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The rationale of the current study was to test the clinical utility of the folate pathway genetic polymorphisms in predicting the risk for autism spectrum disorders (ASD) and to address the inconsistencies in the association of MTHFR C677T and hyperhomocysteinemia with ASD.An artificial neural network (ANN) model was developed from the data of 138 autistic and 138 nonautistic children using GCPII C1561T, SHMT1 C1420T, MTHFR C677T, MTR A2756G, and MTRR A66G as the predictors of autism risk. A neuro fuzzy model was developed to explore the genetic determinants of homocysteine. Meta-analyses were carried out on 1361 ASD children and 6591 nonautistic children to explore the association of MTHFR C677T and homocysteine with the risk for ASD.The ANN model showed 63.8% accuracy in predicting the risk of autism. Hyperhomocysteinemia was observed in autistic children (9.67±4.82 vs. 6.99±3.21 μmol/l). The neuro fuzzy model showed synergistic interactions between MTHFR C677T and MTRR A66G inflating homocysteine levels. The meta-analysis showed MTHFR to be a genetic risk factor for autism in both fixed-effects (odds ratio: 1.47, 95% confidence interval: 1.31-1.65) and random-effects (odds ratio: 1.57, 95% confidence interval: 1.16-2.11) models. The meta-analysis of nine studies showed hyperhomocysteinemia as a significant risk factor for autism in both fixed-effects (P0.0001) and random-effects (P=0.026) models.Genetic polymorphisms of the folate pathway were moderate predictors of autism risk. MTHFR C677T and hyperhomocysteinemia have been identified as risk factors for autism worldwide. Synergistic interactions between MTHFR C677T and MTRR A66G increase homocysteine.

Beta-ketothiolase deficiency (mitochondrial acetoacetyl-CoA thiolase (T2) deficiency) is an inherited disease of isoleucine catabolism and ketone body utilization caused by ACAT1 mutations. We identified ten Indian patients who manifested with ketoacidotic episodes of variable severity. The patients showed increased urinary excretion of isoleucine-catabolic intermediates: 2-methyl-3-hydroxybutyrate, 2-methylacetoacetate, and tiglylglycine. Six patients had a favorable outcome, one died, and three developed neurodevelopmental sequela. Mutational analysis revealed a common (p.Met193Arg) and four novel (p.Ile323Thr, p.Ala215Asn, c.1012_1015dup, and c.730+1G>A) ACAT1 mutations. Transient expression analyses of wild-type and mutant cDNA were performed at 30, 37, and 40°C. A p.Ile323Thr mutant T2 was detected with relative enzyme activity and protein amount of 20% and 25%, respectively, compared with wild type at 37°C; it was more prevalent at 30°C but ablated at 40°C. These findings showed that p.Ile323Thr had a significant residual T2 activity with temperature-sensitive instability. Neither residual enzymatic activity nor mutant T2 protein was identified in p.Met193Arg, p.Ala215Asn, and c.1012_1015dup mutations using supernatants; however, these mutant T2 proteins were detected in insoluble pellets by immunoblot analysis. Expression analyses confirmed pathogenicity of these mutations. T2 deficiency has a likely high incidence in India and p.Met193Arg may be a common mutation in the Indian population.

Objectives In view of high incidence of methylmalonic aciduria (MMA) among South Indians, we have performed clinical, biochemical and molecular genetic evaluation of fifteen patients. Design and methods Targeted exome sequencing was performed for a panel of MMA causing genes i.e. MUT , ABCD4 , ACSF3 , CD320 , LMBRD1 , MCEE , MMAA , MMAB , MMACHC , MMADHC . Results Methylmalonyl-CoA mutase ( MUT ), MMAB and MMAA genetic variants were found to contribute towards 40%, 33.3% and 6.6% etiology, respectively. Early onset of the disease (during the neonatal period) and presence of MUT and MMAB genetic variants was shown to be associated with higher mortality. The patients with MMAA variants had a milder disease. Among the identified mutations, 66% were already known. Three novel mutations, i.e. MUT p.Ala376Serfs, MMAB p.Glu112* and MMAA p.Tyr24* were identified. We also report three novel variants with predicted pathogenicity, MMAA intron 3 c.562 + 1_562 + 2insT, p.Ala668Pro in exon 12 of one of the alleles of the MUT gene and c.519 + 1G > A in intron 6 of one of the alleles in MMAB gene. We performed prenatal diagnosis in five of these families. Conclusions MMA among South Indian patients is genetically heterogeneous, caused by different complementation groups. Both B12-responsive and non-responsive patients were diagnosed. In biochemically diagnosed patients, targeted exome sequencing is cost effective to identify different MMA causing mutations and facilitate genetic counseling.

