of Foxe3 expression, complete absence of Prox1 expression, reduced expression of epsilon-tubulin and earlier expression of gamma-crystallin during lens development. Using EMSA and ChIP assays, we demonstrated that Pitx3 binds to an evolutionary conserved bicoid-binding site on the 5'-upstream region of Foxe3. Finally, Pitx3 binding to 5'-upstream region of Foxe3 increased transcriptional activity significantly in a cell-based reporter assay. Identification of Foxe3 as a transcriptional target of Pitx3 explains at least in part some of the phenotypic similarities of the ak and dyl mice (dysgenic lens, a Foxe3 allele). These findings enhance our understanding of the molecular cascades which subserve lens development.

An epidemiological investigation of a Forkhead box protein E3 founder mutation underlying the high frequency of sclerocornea, aphakia, and microphthalmia in a Mexican village.

PURPOSE: To investigate the molecular epidemiological basis for the unusually high incidence of sclerocornea, aphakia, and microphthalmia in a village in the Tlaxcala province of central Mexico. METHODS: A population census was performed in a village to identify all sclerocornea, aphakia, and microphthalmia cases. Molecular analysis of the previously identified Forkhead box protein E3 (FOXE3) mutation, c.292T>C (p.Y98H), was performed with PCR amplification and direct DNA sequencing. In addition, DNA from 405 randomly selected unaffected villagers was analyzed to establish the carrier frequency of the causal mutation. To identify the number of generations since the mutation arose in the village, 17 polymorphic markers distributed in a region of 6 Mb around the mutated locus were genotyped in the affected individuals, followed by DMLE software analysis to calculate mutation age. RESULTS: A total of 22 patients with sclerocornea, aphakia, and microphthalmia were identified in the village, rendering a disease prevalence of 2.52 cases per 1,000 habitants (1 in 397). The FOXE3 homozygous mutation was identified in all 17 affected subjects who consented to molecular analysis. Haplotype analysis indicated that the mutation arose 5.0-6.5 generations ago (approximately 106-138 years). Among the 405 unaffected villagers who were genotyped, ten heterozygote carriers were identified, yielding a population carrier frequency of approximately 1 in 40 and a predicted incidence of affected of 1 in 6,400 based on random marriages between two carriers in the village. CONCLUSIONS: This study demonstrates that a cluster of patients with sclerocornea, aphakia, and microphthalmia in a small Mexican village is due to a FOXE3 p.Y98H founder mutation that arose in the village just over a century ago at a time when a population migrated from a nearby village because of land disputes. The actual disease incidence is higher than the calculated predicted value and suggests non-random marriages (i.e., consanguinity) within the population. We can now offer the community more informed genetic counseling based on an accurate genetic test, thus increasing the likelihood of a better outcome for the families.

Dopaminergic neurons modulate GABA neuron migration in the embryonic midbrain.

Neuronal migration, a key event during brain development, remains largely unexplored in the mesencephalon, where dopaminergic (DA) and GABA neurons constitute two major neuronal populations. Here we study the migrational trajectories of DA and GABA neurons and show that they occupy ventral mesencephalic territory in a temporally and spatially specific manner. Our results from the Pitx3-deficient aphakia mouse suggest that pre-existing DA neurons modulate GABA neuronal migration to their final destination, providing novel insights and fresh perspectives concerning neuronal migration and connectivity in the mesencephalon in normal as well as diseased brains.

Lens induction requires attenuation of ERK signaling by Nf1.

Aphakia (lack of lens) is a rare human congenital disorder with its genetic etiology largely unknown. Even in model organisms, very few mutations are known to result in such a drastic ocular defect. In this study, we have shown that homozygous deletion of Nf1, the Ras GTPase gene underlying human neurofibromatosis type 1 syndrome, causes lens dysgenesis in mouse. Although early lens specification proceeded normally in Nf1 mutants, lens induction was disrupted due to deficient cell proliferation. Further analysis showed that extracellular signal-regulated kinase (ERK) signaling was initially elevated in the invaginating lens placode, but by the lens vesicle stage, ERK phosphorylation was significantly reduced. Only after intraperitoneal treatment of U0126, an inhibitor of ERK phosphorylation, was lens development restored in Nf1 mutants. Hyperactive Ras-mitogen-activated protein kinase (MAPK) signaling is known to cause neuro-cardiofacial-cutaneous (NCFC) syndromes in humans. As a member of NCFC family genes, Nf1 represents the first example that attenuation of Ras-MAPK kinase signaling pathway is essential for normal lens development.

