PAX6 Mutations Research Articles

Mutational and Clinical Spectrum of the PAX6 Gene in Bulgarian Patients with Aniridia

The PAX6 gene has highly conservative structure and developmentally essential function and is expressed in structurally different organs and systems. Haploinsufficiency of the PAX6 gene product leads to aniridia and aniridia-like phenotypes. A total of 9 patients and 115 controls were examined with the use of a variety of molecular-genetics methods (SNP array, Sanger sequencing, NGS, WES) and in collaboration with different clinicians. Two pathogenic CNVs, three potentially pathogenic variants and two nonsynonymous SNVs in the PAX6 gene were identified: two out of the three potentially pathogenic variants have not been previously reported. The heterogeneous nature of aniridia and the variable spectrum of the PAX6 mutations were confirmed by our study. Approximately 75% of the registered cases in the Bulgarian population were studied and five disease-related variants were discovered. The small number of polymorphic variants in the controls supports the highly conserved role and nature of the PAX6 and its product.

Genetic analysis using next-generation sequencing and multiplex ligation probe amplification in Chinese aniridia patients

BackgroundCongenital aniridia is a rare pan-ocular disease characterized by complete irideremia, partial iridocoloboma. The progressive nature of aniridia is frequently accompanied by secondary ocular complications such as glaucoma and aniridia-associated keratopathy, which can lead to severely impaired vision or blindness. The genetic basis of aniridia has been the subject of numerous studies, leading to the development of innovative therapeutic options based on PAX6 nonsense mutations. Specific knowledge of the genetics of aniridia has become increasingly important. To report the clinical features, elucidate the genetic etiology, and reveal the mutational spectrum of congenital aniridia in the Chinese population, sixty patients with congenital aniridia from 51 families were recruited. Candidate genes associated with developmental eye diseases were identified and analyzed using panel-based next-generation sequencing (NGS), and mutations were confirmed through polymerase chain reaction and Sanger sequencing. Multiplex ligation probe amplification (MLPA) of PAX6 and FOXC1 was performed to detect copy number variations in the patients without intragenic mutations.ResultsClinical examination revealed complete iris hypoplasia in 58 patients and partial iris hypoplasia in two patients. Additionally, two patients were diagnosed with Wilms’ tumor-aniridia-genital anomalies-retardation syndrome and nephroblastoma. By combining panel-based NGS and MLPA, 43 intragenic mutations or deletions of PAX6, FOXC1, and BCOR were identified in 59 patients, including 33 point mutations (76.7%) in 43 patients and 10 deletions (23.3%) in 16 patients. The total detection rate was 98.3%. Phenotypic variation was observed between and within families.ConclusionsVariations in PAX6 and its adjacent regions were the predominant causes of aniridia in China. In addition to intragenic point mutations in PAX6, deletion of PAX6 or its adjacent genes is a common cause of congenital aniridia. Furthermore, FOXC1 is an important gene associated with congenital aniridia. The combination of panel-based NGS and MLPA significantly enhanced the detection rate of gene mutations in patients with congenital aniridia.

Pax2 Mutant Mice Have Dysregulated Nuclear Maintenance, Cell Proliferation, and Motility Associated with Abnormal Glomerular Repair

Pax2 Mutant Mice Have Dysregulated Nuclear Maintenance, Cell Proliferation, and Motility Associated with Abnormal Glomerular Repair

Analysis of Phenotypes Associated with Deficiency of PAX6 Haplotypes in Chinese Aniridia Families.

