Multimorbidity due to novel pathogenic variants in the WFS1/RP1/NOD2 genes: autosomal dominant congenital lamellar cataract, retinitis pigmentosa and Crohn’s disease in a British family

Background: A five generation family has been analysed by whole exome sequencing (WES) for genetic associations with the multimorbidities of congenital cataract (CC), retinitis pigmentosa (RP) and Crohn’s disease (CD). // Methods: WES was performed for unaffected and affected individuals within the family pedigree followed by bioinformatic analyses of these data to identify disease-causing variants with damaging pathogenicity scores. // Results: A novel pathogenic missense variant in WFS1: c.1897G>C; p.V633L, a novel pathogenic nonsense variant in RP1: c.6344T>G; p.L2115* and a predicted pathogenic missense variant in NOD2: c.2104C>T; p.R702W are reported. The three variants cosegregated with the phenotypic combinations of autosomal dominant CC, RP and CD within individual family members. // Conclusions: Here, we report multimorbidity in a family pedigree listed on a CC register, which broadens the spectrum of potential cataract associated genes to include both RP1 and NOD2

A novel 1-bp deletion in PITX3 causing congenital posterior polar cataract

Purpose: Cataracts are the most common cause of blindness worldwide. Inherited cataract is a clinically and genetically heterogeneous disease. Here we report a novel mutation in the paired-like homeodomain 3 (PITX3) gene segregating in a four generation English family with an isolated autosomal dominant posterior polar cataract.Methods: A genome-wide linkage was performed by means of single nucleotide polymorphism (SNP) and microsatellite markers. Linkage analyses were performed with the GeneHunter and MLINK programs. Direct sequencing of PCR products was performed to detect mutation in the gene, using the BigDye version 3.1 and analyzed using Sequence analysis version 5.2.Results: Genome-wide linkage analysis with SNP markers, identified a disease-haplotype interval on chromosome 10q. Two point positive logarithm of odds (LOD) scores was obtained with markers D10S205 (Z=3.10 at theta=0.00), flanked by markers D10S1709 and D10S543, which harbors the homeobox gene PITX3. Sequence analysis of PITX3 revealed a 1-bp deletion that cosegregated with all the affected members of this family which resulted in a frameshift in codon 181 and likely to produce an aberrant protein consisting of 127 additional residues.Conclusions: The 542delC is a novel mutation in PITX3 causing an isolated posterior polar cataract

A novel frameshift variant in BCOR causes congenital nuclear cataract

BackgroundBCL6 co-repressor (BCOR) gene variants are involved in oculofaciocardiodental (OFCD) syndrome, acute myeloid leukaemia, renal tumours, and photoreceptor degenerative diseases. Here, we describe a British family with a pathogenic heterozygous variant in the BCOR gene causing congenital nuclear cataract.MethodsWhole-exome sequencing was conducted on an individual affected by X-linked dominant congenital cataract in a three-generation family to establish the underlying genetic basis. Bioinformatics analysis confirmed the variants with damaging pathogenicity scores.ResultsA novel likely pathogenic frameshift variant BCOR NM_001123385.1: c.3621del; p.Lys1207AsnfsTer31, was identified and found to co-segregate with the disease in this family.ConclusionsThis is apparently the first report of a variant in BCOR causing X-linked dominant congenital cataract which is potentially isolated or presenting with a remarkably mild systemic phenotype. Our findings extend the genetic basis for congenital cataract and add to the phenotypic spectrum of BCOR variants

The genetic landscape of crystallins in congenital cataract

Background: The crystalline lens is mainly composed of a large family of soluble proteins called the crystallins, which are responsible for its development, growth, transparency and refractive index. Disease-causing sequence variants in the crystallins are responsible for nearly 50% of all non-syndromic inherited congenital cataracts, as well as causing cataract associated with other diseases, including myopathies. To date, more than 300 crystallin sequence variants causing cataract have been identified. Methods: Here we aimed to identify the genetic basis of disease in five multi-generation British families and five sporadic cases with autosomal dominant congenital cataract using whole exome sequencing, with identified variants validated using Sanger sequencing. Following bioinformatics analysis, rare or novel variants with a moderate to damaging pathogenicity score, were filtered out and tested for segregation within the families. Results: We have identified 10 different heterozygous crystallin variants. Five recurrent variants were found: family-A, with a missense variant (c.145C>T; p.R49C) in CRYAA associated with nuclear cataract; family-B, with a deletion in CRYBA1 (c.272delGAG; p.G91del) associated with nuclear cataract; and family-C, with a truncating variant in CRYGD (c.470G>A; W157*) causing a lamellar phenotype; individuals I and J had variants in CRYGC (c.13A>C; T5P) and in CRYGD (c.418C>T; R140*) causing unspecified congenital cataract and nuclear cataract, respectively. Five novel disease-causing variants were also identified: family D harboured a variant in CRYGC (c.179delG; R60Qfs*) responsible for a nuclear phenotype; family E, harboured a variant in CRYBB1 (c.656G>A; W219*) associated with lamellar cataract; individual F had a variant in CRYGD (c.392G>A; W131*) associated with nuclear cataract; and individuals G and H had variants in CRYAA (c.454delGCC; A152del) and in CRYBB1 (c.618C>A; Y206*) respectively, associated with unspecified congenital cataract. All novel variants were predicted to be pathogenic and to be moderately or highly damaging. Conclusions: We report five novel variants and five known variants. Some are rare variants that have been reported previously in small ethnic groups but here we extend this to the wider population and record a broader phenotypic spectrum for these variants

Dysfunctional LAT2 amino acid transporter is associated with cataract in mouse and humans

Cataract, the loss of ocular lens transparency, accounts for ∼50% of worldwide blindness and has been associated with water and solute transport dysfunction across lens cellular barriers. We show that neutral amino acid antiporter LAT2 (Slc7a8) and uniporter TAT1 (Slc16a10) are expressed on mouse ciliary epithelium and LAT2 also in lens epithelium. Correspondingly, deletion of LAT2 induced a dramatic decrease in lens essential amino acid levels that was modulated by TAT1 defect. Interestingly, the absence of LAT2 led to increased incidence of cataract in mice, in particular in older females, and a synergistic effect was observed with simultaneous lack of TAT1. Screening SLC7A8 in patients diagnosed with congenital or age-related cataract yielded one homozygous single nucleotide deletion segregating in a family with congenital cataract. Expressed in HeLa cells, this LAT2 mutation did not support amino acid uptake. Heterozygous LAT2 variants were also found in patients with cataract some of which showed a reduced transport function when expressed in HeLa cells. Whether heterozygous LAT2 variants may contribute to the pathology of cataract needs to be further investigated. Overall, our results suggest that defects of amino acid transporter LAT2 are implicated in cataract formation, a situation that may be aggravated by TAT1 defects