Summary Background Hypohidrotic/anhidrotic ectodermal dysplasia (HED) is a rare Mendelian disorder affecting ectodermal tissues. The disease is primarily caused by inactivation of any one of three genes, namely ectodysplasin A1 (EDA-A1), which encodes a ligand belonging to the tumour necrosis factor (TNF) superfamily; ectodysplasin A receptor (EDAR), encoding the EDA-A1 receptor and ectodysplasin A receptor-associated death domain (EDARADD), encoding an adaptor protein. X-linked recessive (EDA-A1), the predominant form of HED, as well as autosomal recessive and dominant (EDAR and EDARADD) inheritance patterns have been identified in affected families. Objectives To determine the common genes causing HED in India. Methods We performed mutation analysis on 26 HED families from India (including 30 patients). In addition, we carried out sequence and structural analysis of missense/nonsense and insertion/deletion mutations. Results Among the 26 families analysed, disease-causing EDAR mutations were identified in 12 (46%) while EDA-A1 mutations were detected in 11 (42%). Four novel mutations in EDAR and five in EDA-A1 were identified. More importantly, a possible founder EDAR mutation, namely c.1144G>A, was identified in five independent families, thus accounting for about one-fifth of affected families in whom mutation was detected. A majority of EDA-A1 mutations localized to the TNF-like domain while the location of EDAR mutations was more widespread. Conclusions This is the first report of a founder EDAR mutation and of a significantly high frequency of autosomal recessive HED.

SummaryNephronophthisis (NPHP), Joubert (JBTS), and Meckel-Gruber (MKS) syndromes are autosomal-recessive ciliopathies presenting with cystic kidneys, retinal degeneration, and cerebellar/neural tube malformation. Whether defects in kidney, retinal, or neural disease primarily involve ciliary, Hedgehog, or cell polarity pathways remains unclear. Using high-confidence proteomics, we identified 850 interactors copurifying with nine NPHP/JBTS/MKS proteins and discovered three connected modules: “NPHP1-4-8” functioning at the apical surface, “NPHP5-6” at centrosomes, and “MKS” linked to Hedgehog signaling. Assays for ciliogenesis and epithelial morphogenesis in 3D renal cultures link renal cystic disease to apical organization defects, whereas ciliary and Hedgehog pathway defects lead to retinal or neural deficits. Using 38 interactors as candidates, linkage and sequencing analysis of 250 patients identified ATXN10 and TCTN2 as new NPHP-JBTS genes, and our Tctn2 mouse knockout shows neural tube and Hedgehog signaling defects. Our study further illustrates the power of linking proteomic networks and human genetics to uncover critical disease pathways.

Analysis of seven Indian phenylketonuria families has revealed four novel mutations in the phenylalanine hydroxylase gene; two affected consensus splice sequence and the 3' UTR, respectively, while the other two were single base insertion and deletion mutations, respectively. A novel 3' splice site mutation c.168-2A>G resulted in the activation of a cryptic 3' splice site that generated a premature termination codon leading to very low levels of the mutant transcript, probably due to activation of the nonsense-mediated decay (NMD) pathway. This is probably the first report of PKU caused by the activation of NMD.