To examine the clinical phenotype and genetic deficiencies present in Chinese aniridia families with PAX6 haplotype deficiency. A comprehensive questionnaire and ophthalmological assessments were administered to both affected patients and unaffected relatives. The clinical feature analysis included the evaluation of visual acuity, intraocular pressure, slit-lamp anterior segment examination, fundus photography, and spectral domain optical coherence tomography. To identify the mutation responsible for aniridia, targeted next-generation sequencing was used as a beneficial technique. A total of 4 mutations were identified, consisting of two novel frameshift mutations (c.314delA, p.K105Sfs*33 and c.838_845dup AACACACC, p.S283Tfs*85), along with two recurring nonsense mutations (c.307C>T, p.R103X and c.619A>T, p.K207*). Complete iris absence, macular foveal hypoplasia, and nystagmus were consistent in these PAX6 haplotype-deficient Chinese aniridia families, while corneal lesions, cataracts, and glaucoma exhibited heterogeneity both among the families and within the same family. In our study, two novel PAX6 mutations associated with aniridia were identified in Chinese families, which expanded the phenotypic and genotypic spectrum of PAX6 mutations. We also analyzed the clinical characteristics of PAX6 haplotype deficiency in Chinese aniridia families.

Clinical Results of Prosthetic Eye Wear in Patients with Congenital Microphthalmos

Purpose: To report the long-term clinical outcomes of non-surgical treatment involving prosthetic eye wear in patients diagnosed with congenital microphthalmos.Methods: A retrospective review of the medical records of 20 patients was conducted. In total, 21 eyes were diagnosed with congenital microphthalmos between May 2008 and December 2022 at Seoul St. Mary’s Hospital in Korea.Results: This study included 20 patients (12 males and 8 females) with an average age of 4 months at diagnosis. The observed ophthalmic anomalies included two cases of congenital cataract, one of posterior embryotoxon, one of corneo-iris strand, four of iris coloboma, five of central corneal opacity, one of Peter's anomaly, and one of retrobulbar cyst. Accompanying systemic abnormalities were noted, such as lateral ventricle atrophy, corpus callosum atrophy, patent ductus arteriosus, atrial septal defect, and developmental language disorder. Genetic anomalies included anti SS-A/Ro antibody positivity, a 1:100 titer of anti-nuclear antibody, and a PAX6 mutation identified through next-generation sequencing. No specific family histories or pregnancy-related factors were noted. The average follow-up duration was 5.94 years (range: 1 month to 18 years), the average corneal diameter was 4.6 mm, the average axial length was 17.44 mm, the average age for first artificial eye trial was 5.96 years (range: 7 months to 19 years), and the average interval for artificial eye replacement was 22 months (range: 4 months to 5 years and 8 months).Conclusions: Twenty patients with congenital microphthalmos underwent gradual expansion of their prosthetic eyes by regular replacement and size increase without severe complications. This approach led to aesthetically and emotionally positive outcomes for the patients.

Deep mutational scanning quantifies DNA binding and predicts clinical outcomes of PAX6 variants.

Nonsense and missense mutations in the transcription factor PAX6 cause a wide range of eye development defects, including aniridia, microphthalmia and coloboma. To understand how changes of PAX6:DNA binding cause these phenotypes, we combined saturation mutagenesis of the paired domain of PAX6 with a yeast one-hybrid (Y1H) assay in which expression of a PAX6-GAL4 fusion gene drives antibiotic resistance. We quantified binding of more than 2700 single amino-acid variants to two DNA sequence elements. Mutations in DNA-facing residues of the N-terminal subdomain and linker region were most detrimental, as were mutations to prolines and to negatively charged residues. Many variants caused sequence-specific molecular gain-of-function effects, including variants in position 71 that increased binding to the LE9 enhancer but decreased binding to a SELEX-derived binding site. In the absence of antibiotic selection, variants that retained DNA binding slowed yeast growth, likely because such variants perturbed the yeast transcriptome. Benchmarking against known patient variants and applying ACMG/AMP guidelines to variant classification, we obtained supporting-to-moderate evidence that 977 variants are likely pathogenic and 1306 are likely benign. Our analysis shows that most pathogenic mutations in the paired domain of PAX6 can be explained simply by the effects of these mutations on PAX6:DNA association, and establishes Y1H as a generalisable assay for the interpretation of variant effects in transcription factors.

