Variable Anterior Segment Dysgenesis and Cardiac Anomalies Caused by a Novel Truncating Variant of FOXC1.

Anterior segment dysgenesis (ASD) encompasses a wide spectrum of developmental abnormalities of the anterior ocular segment, including congenital cataract, iris hypoplasia, aniridia, iridocorneal synechiae, as well as Peters, Axenfeld, and Rieger anomalies. Here, we report a large five-generation Caucasian family exhibiting atypical syndromic ASD segregating with a novel truncating variant of FOXC1. The family history is consistent with highly variable autosomal dominant symptoms including isolated glaucoma, iris hypoplasia, aniridia, cataract, hypothyroidism, and congenital heart anomalies. Whole-exome sequencing revealed a novel variant [c.313_314insA; p.(Tyr105*)] in FOXC1 that disrupts the α-helical region of the DNA-binding forkhead box domain. In vitro studies using a heterologous cell system revealed aberrant cytoplasmic localization of FOXC1 harboring the Tyr105* variant, likely precluding downstream transcription function. Meta-analysis of the literature highlighted the intrafamilial variability related to FOXC1 truncating alleles. This study highlights the clinical variability in ASD and signifies the importance of combining both clinical and molecular analysis approaches to establish a complete diagnosis.

Mutations in FYCO1 identified in families with congenital cataracts.

Purpose: This study was designed to identify the pathogenic variants in three consanguineous families with congenital cataracts segregating as a recessive trait. Methods: Consanguineous families with multiple individuals manifesting congenital cataracts were ascertained. All participating members underwent an ophthalmic examination. A small aliquot of the blood sample was collected from all participating individuals, and genomic DNAs were extracted. Homozygosity-based linkage analysis was performed using short tandem repeat (STR) markers. The haplotypes were constructed with alleles of the STR markers, and the two-point logarithm of odds (LOD) scores were calculated. The candidate gene was sequenced bidirectionally to identify the disease-causing mutations. Results: Linkage analysis localized the disease interval to chromosome 3p in three families. Subsequently, bidirectional Sanger sequencing identified two novel mutations-a single base deletion resulting in a frameshift (c.3196delC; p.His1066IlefsTer10) mutation and a single base substitution resulting in a nonsense (c.4270C>T; p.Arg1424Ter) mutation-and a known missense (c.4127T>C, p.Leu1376Pro) mutation in FYCO1. All three mutations showed complete segregation with the disease phenotype and were absent in 96 ethnically matched control individuals. Conclusions: We report two novel mutations and a previously reported mutation in FYCO1 in three large consanguineous families. Taken together, mutations in FYCO1 contribute nearly 15% to the total genetic load of autosomal recessive congenital cataracts in this cohort.

Generation and Proteome Profiling of PBMC-Originated, iPSC-Derived Corneal Endothelial Cells.

Purpose: Corneal endothelial cells (CECs) are critical in maintaining clarity of the cornea. This study was initiated to develop peripheral blood mononuclear cell (PBMC)-originated, induced pluripotent stem cell (iPSC)-derived CECs. Methods: We isolated PBMCs and programmed the mononuclear cells to generate iPSCs, which were differentiated to CECs through the neural crest cells (NCCs). The morphology of differentiating iPSCs was examined at regular intervals by phase contrast microscopy. In parallel, the expression of pluripotent and corneal endothelium (CE)-associated markers was investigated by quantitative real-time PCR (qRT-PCR). The molecular architecture of the iPSC-derived CECs and human corneal endothelium (hCE) was examined by mass spectrometry-based proteome sequencing. Results: The PBMC-originated, iPSC-derived CECs were tightly adherent, exhibiting a hexagonal-like shape, one of the cardinal characteristics of CECs. The CE-associated markers expressed at significantly higher levels in iPSC-derived CECs at days 13, 20, and 30 compared with their respective levels in iPSCs. It is of importance that only residual expression levels of pluripotency markers were detected in iPSC-derived CECs. Cryopreservation of iPSC-derived CECs did not affect the tight adherence of CECs and their hexagonal-like shape while expressing high levels of CE-associated markers. Mass spectrometry-based proteome sequencing identified 10,575 proteins in the iPSC-derived CEC proteome. In parallel, we completed proteome profiling of the hCE identifying 6345 proteins. Of these, 5763 proteins were identified in the iPSC-derived CECs, suggesting that 90.82% of the hCE proteome overlaps with the iPSC-derived CEC proteome. Conclusions: We have successfully developed a personalized approach to generate CECs that closely mimic the molecular architecture of the hCE. To the best of our knowledge, this is the first report describing the development of PBMC-originated, iPSC-derived CECs.