Publications by authors named "S T Santhiya"

40 Publications

Application of WES Towards Molecular Investigation of Congenital Cataracts: Identification of Novel Alleles and Genes in a Hospital-Based Cohort of South India.

Int J Mol Sci 2020 Dec 16;21(24). Epub 2020 Dec 16.

Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Tamil Nadu 600 113, India.

Congenital cataracts are the prime cause for irreversible blindness in children. The global incidence of congenital cataract is 2.2-13.6 per 10,000 births, with the highest prevalence in Asia. Nearly half of the congenital cataracts are of familial nature, with a predominant autosomal dominant pattern of inheritance. Over 38 of the 45 mapped loci for isolated congenital or infantile cataracts have been associated with a mutation in a specific gene. The clinical and genetic heterogeneity of congenital cataracts makes the molecular diagnosis a bit of a complicated task. Hence, whole exome sequencing (WES) was utilized to concurrently screen all known cataract genes and to examine novel candidate factors for a disease-causing mutation in probands from 11 pedigrees affected with familial congenital cataracts. Analysis of the WES data for known cataract genes identified causative mutations in six pedigrees (55%) in (two variants), and an additional likely causative mutation in a novel gene , which represents the first dominant mutation in this gene. This study identifies a novel cataract gene not yet linked to human disease. NCOA6 is a transcriptional coactivator that interacts with nuclear hormone receptors to enhance their transcriptional activator function.
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http://dx.doi.org/10.3390/ijms21249569DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7765966PMC
December 2020

A novel E128* mutation underlying an autosomal dominant nuclear cataract in a south Indian kindred.

Ophthalmic Genet 2020 12 18;41(6):556-562. Epub 2020 Aug 18.

Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras , Chennai, India.

Purpose: To identify the mutation causing an autosomal dominant congenital nuclear cataract in a south Indian family by whole exome sequencing and to characterize further phenotypically the same in a zebra fish model.

Methods: A six-generation family (DKEC1) with several affected members registered at the Regional Institute of Ophthalmology (RIO), Chennai was documented to have congenital nuclear cataract. Detailed clinical history and blood samples were collected from all available family members. Genomic DNA of the proband was subjected to whole exome sequencing. Sequence variations suggestive of putative mutations were further confirmed by bidirectional sequencing and restriction site analysis. Functional analysis of the mutant E128* in zebrafish embryos was done to dissect out the pathogenicity.

Results: A unique variation viz., c.382 G > T in the coding region of the gene, resulting in a premature stop codon at position 128 (E128*) was documented in the affected family members. The same was absent in unaffected family members and in 120 unrelated population controls checked. Bioinformatic tools predicted that the mutation might cause a deleterious effect on protein structure and function. Molecular function analysis of this novel mutation (p. E128*, ) in the zebrafish indicated this mutation to impair lens transparency.

Conclusion: This study identified a novel mutation, E128* to cause autosomal dominant congenital nuclear cataract in a large south Indian family. Our study provides a new insight onto how the mutation might affect the γC-crystallin structure and function besides emphasizing the need for genetic diagnosis toward vision restoration.
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http://dx.doi.org/10.1080/13816810.2020.1807027DOI Listing
December 2020

Furosemide-induced tubular dysfunction responding to prostaglandin synthesis inhibitor therapy in a child with nephrotic syndrome.

CEN Case Rep 2018 11 22;7(2):195-197. Epub 2018 Mar 22.

Department of Pediatrics, Post Graduate Institute of Medical Education and Research, Chandigarh, 160012, India.

Furosemide is one of the most common drug used to treat anasarca in childhood nephrotic syndrome. It has minimal side effects on short-term usage, but prolonged use can result in polyuria, hypokalemia and metabolic alkalosis. This pseudo-bartter complication can be treated by discontinuation of the drug with adequate potassium replacement. We report a child who was given furosemide for 20 days elsewhere to treat the edema due to nephrotic syndrome and then presented to us with bartter-like syndrome. Furosemide was discontinued and potassium replacement was initiated. However, the child continued to have polyuria leading to repeated episodes of hypotensive shock. In view of severe symptoms, she was given a short course of oral indomethacin for 6 days, to which she responded. This case highlights the fact that indomethacin can provide symptomatic improvement in furosemide induced pseudo-bartter.
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http://dx.doi.org/10.1007/s13730-018-0324-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6181891PMC
November 2018

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

J Clin Diagn Res 2017 Jun 1;11(6):QD01-QD03. Epub 2017 Jun 1.

