Gustavo Barcelos Barra

Selenoprotein-Related Disease in a Young Girl Caused by Nonsense Mutations in the SBP2 Gene

CONTEXT Selenoproteins are essential for life, and their biosynthesis requires the incorporation of the rare amino acid selenocysteine (Sec) in a process mediated by the Sec insertion sequence-binding protein 2 (SBP2). Although SBP2 is considered a rate-limiting factor mediating Sec incorporation, there has been little evidence so far linking SBP2 dysfunction to widespread selenoprotein-related disease. OBJECTIVE The objective of the study was to report the discovery of novel truncation mutations in the SBP2 gene (R120X/R770X) in a female adolescent and the clinical consequences of the combined deficiency of selenoproteins. SUBJECTS AND METHODS A 12-yr-old girl who presented with a syndrome of abnormal thyroid hormone metabolism, delayed bone maturation, congenital myopathy, and impaired mental and motor coordination development and her family were studied. The coding region of the SBP2 gene was analyzed by sequencing, and gel shift assays were performed to address the in vitro binding properties of the mutant SBP2 protein. RESULTS Serum levels of selenium and glutathione peroxidase in the proband were reduced, and selenoprotein P levels were undetectable. DNA sequencing of the SBP2 gene revealed a compound heterozygous mutation (R120X/R770X). The R120X mutation disrupted all functional motifs and the R770X inhibited the binding of SBP2 to Sec insertion sequence elements. Interestingly, selenium supplementation normalized serum selenium and glutathione peroxidase but not selenoprotein P levels and did not restore thyroid hormone metabolism dysfunction. CONCLUSIONS This distinctive phenotype can only be explained by the combined deficiency of functionally important selenoproteins and pinpoints the clinical relevance of selenoproteins and selenium economy in human development.

The Wnt signaling pathway and rheumatoid arthritis.

The Wnt signaling pathways play a key role in cell renewal, and there are two such pathways. In patients with rheumatoid arthritis (RA), the synovial membrane expresses genes such as Wnt and Fz at higher levels than those observed in patients without RA. The Wnt proteins are glycoproteins that bind to receptors of the Fz family on the cell surface. The Wnt/Fz complex controls tissue formation during embryogenesis, as well as throughout the process of limb development and joint formation. Recent studies have suggested that this signaling pathway plays a role in the pathophysiology of RA. Greater knowledge of the role of the Wnt signaling pathway in RA could improve understanding of the differences in RA clinical presentation and prognosis. Further studies should also focus on Wnt family members as molecular targets in the treatment of RA.

Mecanismo molecular da ação do hormônio tireoideano

Thyroid hormones (TH) are involved in normal differentiation, growth, and metabolism in several tissues of all vertebrates. Their actions are mediated by the TH receptors (TRs), members of the nuclear hormone receptor superfamily. These receptors are transcription factors that bind to DNA on specific sequences, the TR response element (TREs), in promoters of target genes. Two genes encode TRs, a e b, located in chromosomes 17 and 3, respectively. These isoforms show different functions and exhibit a tissue specific expression. TRs function as monomers, homodimers or heterodimers with retinoid X receptor (RXR) and modulate transcription activity (repression or activation) by interacting with co-repressor and co-activators, which associate with TR in the absence or presence of T3, respectively. Understanding the molecular mechanism of TR action and the definition of its crystallographic structure will provide new insights into transcription mechanisms and will facilitate the design of new drugs with greater therapeutic value.

Pendred Syndrome in a large consanguineous Brazilian family caused by a homozygous mutation in the SLC26A4 gene

Pendred Syndrome (PS) is an autossomal recessive disorder characterized by sensorineural deafness, goiter and iodide organification defect. The hearing loss is associated with inner ear abnormalities, ranging from an isolated enlarged vestibular aqueduct (EVA) to a typical coclear dysplasia. Mutations in the gene that encodes pendrin (SLC26A4), a chloride/iodide transporter, have been shown to be associated with PS. We describe the clinical and molecular characteristics of a large consanguineous family harboring a mutation in the SLC26A4 gene. The proband was a 26-year-old deaf Brazilian woman who presented a bulky multinodular goiter and hypothyroidism since puberty. Five other siblings were deaf: one brother had a similar phenotype, three siblings also had goiters but normal thyroid function tests, and one brother had only a subtle thyroid enlargement. Other 4 siblings had no thyroid or hearing disorder. Parents were first degree cousins and had normal hearing. The mother was healthy, except for subclinical hypothyroidism; the father was deceased. A perchlorate test in the proband showed a discharge of 21% of the incorporated iodide 2h after the administration of 1g of KClO4. Audiological examinations showed profound hearing loss in all deaf subjects; CT and MRI of the temporal bones showed EVA in all of them. Genomic DNA was isolated from whole blood, from the 6 affected and 4 unaffected siblings, the mother and control. The coding region of the PDS gene (exons 2-21), including exon/intron boundaries, were amplified by PCR and sequenced. A single base-pair (T) deletion at position 1197 of exon 10 was detected in homozygous state in the 6 deaf siblings. The mother and 2 unaffected siblings were heterozygous for this mutation, which has been described by Everett et al. The 1197delT mutation is predicted to result in a frameshift and a truncated protein. The existence of PS phenocopies and intrafamilial phenotypic variability are well documented. The definite diagnosis requires molecular analysis. Our study illustrates the value and challenges of mutational analysis in selected patients with PS.

