Abstract Deletion-induced hemizygosity may unmask deleterious autosomal recessive variants and be a cause of the phenotypic variability observed in microdeletion syndromes. We performed complete exome sequencing (WES) analysis to examine this possibility in a patient with 1p13.2 microdeletion. Since the patient displayed clinical features suggestive of Noonan Syndrome (NS), we also used WES to rule out the presence of pathogenic variants in any of the genes associated with the different types of NS. We concluded that the clinical findings could be attributed solely to the 1p13.2 haploinsufficiency. Retrospective analysis of other nine reported patients with 1p13.2 microdeletions showed that six of them also presented some characteristics of NS. In all these cases, the deleted segment included the NRAS gene. Gain-of-function mutations of NRAS gene are causally related to NS type 6. Thus, it is conceivable that NRAS haploinsufficiency and gain-of-function mutations may have similar clinical consequences. The same phenomenon has been described for two other genes belonging to the Ras/MAPK pathway: MAP2K2 and SHOC2. In conclusion, we here report genotype-phenotype correlations in patients with chromosome 1p13.2 microdeletions and we propose that NRAS may be a critical gene for the NS characteristics in the patients.

RESUMO Objetivo: descrever as alterações cromossômicas em pacientes com retardo mental (RM) pela análise do cariótipo com bandas G. Método: foi realizado um estudo retrospectivo dos resultados de cariótipo com bandas G de 369 pacientes em investigação de RM. A partir dos rearranjos estruturais encontrados, foram levantadas todas as regiões cromossômicas envolvidas nos pontos de quebra e elas foram comparadas com a literatura para RM e bancos de dados. Resultados: foram identificados 338 (91,6%) casos normais e 31 (8,4%) com algum tipo de alteração cromossômica. Dentre os casos alterados, 21 pacientes (67,8%) foram identificados com alterações cromossômicas estruturais, 9 (29%) com alterações numéricas e 1 (3,2%) com alteração numérica e estrutural. Conclusão: as alterações cromossômicas estruturais foram aquelas observadas com maior frequência. O cariótipo com bandas G contribui para a investigação das causas de RM, mostrando que essa técnica pode ser útil como uma primeira triagem dos pacientes. No entanto, técnicas mais resolutivas como o array based comparative genomic hibridization (aCGH) e o multiplex ligation dependent probe amplification (MLPA) permitem detectar alterações submicroscópicas comumente associadas ao RM.

SUMMARY Objective: To describe the chromosomal alterations in patients with mental retardation (MR) using G-banding karyotype analysis. Method: A retrospective study of the results G-banding karyotype analysis of 369 patients investigated for MR was performed. Based on the structural rearrangements found, the authors searched all chromosomal regions related with breakpoints, and these were compared with the literature on MR and databases. Results: 338 (91.6%) normal cases, and 31 (8.4%) with some type of chromosomal abnormality were identified. Among the altered cases, 21 patients (67.8%) were identified with structural chromosomal alterations, nine (29%) with numerical alterations, and one (3.2%) with numerical and structural alterations. Conclusion: Structural chromosomal abnormalities were observed more frequently in this study. G-banding karyotyping contributes to the investigation of the causes of MR, showing that this technique can be useful for initial screening of patients. However, higher resolution techniques such as array based comparative genomic hybridization (aCGH) and multiplex ligation-dependent probe amplification (MPLA) can detect submicroscopic alterations commonly associated with MR.

β-tubulins are structural components of microtubules and the targets of benzimidazole fungicides used to control many diseases of agricultural importance. Intron polymorphisms in the intron-rich genes of these proteins have been used in phylogeographic investigations of phytopathogenic fungi. In this work, we sequenced 2764 nucleotides of the β-tubulin gene (Pp tubB) in samples of Phakopsora pachyrhizi collected from seven soybean fields in Brazil. Pp tubB contained an open reading frame of 1341 nucleotides, including nine exons and eight introns. Exon length varied from 14 to 880 nucleotides, whereas intron length varied from 76 to 102 nucleotides. The presence of only four polymorphic sites limited the usefulness of Pp tubB for phylogeographic studies in P. pachyrhizi. The gene structures of Pp tubB and orthologous β-tubulin genes of Melampsora lini and Uromyces viciae-fabae were highly conserved. The amino acid substitutions in β-tubulin proteins associated with the onset of benzimidazole resistance in model organisms, especially at His6, Glu198 and Phe200, were absent from the predicted sequence of the P. pachyrhizi β-tubulin protein.