Professor and Head (Retd.), Department of of Genetics, Dr. ALM Postgraduate Institute of Basic Medical Sciences, University of Madras, Taramani, Chennai, Tamil Nadu, India.

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.
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http://dx.doi.org/10.7860/JCDR/2017/26545.10043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5532538PMC
June 2017

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

J Genet 2016 Dec;95(4):911-921

Department of Genetics, Dr. ALMPG Institute of Basic Medical Sciences, University of Madras, Taramani, Chennai 600 113, India.

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.
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http://dx.doi.org/10.1007/s12041-016-0716-0DOI Listing
December 2016

The E368Q Mutant Allele of is Associated with Congenital Cataracts with Intrafamilial Variation in a South Indian Family.

Open Access J Ophthalmol 2016 28;1(1). Epub 2016 Jul 28.

Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, India.

Purpose: To determine the basis of the autosomal dominant congenital cataracts in a three generation south Indian pedigree.

Methods: The proband and several family members underwent a complete ophthalmic examination. The coding regions of eight candidate genes ( and ) were amplified by PCR and directly sequenced. Wild type and mutant connexin50 (Cx50) were expressed by stable transfection of HeLa cells. Their cellular distributions and function were examined by immunofluorescence microscopy and by microinjection of gap junction permeant tracers, respectively.

Results: Congenital cataracts (with some variations in phenotype) segregated as an autosomal dominant trait within a three generation pedigree. Three affected individuals (proband, sibling and mother) showed a sequence variation in the candidate gene encoding Cx50: a c.1102G>C transversion encoding a substitution of glutamate for glutamine at position 368 (E368Q). This substitution was absent from an unaffected family member (paternal aunt) and 100 healthy controls of the same ethnicity. In transfected HeLa cells, both wild type Cx50 and E368Q localized to gap junction plaques, and supported similar levels of intercellular transfer of Neurobiotin.

Conclusions: The E368Q mutant allele of is associated with autosomal dominant congenital cataracts with phenotypic variability. E368Q forms gap junction plaques and functional channels in transfected HeLa cells.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5438206PMC
July 2016

(1S,1'S,2'R,4a'S,9a'S,9b'R)-1'-Acet-yloxy-2,4'-dioxo-2',4',4a',7',8',9',9a',9b'-octa-hydro-1'H,2H-spiro-[ace-naphthyl-ene-1,5'-pyrano[4,3-a]pyrrolizin]-2'-ylmethyl acetate.

Acta Crystallogr Sect E Struct Rep Online 2013 Oct 2;69(Pt 11):o1601. Epub 2013 Oct 2.

Research Department of Physics, SDNB Vaishnav College for Women, Chennai 600 004, India.

In the title compound C26H25NO7, the mean plane through the lactone-substituted ring of the pyrrolizidine moiety forms dihedral angles of 78.46 (6) and 58.28 (8)° with the ace-naphthyl-ene moiety and the sugar based-lactone ring, respectively. The sum of the angles at the the N atom of the pyrrolizidine ring (335.0°) is in accordance with sp (3) hybridization. Some atoms of the acetate group are disordered and were refined using a split model [occupancy ratio 0.673 (10):0.327 (10)].
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http://dx.doi.org/10.1107/S1600536813026111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3884278PMC
October 2013

1-(3,5-Di-meth-oxy-phen-yl)-4,5-dimethyl-2-phenyl-1H-imidazole.

Acta Crystallogr Sect E Struct Rep Online 2013 4;69(Pt 10):o1502. Epub 2013 Sep 4.

Research Department of Physics, SDNB Vaishnav College for Women, Chennai 600 044, India.

In the title mol-ecule, C19H20N2O2, the imidazole ring makes dihedral angles of 57.29 (5) and 31.54 (5)° with the attached di-meth-oxy-phenyl residue and the phenyl ring, respectively. The dihedral angle between the di-meth-oxy-phenyl and phenyl rings is 61.15 (5)°. In the crystal, pairs of C-H⋯N hydrogen bonds connect the mol-ecules into inversion dimers.
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http://dx.doi.org/10.1107/S1600536813023684DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3790376PMC
October 2013

Translocation t(X;11)(q22;q25) in a woman with premature ovarian failure.