Background Hyperhomocysteinemia, a documented risk factor for CAD is highly prevalent in Indians. The rationale behind the current study is to explore the genetic and environmental causes for such high prevalence as there are limited studies in this context. Methods A total of 108 CAD cases and 108 controls were analyzed for tHcy and 4 folate pathway genetic polymorphisms [methylene tetrahydrofolate reductase (MTHFR) C677T, 5-methyltetrahydrofolate homocysteine methyl transferase (MTR) A2756G, methionine synthase reductase (MTRR) A66G and glutamate carboxypeptidase II (GCPII) C1561T] using reverse phase HPLC and PCR–RFLP methods respectively. Results MTHFR 677T, MTRR 66A, GCPII 1561T, male gender, alcohol intake, smoking, diabetes, creatinine and hypertension were found to influence tHcy. After controlling for confounding factors, Hyperhomocysteinemia and two of its genetic determinants i.e. MTHFR C677T [OR: 1.96, 95% CI: 1.06–3.61] and GCP II C1561T [OR: 2.09, 95% CI: 1.09–3.97] were found to be associated with risk for CAD. Significant epistatic interactions were observed between MTHFR 677T/MTR 2756G and GCP II 1561T/MTRR 66G. Alcohol intake in subjects with MTR 2756G allele was found to inflate the risk for CAD [OR: 4.15, 95% CI: 1.35–12.69]. Conclusion Hyperhomocysteinemia, C677T MTHFR and C1561T GCPII are risk factors for CAD. Potential gene — gene and gene — environment interactions indicate the need for multi-variate analyses for risk prediction.

To investigate the role of methylene tetrahydrofolate reductase (MTHFR) (677 C-->T and 1298 A-->C), factor V (1691 G-->A), factor II (20210 G-->A) genetic polymorphisms and hyperhomocysteinemia in the aetiology of deep vein thrombosis (DVT) in 163 cases and 163 controls. Polymerase chain reaction-restriction fragment length polymorphism was used for genotyping, reverse-phase high-performance liquid chromatography for plasma homocysteine, and Student's t-test and Fisher exact tests were used for statistical analysis. Elevated mean plasma homocysteine levels were observed in DVT cases irrespective of gender differences. Homocysteine elevation above the 95th percentile of the control group associated with 9.4-fold and 7.6-fold increased risk for DVT in men and women, respectively. Genotyping showed the MTHFR 677CT/1298AC genotype (i.e. compound heterozygosity) is associated with 3.5-fold risk for thrombosis. The factor V Leiden mutation frequency was higher in DVT cases, but not statistically significant; however, genetic predisposition to this mutation was associated with early age of DVT onset. Factor II mutation was absent in cases and controls. Co-segregation of two or more risk factors was associated with 11.7-fold increased risk for thrombosis. This study projects that hyperhomocysteinemia and compound heterozygous state for MTHFR are independent risk factors for DVT among South Indians.

Farber disease is a rare lysosomal storage disorder caused by a deficiency of the acid ceramidase enzyme, leading to the accumulation of ceramide in various tissues. It usually manifests within a few months after birth with a unique triad of symptoms, including painful and progressive deformed joints, progressive hoarseness and subcutaneous nodules. The disease is inherited as an autosomal recessive trait, and mutations in the N-acylsphingosine amidohydrolase (ASAH1) gene, which codes for the acid ceramidase enzyme, have been shown to cause the disease. In the current study, we report the identification of a novel disease-causing mutation in the ASAH1 gene that results in Farber disease in an Indian family. The mutation was identified in the eighth exon and is a missense mutation resulting in replacement of Valine by Leucine at codon 182. Two affected siblings harboured the identical mutation. The possible mechanism(s) of disease caused by this mutation are discussed.

Expanded newborn screening (NBS) is aimed for early detection and intervention of treatable inborn errors of metabolism and also to establish incidence of these disorders in this part of the globe. The first expanded NBS programme initiated in the capital city of Andhra Pradesh to screen all the newborns born in four major Government Maternity Hospitals in Hyderabad by heel prick capillary blood collected on SS 903 filter paper. Chromatographic (TLC and HPLC), electrophoretic (cellulose acetate and agarose) and ELISA based assays have been employed for screening of common inborn errors of metabolism. This study has shown a high prevalence of treatable Inborn errors of metabolism. Congenital hypothyroidsm is the most common disorder (1 in 1700) followed by congenital Adrenal Hyperplasia (1 in 2575) and Hyperhomocystenemia (1 in 100). Interestingly, a very high prevalence of inborn errors of metabolism to the extent of 1 in every thousand newborns was observed. The study reveals the importance of screening in India, necessitating nation wide large-scale screening.