Homozygous FOXE3 mutations cause non-syndromic, bilateral, total sclerocornea, aphakia, microphthalmia and optic disc coloboma.

PURPOSE: To investigate the genetic basis of recessively-inherited congenital, non syndromic, bilateral, total sclerocornea in two consanguineous pedigrees, one from the Punjab province of Pakistan and the other from the Tlaxcala province of Mexico. METHODS: Ophthalmic examinations were conducted on each family member to confirm their diagnosis and magnetic resonance imaging (MRI) or ultrasonography of the eyes was performed on some family members. Genomic DNA was analyzed by homozygosity mapping using the Affymetrix 6.0 SNP array and linkage was confirmed with polymorphic microsatellite markers. Candidate genes were sequenced. RESULTS: A diagnosis of autosomal recessive sclerocornea was established for 7 members of the Pakistani and 8 members of the Mexican pedigrees. In the Pakistani family we established linkage to a region on chromosome 1p that contained Forkhead Box E3 (FOXE3), a strong candidate gene since FOXE3 mutations had previously been associated with various anterior segment abnormalities. Sequencing FOXE3 identified the previously reported nonsense mutation, c.720C>A, p.C240X, in the Pakistani pedigree and a novel missense mutation which disrupts an evolutionarily conserved residue in the forkhead domain, c.292T>C, p.Y98H, in the Mexican pedigree. Individuals with heterozygous mutations had no ocular abnormalities. MRI or ultrasonography confirmed that the patients with sclerocornea were also aphakic, had microphthalmia and some had optic disc coloboma. CONCLUSIONS: This is the fourth report detailing homozygous FOXE3 mutations causing anterior segment abnormalities in human patients. Previous papers have emphasized aphakia and microphthalmia as the primary phenotype, but we find that the initial diagnosis - and perhaps the only one possible in a rural setting - is one of non-syndromic, bilateral, total sclerocornea. Dominantly inherited anterior segment defects have also been noted in association with heterozygous FOXE3 mutations. However the absence of any abnormalities in the FOXE3 heterozygotes described suggests that genetic background and environmental factors plays a role in the penetrance of the mutant allele.

A mutation in the FOXE3 gene causes congenital primary aphakia in an autosomal recessive consanguineous Pakistani family.

PURPOSE: Aphakia is the complete absence of any lens in the eye, either due to surgical removal of the lens as a result of a perforating wound or ulcer, or due to a congenital anomaly. The purpose of this study was to elucidate the molecular genetics for a large consanguineous Pakistani family with a clear aphakia phenotype. METHODS: The initial homozygosity screening of the family was extended to all the known autosomal recessive cataract loci in order to exclude the possibility of surgical cataract removal leading to aphakia. The screening was performed using polymorphic nucleotide repeat markers, followed by DNA sequencing of a possible candidate gene, the forkhead box protein E3 gene (FOXE3). The identified mutation was counter-checked by a diagnostic restriction enzyme digest of all the family members, and an analysis of the normal population. RESULTS: The initial homozygosity screening of 13 known autosomal recessive loci resulted in negative LOD (logarithm of odds) scores. The aphakia phenotype suggested a mutation in FOXE3 close to the AR-locus 1p34.3-p32.2, and sequence analyses revealed the nonsense mutation c.720C>A, changing cysteine 240 to a stop codon. Segregation in the family was shown by diagnostic restriction enzyme digest, and marker analysis of another aphakia family from Madagascar carrying the same mutation excluded the presence of a founder mutation. Clinical re-examination of the family was not possible due to the escalating security concerns and internal displacement of the population in this region of Pakistan which has prevailed for many months. CONCLUSIONS: FOXE3 is responsible for the early developmental arrest of the lens placode, and the complete loss of a functional FOXE3 protein results in primary aphakia. It can also be deduced that this mutation is quite primitive in origin since the same mutation is responsible for the same phenotypic outcome in two families of geographically different descent.