Sex Dev 2013 16;7(4):216-21. Epub 2013 Feb 16.

Department of Genetics, Dr. ALMPG Institute of Basic Medical Sciences, University of Madras, Chennai, India.

Genetic, autoimmune, environmental, iatrogenic, and idiopathic factors are known to cause premature ovarian failure (POF). This report describes an X;11 translocation, t(X;11)(q22;q25), in a woman diagnosed with POF. The FSH level was found to be elevated. Menstrual cycle was regular initially, and she had a spontaneous abortion at the 5th month of gestation at 16 years of age. Her mother was karyotypically normal while her father was not investigated. Male carriers of X;autosome translocations are mostly infertile, and hence the translocation is presumed to be of de novo origin. Fluorescence in situ hybridization using whole chromosome paint probes confirmed the rearrangement.
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http://dx.doi.org/10.1159/000346958DOI Listing
April 2014

An MIP/AQP0 mutation with impaired trafficking and function underlies an autosomal dominant congenital lamellar cataract.

Exp Eye Res 2013 May 29;110:136-41. Epub 2012 Oct 29.

Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Chennai, India.

Autosomal dominant congenital cataracts have been associated with mutations of genes encoding several soluble and membrane proteins. By candidate gene screening, we identified a novel mutation in MIP (c.494 G > A) that segregates with a congenital lamellar cataract within a south Indian family and causes the replacement of a highly conserved glycine by aspartate (G165D) within aquaporin0 (AQP0). Unlike wild type AQP0, expression of AQP0-G165D in Xenopus oocytes did not facilitate swelling in hypotonic medium. In transfected HeLa cells, wild type AQP0 localized at the plasma membrane while AQP0-G165D was retained within the secretory pathway, and localized mainly within the endoplasmic reticulum. These results suggest that mutation of this conserved glycine residue leads to improper trafficking of AQP0-G165D and loss of water channel function. They emphasize the importance of AQP0 for maintenance of lens transparency and identify a critical residue that is conserved among aquaporins, but has not previously been associated with disease-associated replacement.
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http://dx.doi.org/10.1016/j.exer.2012.10.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3570674PMC
May 2013

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

Genet Test Mol Biomarkers 2012 Jul;16(7):749-55

Department of Genetics, Dr. ALM. PG. Institute of Basic Medical Sciences, University of Madras, Chennai, India.

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.
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http://dx.doi.org/10.1089/gtmb.2011.0292DOI Listing
July 2012

Molecular analysis of cataract families in India: new mutations in the CRYBB2 and GJA3 genes and rare polymorphisms.

Mol Vis 2010 Sep 10;16:1837-47. Epub 2010 Sep 10.

Dr. ALM Postgraduate Institute of Basic Medical Sciences, Department of Genetics, University of Madras, Taramani, Chennai, India.

Purpose: The aim of the study was to resolve the genetic etiology in families having inherited cataracts.

Methods: Families afflicted with congenital/childhood cataracts were registered in Chennai and Orissa (India). Blood samples were collected from the probands and available family members. Selected functional candidate genes were amplified by polymerase chain reaction (PCR) and characterized by direct sequencing. Putative mutations were confirmed in healthy controls.

Results: We observed interesting new polymorphisms of ethnic specificity, some of frequent nature, such as a 3-bp deletion in intron 3 of CRYBB2 (encoding βB2-crystallin) and IVS1+9 c>t variation in HSF4 (encoding heat-shock factor 4). Some rare single nucleotide polymorphisms (SNPs) co-segregate with the respective phenotype such as IVS3+120c>a of CRYBB2, while M44V of CRYGD (encoding γD-crystallin), although found in association with blue dot opacity was seen in a few healthy controls too. We identified two new mutations co-segregating along with the respective cataract phenotype within the families that were not seen in healthy controls from India or Germany. These include two missense mutations; one in GJA3 (encoding gap junction protein α3, which is also referred to as connexin 46); the mutation affects codon 19 (T19M), and the corresponding phenotype is a posterior-polar cataract. The other missense mutation affects CRYBB2 (W59C; total cataract). Additionally, a cDNA variation (G54A) identified in a zonular cataract affects a highly conserved splice site of CRYBB2. This mutation, however, showed reduced penetrance in the family, which might be explained by different molecular consequences in the affected family members: nonsense-mediated decay of the mutated mRNA might have no clinical phenotype in heterozygotes, whereas the translation of the mutated mRNA is predicted to lead to a small hybrid protein (consisting of 16 amino acids of the βB2-crystallin and 18 new amino-acids), which might have a dominant-negative function in the lens.