#1792 Phenotypic variability in PAX2-related nephropathies: a monocentric study

Abstract Background and Aims Pax2 mutations are known to cause kidney disease; both syndromic conditions, as kidney coloboma syndrome, and kidney specific disorders, as FSGS, have been described. Due to the rarity of Pax2-related nephropathies, data on genotype-phenotype correlation are limited. Method This observational and mono-centric study describes three families (A, G, P) referring to our Nephrology center, carrying Pax2 mutations. A total of 12 subjects were investigated: 2 individuals in family A, 4 in family G and 6 in the family P. Genetic analysis was carried out by NGS; detected mutations were confirmed by Sanger sequencing. Results Family A It includes 2 affected subjects, a 40 year-old woman and her mother (Fig. 1A). The mother had chorioretinic coloboma and was under hemodialytic therapy since the age of 50. The daughter had chorioretinic coloboma and bilateral renal hypodysplasia, proteinuria and a progressive decline of the eGFR since 34 years; renal biopsy excluded the presence of GN (Table 1). Both have the heterozygote c.890delC variant (p.Thr297fs) in Pax2. Family G It includes 4 affected individuals belonging to 3 different generations (Fig. 1B). The disorder was discovered after the evidence of advanced renal failure in a pregnant 27 y-old lady. The study of her family revealed the presence of kidney disease in her sister (transplanted on young age) and her father; one of her children has the mutation (Table 1). The PAX2 c.194T>C(p.Val65Ala HET) mutation segregates with the phenotype in the family. Family P It includes 6 affected individuals of 3 different generations (Fig. 1C); the index-case presented with heavy proteinuria: kidney biopsy revealed a C3 nephropathy. His son was transplanted when 18 years old for bilateral renal hypoplasia. His mother died after some years of dialysis (Table 1). PAX2 mutation on exon3: c.361G>A(p.Glu121Lys HET). Conclusion This case series demonstrates the phenotypic variability of patients with Pax2 mutations and suggests the utility of new generation genetics (NGS) to get the diagnosis in atypical conditions. The implementation of international registers and basic studies will be indispensable to define the mechanisms involved in the development of the disease and to address the reasons of clinical variability.

Pax6 isoforms shape eye development: Insights from developmental stages and organoid models

Pax6 is a critical transcription factor involved in the development of the central nervous system. However, in humans, mutations in Pax6 predominantly result in iris deficiency rather than neurological phenotypes. This may be attributed to the distinct functions of Pax6 isoforms, Pax6a and Pax6b. In this study, we investigated the spatial and temporal expression patterns of Pax6 isoforms during different stages of mouse eye development. We observed a strong correlation between Pax6a expression and the neuroretina gene Sox2, while Pax6b showed a high correlation with iris-component genes, including the mesenchymal gene Foxc1. During early patterning from E10.5, Pax6b was expressed in the hinge of the optic cup and neighboring mesenchymal cells, whereas Pax6a was absent in these regions. At E14.5, both Pax6a and Pax6b were expressed in the future iris and ciliary body, coinciding with the integration of mesenchymal cells and Mitf-positive cells in the outer region. From E18.5, Pax6 isoforms exhibited distinct expression patterns as lineage genes became more restricted. To further validate these findings, we utilized ESC-derived eye organoids, which recapitulated the temporal and spatial expression patterns of lineage genes and Pax6 isoforms. Additionally, we found that the spatial expression patterns of Foxc1 and Mitf were impaired in Pax6b-mutant ESC-derived eye organoids. This in vitro eye organoids model suggested the involvement of Pax6b-positive local mesodermal cells in iris development. These results provide valuable insights into the regulatory roles of Pax6 isoforms during iris and neuroretina development and highlight the potential of ESC-derived eye organoids as a tool for studying normal and pathological eye development.

