Itpr1 regulates the formation of anterior eye segment tissues derived from neural crest cells.

Mutations in ITPR1 cause ataxia and aniridia in individuals with Gillespie syndrome (GLSP). However, the pathogenic mechanisms underlying aniridia remain unclear. We identified a de novo GLSP mutation hotspot in the 3'-region of ITPR1 in five individuals with GLSP. Furthermore, RNA-sequencing and immunoblotting revealed an eye-specific transcript of Itpr1, encoding a 218amino acid isoform. This isoform is localized not only in the endoplasmic reticulum, but also in the nuclear and cytoplasmic membranes. Ocular-specific transcription was repressed by SOX9 and induced by MAF in the anterior eye segment (AES) tissues. Mice lacking seven base pairs of the last Itpr1 exon exhibited ataxia and aniridia, in which the iris lymphatic vessels, sphincter and dilator muscles, corneal endothelium and stroma were disrupted, but the neural crest cells persisted after completion of AES formation. Our analyses revealed that the 218-amino acid isoform regulated the directionality of actin fibers and the intensity of focal adhesion. The isoform might control the nuclear entry of transcriptional regulators, such as YAP. It is also possible that ITPR1 regulates both AES differentiation and muscle contraction in the iris.

Autologous serum eyedrops in the treatment of aniridic keratopathy.

OBJECTIVE: To study the effect of autologous serum eyedrop application in aniridic keratopathy. DESIGN: Prospective, consecutive, comparative, interventional case series. PARTICIPANTS: Twenty-six eyes from 13 patients (7 males and 6 females) with aniridic keratopathy treated with autologous serum eyedrops. METHODS: All patients underwent a complete ophthalmic examination. The ocular surface examinations included corneal impression cytologic analysis and tear film evaluation. The eyes were divided into 4 groups according to the Mackman classification. Ocular surface photography was used to evaluate the corneal surface and tear film before treatment and every 2 or 3 days until serum drops were stopped. Tear films were evaluated by tear film break-up time (BUT) (normal, 10 seconds or more), Schirmer's test with anesthesia (normal, 10 mm/5 minutes or more), tear meniscus level (normal, 0.5 mm or more), and rose bengal and fluorescein staining pattern of the cornea. Impression cytologic analysis was carried out both before starting the serum eyedrops treatment and a few days after its finalization. MAIN OUTCOMES MEASURES: Tear film production and stability, corneal epithelialization, and corneal epithelium squamous metaplasia. RESULTS: There were no local side effects from autologous serum treatment. Clinical manifestations and slit-lamp findings were in relation to the severity of keratopathy. All patients showed a subjective improvement of keratopathy symptoms after the autologous serum applications. The corneal epithelialization, corneal epithelial cell squamous metaplasia, and tear stability improved significantly with the treatment, but visual acuity, regression of vascular pannus, and subepithelial scarring showed only slight improvement with treatment. CONCLUSIONS: Autologous serum eyedrops improved the aniridic keratopathy in all patients, particularly in patients with light or moderate severity. In these patients, use of autologous serum eyedrops was superior to conventional therapy with substitute tears for improving the ocular surface and subjective comfort.

PAX6 mutation as a genetic factor common to aniridia and glucose intolerance.

A paired homeodomain transcription factor, PAX6, is a well-known regulator of eye development, and its heterozygous mutations in humans cause congenital eye anomalies such as aniridia. Because it was recently shown that PAX6 also plays an indispensable role in islet cell development, a PAX6 gene mutation in humans may lead to a defect of the endocrine pancreas. Whereas heterozygous mutations in islet-cell transcription factors such as IPF1/IDX-1/STF-1/PDX-1 and NEUROD1/BETA2 serve as a genetic cause of diabetes or glucose intolerance, we investigated the possibility of PAX6 gene mutations being a genetic factor common to aniridia and diabetes. In five aniridia and one Peters' anomaly patients, all of the coding exons and their flanking exon-intron junctions of the PAX6 gene were surveyed for mutations. The results of direct DNA sequencing revealed three different mutations in four aniridia patients: one previously reported type of mutation and two unreported types. In agreement with polypeptide truncation and a lack of the carboxyl-terminal transactivation domain in all of the mutated PAX6 proteins, no transcriptional activity was found in the reporter gene analyses. Oral glucose tolerance tests revealed that all of the patients with a PAX6 gene mutation had glucose intolerance characterized by impaired insulin secretion. Although we did not detect a mutation within the characterized portion of the PAX6 gene in one of the five aniridia patients, diabetes was cosegregated with aniridia in her family, and a single nucleotide polymorphism in intron 9 of the PAX6 gene was correlated with the disorders, suggesting that a mutation, possibly located in an uncharacterized portion of the PAX6 gene, can explain both diabetes and aniridia in this family. In contrast, the patient with Peters' anomaly, for which a PAX6 gene mutation is a relatively rare cause, showed normal glucose tolerance (NGT) and did not show a Pax6 gene mutation. Taken together, our present observations suggest that heterozygous mutations in the PAX6 gene can induce eye anomaly and glucose intolerance in individuals harboring these mutations.