Conclusions: This report identifies in families with childhood cataract some new alleles, which may be considered as causative for cataracts. Furthermore, we report some geographically restricted rare polymorphic sites, whose significance might be considered in some context as modifiers or alleles in sensitizing ocular lens toward cataractogenesis.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2956670PMC
September 2010

A novel human CRYGD mutation in a juvenile autosomal dominant cataract.

Mol Vis 2010 May 22;16:887-96. Epub 2010 May 22.

Department of Biotechnology, Manipal Life Sciences Centre, Manipal University, Manipal, Karnataka state, India.

Purpose: Identification of causal mutation in the crystallin, connexin, and paired box gene 6 (PAX6) genes associated with childhood cataract in patients from India.

Methods: In this study, forty eight members from seventeen families and 148 sporadic cases of childhood cataract were evaluated. Clinical and ophthalmologic examinations were performed on available affected and unaffected family members. Samples of genomic DNA were PCR amplified to screen for mutations in the candidate genes viz., alpha-A crystallin (CRYAA), beta- B2 crystallin (CRYBB2), gamma-A crystallin (CRYGA), gamma-B crystallin (CRYGB), gamma-C crystallin (CRYGC), gamma-D crystallin (CRYGD), gap junction alpha-3 (GJA3), gap junction alpha-8 (GJA8), and PAX6 based on polymerase chain reaction and single strand conformation polymorphism (PCR-SSCP) analysis. Samples showing any band mobility shift were subjected to bidirectional sequencing to confirm the variation. Co-segregation of the observed change with the disease phenotype was further tested by restriction fragment length polymorphism (RFLP) for the appropriate restriction site.

Results: DNA sequencing analysis of CRYAA, CRYBB2, CRYGA-D, GJA3, GJA8, and PAX6 of the affected members of a family (C-35) showed a novel heterozygous missense mutation C>A at position 229 in CRYGD in three affected members of family C-35 with anterior polar coronary cataract. This variation C229A substitution created a novel restriction site for AluI and resulted in a substitution of highly conserved arginine at position 77 by serine (R77S). AluI restriction site analysis confirmed the transversion mutation. Analysis of the available unaffected members of the family (C-35) and 100 unrelated control subjects (200 chromosomes) of the same ethnic background did not show R77S variation. Data generated using ProtScale and PyMOL programs revealed that the mutation altered the stability and solvent-accessibility of the CRYGD protein.

Conclusions: We describe here a family having anterior polar coronary cataract that co-segregates with the novel allele R77S of CRYGD in all the affected members. The same was found to be absent in the ethnically matched controls (n=100) studied. Interestingly the residue Arg has been frequently implicated in four missense (R15C, R15S, R37S, and R59H) and in one truncation mutation (R140X) of CRYGD. In two of the reported mutations Arg residues have been replaced with Serine. This finding further expands the mutation spectrum of CRYGD in association with childhood cataract and demonstrates a possible mechanism of cataractogenesis. Screening of other familial (n=48) and sporadic (n=148) cases of childhood cataract, did not reveal any previously reported or novel mutation in the candidate genes screened.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2875257PMC
May 2010

Protective effect of Hemidesmus indicus R.Br. root extract against cisplatin-induced cytogenetic damage in mouse bone marrow cells.

Genet Mol Biol 2010 Jan 1;33(1):182-5. Epub 2010 Mar 1.

Department of Genetics, Dr. ALMPGIBMS, University of Madras, Tamil Nadu India.