In order to ascertain whether autistic children display characteristic metabolic signatures that are of diagnostic value, plasma amino acid analyses were carried out on a cohort of 138 autistic children and 138 normal controls using reverse-phase HPLC. Pre-column derivatization of amino acids with phenyl isothiocyanate forms phenyl thio-carbamate derivates that have a lamba(max) of 254 nm, enabling their detection using photodiode array. Autistic children showed elevated levels of glutamic acid (120 +/- 89 vs. 83 +/- 35 micromol/L) and asparagine (85 +/- 37 vs. 47 +/- 19 micromol/L); lower levels of phenylalanine (45 +/- 20 vs. 59 +/- 18 micromol/L), tryptophan (24 +/- 11 vs. 41 +/- 16 micromol/L), methionine (22 +/- 9 vs. 28 +/- 9 micromol/L) and histidine (45 +/- 21 vs. 58 +/- 15 micromol/L). A low molar ratio of (tryptophan/large neutral amino acids) x 100 was observed in autism (5.4 vs 9.2), indicating lesser availability of tryptophan for neurotransmitter serotonin synthesis. To conclude, elevated levels of excitatory amino acids (glutamate and asparagine), decreased essential amino acids (phenylalanine, tryptophan and methionine) and decreased precursors of neurotransmitters (tyrosine and tryptophan) are the distinct characteristics of plasma amino acid profile of autistic children. Thus, such metabolic signatures might be useful tools for early diagnosis of autism.

Methylene tetrahydrofolate reductase (MTHFR) C677T polymorphism shows considerable heterogeneity in its distribution in humans worldwide. The current study was conducted to investigate whether this polymorphism exhibited adaptive developmental plasticity in the control of the TT-genotype frequency. We screened 1,818 South Indian subjects (895 males and 923 females) for MTHFR C677T polymorphism using PCR–restriction fragment length polymorphism approach. MTHFR 677T-allele frequency in males and females was 9.1 and 11.0 %, respectively. Compared to females, males had lower frequency of TT-genotype [odds ratio 0.31, 95 % confidence interval (CI) 0.08–1.01]. The frequency of MTHFR 677T-allele was highest in the age group of 20–40 years and it gradually decreased from 40–60 to 60–80 years (P trend

Phenylketonuria (PKU) is an autosomal recessive metabolic disorder caused by mutational inactivation of the phenylalanine hydroxylase (PAH) gene. Missense mutations are the most common PAH mutation type detected in PKU patients worldwide. We performed PAH mutation analysis in 27 suspected Indian PKU families (including 7 from our previous study) followed by structure and function analysis of specific missense and splice/insertion-deletion/nonsense mutations, respectively. Of the 27 families, disease-causing mutations were detected in 25. A total of 20 different mutations were identified of which 7 "unique" mutations accounted for 13 of 25 mutation positive families. The unique mutations detected exclusively in Indian PKU patients included three recurrent mutations detected in three families each. The 20 mutations included only 5 missense mutations in addition to 5 splice, 4 each nonsense and insertion-deletion mutations, a silent variant in coding region and a 3'UTR mutation. One deletion and two nonsense mutations were characterized to confirm significant reduction in mutant transcript levels possibly through activation of nonsense mediated decay. All missense mutations affected conserved amino acid residues and sequence and structure analysis suggested significant perturbations in the enzyme activity of respective mutant proteins. This is probably the first report of identification of a significantly low proportion of missense PAH mutations from PKU families and together with the presence of a high proportion of splice, insertion-deletion, and nonsense mutations, points to a unique PAH mutation profile in Indian PKU patients.

Beta-ketothiolase deficiency, or mitochondrial acetoacetyl-CoA thiolase (T2) deficiency, is a rare autosomal recessive disorder affecting isoleucine catabolism and ketone body metabolism. A patient from South India presented with acute ketoacidosis at 11 months of age. During the acute crisis the C5OH (2-methyl-3-hydroxybutyryl) carnitine and C5:1 (tiglyl) carnitine were elevated and large amounts of 2-methyl-3-hydroxybutyrate, tiglylglycine, and 2-methylacetoacetate were excreted. Brain CT showed bilateral basal ganglia lesions. Potassium ion-activated acetoacetyl-CoA thiolase activity was deficient in the patient's fibroblasts. The patient is a homozygote for a novel c.578T>G (M193R) mutation. This is the first report of T2 deficiency confirmed by enzyme and molecular analysis from India.

