Ana Beatriz Alvarez Perez

Relationship Between Polymorphisms in Genes Involved in Homocysteine Metabolism and Maternal Risk for Down Syndrome in Brazil

Associations between specific alleles of genes encoding enzymes in the methionine/homocysteine pathway and plasma homocysteine levels have been examined in different populations. In the present study, we determined polymorphisms of MTHFR A222V (677C > T), MTHFR E429A (1298A > C), MTRR I22M (66A > G), MTR D919G (2756A > G), and CBS 844ins68 and total plasma homocysteine levels (tHcy) among 154 mothers of children with Down syndrome (DS) and 158 control mothers from Brazil. Homocysteine levels were higher among DS mothers compared to control groups (10.437 vs. 8.600 respectively, P = 0.002). Only the 677T allele was associated with altered levels of tHcy in the case group (F(2,153) = 5.300; P = 0.006), primarily when homozygous. In the control group, the association of the TT genotype with higher levels of tHcy showed borderline significance (F(2,157) = 2.974; P = 0.054). All genotype distributions were similar in the two groups (P > 0.05), but the frequency of the 677T allele in the case group was significantly higher (χ2 = 3.862; DF = 1; P = 0.049; OR = 1.437 (1.001–2.062)). Although the 677T allele is associated with increased homocysteine levels, its presence has only a modest impact as an independent risk factor for DS. All the other polymorphisms did not show an association with risk for the syndrome, when evaluated separately (P > 0.05). However, when the presence of 677T, 1298C, 2756G, 66G, and 844ins68 alleles were evaluated together, the mothers of children with DS tend to have a higher number of uncommon alleles than the mothers with no previous affected child.

Methylenetetrahydrofolate reductase (MTHFR): incidence of mutations C677T and A1298C in Brazilian population and its correlation with plasma homocysteine levels in spina bifida

Homocysteine (Hcy) is converted to cysteine or is remethylated to methionine by methylenetetrahydrofolate reductase (MTHFR). MTHFR plays a central role in the metabolism of folate. Two common polymorphisms in the MTHFR gene (C677T and A1298C) have been described and studies suggest that these polymorphisms are positively associated with the occurrence of spina bifida (SB). Among Brazilians, the incidence of 677T allele homozygosity is 4%. We compared Hcy levels with the genotypes obtained for the mutations C677T and A1298C in the gene MTHFR. Levels of plasma Hcy were higher in children with SB than in controls (average 7.95 vs. 5.55 (μmol/L); P < 0.001). There was no significant difference in the levels of Hcy for these childrenss mothers and controls (average 7.76 vs. 8.36 (μmol/L); P = 0.27). Eighty one (61.8%) of the affected children were white and 50 (38.2%) were non‐white. A similar ratio was observed in the mothers. In the control group, 51 children (40.5%) were white and 75 (59.5%) were non‐white, and 52 mothers (41.3%) were white and 74 (58.7%) were non‐white. There was no significant difference in the homozygous frequency for the mutated allele 677T among different racial groups. We obtained a prevalence of TT homozygosity of 10/131 (7.64%) in affected children and 13/126 (10.32%) in controls. With respect to the mutation A1298C, the homozygous prevalence for the wild allele was greater among non‐white individuals than in white individuals both in case and control groups. Hyperhomocysteinemia is a risk factor for SB. However, in our population, the increase in plasma levels of Hcy is not explained by the presence of the homozygous TT. It is possible that low folic acid intake combined with other genetic factors plays a more important role in the cause of this disease.

Mutations in KCTD1 Cause Scalp-Ear-Nipple Syndrome

Scalp-ear-nipple (SEN) syndrome is a rare, autosomal-dominant disorder characterized by cutis aplasia of the scalp; minor anomalies of the external ears, digits, and nails; and malformations of the breast. We used linkage analysis and exome sequencing of a multiplex family affected by SEN syndrome to identify potassium-channel tetramerization-domain-containing 1 (KCTD1) mutations that cause SEN syndrome. Evaluation of a total of ten families affected by SEN syndrome revealed KCTD1 missense mutations in each family tested. All of the mutations occurred in a KCTD1 region encoding a highly conserved bric-a-brac, tram track, and broad complex (BTB) domain that is required for transcriptional repressor activity. KCTD1 inhibits the transactivation of the transcription factor AP-2α (TFAP2A) via its BTB domain, and mutations in TFAP2A cause cutis aplasia in individuals with branchiooculofacial syndrome (BOFS), suggesting a potential overlap in the pathogenesis of SEN syndrome and BOFS. The identification of KCTD1 mutations in SEN syndrome reveals a role for this BTB-domain-containing transcriptional repressor during ectodermal development.