The aqueous extract of Hemidesmus indicus roots was investigated for its in vivo antigenotoxic effect against cisplatin-induced cytogenetic damage. Swiss albino mice were administered with various doses of the extract either singly (50, 100 and 200 mg/kg body weight) or as split doses (10, 20 and 40 mg/kg bw/day) for five consecutive days by oral gavage. As endpoints, chromosome aberrations, micronuclei in polychromatic erythrocytes, mitotic index and PCE/NCE ratio were estimated. The extract protected the bone marrow cells from cisplatin-induced genotoxicity in an inverse dose-dependent manner. However, the extract was cytotoxic at all doses. But, under split dose regime it conferred a higher level of genoprotection and was not cytotoxic at the lower two doses. The presence of saponins, tannins, phenols, terpenoids, flavonoids and coumarins in the crude extract could explain these effects.
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http://dx.doi.org/10.1590/S1415-47572010005000011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3036083PMC
January 2010

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

J Cancer Res Ther 2009 Sep;5 Suppl 1:S53-6

Department of Genetics, Dr. ALM PG Institute of Basic Medical Sciences, University of Madras, Taramani, Chennai, India.

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.
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http://dx.doi.org/10.4103/0973-1482.55144DOI Listing
September 2009

Genotoxic and antigenotoxic effects of Hemidesmus indicus R. Br. root extract in cultured lymphocytes.

J Ethnopharmacol 2010 Feb 5;127(2):558-60. Epub 2009 Nov 5.

Dr ALMPGIBMS, University of Madras, Taramani Campus, Chennai 600113, Tamil Nadu, India.

Aim Of The Study: The genotoxic and antigenotoxic potential of the ethanolic extract of Hemidesmus indicus roots were evaluated in cultured human lymphocytes using cisplatin as the positive mutagen.

Materials And Methods: Cytogenetic damage and cytotoxicity were determined in cells exposed to different doses of the extract, ranging from 2 to 32 microg/ml of culture medium, either alone or together with cisplatin.

Results: There was a significant reduction in cisplatin-induced frequencies of sister chromatid exchanges, chromosome aberrations and micronucleated binucleate cells at the lower concentrations of 4 and 8 microg/ml (P<0.05). However, the extract by itself reduced the proliferative rate index, mitotic index and cytokinesis-block proliferative index (P<0.05). Further, a significant increase in the percentage of chromosome aberrations was noticed at the higher concentrations.

Conclusion: Hemidesmus indicus root extract possesses significant genoprotective effect at the lower concentrations although it is cytotoxic and probably genotoxic at higher doses.
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http://dx.doi.org/10.1016/j.jep.2009.10.034DOI Listing
February 2010

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

Genet Test Mol Biomarkers 2009 Aug;13(4):533-6

Department of Genetics, Dr. A.L.M. P.G. Institute of Basic Medical Sciences, University of Madras, Chennai, India.

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.
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http://dx.doi.org/10.1089/gtmb.2009.0051DOI Listing
August 2009

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

Fertil Steril 2008 Nov 4;90(5):2017.e15-7. Epub 2008 Mar 4.

Department of Genetics, Dr ALM PG Institute of Basic Medical Sciences, University of Madras, Taramani, Chennai, India.

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.
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http://dx.doi.org/10.1016/j.fertnstert.2007.12.017DOI Listing
November 2008

CRYBA4, a novel human cataract gene, is also involved in microphthalmia.

Am J Hum Genet 2006 Oct 17;79(4):702-9. Epub 2006 Aug 17.

Program of Genetics and Genomic Biology, The Hospital for Sick Children, Toronto, Ontario, M5G 1X8, Canada.

Genetic analysis of a large Indian family with an autosomal dominant cataract phenotype allowed us to identify a novel cataract gene, CRYBA4. After a genomewide screen, linkage analysis identified a maximum LOD score of 3.20 (recombination fraction [theta] 0.001) with marker D22S1167 of the beta -crystallin gene cluster on chromosome 22. To date, CRYBA4 was the only gene in this cluster not associated with either human or murine cataracts. A pathogenic mutation was identified in exon 4 that segregated with the disease status. The c.317T-->C sequence change is predicted to replace the highly conserved hydrophobic amino acid phenylalanine94 with the hydrophilic amino acid serine. Modeling suggests that this substitution would significantly reduce the intrinsic stability of the crystalline monomer, which would impair its ability to form the association modes critical for lens transparency. Considering that CRYBA4 associates with CRYBB2 and that the latter protein has been implicated in microphthalmia, mutational analysis of CRYBA4 was performed in 32 patients affected with microphthalmia (small eye). We identified a c.242T-->C (Leu69Pro) sequence change in exon 4 in one patient, which is predicted here to disrupt the beta -sheet structure in CRYBA4. Protein folding would consequently be impaired, most probably leading to a structure with reduced stability in the mutant. This is the first report linking mutations in CRYBA4 to cataractogenesis and microphthalmia.
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http://dx.doi.org/10.1086/507712DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1592554PMC
October 2006