Background: Androgen insensitivity syndrome (AIS) is a rare X-linked disorder due to mutations in the androgen receptor (AR) gene causing end-organ resistance to the androgenic hormone. Subjects and Methods: Genetic studies were carried out in two families by karyotype and targeted exome sequencing of the AR gene. Results: Two novel missense mutations were identified, p.L822P and p.P392S, in two families with complete androgen insensitivity (CAIS) and partial androgen insensitivity (PAIS), respectively. Both had 46, XY karyotype. The mother was a heterozygous carrier in PAIS and negative in CAIS. These two were novel mutations, reported for the first time, in the AR gene. In silico analysis predicted that both mutations were damaging. We reviewed the various reported Indian mutations in the AR gene. Conclusion: AR gene mutations cause a wide spectrum of disorders from CAIS to male infertility or primary amenorrhea. Early diagnosis is essential for gender assignment and further management, family counseling, and prenatal diagnosis.

Maple Syrup Urine Disease is a rare metabolic disorder caused by reduced/absent activity of the branched chain a-Ketoacid dehydrogenase enzyme complex. Mutations in BCKDHA, BCKDHB, and DBT, that encode important subunits of the enzyme complex namely E1a ,E 1b, and E2, are the primary cause for the disease. We have performed the first molecular genetic analysis of MSUD from India on nine patients exhibiting classical MSUD symptoms. BCKDHA and BCKDHB mutations were identified in four and five patients, respectively including seven novel mutations namely the BCKDHA c.1249delC, c.1312T>C, and c.1561T>A and the BCKDHB c.401T>A, c.548G>A, c.964A>G, and c.1065delT. The BCKDHB c.970C>T (p.R324X) mutation was shown to trigger nonsense mediated decay-based degradation of the transcript. Seven of the total 11 mutations resulted in perturbations in the E1a or E1b C-termini either through altered termination or through an amino acid change; these are expected to result in disruption of E1 enzyme complex assembly. Our study has therefore revealed that BCKDHA and BCKDHB mutations might be primarily responsible for MSUD in the Indian population. J. Cell. Biochem. 113: 3122–3132, 2012.

Aim: To investigate the role of four parental folate pathway single nucleotide polymorphisms (SNPs) i.e., methylene tetrahydrofolate reductase (MTHFR) 677C>T, MTHFR 1298A>C, methionine synthase reductase (MTRR) 66A>G and glutamate carboxypeptidase (GCP) II 1561C>T on susceptibility to neural tube defects (NTDs) in 50 couples with NTD offspring and 80 couples with normal pregnancy outcome. Results: Maternal MTHFR 677C→T (odds ratio (OR): 2.69, 95% confidence interval (CI): 1.35–5.34) and parental GCP II 1561C→T (maternal: OR: 1.89, 95% CI: 1.12–3.21 and paternal: OR: 3.23, 95% CI: 1.76–5.93) were found to be risk factors for a NTD. Both paternal and maternal GCP II T-variant alleles were found to interact with MTHFR 677T- and MTRR G-variant alleles in increasing the risk for NTD. Segregation of data based on type of defect revealed an association between maternal 677T-allele and meningomyelocele (OR: 9.00, 95% CI: 3.77–21.55, P

