Rajagopal Krishnamoorthy

Chronic low-grade inflammation is believed to contribute, at least in a subset of patients, to the development of bipolar disorder (BD). In this context, the most investigated biological marker is the acute phase response molecule, C-reactive protein (CRP). While the genetic diversity of CRP was amply studied in various pathological settings, little is known in BD. 568 BD patients along with 163 healthy controls (HC) were genotyped for the following single-nucleotide polymorphisms (SNPs) on the CRP gene: intron rs1417938 (+ 29) T/A, 3′-UTR rs1130864 (+ 1444) G/A, and downstream rs1205 (+ 1846) (C/T). The statistical analysis was performed using Chi-square testing and consisted of comparisons of allele/genotype frequencies between patients and controls and within patient sub-groups according to BD clinical phenotypes and the presence of thyroid disorders. We found that the frequencies of the studied SNPs were similar in BD and HC groups. However, the CRP rs1130864 A allele carrier state was significantly more frequent: (i) in BD patients with thyroid disorders than in those without (pc = 0.046), especially among females (pc = 0.01) and independently of lithium treatment, (ii) in BD patients with rapid cycling than in those without (pc = 0.004). Overall, our findings suggest the possibility that CRP genetic diversity may contribute to the development of auto-immune comorbid disorders and rapid cycling, both proxy of BD severity. Such findings, if replicated, may allow to predict complex clinical presentations of the disease, a possible step towards precision medicine in psychiatry.

Genetic vulnerability to environmental stressors is yet to be clarified in bipolar disorder (BD), a complex multisystem disorder in which immune dysfunction and infectious insults seem to play a major role in the pathophysiology. Association between pattern-recognition receptor coding genes and BD had been previously reported. However, potential interactions with history of pathogen exposure are yet to be explored. 138 BD patients and 167 healthy controls were tested for serostatus of Toxoplasma gondii, CMV, HSV-1 and HSV-2 and genotyped for TLR2 (rs4696480 and rs3804099), TLR4 (rs1927914 and rs11536891) and NOD2 (rs2066842) polymorphisms (SNPs). Both the pathogen-specific seroprevalence and the TLR/NOD2 genetic profiles were compared between patients and controls followed by modelling of interactions between these genes and environmental infectious factors in a regression analysis. First, here again we observed an association between BD and Toxoplasma gondii (p = 0.045; OR = 1.77; 95 % CI 1.01–3.10) extending the previously published data on a cohort of a relatively small number of patients (also included in the present sample). Second, we found a trend for an interaction between the TLR2 rs3804099 SNP and Toxoplasma gondii seropositivity in conferring BD risk (p = 0.017, uncorrected). Pathogen exposure may modulate the influence of the immunogenetic background on BD. A much larger sample size and information on period of pathogen exposure are needed in future gene–environment interaction studies.

Chronic granulomatous disease (CGD), a rare inherited disorder of the innate immune system, results from mutations in any one of the five genes encoding the subunits of the nicotinamide adenine dinucleotide phosphate‐oxidase (NADPH) oxidase enzyme, and is characterized by recurrent life‐threatening bacterial and fungal infections. Molecular analysis of 14 Omani CGD patients from 10 families, diagnosed to have CGD on clinical (recurrent infections) and biochemical grounds (positive for both the nitroblue tetrazolium (NBT) test and the dihydrorhodamine (DHR‐1,2,3 assay), revealed that only one patient had X‐linked CGD, with a large deletion involving both the gp91‐phox gene (CYBB) and the McLeod gene (XK). The remaining 13 patients were all homozygotes from a previously described c.579G>A (p.Trp193X) mutation in the NCF1 gene on chromosome 7, responsible for autosomal recessive CGD (AR‐CGD). Although X‐linked CGD is the most common type of CGD disorder in most population groups, AR‐CGD is the most prevalent type in Oman.