A novel human sex-determining gene linked to Xp11.21-11.23.

J Clin Endocrinol Metab 2006 Oct 25;91(10):4028-36. Epub 2006 Jul 25.

Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.

Context: The molecular basis for about 70-80% of 46,XY sex-reversed females remains unexplained, because they carry normal copies of the genes (SRY, SOX9, DAX1, DMRT, SF1, WT1) involved in sex determination pathway.

Objective: The objective of this study is to map the chromosomal locus responsible for an unexplained sex-reversed phenotype.

Design: The study implemented a genome-wide scan using families with multiple sex-reversed individuals.

Setting: The patients, along with the family members, were selected from different hospitals/reproductive centers.

Participants: Sex-reversed individuals and their siblings and parents participated in the study.

Main Outcome Measures: Identification of the chromosomal locus responsible for sex reversal in these families and sequence analysis of candidate genes were the main outcome measures.

Results: Parametric linkage analysis revealed a maximum two-point LOD score of 5.70 with marker DXS991 (Xp11.21) and 4.57 with marker DXS1039 (Xp11.23-Xp11.22), and a multipoint LOD score of 5.77 with marker DXS991 and 5.22 with marker DXS1039. The two markers (DXS991 and DXS1039) with highest LOD score span approximately 3.41 cM (75.79-79.2 cM) on the short arm of the X-chromosome.

Conclusion: Our findings provide evidence for a major susceptibility locus for sex reversal/gonadal dysgenesis on the short arm of the X-chromosome (Xp11.21-11.23). Furthermore, molecular exploration of the expression of candidate genes in the embryonic gonad/gonadal ridge will help in the identification of the underlying gene for sex reversal.
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http://dx.doi.org/10.1210/jc.2006-0950DOI Listing
October 2006

Identification of a novel, putative cataract-causing allele in CRYAA (G98R) in an Indian family.

Mol Vis 2006 Jul 12;12:768-73. Epub 2006 Jul 12.

Dr. ALM. Postgraduate Institute of Basic Medical Sciences, Department of Genetics, University of Madras, Taramani, Chennai, India.

Purpose: The aim of the present study was to investigate the molecular basis underlying a nonsyndromic presenile autosomal dominant cataract in a three-generation pedigree. The phenotype was progressive from a peripheral ring-like opacity to a total cataract with advancing age from teenage to adulthood. The visual impairment started as problem in distant vision at the age of 16 years, to diminishing vision by the age of 24.

Methods: Clinical interventions included complete ophthalmological examination, a collection of case history, and pedigree details. Blood samples were collected from available family members irrespective of their clinical status. A functional candidate gene approach was employed for PCR screening and sequencing of the exons and their flanking regions of CRYGC, CRYGD, and CRYAA genes. For structural consequences of the mutated alphaA-crystallin we used the bioinformatics tool of the ExPASy server.

Results: Sequence analysis of CRYGC and CRYGD genes excluded possible causative mutations but identified known polymorphisms. Sequencing of the exons of the CRYAA gene identified a sequence variation in exon 2 (292 G->A) with a substitution of Gly to Arg at position 98. All three affected members revealed this change but it was not observed in the unaffected father or sister. The putative mutation obliterated a restriction site for the enzyme BstDSI. The same was checked in controls representing the general population of the same ethnicity (n=30) and of randomly selected DNA samples from ophthalmologically normal individuals from the population-based KORA S4 study (n=96). Moreover, the Gly at position 98 is highly conserved throughout the animal kingdom. For the mutant protein, the isoelectric point was raised from pH 5.77 to 5.96. Moreover, an extended alpha-helical structure is predicted in this region.