Conventional and molecular cytogenetic characterization of a Moroccan patient with WAGR syndrome

BackgroundWAGR syndrome is a rare genetic disorder characterized by a de novo deletion of 11p13 and is usually clinically associated with Wilms’ tumor, aniridia, genitourinary anomalies, and mental retardation (W-A-G-R). Although the genotypic defects in WAGR syndrome have been well established. The congenital aniridia is caused, in nearly 90% of cases by mutations in the gene PAX6. In the face of congenital aniridia, it is imperative to specify whether it falls within the scope of a WAGR syndrome or if it is an isolated congenital aniridia or inherited by performing karyotype, FISH (Fluorescence In Situ Hybridization) or a CGH array for genetic counseling.Case presentationWe report here a case of genetic testing for newborn with aniridia, to detect 11p13 rearrangements, using karyotyping and CGH array to complete picture of the chromosomal deletions and breakpoints in aniridia. Results show either a loss of 3811.196 kb on chromosome 11 delimited by the bands p14.1 and p13 with formula or a loss of a 1867.287 kb on chromosome 18 fragment delimited by q21.33 and q22.1 bands, that has not been detected by karyotype analysis.ConclusionsCytogenetics screening is a good strategy for the genetic diagnosis of aniridia and associated syndromes, allowing for a better identification of breakpoints. Our results underline the clinical importance of performing exhaustive and accurate analysis of chromosomal rearrangements for patients with aniridia, especially newborns to improve survival and quality of life for affected individuals.

A rare missense PAX6 mutation causes atypical aniridia in a three-generation Chinese family.

To investigate the molecular diagnosis of a three-generation Chinese family affected with aniridia, and further to identify clinically a PAX6 missense mutation in members with atypical aniridia. Eleven family members with and without atypical aniridia were recruited. All family members underwent comprehensive ophthalmic examinations. A combination of whole exome sequencing (WES) and direct Sanger sequencing were performed to uncover the causative mutation. Among the 11 family members, 8 were clinically diagnosed with congenital aniridia (atypical aniridia phenotype). A rare heterozygous mutation c.622C>T (p.Arg208Trp) in exon 8 of PAX6 was identified in all affected family members but not in the unaffected members or in healthy control subjects. A rare missense mutation in the PAX6 gene is found in members of a three-generation Chinese family with congenital atypical aniridia. This result contributes to an increase in the phenotypic spectrum caused by PAX6 missense heterozygous variants and provides useful information for the clinical diagnosis of atypical aniridia, which may also contribute to genetic counselling and family planning.

Novel and recurrent variants in PAX6 in four patients with ocular phenotypes from Southeast Asia.

Aniridia is an autosomal dominant condition characterized by the complete or partial absence of the iris, often with additional presentations such as foveal hypoplasia, nystagmus, cataract, glaucoma and other ocular abnormalities. Most cases are caused by heterozygous mutations in the paired box 6 gene (PAX6), which codes for a transcription factor that regulates eye development. Four patients from our hospital who presented with ocular phenotypes were recruited for research sequencing with informed consent. Sanger sequencing of PAX6 coding exons or exome sequencing was performed on genomic DNA from venous blood samples. Variants in PAX6 were identified in the four patients. Two variants are recurrent single-nucleotide substitutions - one is a substitution found in a patient with bilateral aniridia, whereas the other is a splice variant in a patient with nystagmus and neuroblastoma. The other two variants are novel and found in two patients with isolated aniridia. Both are small duplications that are predicted to lead to premature termination. For the recurrent variants, the comparison of phenotypes for patients with identical variants would shed light on the mechanisms of pathogenesis, and the discovery of two novel variants expands the spectrum of PAX6 mutations.

Novel PAX9 Mutations Causing Isolated Oligodontia.

Hypodontia, i.e., missing one or more teeth, is a relatively common human disease; however, oligodontia, i.e., missing six or more teeth, excluding the third molars, is a rare congenital disorder. Many genes have been shown to cause oligodontia in non-syndromic or syndromic conditions. In this study, we identified two novel PAX9 mutations in two non-syndromic oligodontia families. A mutational analysis identified a silent mutation (NM_006194.4: c.771G>A, p.(Gln257=)) in family 1 and a frameshift mutation caused by a single nucleotide duplication (c.637dup, p.(Asp213Glyfs*104)) in family 2. A minigene splicing assay revealed that the silent mutation resulted in aberrant pre-mRNA splicing instead of normal splicing. The altered splicing products are ones with an exon 4 deletion or using a cryptic 5' splicing site in exon 4. Mutational effects were further investigated using protein expression, luciferase activity assay and immunolocalization. We believe this study will not only expand the mutational spectrum of PAX9 mutations in oligodontia but also strengthen the diagnostic power related to the identified silent mutation.