Introduction: Coinheritance of α‐thalassemia influences the clinical and hematological phenotypes of β‐hemoglobinopathies (β‐thalassemia and sickle cell disease) and when present together in significant frequency within a population, a spectrum of clinical forms is observed. Precise molecular characterization of α‐thalassemia is important in understanding their disease‐modifying role in β‐hemoglobinopathies and for diagnostic purposes.Patients and methods: Because currently used approaches are labor/cost‐intensive, time‐consuming, error‐prone in certain genotype combinations and not applicable for large epidemiological screening, we developed a systematic stepwise strategy to overcome these difficulties. We successfully applied this to characterize the α‐globin gene status in 150 Omani cord blood samples with Hb Barts and 32 patients with HbH disease.Results: We observed a good correlation between α‐globin genotypes and level of Hb Bart's with the Hb Bart's levels significantly higher in both deletional and non‐deletional α‐globin genotypes. The most common α‐globin genotype in HbH cases was α^TSaudiα/α^TSaudiα (n = 16; 50%) followed by −α^3.7/–^MED (n = 10; 31%). This approach detects also the α‐globin gene triplication as exemplified by the study of a family where the β‐globin gene defect failed to explain the β‐thalassemia intermedia phenotype.Conclusion: Molecular characterization of α‐thalassemia is complex due to high sequence homology between the duplicated α‐globin genes and to the existence of a variety of gene rearrangements (small and large deletions of various sizes) and punctual substitutions (non‐deletional alleles). The novelty of our strategy resides, not in the individual technical steps per se but in the reasoned sequential order of their use taking into consideration the hematological phenotype as well.

A novel β-globin gene promoter (−71 C>T) nucleotide change was recently posted to the HbVar database (ID 2701) without precision on phenotype and ethnicity. We found the same change in compound heterozygosity with Hb S [β6(A3)Glu>Val] in an Omani family with almost equal expression of Hb A and Hb S. This suggested that the −71 C to T mutation may be a mild β-thalassemic allele. Subsequent search found three other independent cases with the same atypical Hb A:Hb S ratio, further confirming the mild thalassemic feature of this mutation. In addition, molecular screening of a set of subjects (with only Hb A) with borderline Hb A₂ or MCV values revealed the presence of −71 C>T change in heterozygous state, altogether assigning the mutation as a mild β⁺ thalassemic allele. In a region such as Oman, where several genetic conditions of the red blood cell coexist (α- and β-thalassemia, Hb S, Hb D, Hb E) in significant frequencies, it is crucial to decipher the molecular basis of these atypical forms of β⁺ thalassemias, especially in a genetic counseling setting.

The N-acetyltransferase 2 (NAT2) gene plays a crucial role in the metabolism of many drugs and xenobiotics. As it represents a likely target of population-specific selection pressures, we fully sequenced the NAT2 coding region in 97 Mandenka individuals from Senegal, and compared these sequences to extant data on other African populations. The Mandenka data were further included in a worldwide dataset composed of 41 published population samples (6,727 individuals) from four continental regions that were adequately genotyped for all common NAT2 variants so as to provide further insights into the worldwide haplotype diversity and population structure at NAT2.

Busulfan-mediated endothelial damage is believed to be a common mechanism in a variety of vascular disorders that occur during haematopoietic stem cell transplantation. The alkylating capacity of busulfan is compromised in vivo by enzymatic conjugation with glutathione, principally catalysed by glutathione S-transferase alpha (GST alpha). We investigated whether the susceptibility of endothelial cells to busulfan-mediated damage is related to their intrinsic deficiency in GST alpha expression. We tested for the expression of GST alpha mRNA by real-time quantitative PCR and the GST protein by enzyme-linked immunosorbent assay in various independently derived endothelial cell types (human bone marrow-derived endothelial cell line and endothelial cells from human vein umbilical cord ) and in a control hepatic cell line, HepG2. We demonstrate that endothelial cells, contrary to hepatic cells do not express GST alpha either at mRNA or protein levels and hence are potentially susceptible to busulfan-mediated cytotoxic damage.