Conclusions: The G98R mutation segregates only in affected family members and is not seen in representative controls. It represents very likely the fourth dominant cataract-causing allele in CRYAA. In all reported alleles the basic amino acid Arg is involved, suggesting the major importance of the net charge of the alphaA-crystallin for functional integrity in the lens.
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July 2006

Protective effect of saffron (Crocus sativus L.) aqueous extract against genetic damage induced by anti-tumor agents in mice.

Hum Exp Toxicol 2006 Feb;25(2):79-84

Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani, Chennai 600-113, India.

The genotoxic potential of anti-tumor drugs limits their efficacy in the treatment of cancers. Since ancient times, saffron (dried stigmas of Crocus sativus L.) has been used as a spice and medicinal herb. Saffron is a rich source of carotenoids and is known for its anti-cancer and anti-tumor properties. The present study was designed to ascertain the chemoprotective potential of saffron against the genotoxicity of three well-known anti-tumor drugs-cisplatin (CIS), cyclophosphamide (CPH) and mitomycin-C (MMC)--using comet assay. Three doses of saffron (20, 40 and 80 mg/kg b.w.) were orally administered to mice for five consecutive days prior to the administration of anti-tumor drugs under investigation. Pre-treatment with saffron significantly inhibited anti-tumor drugs induced cellular DNA damage (strand breaks) as revealed by decreased comet tail length, tail moment and percent DNA in the tail. These findings, together with our previous results, suggest a potential role for saffron as an anti-genotoxic, anti-oxidant and chemopreventive agent and could be used as an adjuvant in chemotherapeutic applications.
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http://dx.doi.org/10.1191/0960327106ht589oaDOI Listing
February 2006

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

Asia Pac J Clin Nutr 2006 ;15(1):119-24

Department of Genetics, Dr. A. L. M. Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani. Chennai--600113, India.

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.
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June 2006

Mutation analysis of congenital cataracts in Indian families: identification of SNPS and a new causative allele in CRYBB2 gene.

Invest Ophthalmol Vis Sci 2004 Oct;45(10):3599-607

Dr. ALM Postgraduate Institute of Basic Medical Sciences, Department of Genetics, University of Madras, Taramani, Chennai, India.

Purpose: To study some functional candidate genes in cataract families of Indian descent.

Methods: Nine Indian families, clinically documented to have congenital/childhood cataracts, were screened for mutations in candidate genes such as CRYG (A-->D), CRYBB2, and GJA8 by PCR analyses and sequencing. Genomic DNA samples of either probands or any representative affected member of each family were PCR amplified and sequenced commercially. Documentation of single nucleotide polymorphisms (SNPs) and candidate mutations was done through BLAST SEARCH (http://www.ncbi.nlm.nih.gov/blast/Blast.cgi?).

Results: Several single nucleotide polymorphisms in CRYG, CRYBB2, and GJA8 genes were observed. Because they do not co-segregate with the phenotype, they were excluded as candidates for the cataract formation in these patients. However, a substitution (W151C in exon 6 of CRYBB2) was identified as the most likely causative mutation underlying the phenotype of central nuclear cataract in all affected members of family C176. Protein structural interpretations demonstrated that no major structural alterations could be predicted and that even the hydrogen bonds to the neighboring Leu166 were unchanged. Surprisingly, hydropathy analysis of the mutant betaB2-crystallin featuring the amino acids at position 147 to 155, further increased the hydrophobicity, which might impair the solubility of the mutant protein. Finally, the Cys residue at position 151 might possibly be involved in intramolecular disulphide bridges with other cysteines during translation, possibly leading to dramatic structural changes.

Conclusions: Exon 6 of CRYBB2 appears to be a critical region susceptible for mutations leading to lens opacity.
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http://dx.doi.org/10.1167/iovs.04-0207DOI Listing
October 2004

Interactive effects of saffron with garlic and curcumin against cyclophosphamide induced genotoxicity in mice.

Asia Pac J Clin Nutr 2004 ;13(3):292-4

Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras,Taramani, Chennai 600-113, India.

