Lack of evidence for monosomy 1p36 in patients with Prader-Willi-like phenotype

Monosomy 1p36 is the most common subtelomeric microdeletion syndrome with an incidence rate estimated to be 1 in 5000 births. A hypothesis of a similarity between patients with 1p36 deletion and those with Prader-Willi syndrome and the existence of two different phenotypes for 1p36 microdeletion has been suggested. The main objective of the present study was to determine the existence of 1p36 microdeletion in a sample of patients with mental retardation, obesity and hyperphagia who tested negative by the methylation test for Prader-Willi syndrome. Sixteen patients (7 females, 9 males), 16-26 years old, were evaluated with high-resolution cytogenetic analysis at 550-850 band levels and with 11 polymorphic microsatellite markers located in the 1p36 region. All patients had normal cytogenetic and molecular results. The results obtained by high-resolution cytogenetic methodology were confirmed by the molecular analyses. We did not detect a 1p36 microdeletion in 16 subjects with the Prader-Willi-like phenotype, which reinforces that no correlation seems to exist between Prader-Willi-like phenotype and the 1p36 microdeletion syndrome.

Somatic cytogenetic and azoospermia factor gene microdeletion studies in infertile men

The objective of the present study was to determine the frequency of somatic chromosomal anomalies and Y chromosomal microdeletions (azoospermia factor genes, AZF) in infertile males who seek assisted reproduction. These studies are very important because the assisted reproduction techniques (mainly intracytoplasmic sperm injection) bypass the natural selection process and some classical chromosomal abnormalities, microdeletions of AZF genes or some deleterious genic mutations could pass through generations. These genetic abnormalities can cause in the offspring of these patients male infertility, ambiguous external genitalia, mental retardation, and other birth defects. We studied 165 infertile men whose infertility was attributable to testicular problems (60 were azoospermic, 100 were oligospermic and 5 were asthenospermic). We studied 100 metaphases per patient with GTG banding obtained from temporary lymphocyte culture for chromosomal abnormality detection and performed a genomic DNA analysis using 28 Y chromosome-specific sequence-tagged sites for Y AZF microdeletion detection. Karyotyping revealed somatic anomalies in 16 subjects (16/165 = 9.6 percent). Of these 16, 12 were in the azoospermic group (12/60 = 20 percent) and 4 were in the oligospermic group (4/100 = 4 percent). The most common chromosomal anomaly was Klinefelter syndrome (10/165 = 6 percent). Microdeletions of AZF genes were detected in 12 subjects (12/160 = 7.5 percent). The frequencies detected are similar to those described previously. These results show the importance of genetic evaluation of infertile males prior to assisted reproduction. Such evaluation can lead to genetic counseling and, consequently, to primary and secondary prevention of mental retardation and birth defects.

DNA extraction and quantification from touch and scrape preparations obtained from autopsy liver cells

The objective of the present study was to develop a simplified low cost method for the collection and fixation of pediatric autopsy cells and to determine the quantitative and qualitative adequacy of extracted DNA. Touch and scrape preparations of pediatric liver cells were obtained from 15 cadavers at autopsy and fixed in 95 percent ethanol or 3:1 methanol:acetic acid. Material prepared by each fixation procedure was submitted to DNA extraction with the Wizard© genomic DNA purification kit for DNA quantification and five of the preparations were amplified by multiplex PCR (azoospermia factor genes). The amount of DNA extracted varied from 20 to 8,640 æg, with significant differences between fixation methods. Scrape preparation fixed in 95 percent ethanol provided larger amount of extracted DNA. However, the mean for all groups was higher than the quantity needed for PCR (50 ng) or Southern blot (500 ng). There were no qualitative differences among the different material and fixatives. The same results were also obtained for glass slides stored at room temperature for 6, 12, 18 and 24 months. We conclude that touch and scrape preparations fixed in 95 percent ethanol are a good source of DNA and present fewer limitations than cell culture, tissue paraffin embedding or freezing that require sterile material, culture medium, laboratory equipment and trained technicians. In addition, they are more practical and less labor intensive and can be obtained and stored for a long time at low cost.

A viable fetus presenting 68, XX[73]/69, XXX[27] triploid mosaicism

A triploidia é uma anomalia cromossômica comum encontrada em 1 a 2 por cento das gestaçöes clinicamente reconhecidas e em cerca de 15 a 20 por cento dos abortos espontâneos de causa cromossômica. Em aproximadamente 5 por cento dos casos, uma aneuploidia pode estar também associada (Boué et al., 1985). Descrevemos um recém-nascido do sexo feminino, prematuro (30 semanas de idade gestacional), com microcefalia, dismorfias faciais e alteraçöes de membros, que foi a óbito com 1 dia de vida por insuficiência respiratória. O exame anátomo-patológico da placenta revelou alteraçöes compatíveis com degeneraçäo molar. A necrópsia da criança näo evidenciou malformaçöes internas. A análise citogenética de 100 metástases, obtidas a partir de cultura de tecido renal, evidenciou cariótipo 68,XX[73]/69,XXX[27]. Apenas 9 casos de triploidia 68,XX foram descritos anteriormente, sendo 7 em abortos, 1 em feto de 21 semanas e 1 em recém-nascido a termo. Consideramos que este estudo seja o primeiro da literatura relatando a ocorrência de mosaicismo 69,XXX/68,XX em um recém-nascido vivo. Os autores discutem os achados clínicos e os possíveis mecanismos envolvidos nesta aberraçäo cromossômica.

Trisomy 13 mosaicism demonstrated only in skin fibroblasts in a patient presenting psychomotor retardation, pigmentary dysplasia and some dysmorphic features

Os autores descrevem uma criança do sexo feminino com atraso do desenvolvimento neuropsicomotor, manchas hipercrômicas na pele e algumas características dismórficas. O cariótipo em linfócitos de sangue periférico foi normal e a cultura de fibroblastos a partir de biópsia de pele revelou trissomia do cromossomo 13 em 50 por cento das metáfases analisadas. Enfatizam a importância do cariótipo de pele nas situaçöes clínicas em que o retardo psicomotor ou mental está associado com displasia pigmentar de pele e cromossomos normais nos linfócitos.