Obesity with associated developmental delay and/or learning disability in patients exhibiting additional features: Report of novel pathogenic copy number variants

Obesity is a major threat to public health worldwide, and there is now mounting evidence favoring a role for the central nervous system (CNS) in weight control. A causal relationship has been recognized in both monogenic (e.g., BDNF, TRKB, and SIM1 deficiencies) and syndromic forms of obesity [e.g., Prader–Willi syndrome (PWS)]. Syndromic obesity arising from chromosomal abnormalities, that typically also affect learning and development, are often associated with congenital malformations and behavioral characteristics. We report on nine unrelated patients with a diagnosis of learning disability and/or developmental delay (DD) in addition to obesity that were found to have copy number variants (CNVs) by single nucleotide polymorphism array‐based analysis. Each patient also had a distinct and complex phenotype, and most had hypotonia and other neuroendocrine issues, such as hyperphagia and hypogonadism. Molecular and clinical characterization of these patients enabled us to determine with confidence that the CNVs we observed were pathogenic or likely to be pathogenic. Overall, the CNVs reported here encompassed a candidate gene or region (e.g., SIM1) that has been reported in patients associating obesity and DD and/or intellectual disability (ID) and novel candidate genes and regions.

Avaliação clínico-cardiológica e ecocardiográfica, seqüencial, em crianças portadoras da síndrome de Marfan

OBJETIVO: Descrever a apresentacao clinica cardiologica e a evolucao temporal, estimar a incidencia de ectasia ânulo-aortica e de prolapso da valva mitral, e avaliar a tolerância e a efetividade dos betabloqueadores em criancas com sindrome de Marfan. METODOS: Foram submetidas a exame clinico e ecocardiografico seriado, durante um ano, 21 criancas com sindrome de Marfan. No ecocardiograma foram analisados: presenca de prolapso mitral, diâmetro da raiz aortica, refluxos das valvas mitral e aortica, e o crescimento dos diâmetros aorticos na vigencia de betabloqueadores. Em 11 pacientes foi possivel obter duas medidas da raiz aortica no intervalo de um ano. RESULTADOS: Durante o estudo as criancas nao apresentaram sintomas. Prolapso mitral foi encontrado em 11 (52%) criancas. Ectasia ânulo-aortica ocorreu em 16 (76%) pacientes, sendo de grau discreto em 42,8%, moderado em 9,5%, e importante em 23,8%. Um desses pacientes foi submetido com sucesso a cirurgia de Bentall DeBono. Com o uso de betabloqueador a frequencia cardiaca diminuiu 13,6% (de 85 para 73 bpm; p < 0,009), mas houve um crescimento da raiz aortica de 1,4 mm/ano (p < 0,02). Uma crianca nao pode receber betabloqueador em razao de asma bronquica, e nao foram observados efeitos colaterais significativos nas outras criancas, incluindo uma com asma bronquica. CONCLUSAO: Os resultados obtidos sugerem que, no periodo observado, as criancas permaneceram assintomaticas, o uso de betabloqueadores diminuiu significativamente a frequencia cardiaca e nao se acompanhou de efeitos adversos significativos. Ao contrario da literatura, a incidencia de ectasia ânulo-aortica foi elevada e maior do que a de prolapso valvar mitral, tendo crescimento mesmo na vigencia de uso eficaz de betabloqueador.

Novel mutations in the TBX5 gene in patients with Holt-Oram Syndrome

The Holt-Oram syndrome (HOS) is an autosomal dominant condition characterized by upper limb and cardiac malformations. Mutations in the TBX5 gene cause HOS and have also been associated with isolated heart and arm defects. Interactions between the TBX5, GATA4 and NKX2.5 proteins have been reported in humans. We screened the TBX5, GATA4, and NKX2.5 genes for mutations, by direct sequencing, in 32 unrelated patients presenting classical (8) or atypical HOS (1), isolated congenital heart defects (16) or isolated upper-limb malformations (7). Pathogenic mutations in the TBX5 gene were found in four HOS patients, including two new mutations (c.374delG; c.678G > T) in typical patients, and the hotspot mutation c.835C > T in two patients, one of them with an atypical HOS phenotype involving lower-limb malformations. Two new mutations in the GATA4 gene were found in association with isolated upper-limb malformations, but their clinical significance remains to be established. A previously described possibly pathogenic mutation in the NKX2.5 gene (c.73C > 7) was detected in a patient with isolated heart malformations and also in his clinically normal father.

