Mutations within the cGMP-binding domain of CNGA1 causing autosomal recessive retinitis pigmentosa in human and animal model.

Retinitis pigmentosa is a group of progressive inherited retinal dystrophies that may present clinically as part of a syndromic entity or as an isolated (nonsyndromic) manifestation. In an Indian family suffering from retinitis pigmentosa, we identified a missense variation in CNGA1 affecting the cyclic nucleotide binding domain (CNBD) and characterized a mouse model developed with mutated CNBD. A gene panel analysis comprising 105 known RP genes was used to analyze a family with autosomal-recessive retinitis pigmentosa (arRP) and revealed that CNGA1 was affected. From sperm samples of ENU mutagenesis derived F1 mice, we re-derived a mutant with a Cnga1 mutation. Homozygous mutant mice, developing retinal degeneration, were examined for morphological and functional consequences of the mutation. In the family, we identified a rare CNGA1 variant (NM_001379270.1) c.1525 G > A; (p.Gly509Arg), which co-segregated among the affected family members. Homozygous Cnga1 mice harboring a (ENSMUST00000087213.12) c.1526 A > G (p.Tyr509Cys) mutation showed progressive degeneration in the retinal photoreceptors from 8 weeks on. This study supports a role for CNGA1 as a disease gene for arRP and provides new insights on the pathobiology of cGMP-binding domain mutations in CNGA1-RP.

Enhanced Expression of FRA16B using AT-Rich DNA Binding Chemicals in a Woman with Secondary Amenorrhoea.

Fragile sites represent regions of chromatin that fail to compact during mitosis. Based on the prevalence and pattern of inheritance they are classified as rare fragile sites or common fragile sites. Rare fragile sites either occur spontaneously or can be induced by certain AT-specific binding chemicals namely distamycin, Hoechst 33258, Berenil and others. The most common of all rare autosomal fragile sites is fra(16)(q22) with a heterozygote frequency of ~5%. FRA16B results from an expansion of a 33 bp AT-rich Minisatellite repeat. These rare forms are usually heritable and segregate in a Mendelian fashion. The proband who was referred for secondary amenorrhoea, revealed 46,XX,fra(16)(q22.1)pat karyotype. Her father and younger sibling were also found to be carriers. This study aimed to delineate the genotypic and phenotypic features exhibited by these carriers and to evaluate FRA16B expression using AT-specific binding chemicals. The additives employed were Berenil, BrdU and Hoechst 33258. Berenil at a concentration of 150 µg/ml showed the highest expression of FRA16B. Although the recent breakthrough in molecular characterization of fragile sites plays a critical role in comprehending their association with various diseases, the physiological link between them and amenorrhoea is not clearly understood.

Three novel and two known androgen receptor gene mutations associated with androgen insensitivity syndrome in sex-reversed XY female patients.

Molecular characterization of 23 cytogenetically confirmed XY females was attempted by screening coding regions of SRY and androgen receptor (AR) genes. Five of the index cases showed sequence variations in various exons of the AR gene: a deletion (n.1911delG) and substitutions n.1761G>A and n.1317C>T in exon 1; n.3510C>T transition in exon 6 and deletion mutation (n.3672delT) in exon 7. Four mutations identified here lead to the formation of truncated receptor protein, involving a substantial loss of AR functional domains which explains the phenotype in the subjects. The n.1761G>A substitution has been previously reported in cases with mild androgen insensitivity. Although the ligand-binding domain was considered as the mutational hot spot in AR gene, we report here 3/5 variations in the N-terminal domain emphasizing the significance of considering the N-terminal domain of AR as well for mutation screening. Our present observation also strengthens the role of AR gene and its direct association with AIS.

A novel splice site and two known mutations of androgen receptor gene in sex-reversed XY phenotype.

Molecular characterization of 27 cytogenetically confirmed Indian XY females was attempted by screening selected regions of candidate genes namely SRY (HMG box) and the ligand-binding domain of androgen receptor (AR) (Exons 5-8). Three of the index cases showed sequence variations in exons of the AR gene: a deletion mutation in exon 6 (c.2762 del C), a substitution mutation (c.2925 C>T), and a novel splice donor site mutation (IVS5+1 g>a; exon 5/intron 5). The proband's (case VA156) mother and one of the sisters were heterozygous for the novel splice donor site mutation while the father was normal. Review of literature suggested that an alternate spice donor site could be utilized leading to an aberrant splicing resulting in a truncated receptor. This could not be validated further through reverse transcriptase-polymerase chain reaction as the patient failed to cooperate for follow-up. Of the 16 spice site variations reported in various ethnic groups, this is a novel variation in the AR gene to be associated with Androgen Insensitivity Syndrome. The proband's sister, noted to be a heterozygous carrier, has high risk of having XY female progeny; hence prenatal screening of the mutation in case of an XY fetus is recommended.

Modulatory action of 2-deoxy-D-glucose on mitomycin C-and 4-nitroquinoline-1-oxide-induced genotoxicity in Swiss albino mice in vivo.