Loss of Pax3 causes reduction of melanocytes in the developing mouse cochlea

Cochlear melanocytes are intermediate cells in the stria vascularis that generate endocochlear potentials required for auditory function. Human PAX3 mutations cause Waardenburg syndrome and abnormalities of skin and retinal melanocytes, manifested as congenital hearing loss (~ 70%) and hypopigmentation of skin, hair and eyes. However, the underlying mechanism of hearing loss remains unclear. Cochlear melanocytes in the stria vascularis originated from Pax3-traced melanoblasts and Plp1-traced Schwann cell precursors, both of which derive from neural crest cells. Here, using a Pax3-Cre knock-in mouse that allows lineage tracing of Pax3-expressing cells and disruption of Pax3, we found that Pax3 deficiency causes foreshortened cochlea, malformed vestibular apparatus, and neural tube defects. Lineage tracing and in situ hybridization show that Pax3+ derivatives contribute to S100+, Kir4.1+ and Dct+ melanocytes (intermediate cells) in the developing stria vascularis, all of which are significantly diminished in Pax3 mutant animals. Taken together, these results suggest that Pax3 is required for the development of neural crest cell-derived cochlear melanocytes, whose absence may contribute to congenital hearing loss of Waardenburg syndrome in humans.

H3 Acetylation-Induced Basal Progenitor Generation and Neocortex Expansion Depends on the Transcription Factor Pax6.

Enrichment of basal progenitors (BPs) in the developing neocortex is a central driver of cortical enlargement. The transcription factor Pax6 is known as an essential regulator in generation of BPs. H3 lysine 9 acetylation (H3K9ac) has emerged as a crucial epigenetic mechanism that activates the gene expression program required for BP pool amplification. In this current work, we applied immunohistochemistry, RNA sequencing, chromatin immunoprecipitation and sequencing, and the yeast two-hybrid assay to reveal that the BP-genic effect of H3 acetylation is dependent on Pax6 functionality in the developing mouse cortex. In the presence of Pax6, increased H3 acetylation caused BP pool expansion, leading to enhanced neurogenesis, which evoked expansion and quasi-convolution of the mouse neocortex. Interestingly, H3 acetylation activation exacerbates the BP depletion and corticogenesis reduction effect of Pax6 ablation in cortex-specific Pax6 mutants. Furthermore, we found that H3K9 acetyltransferase KAT2A/GCN5 interacts with Pax6 and potentiates Pax6-dependent transcriptional activity. This explains a genome-wide lack of H3K9ac, especially in the promoter regions of BP-genic genes, in the Pax6 mutant cortex. Together, these findings reveal a mechanistic coupling of H3 acetylation and Pax6 in orchestrating BP production and cortical expansion through the promotion of a BP gene expression program during cortical development.

PAX3 mutation suppress otic progenitors proliferation and induce apoptosis by inhibiting WNT1/β-catenin signaling pathway in WS1 patient iPSC-derived inner ear organoids

Waardenburg syndrome type 1 (WS1) is a hereditary disease mainly characterized by sensorineural hearing loss, dystopia canthorum, and pigmentary defects. To elucidate molecular mechanisms underlying PAX3-associated hearing loss, we developed inner ear organoids model using induced pluripotent stem cells (iPSCs) derived from WS1 patient and healthy individual. Our results revealed a significant reduction in the size of inner ear organoids, accompanied by an increased level of apoptosis in organoids derived from WS1 patient-iPSCs carrying PAX3 c.214A > G. Transcriptome profiling analysis by RNA-seq indicated that inner ear organoids from WS1 patients were associated with suppression of inner ear development and WNT signaling pathway. Furthermore, the upregulation of the WNT1/β-catenin pathway which was achieved through the correction of PAX3 isogenic mutant iPSCs using CRISPR/Cas9, contributed to an increased size of inner ear organoids and a reduction in apoptosis. Together, our results provide insight into the underlying mechanisms of hearing loss in WS.

