Adult‐onset cataract (AOC) is a major ocular health problem and is the number one cause of blindness in the world. It is interesting to note that if the development of cataract is delayed by 10 years, the number of cataract surgeries needed would decrease by 45%. To prevent or delay cataract, the molecular pathological mechanisms underlying the lens change have to be understood, and this requires that the genes involved in such mechanisms should be identified. Hence, in this study we aim to identify AOC families which show a clear mendelian inheritance pattern, as only these families would be ideal for mapping the genes responsible. Over a period of 8 months, from September 1995—April 1996, 17 families with two or more affected members were identified. Segregation analysis showed autosomal dominant inheritance in multiple affected families. We propose to map the genes responsible for cataract in these families by linkage analysis and mutational screening of candidate genes.

The effect of oxalate, a constituent of renal stone, on the expression of nuclear pore complex oxalate binding protein (gp210) in Vero monkey kidney cells was examined. The expression of this protein was found to increase more in mitotic phase than in S phase, suggesting cell cycle dependency. Exposure of cells to oxalate-containing growth medium resulted in a relative increase in nuclear pore complex oxalate binding protein in each stage of cell cycle. The concentration of this protein was found to increase six times in the telophase stage of the cells exposed to high concentrations of oxalate in the growth medium, though slight reduction in cell density was observed. Urolithiasis is a process of biomineralixation in the urinary tract. Perturbations in renal oxalate handling play a major role in renal stone disease (1). Our earlier studies have shown the presence of about 70% of total oxalate binding to nuclei while only 30% binding to the mitochondria (2,3). Our earlier studies have reported the presence of oxalate binding protein in the nuclear envelope (4). Our preliminary studies have shown that the nuclear pore complex protein gp210 is an oxalate binding protein (5). Oxalate has been shown to induce mitosis (6), DNA synthesis (7), and expression of certain genes (8). The physiological significance of the presence of oxalate binding protein in the nuclear pore complex is not well understood. In order to study its functions, the expression of this protein during different stages of cell cycle was studied in the presence of oxalate. MATERIALS AND METHODSMinimum essential medium, penicillin, streptomycin, sodium bicarbonate, fetal calfserum, methotrexate, colchicin, Cytochalasin B, trypsin-EDTA solution, and molecular weight markers were obtained from Sigma Chemical Company, St. Louis, Missouri. Sodium oxalate, oxamate, malate, citrate. and other chemicals were purchased from Sisco Research Laboratories, Mumbai. Other chemicals used were of analytical grade and purity.Human primary biliary cirrhosis (PBC) serum containing autoantibodies against nuclear pore complex protein gp210 was a gift from Professor Howard J. Worman, Columbia University, New York (9). Goat anti-human IgG horseradish peroxidase was a gift from NII, New Delhi.Cell line and cell culture. Vero monkey kidney cells were serially passaged in minimal essential medium (MEM) supplemented with 10% fetal calf serum, penicillin (100 U/ml), and streptomycin (100 µg/ml). The cells were maintained in an atmosphere of 5% CO 2 /95% air in a humidified 37°C incubator.Oxalate concentration. Oxalate concentration in the medium was fixed according to (10) to be 0.1 mM (low), 0.3 mM (medium), and 1 mM (high/toxic) total oxalate (which is equivalent to 30, 100, and 350 µM free oxalate concentrations, respectively). 1 x 10 5 cells were incubated with MEM containing specified concentrations of oxalate.Synchronization at different stages of cell cycle. 1 x 10 5 cells were incubated with MEM containing corresponding cell cycle blockers in 25-ml culture flasks. Cell...

Both rat and human kidney nuclei exhibited time and pH dependent oxalate or histone-oxalate uptake which was inhibited by anion transport inhibitor, 4,4'-dithiocyanostilbene-2,2'-disulphonic acid. Sodium chloride had no effect. Nuclear membrane had oxalate binding at pH 7.4. Extraction of nuclear membrane by Triton-high salt mixture showed maximal oxalate binding activity with nuclear pore complex while nuclear lamin had no oxalate binding. The rat and human kidney nuclear pore complex showed oxalate binding of 144 and 220 pmoles/mg protein respectively. Subsequent purification of the protein on diethyl amino ethyl-Sephadex A 50 column and Sephadex G-200 column yielded 4-fold purification. The protein revealed a molecular weight of 205 kDa on SDS-PAGE. The protein was found to be saturable at 2 microM oxalate and had a Kd of 2.98 pM and a Bmax of 197 pmoles. Antibody for 205 kD was separated from primary biliary cirrhosis serum containing auto antibody against 205 kDa using affinity column chromatography. The oxalate binding activity as well as the nuclear uptake of oxalate or histone-oxalate were inhibited by its antibody.