BACKGROUND: 2-Deoxy-D-glucose (2-DG), a structural analog of glucose is an effective inhibitor of glucose metabolism and ATP production. It selectively accumulates in cancer cells and interferes with glycolysis leading to cell death. 2-DG is shown to differentially enhance the radiation-induced damage in cancer cells both under euoxic and hypoxic conditions. A combination of 2-DG and ionizing radiation selectively destroys tumors while protecting the normal tissue. 2-DG is being advocated as an adjuvant in the radiotherapy and chemotherapy of cancer. OBJECTIVE: The present investigation focuses on the modulatory effect of 2-DG on mitomycin C- (MMC) and 4-nitroquinoline-1-oxide (4-NQO)-induced cytogenetic damage in bone marrow cells of Swiss albino mice in vivo. MATERIALS AND METHODS: Experimental animals were pretreated with 2-DG (500 mg/kg, i.p.) for five consecutive days followed by MMC (2 mg/kg, i.p) or 4-NQO (15 mg/kg, i.p.), 24 h prior to sacrifice. Control animals were given either the mixture of olive oil and acetone (3:1) or distilled water. Bone marrow cells were processed for the micronucleus assay and metaphase analysis for estimating cytogenetic damage. RESULTS: 2-DG significantly (P < 0.001) reduced the frequency of aberrant cells induced by MMC (approximately 90%) and 4-NQO (approximately 74%). Incidence of micronucleated polychromatic erythrocytes (MnPCEs) induced by the mutagens were reduced up to 68%. CONCLUSION: 2-DG effectively reduces the MMC-and 4-NQO-induced genotoxicity.

X;7 translocation in an Indian woman with hypergonadotropic amenorrhea-a case report.

Translocations involving X chromosome and an autosome are rather rare due to the associated infertility in men and subfertility in women. X-autosome translocations are frequently associated with primary or secondary ovarian failure and at times Turner syndrome-like features if there is an involvement of the critical region of Xq13-q26. A 19-year-old proposita with a complaint of amenorrhea was found to have hypoplastic uterus and streak ovaries. Hormonal profile revealed hypergonadotropic hypogonadism. Chromosomal analysis of 25 conventionally stained metaphases revealed the karyotype to be 46,X,t(X;7)(q13;p15)de novo. This rare finding is the first report from India, to the best of our knowledge. She also exhibited the maternally inherited heteromorphic variant of chromosome 21. The occurrence of t(X;7) in the proposita with hypergonadotropic amenorrhea confirms the role of X-autosome translocations in ovarian dysfunction.

Klinefelter variant mosaic with a reciprocal translocation t(1;7).

OBJECTIVE: To determine the constitutional karyotype in a provisional diagnosis of Klinefelter syndrome. DESIGN: Case report. SETTING: University research facility in collaboration with a government hospital. PATIENT(S): Male patient with provisional diagnosis of Klinefelter syndrome. INTERVENTION(S): Chromosomal analysis of phytohemagglutinin-stimulated peripheral blood lymphocytes using conventional cytogenetic techniques. MAIN OUTCOME MEASURE(S): Chromosome number and structure, hormonal profile. RESULT(S): Analysis of GTG-banded metaphases of the proband revealed the karyotype to be mos 48,XXXY,t(1;7)(q42;q32)pat[71%]/47,XXY,t(1;7)(q42;q32)pat[29%]. This is the first report of its kind, to the best of our knowledge. His father and elder brother were also found to be carriers of the same translocation with the karyotype 46,XY,t(1;7)(q42;q32). CONCLUSION(S): An alternate segregation of the translocation t(1;7) in spermatogenesis could have led to meiotic nondisjunction, thus supporting the hypothesis of interchromosomal effect. This case study truly emphasizes the clinical relevance of cytogenetic diagnosis in the better management of genetic disorders.

Antioxidant activity measured in different solvent fractions obtained from Mentha spicata Linn.: an analysis by ABTS*+ decolorization assay.

Antioxidant compounds are abundantly available in plants and play an important role in scavenging free radicals, thus providing protection to humans against oxidative DNA damage. Mentha spicata Linn., commonly called spearmint, belongs to the family lamiaceae. It was selected in the present study because Mentha extracts have antioxidant properties due to the presence of eugenol, caffeic acid, rosmarinic acid and alpha-tocopherol. Four solvent fractions (hexane, chloroform, ethyl acetate and water) of ethanolic extract of dried leaves powder of M. spicata were analyzed for total antioxidant activity (TAA) and relative antioxidant activity (RAA) and compared with standard antioxidants such as Quercetin, beta-carotene, L-ascorbic acid and glutathione using ABTS*+ decolorization assay (ABTS/Potassium persulphate). The antioxidant activity was assumed to be from the total phenolic content of the ethanolic extract. Total phenolics are found to be highest in ethyl acetate fraction (54 mg/g) and least in hexane fraction (13 mg/g) and more or less similar in water and chloroform fractions (30-32 mg/g). TAA is found to be less in hexane and chloroform fractions (<53% at 50 microg/ml) and highest in ethyl acetate (95% at 20 microg/ml) and water (84% at 30 microg/ml) fractions. The RAA of ethyl acetate fraction is 1.1 compared to quercetin (at 5 microM/ml), but greater when compared to beta-carotene (15 microM/ml), L-ascorbic acid (15 microM/ml) and glutathione (15 microM/ml). The RAAs with these antioxidants are in the range of 1.31 -1.6. The values of RAAs for water fraction also show similar trend and are in the range of 1.0-1.4. The antioxidant activities of the solvent factions are closely related to the content of total phenolics present in them.