Objective To investigate whether genetic polymorphismsare the underlying causes for aberrations in folate pathwaythat was reported in autistic children.Basic methods A total of 138 children diagnosed asautistic based on Diagnostic and Statistical Manualof Mental Disorders, fourth edition criteria and AutismBehavior Checklist scoring and 138 age and sex matchedchildren who are nonautistic were tested for five geneticpolymorphisms, that is, cytosolic serine hydroxyl methyltransferase (SHMT1 C1420T), methylene tetrahydrofolatereductase (MTHFR C677T and MTHFR A1298C),methionine synthase reductase (MTRR A66G),methionine synthase (MS A2756G) using PCR-restrictionfragment length polymorphism methods. Fisher exacttest and logistic regression analysis were used forstatistical analyses.Results MTHFR 677T-allele frequency was found tobe higher in autistic children compared with nonautisticchildren (16.3 vs. 6.5%) with 2.79-fold increased riskfor autism [95% confidence interval (CI): 1.58–4.93]. Thefrequencies of MTRR 66A allele (12.7 vs. 21.0%) and SHMT1420T allele (27.9 vs. 45.3%) were lower in autistic groupcompared with nonautistic group with odds ratios 0.55(95% CI: 0.35–0.86) and 0.44 (95% CI: 0.31–0.62),respectively, indicating reduced risk. MTHFR 1298C-allelefrequency was similar in both the groups (53.3 vs.53.6%) and hence individually not associated withany risk. However, this allele was found to act additivelyin presence of MTHFR 677T allele as evidenced by8.11-fold (95% CI: 2.84–22.92) risk associated withMTHFR 677CT+TT/1298AC+CC genotypes cumulatively.Conclusion MTHFR C677T is a risk factor, whereasMTRR A66G and SHMT C1420T polymorphismsreduce risk for autism. MTHFR A1298C actsadditively in increasing the risk for autism. Psychiatr Genet00:000–000

Objectives To investigate the association of parental hyperhomocysteinemia, C677T Methylene tetrahydrofolate reductase (MTHFR) polymorphism and DNA damage with recurrent pregnancy loss (RPL). Design and methods A case-control study. Reverse phase HPLC, PCR-RFLP and Cytokinesis blocked micronuclei assay were used to assess total plasma homocysteine, C677T MTHFR polymorphism and DNA damage respectively. Student t-test, ANOVA and Fisher exact test were used for statistical analysis. Results Maternal [mean: 11.6 ± 5.0 versus 8.6 ± 4.2 μmol/L, odds ratio (OR): 4.48] and paternal [mean: 19.6 ± 9.5 versus 14.2 ± 7.4 μmol/L, OR: 6.92] hyperhomocysteinemia, paternal age [OR: 1.16], paternal MTHFR 677T allele [OR: 2.30] and DNA damage were found to increase the risk for RPL. DNA damage showed positive correlation with plasma homocysteine and MTHFR 677T allele. Conclusions Parental hyperhomocysteinemia, paternal age, paternal C677T MTHFR polymorphism and DNA damage are risk factors for RPL. DNA damage showed positive correlation with plasma homocysteine and MTHFR 677T allele.

Background The rationale behind this study was to examine the relationship between polymorphisms in genes that regulate remethylation of homocysteine to methionine, i.e., methionine synthase (MTR A2756G) and methionine synthase reductase (MTRR A66G), and risk of deep vein thrombosis (DVT) in a South Indian cohort (163 DVT cases and 163 controls), as elevated homocysteine has been documented as an independent risk factor for DVT in the same cohort. Methods Plasma homocysteine analysis was carried out by reverse phase HPLC. The MTR A2756G and MTRR A66G genetic polymorphisms were detected using PCR-restriction fragment length polymorphism method. For statistical analyses, Fisher's exact test was used for categorical variables and Student's t-test and analysis of variance were used for continuous variables. Results The MTRR 66GG genotype was associated with a 2.74-fold [95% confidence interval (CI): 1.73, 4.34] risk of DVT. The MTR A2756G polymorphism was not a risk factor. MTRR GG/MTR AG and MTRR GG/MTR GG genotypes cumulatively were found to increase the risk of DVT by 2.38-fold (95% CI: 1.43, 3.96). A positive association was observed between plasma homocysteine and the MTRR G allele, and the MTR G allele was shown to have an additive effect. The risk associated with the MTRR 66GG genotype was further increased in subjects compound heterozygous for methylene tetrahydrofolate reductase (MTHFR) [odds ratio (OR): 3.46, 95% CI: 1.38, 8.63]. Conclusions The MTRR 66GG genotype is a risk factor for DVT among South Indians. This risk is increased further in the presence of the MTHFR 677CT/1298AC genotype.

