Daljit Singh

A novel mutation in the DNA-binding domain of MAF at 16q23.1 associated with autosomal dominant cerulean cataract in an Indian family

Congenital cataract, a clinically and genetically highly heterogeneous eye disorder, is one of the significant causes of visual impairment or blindness in children. It is frequently inherited as an autosomal dominant trait. We investigated a three‐generation family of Indian origin with 12 members affected with cerulean cataract. Linkage analysis was carried out in this family using more than 100 microsatellite markers for the known cataract candidate gene loci. A positive two‐point lod score of 3.9 at θ = 0.000, indicative of linkage, was obtained with three microsatellite markers for chromosome 16. Multipoint and haplotype analysis narrowed the cataract locus to a 15.3 cM region between markers D16S518 and D16S511 that corresponds to the region 16q23.1. Direct sequencing of the candidate gene MAF, which lies in the critical linked region, revealed a novel heterozygous missense mutation in the basic region (BR) of the DNA‐binding domain. This sequence change was considered pathogenic as it segregated in all affected family members, neither seen in unaffected family members nor in 106 unrelated controls. The mutation also results in substitution of highly conserved lysine 297 by arginine (K297R) that affects a residue that forms a part of a predicted DNA‐interaction region of the protein. The association of microcornea with congenital cataract in some affected individuals further underlines the role of the MAF transcription factor in lens and anterior ocular development. Our findings expand the mutation spectrum of MAF in association with congenital cataract and highlight the genetic and phenotypic heterogeneity of congenital cataract.

Availability and maintenance scheduling of a repairable block-board manufacturing system

The main objective of this paper is to develop a reliability model of a block-board manufacturing system in the plywood industry. The system discussed here undergoes partial as well as direct total failure. The model discussed here helps in calculating both time dependent and steady state availability under idealised as well as faulty Preventive Maintenance (PM). The PM rates and corrective repair rates are taken as arbitrarily distributed. Corrective repair of units is performed on the basis of preemptive resume priority discipline. The supplementary variable method is used to develop generalised expressions of state probabilities and system availabilities. Runge-Kutta method is used to calculate the availability of the system for transient state. Long run availability is carried out making use of software package Matlab 5.1. The tables for various parameters are given which are useful to the management for improving and planning the maintenance schedule.

A missense mutation in CRYGD linked with autosomal dominant congenital cataract of aculeiform type.

To detect the underlying genetic defects in two autosomal dominant congenital cataract (ADCC) families, having respectively twenty and four members affected with bilateral congenital cataract. Detailed family history and clinical data were recorded. Mutation screening in twenty three candidate genes including crystallins (CRYAA, CRYAB, CRYBA1/A3, CRYBA2, CRYBA4, CRYBB1, CRYBB2, CRYBB3, CRYGA, CRYGB, CRYGC, CRYGD, and CRYGS), gap junctional channels; connexins (GJA8, GJA3), beaded filament chain proteins (BFSP1, BFSP2), major intrinsic protein (MIP), lens intrinsic membrane protein-2 (LIM2), transcriptional factor (MAF), and in genes encoding for membrane-associated proteins (TMEM114, CHMP4B, EPHA2) was performed by bi-directional sequence analysis of the amplified products. In family A twenty members in six generations were affected by bilateral aculeiform type cataract and in family B four affected members in three generations had granular nuclear cataract. Mutation screening in already known candidate genes by sequence analyses revealed proline to threonine substitution at codon 23 (p.Pro23Thr) in CRYGD for aculeiform type cataract in family A. The family B with four members affected by granular nuclear cataract, however, could not be linked with any of these analyzed 23 candidate genes. The present study describes identification of p.Pro23Thr mutation in CRYGD for aculeiform type cataract in an ADCC family of Indian origin. The identical mutation has previously been reported to be linked with different phenotypes; lamellar cataract, cerulean cataract, coralliform cataract, flaky silica-like nuclear cataract and fasciculiform type cataract in different ADCC families. Interestingly, a mutation of different codon, i.e., p.Arg58His in CRYGD has been reported to be linked with aculeiform cataract in four different families; two from Switzerland, one from Macedonia and in a Mexican family. The findings in present study thus expand the genetic heterogeneity for aculeiform type cataract. Further, exclusion of these twenty three known candidate genes in family B having ADCC of granular nuclear type indicates the role of some other gene apart from for crystallins, gap junction channels, beaded filaments and membrane-associated proteins, and MAF for this phenotype.

The conjunctival lymphatic system

The conjunctival lymphatic system of the eye is presented and research in this field is evaluated. Extensive photographic documentation of the lymphatic system is shown. The microanatomy of the conjunctival lymphatic system is presented. The importance of the ocular lymphatic system is also evaluated.