Saffron is a well-known spice and food colorant commonly consumed in different parts of the world. Recently, much attention has been focused on the biological and medicinal properties of saffron. In the present study the interactive effects of saffron with two commonly consumed dietary agents, garlic and curcumin was evaluated for anti-genotoxic effects against cyclophosphamide (CPH) in the mouse bone marrow micronucleus test. Experimental animals were orally pretreated with saffron (100 mg/kg body weight), garlic (250 mg/kg body weight) and curcumin (10 mg/kg body weight), either alone or in combination for five consecutive days, 2h prior to the administration of CPH. Maximum reduction in the frequencies of micronucleated polychromatic erythrocytes (Mn PCEs) induced by CPH was observed when all the three test compounds were administered together. Furthermore, the protective effects were more pronounced in the garlic-administered groups compared to curcumin and/or saffron administered groups.
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April 2005

Protective effect of S-allylcysteine and lycopene in combination against N-methyl-N'-nitro-N-nitrosoguanidine-induced genotoxicity.

Pol J Pharmacol 2004 Mar-Apr;56(2):241-5

Department of Biochemistry, Faculty of Science, Annamalai University, Annamalainagar-608 002, Tamil Nadu, India.

Chemoprotection by diet-derived antioxidants has emerged as a cost-effective approach in preventing genotoxicity and carcinogenicity. In this study, we investigated the protective effects of S-allylcysteine (SAC) and lycopene against N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced genotoxicity. Quantification of bone marrow micronuclei and chromosomal aberrations in male Wistar rats was used to monitor the protective effects of SAC and lycopene. Intragastric administration of MNNG (40 mg/kg) induced a significant increase in the frequency of micronuclei and chromosomal aberrations. Although pretreatment with SAC and lycopene significantly reduced the frequency of MNNG-induced bone marrow micronuclei and chromosomal aberrations, the combination of SAC and lycopene exerted a greater protective effect. These findings indicate that antioxidants such as SAC and lycopene, are effective chemoprotective agents against genotoxicity and carcinogenicity especially when used in combination.
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January 2005

Protective effect of Spirulina fusiformis on chemical-induced genotoxicity in mice.

Fitoterapia 2004 Jan;75(1):24-31

Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani, Chennai 600-113, India.

Spirulina fusiformis given by oral route to mice at doses of 250, 500 and 1000 mg kg(-1) significantly inhibit the genotoxicity induced by cisplatin and urethane. In addition, a significant reduction in the extent of lipid peroxidation with concomitant increase in the liver enzymatic (GPx, GST, SOD, CAT) and non-enzymatic (reduced glutathione) antioxidants were observed.
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http://dx.doi.org/10.1016/j.fitote.2003.07.008DOI Listing
January 2004

Inhibitory effects of aqueous crude extract of Saffron (Crocus sativus L.) on chemical-induced genotoxicity in mice.

Asia Pac J Clin Nutr 2003 ;12(4):474-6

Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani, Chennai, India.

Saffron (dried stigmas of Crocus sativus L.), was evaluated in the mouse bone marrow micronucleus test for its possible protective effects against chromosomal damage induced by cisplatin (CIS), mitomycin-C (MMC) and urethane (URE). Three doses of saffron (25, 50 and 100 mg/kg body weight) were orally administered to mice for five consecutive days prior to administration of genotoxins under investigation. From the results obtained, it was evident that the administration of 50 and 100 mg saffron/kg body weight could significantly inhibit the in vivo genotoxicity of these genotoxins. However, all the three doses of saffron were effective in exerting a protective effect against urethane.
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April 2006

N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced in vivo clastogenicity: protective effects of aqueous neem leaf extract.

Pharmazie 2003 Oct;58(10):750-2

Department of Biochemistry, Faculty of Science, Annamalai University, Annamalainagar, Tamil Nadu, India.

We evaluated the modifying effects of aqueous neem leaf extract on the in vivo clastogenicity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a potent gastric carcinogen by quantitation of micronuclei and chromosomal aberrations in metaphase cells from the bone marrow of male Wistar rats. Intraperitoneal injection of MNNG (40 mg/kg body weight) induced a significant increase in the frequency of micronuclei and chromosomal aberrations. Pretreatment with aqueous neem leaf extract (100 mg/kg body weight) significantly reduced MNNG-induced increase in micronuclei and chromosomal aberrations. These results reveal the chemoprotective potential of aqueous neem leaf extract against the clastogenic effects of MNNG.
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October 2003