beta-Thalassemia is the most prevalent single-gene disorder. Since no viable forms of treatment are available, the best course is prevention through prenatal diagnosis. In the present study, the prevalence of beta-thalassemia was extensively investigated in the South Indian population, especially from the state of Andhra Pradesh. Screening for causal mutations was carried out on genomic DNA isolated from patient blood samples by using the routine reverse dot blot (RDB) and amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) techniques. DNA sequencing was performed wherever necessary. Among the nine mutations identified, four, including IVS-1-5 (G-C) (IVS1+5GT), codon 41/42 (-TTCT) (c.124_127delTTCT), codon 15 (G-A) (c.47GA), and HbS (sickle mutation) (c.20AT) mutations, accounted for about 98% of the total positive cases. Two mutations viz. codon 8/9 (+G) (c.27_28insG) and HbE (codon 26 G-A) (c.79GA) exhibited a very low frequency of occurrence, whereas the IVS-1-1 (G-T) (IVS1+1GT) and the 619 bp deletion (c.366_494del) mutations were absent. We also identified certain rare mutations during the diagnostic evaluation. Gene sequencing confirmed the codon 30 (G-C) (c.92GC) mutation and the rare codon 5 (-CT) (c.17_18delCT) and IVS-II-837 (T-G) (IVSII-14TG) mutations. This is the first report of the IVS II 837 mutation in the Indian population. We also report a novel diagnostic application during RDB-based screening for the detection of the (c.92GC) mutations. Such a comprehensive mutation screening is essential for prenatal diagnosis of beta-thalassemia and control of this highly prevalent monogenic disorder in the Indian population.

a Laboratory of Molecular Oncology, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, India Diagnostics Division, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, India c Laboratory of Molecular and Cellular Biology, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, India d Sir Ganga Ram Hospital, Delhi, India Amrita Institute of Medical Sciences and Research Center, Cochin, India Centre for Human Genetics, Bangalore, India

Consanguineous marriages are strongly favoured in the state of Karnataka. Of 65,492 marriages studied 33.07% were consanguineous, equivalent to a coefficient of inbreeding (F) of 0.0298. The twinning rate was low, 6.9 per thousand, whereas the secondary sex ratio, 0.5221, was higher than in comparable major human populations. Consanguinity exerted no significant effect on either parameter. The results also indicate that consanguinity is not associated with excess antenatal losses and suggest the possibility of enhanced selection against mutations at X chromosome loci.

Consanguineous marriages have been favoured throughout South India for many generations. On theoretical grounds it was proposed that long-term inbreeding would have resulted in the elimination of deleterious, recessive lethal and sub-lethal genes. As part of a newborn screening programme for amino acidopathies, data were collected on the level of inbreeding in the current populations of the cities of Bangalore and Mysore, and on the relationship between consanguinity and mean numbers of liveborn and living children. Mean cnonsanguinity was 32.24%, equivalent to a cuoefficient of inbreeding in the newborns,F = 00271. There were no significant differences between the various inbreeding classes in the number of liveborn or living children, nor was a significant consanguinity-related effect on the proportion of survivors detectable. In the light of these findings, the effects on the gene pool of multiple generations of inbreeding are discussed.

The inbreeding patterns and coefficient of inbreeding (F) of 3,350 new-borns in Bangalore, Karnataka were determined. A total of 29.24% were born of consanguineous marriages, F = 0.02313. Inbreeding was most common among the Hindus: 23.56% of their marriages were uncle-niece, F for the group was 0.02670.

Consanguineous marriages are strongly favoured among the peoples of South India. Because of the potential genetic risks resulting from inbreeding, a neonatal screening project was established in 1980 in the state of Karnataka for the identification of amino acidaemias. To date, blood samples obtained by toe-stab from 98,256 neonates have been tested by thin layer chromatography, with 46 single and 70 general amino acidaemias detected. The coefficients of inbreeding (F) for the two groups of neonates were 0.0336 and 0.0350, by comparison with a previously determined F value for the general, new-born population of 0.0298. The most common single abnormality detected was tyrosinaemia, with spontaneous resolution in the majority of cases.