Genetic mechanisms leading to primary amenorrhea in balanced X-autosome translocations

OBJECTIVE To map the X-chromosome and autosome breakpoints in women with balanced X-autosome translocations and primary amenorrhea, searching candidate genomic loci for female infertility. DESIGN Retrospective and case-control study. SETTING University-based research laboratory. PATIENT(S) Three women with balanced X-autosome translocation and primary amenorrhea. INTERVENTION(S) Conventional cytogenetic methods, genomic array, array painting, fluorescence in situ hybridization, and quantitative reverse transcription-polymerase chain reaction. MAIN OUTCOME MEASURE(S) Karyotype, copy number variation, breakpoint mapping, and gene expression levels. RESULT(S) All patients presented with breakpoints in the Xq13q21 region. In two patients, the X-chromosome breakpoint disrupted coding sequences (KIAA2022 and ZDHHC15 genes). Although both gene disruptions caused absence of transcription in peripheral blood, there is no evidence that supports the involvement of these genes with ovarian function. The ZDHHC15 gene belongs to a conserved syntenic region that encompasses the FGF16 gene, which plays a role in female germ line development. The break in the FGF16 syntenic block may have disrupted the interaction between the FGF16 promoter and its cis-regulatory element. In the third patient, although both breakpoints are intergenic, a gene that plays a role in the DAX1 pathway (FHL2 gene) flanks distally the autosome breakpoint. The FHL2 gene may be subject to position effect due to the attachment of an autosome segment in Xq21 region. CONCLUSION(S) The etiology of primary amenorrhea in balanced X-autosome translocation patients may underlie more complex mechanisms than interruption of specific X-linked candidate genes, such as position effect. The fine mapping of the rearrangement breakpoints may be a tool for identifying genetic pathogenic mechanisms for primary amenorrhea.

Identification of 8 new mutations in Brazilian families with Marfan syndrome

Marfan Syndrome (MFS) is a connective tissue disease caused by mutations in the fibrillin‐1 (FBN1) gene. Screening for mutations in all the 65 exons of the FBN1 gene in 34 unrelated patients were performed to compare the efficiency of SSCP versus Heteroduplex analysis and to verify if the spectrum of mutations in Brazilian patients is similar to the one previously reported. Fourteen different band shifts were detected by SSCP analysis; among these only 6 were also detected through Heteroduplex analysis, suggesting that SSCP analysis was a more efficient method. Except for one, the molecular alteration was confirmed in the remaining 13 cases by sequencing; five of them were neutral polymorphisms and the eight others are new pathogenic mutations, as follows: 5 missense, one nonsense and two deletions leading to a premature termination codon (PTC). All of them are located in EGF‐like‐calcium binding motifs (EGF‐like‐cb). Our findings reinforce that cysteine substitutions and PTC mutations in the region between exons 24‐32 are more likely not to be associated with the neonatal phenotypes.

Novel Deletion of SERPINF1 Causes Autosomal Recessive Osteogenesis Imperfecta Type VI in Two Brazilian Families.

Autosomal recessive osteogenesis imperfecta (OI) accounts for 10% of all OI cases, and, currently, mutations in 10 genes (CRTAP, LEPRE1, PPIB, SERPINH1, FKBP10, SERPINF1, SP7, BMP1, TMEM38B, and WNT1) are known to be responsible for this form of the disease. PEDF is a secreted glycoprotein of the serpin superfamily that maintains bone homeostasis and regulates osteoid mineralization, and it is encoded by SERPINF1, currently associated with OI type VI (MIM 172860). Here, we report a consanguineous Brazilian family in which multiple individuals from at least 4 generations are affected with a severe form of OI, and we also report an unrelated individual from the same small city in Brazil with a similar but more severe phenotype. In both families the same homozygous SERPINF1 19-bp deletion was identified which is not known in the literature yet. We described intra- and interfamilial clinical and radiological phenotypic variability of OI type VI caused by the same homozygous SERPINF1 19-bp deletion and suggest a founder effect. Furthermore, the SERPINF1 genotypes/phenotypes reported so far in the literature are reviewed.

Marfan syndrome with a complex chromosomal rearrangement including deletion of the FBN1 gene

BackgroundThe majority of Marfan syndrome (MFS) cases is caused by mutations in the fibrillin-1 gene (FBN1), mapped to chromosome 15q21.1. Only few reports on deletions including the whole FBN1 gene, detected by molecular cytogenetic techniques, were found in literature.ResultsWe report here on a female patient with clinical symptoms of the MFS spectrum plus craniostenosis, hypothyroidism and intellectual deficiency who presents a 1.9 Mb deletion, including the FBN1 gene and a complex rearrangement with eight breakpoints involving chromosomes 6, 12 and 15.DiscussionThis is the first report of MFS with a complex chromosome rearrangement involving a deletion of FBN1 and contiguous genes. In addition to the typical clinical findings of the Marfan syndrome due to FBN1 gene haploinsufficiency, the patient presents features which may be due to the other gene deletions and possibly to the complex chromosome rearrangement.