FOXE3 plays a significant role in autosomal recessive microphthalmia.

FOXE3 forkhead transcription factor is essential to lens development in vertebrates. The eyes of Foxe3/foxe3-deficient mice and zebrafish fail to develop normally. In humans, autosomal dominant and recessive mutations in FOXE3 have been associated with variable phenotypes including anterior segment anomalies, cataract, and microphthalmia. We undertook sequencing of FOXE3 in 116 probands with a spectrum of ocular defects ranging from anterior segment dysgenesis and cataract to anophthalmia/microphthalmia. Recessive mutations in FOXE3 were found in four of 26 probands affected with bilateral microphthalmia (15% of all bilateral microphthalmia and 100% of consanguineous families with this phenotype). FOXE3-positive microphthalmia was accompanied by aphakia and/or corneal defects; no other associated systemic anomalies were observed in FOXE3-positive families. The previously reported c.720C > A (p.C240X) nonsense mutation was identified in two additional families in our sample and therefore appears to be recurrent, now reported in three independent microphthalmia families of varied ethnic backgrounds. Several missense variants were identified at varying frequencies in patient and control groups with some apparently being race-specific, which underscores the importance of utilizing race/ethnicity-matched control populations in evaluating the relevance of genetic screening results. In conclusion, FOXE3 mutations represent an important cause of nonsyndromic autosomal recessive bilateral microphthalmia.

Pitx3-deficient aphakia mice display unique behavioral responses to psychostimulant and antipsychotic drugs.

The dorsal (A9) and ventral striatum (A10) of the midbrain mediate many of the effects of psychoactive drugs that alter emotion, cognition, and motor activity within the contexts of therapy or abuse. Although transgenic and knockout technologies have enabled development of genetic models to dissect contributions of specific dopamine (DA) receptor subtypes to psychoactive drug effects, few models exist that can distinguish contributions of A9 versus A10 circuits. Pitx3 is a transcription factor enriched in DA neurons. Aphakia (ak) mice deficient in Pitx3 show selective loss of nigrostriatal DA, while other DA pathways are relatively spared, and therefore could be a useful tool for investigating the role of this subclass of DA projections. We investigated the effects of stimulants amphetamine, apomorphine, and MK-801 and the antipsychotic drug haloperidol on behavior in ak mice. Whereas wild-type mice showed the characteristic locomotor hyperactivity in response to amphetamine (5 mg/kg) and apomorphine (4 mg/kg), these drugs caused a paradoxical suppression of locomotor hyperactivity in ak mice. MK-801 (0.2 mg/kg) induced hyperactivity was maintained in both wt and ak mice. Additionally, mutant but not wild-type mice were insensitive to the cataleptic effects of haloperidol (1 mg/kg). These studies indicate that the nigrostriatal DA circuit plays a critical role in maintaining normal responsiveness to psychotropic drugs that either stimulate or block DA neurotransmission. We propose that ak mice may represent a valuable genetic model not only to study Parkinson's disease, but also to dissect the pathophysiologic and pharmacotherapuetic mechanisms of other DA-mediated disorders such as attention-deficit hyperactivity disorder, drug abuse and schizophrenia.

Jagged 1 is necessary for normal mouse lens formation.

In mammals, two spatially and temporally distinct waves of fiber cell differentiation are crucial steps for normal lens development. In between these phases, an anterior growth zone forms in which progenitor cells migrate circumferentially, terminally exit the cell cycle and initiate differentiation at the lens equator. Much remains unknown about the molecular pathways orchestrating these processes. Previously, the Notch signal transduction pathway was shown to be critical for anterior lens progenitor cell growth and differentiation. However, the ligand or ligand(s) that direct these events are unknown. Using conditional gene targeting, we show that Jagged1 is required for lens fiber cell genesis, particularly that of secondary fiber cells. In the absence of Jagged1, the anterior growth and equatorial transition zones fail to develop fully, with only a handful of differentiated fiber cells present at birth. Adult Jagged1 conditional mutants completely lack lenses, along with severe anterior chamber deformities. Our data support the hypothesis that Jagged1-Notch signaling conveys a lateral inductive signal, which is indispensable for lens progenitor cell proliferation and differentiation.