Genetic analysis of medaka fish illuminates conserved and divergent roles of Pax6 in vertebrate eye development.

Landmark discovery of eye defects caused by Pax6 gene mutations in humans, rodents, and even fruit flies combined with Pax6 gene expression studies in various phyla, led to the master control gene hypothesis postulating that the gene is required almost universally for animal visual system development. However, this assumption has not been broadly tested in genetically trackable organisms such as vertebrates. Here, to determine the functional role of the fish orthologue of mammalian Pax6 in eye development we analyzed mutants in medaka Pax6.1 gene generated by genome editing. We found that transcription factors implicated in vertebrate lens development (Prox1a, MafB, c-Maf, FoxE3) failed to initiate expression in the presumptive lens tissue of Pax6.1 mutant fish resulting in aphakia, a phenotype observed previously in Pax6 mutant mice. Surprisingly, the overall differentiation potential of Pax6.1-deficient retinal progenitor cells (RPCs) is not severely compromised, and the only cell types affected by the absence of Pax6.1 transcription factor are retinal ganglion cells. This is in stark contrast to the situation in mice where the Pax6 gene is required cell-autonomously for the expansion of RPCs, and the differentiation of all retina cell types. Our results provide novel insight into the conserved and divergent roles of Pax6 gene orthologues in vertebrate eye development indicating that the lens-specific role is more evolutionarily conserved than the role in retina differentiation.

Ancestral role of Pax6 in chordate brain regionalization.

The Pax6 gene is essential for eye and brain development across various animal species. Here, we investigate the function of Pax6 in the development of the anterior central nervous system (CNS) of the invertebrate chordate amphioxus using CRISPR/Cas9-induced genome editing. Specifically, we examined Pax6 mutants featuring a 6bp deletion encompassing two invariant amino acids in the conserved paired domain, hypothesized to impair Pax6 DNA-binding capacity and gene regulatory functions. Although this mutation did not result in gross morphological changes in amphioxus larvae, it demonstrated a reduced ability to activate Pax6-responsive reporter gene, suggesting a hypomorphic effect. Expression analysis in mutant larvae revealed changes in gene expression within the anterior CNS, supporting the conserved role of Pax6 gene in brain regionalization across chordates. Additionally, our findings lend support to the hypothesis of a zona limitans intrathalamica (ZLI)-like region in amphioxus, suggesting evolutionary continuity in brain patterning mechanisms. ZLI region, found in both hemichordates and vertebrates, functions as a key signaling center and serves as a restrictive boundary between major thalamic regions.

Phenotype-Genotype Correlations in Three Different Cases of Adult-Onset Genetic Focal Segmental Glomerulosclerosis.

This study highlights the importance of a combined diagnostic approach in the diagnosis of rare diseases, such as adult-onset genetic FSGS. We present three adult patient cases evaluated with kidney biopsy for proteinuria, chronic kidney disease, and hypertension, which were suggestive of adult-onset genetic FSGS. Renal biopsy samples and formalin-fixed, paraffin-embedded fetal kidneys were evaluated using standard light microscopical stainings, direct immunofluorescence on cryostat sections, and electron microscopy. Clinical exome sequencing was performed for each case, and 45 FSGS-related genes were analyzed. Identifying mutations in the PAX2, ACTN4, and COL4A5 genes have prompted a re-evaluation of the previous histopathological examinations. The PAX2 mutation led to a thinner nephrogenic zone and decreased number of glomeruli, resulting in oligohydramnios during fetal development and oligomeganephronia and adaptive focal-segmental glomerulosclerosis in adulthood. The ACTN4 mutation caused distinct electron-dense aggregates in podocyte cell bodies, while the COL4A5 mutation led to segmental sclerosis of glomeruli with marked interstitial fibrosis and tubular atrophy. The identification of specific mutations and their histopathological consequences can lead to a better understanding of the disease and its progression, as well as potential treatment options.