Differential effect of cataract-associated mutations in MAF on transactivation of MAF target genes

Three mutations in the highly conserved DNA-binding region of c-MAF (R288P, K297R, and R299S) are associated with phenotypically distinct forms of autosomal dominant congenital cataract. However, the molecular mechanisms underlying this phenotypic diversity remain unclear. In this work, we have investigated the hypothesis that differential transactivation of MAF target genes could be one factor determining the phenotypic differences. Promoter constructs were generated for four human crystallin genes with conserved half-site MAF responsive elements (MARE). MAF expression constructs were constructed with the wildtype MAF sequence and with each of the three known mutations, i.e., R288P (associated with pulverulent cataract), K297R (associated with cerulean cataract), and R299S (associated with the most severe phenotype, congenital cataract, and microcornea syndrome). Transactivation was measured using luciferase reporter assays following cotransfection in HEK cells. Responsiveness to wildtype c-MAF was established for each of the four crystallin promoter constructs. The same constructs were then investigated using c-MAF mutants corresponding to each of the three mutations. A differential response was noted for each of the tested crystallin genes. The mutation R288P significantly reduced the expression of the CRYGA and CRYBA1 constructs but had no significant effect on the other two constructs. K297R did not lead to a significant reduction in expression of any of the four constructs, although there was a tendency toward reduced expression especially for the CRYGA construct. R299S, which is associated with the most severe phenotype, congenital cataract, and microcornea syndrome, was associated with the most severe overall effect on the transactivation of the four crystallin expression constructs. Our findings suggest that differential effects of mutations on the transactivation potential of c-MAF could be a molecular correlate of the striking genotype–phenotype correlations seen in cataract forms caused by mutations in the MAF gene.

Ablation pit treatment for corneal decompensation.

Historically, the management of cloudy, decompensated corneas centered around replacement of corneal tissue with either a through-and-through or partial-thicknes replacement. This article presents a technique that is a radical departure from prior methods.

Comprehensive classification of pediatric cataracts

A comprehensive classification of pediatric cataracts with extensive bibliography is presented.

A novel mutation in the PRPF31 in a North Indian adRP family with incomplete penetrance

PurposeTo identify the underlying genetic defect for non-syndromic autosomal dominant retinitis pigmentosa (adRP) with incomplete penetrance in a North Indian family.MethodsFamily history and clinical data were collected. Linkage analysis using 72 fluorescently labeled microsatellite markers flanking all the 26 candidate genes known for adRP was performed. Mutation screening in candidate gene at the mapped region was performed by bi-directional DNA sequencing.ResultsPositive two-point lod scores > 1.0 (θ = 0.000) suggestive of linkage were obtained with markers D19S572, D19S927 and D19S926 at 19q13.42, in the vicinity of PRPF31 gene. Mutation screening in all the 14 exonic regions and intron–exon boundaries of PRPF31 revealed a novel change, i.e. c.896G>A (p.Cys299Tyr) in exon eight. The observed change segregated in heterozygous form in all the six affected members and in three carriers, consistent with incomplete penetrance. This substitution was not observed in tested 15 unaffected members and in 200 ethnically matched controls.ConclusionPresent study describes mapping of a locus for non-syndromic adRP with incomplete penetrance at 19q13.42 in a North Indian family and identifies a novel missense mutation (p.Cys299Tyr) in PRPF31 localized at the mapped interval. The observed substitution lies in the NOP domain of PRPF31 that exhibit RNA and protein binding surfaces and thus may interfere in the formation of spliceosome complex. Due to p.Cys299Tyr substitution hydrogen bonds are generated, which may result in conformational changes and PRPF31 protein deformity. Present findings further substantiate the role of PRPF31 in adRP with incomplete penetrance and expand the mutation spectrum of PRPF31.

Iris Claw Intraocular Lens in Posterior Capsule Rent

In the 1970s, Binkhorst two-loop and four-loop pupil-supported lenses were frequently used for implantation in Europe, especially in Holland. Intracapsular lens extraction was the common mode of surgery. Extracapsular surgery was being gradually developed. The problem with pupil-supported lenses was their frequent dislocation. To overcome this, Jan Worst introduced Medallion lenses, which carried slots for the passage of a suture which tied the lens to the iris. Earlier, the sutures were nylon that had the propensity to break; later, Jan Worst used vanadium steel. However, the suturing was not an easy procedure as there were no viscoelastic materials at that time. He hit upon the idea of having a lens that tied itself to the iris, an iris claw lens. Binkhorst lens had an optic that stayed in front of the iris, while its nylon loops stayed on the back of the iris. In contrast, iris claw lens was monoplane lens, with optic in the center, flanked by two rings, one on each side. Each ring haptic had a cut that made it work like the claw of a lobster. For fixation, a piece of iris was pushed into the claw. An iris claw lens, when in position, was away from the angle, away from the corneal endothelium; the pupil was free to dilate and contract, and there was no injury to the posterior pigment epithelium of the iris (as happened with Binkhorst lenses and sulcus-fixated lenses introduced in early 1980s). An iris claw lens was most versatile and suitable for most aphakic situations, at any age, any kind of cataract extraction (intra or extra), in any size of eye, primary or secondary implantation. It still remains most versatile as it was in the beginning. The implantation of iris claw lens has become easier than before because of the availability of viscoelastic materials and better control on cataract removal. In 1978, Dr. Pramilla Lall and Dr. Naval Christy used it after intracapsular extraction, in Mission Hospital Taxilla, Pakistan. We started using iris claw lens in 1979, and till today have an experience of nearly 140,000 cases including over 15,000 secondary iris claw lens implants in intracapsular aphakes. Iris claw lens use is now reduced, but remains a lens of choice under special conditions. Preexisting posterior capsule rent and the problems arising out of surgery in these cases bring in the use of iris claw lens.

Plasma powered squint surgery with the fugo blade

The Fugo Blade™/Plasma Blade™ offers important advantages in many types of surgeries, both inside as well as outside of ophthalmology. As this technology is now mainstream, we evaluated the use of the Fugo Blade™/Plasma Blade™ in strabismus surgery. We demonstrated distinct advantages for using the Fugo Blade™ in squint surgery, which included increased surgeon control and decreased operative time.