Cerebrospinal Fluid CRH Levels in Late Pregnancy Are Not Associated With New-Onset Postpartum Depressive Symptoms.

CONTEXT CRH participates in the hypothalamic-pituitary-adrenal axis and in neural circuits involved in the pathophysiology of depression. During pregnancy, the placenta produces large amounts of CRH, and production ceases abruptly after delivery. The relationship between CRH in the cerebrospinal fluid (CSF) during pregnancy and peripartum mood disorders has not been investigated. OBJECTIVES The objectives were to determine whether there are differences in CSF CRH concentrations of pregnant and nonpregnant women and whether CSF CRH concentrations in late pregnancy are associated with the presence of depressive symptoms during pregnancy and in the early postpartum period. DESIGN This was a prospective cohort study conducted from January to April, 2011. SETTING The study was conducted in one public and two private hospitals in Brasilia, Brazil. PATIENTS Patients included 107 healthy pregnant women who underwent elective cesarean delivery and 22 nonpregnant healthy women who underwent spinal anesthesia for elective surgical sterilization. INTERVENTION CRH in CSF was measured in pregnant and nonpregnant women by ELISA. MAIN OUTCOME MEASURE The association between CSF CRH concentration at delivery and maternal depression assessed before cesarean section and postpartum (4 to 8 wk) with the Edinburgh Postnatal Depression Scale (EPDS), with a cutoff of ≥ 13. RESULTS CRH concentration in the CSF was significantly higher in pregnant (4.1 ± 0.51 log CRH) than in nonpregnant women (3.6 ± 0.26 log CRH) (P < .001). Depressive symptoms starting after delivery occurred in 5.6% of women. CRH concentration in CSF was not different between women without depressive symptoms and women showing such symptoms during pregnancy or in the postpartum period. CONCLUSION CRH concentration in the CSF was higher in pregnant women than in nonpregnant women. However, in this sample, CSF CRH in late pregnancy was not associated with new-onset depressive symptoms in the early postpartum period.

Trp28Arg/Ile35Thr LHB gene variants are associated with elevated testosterone levels in women with polycystic ovary syndrome.

INTRODUCTION Polycystic Ovary Syndrome (PCOS) is a complex endocrine disorder, of multifactorial etiology, which affects 6-10% of women of reproductive age. It is considered the leading cause of anovulatory infertility, menstrual disorders and hyperandrogenism in this population. The genetic basis of PCOS is still largely unknown despite significant family clustering; determining its mode of inheritance is particularly difficult given the heterogenic presentation of the disease. MATERIALS AND METHODS 130 Brazilian women, aged 14-42 years, who met the 2003 Rotterdam criteria for PCOS diagnosis, were included, and 96 healthy women constituted the control group. Presence of hirsutism was classified using the modified Ferriman-Gallwey score (F-G score) as absent (≤7), mild (8-14), and severe (≥15). Blood levels of luteinizing hormone (LH), total testosterone (TT), dehydroepiandrosterone sulfate (DHEA-S) and androstenedione were determined. The coding region of the luteinizing hormone beta-subunit (LHB) gene was amplified and sequenced. Differences in allelic and genotypic frequency distribution of each polymorphism across controls and cases were estimated by the Mantel-Haenszel chi-square or Fishers exact test (p<0.05), and the probability of an association between the detection of a polymorphism and presence of a diagnosis of PCOS, by logistic regression. RESULT(S) Sequencing detected 8 polymorphisms in the LHB gene coding region. Two polymorphisms in linkage disequilibrium were significantly more prevalent in the presence of hyperandrogenemia: rs1800447/rs34349826 (Trp28Arg/Ile35Thr) (p=0.02). CONCLUSION(S) In this series, a modulatory effect of LHB polymorphisms on hyperandrogenemia phenotype of PCOS was observed; however, this finding needs to be replicated in other populations.

Lack of association between the CC genotype of the rs7903146 polymorphism in the TCF7L2 gene and rheumatoid arthritis

INTRODUCTION TCF7L2 is a transcription factor involved in Wnt/beta-catenin signaling and which has a variant known to be consistently associated with type 2 diabetes risk and some studies have also indicated its association with risk of certain types of cancer. OBJECTIVE Since this pathway may be involved in the pathophysiology of other chronic inflammatory diseases such as rheumatoid arthritis, we aimed to investigate the effect of TCF7L2 polymorphism rs7903146 on rheumatoid arthritis severity in a Brazilian population. PATIENTS AND METHODS This polymorphism was genotyped in 208 patients with rheumatoid arthritis and in 104 healthy controls. We also analyzed the association of this polymorphism to smoking history, functional status classification and radiological indicators of disease severity. RESULTS The distribution of CC, CT and TT genotypes of SNP rs7903146 of the TCF7L2 gene was not different between patients and controls, and no association between the genotype and indicators of disease severity or smoking history was found. When data were evaluated using the dominant model, in which carriers of the CT and TT genotypes were grouped, an increase in the T allele was observed in patients positive for rheumatoid factor and erosions, although this was not significant. The frequency of T allele was also increased in patients with functional class II compared to class I (P = 0.032). CONCLUSION It is possible that the small number of patients included in this study may have restrained additional findings. Further studies are therefore needed to investigate the role of TCF7L2 gene variants in the risk of rheumatoid arthritis and its severity.