SMARCB1-deficient sinonasal adenocarcinoma: a rare variant of SWI/SNF-deficient malignancy often misclassified as high-grade non-intestinal-type sinonasal adenocarcinoma or myoepithelial carcinoma

SMARCB1-deficient sinonasal adenocarcinoma is a rare variant of SWI/SNF-deficient malignancies with SMARCB1 loss and adenocarcinoma features. More than 200 high-grade epithelial sinonasal malignancies were retrieved. A total of 14 cases exhibited complete SMARCB1 (INI1) loss and glandular differentiation. SMARCA2 and SMARCA4 were normal, except for one case with a loss of SMARCA2. Next-generation sequencing (NGS) and/or fluorescence in situ hybridization (FISH) revealed an alteration in the SMARCB1 gene in 9/13 cases, while 2/13 were negative. Two tumors harbored SMARCB1 mutations in c.157C > T p.(Arg53Ter) and c.842G > A p.(Trp281Ter). One harbored ARID1B mutations in c.1469G > A p.(Trp490Ter) and MGA c.3724C > T p.(Arg1242Ter). Seven tumors had a SMARCB1 deletion. One carried an ESR1 mutation in c.644-2A > T, and another carried a POLE mutation in c.352_374del p.(Ser118GlyfsTer78). One case had a PAX3 mutation in c.44del p.(Gly15AlafsTer95). Histomorphology of SMARCB1-deficient adenocarcinoma was oncocytoid/rhabdoid and glandular, solid, or trabecular in 9/14 cases. Two had basaloid/blue cytoplasm and one showed focal signet ring cells. Yolk sac tumor-like differentiation with Schiller-Duval-like bodies was seen in 6/14 cases, with 2 cases showing exclusively reticular-microcystic yolk sac pattern. Follow-up of a maximum of 26 months (median 10 months) was available for 8/14 patients. Distant metastasis to the lung, liver, mediastinum, bone, and/or retroperitoneum was seen in 4/8 cases. Locoregional failure was seen in 75% of patients, with 6/8 local recurrences and 3 cervical lymph node metastases. At the last follow-up, 5 of 8 (62%) patients had died of their disease 2 to 20 months after diagnosis (median 8.2 months), and 3 were alive with the disease. The original diagnosis was usually high-grade non-intestinal-type adenocarcinoma or high-grade myoepithelial carcinoma. A correct diagnosis of these aggressive tumors could lead to improved targeted therapies with potentially better overall disease-specific survival.

Reduction of lens size in PAX6-related aniridia

Heterozygous mutation of PAX6 in humans leads to congenital aniridia (OMIM 106210) which is typified by congenital iris and foveal defects, and later onset glaucoma, aniridic keratopathy, and cataract. Mice heterozygous for Pax6 mutations phenocopy many aspects of aniridia including the iris defects, keratopathy and cataract, although Pax6 mutant mice have small lenses, a phenotype which is not typically reported in human aniridia, perhaps due to difficulties in measuring lens diameter during typical ophthalmic examinations as the lens periphery is shielded by the iris. In order to overcome this, records of patients diagnosed with congenital aniridia between April 2015 and May 2021 at the Necker-Enfants Malades Hospital, and genetically confirmed with a disease-causing PAX6 variant, were retrospectively reviewed for those with normal axial length whose iris defects allowed visualization of the lens margins and corneal diameter to allow calculation of a lens/corneal diameter ratio. This value was compared with values obtained from a cohort of patients with Sjödell grade IV oculocutaneous albinism type 1 (OCA1; OMIM 203100) which allowed visualization of the lens periphery via iris transillumination. This analysis revealed that patients with congenital aniridia had a significantly lower lens/corneal ratio when compared to those with albinism, suggesting that humans haploinsufficient for PAX6, like mice, rats, frogs, and zebrafish, exhibit reductions in lens size.