Mosaic proximal trisomy 13q and regular trisomy 13 in a female patient with long survival: Involvement of an incomplete trisomic rescue and a chromothripsis event.

BACKGROUND: Trisomy 13 or Patau syndrome has a prevalence of 1:10,000-20,000 and is characterized by microcephaly, microphthalmia, polydactyly, as well as other dysmorphic features and malformations, with a patient survival of 13% in the first year. Trisomy 13 presents either as a free chromosome 13 trisomy or associated with a chromosomal Robertsonian translocation, as partial trisomy affecting proximal or distal 13q regions, and also as a mosaic. Mosaic trisomy 13 shows a highly variable phenotype, displaying from mild to severe affectations. We present a 12-year-old Mexican female patient with intellectual disability, dysmorphic features, polymenorrhea, and long survival, whose initial cytogenetic study referred to a small supernumerary marker chromosome. METHODS: GTG banding karyotype, high-resolution chromosomal microarray, and fluorescent in situ hybridization analyses were performed in peripheral blood cells. RESULTS: Our analyses demonstrated a de novo mosaicism in our patient, constituted by proximal trisomy 13q10-q14.3 (82%) and free trisomy 13 (18%) cell lines. Her final chromosomal complement is mos 47,XX,+del(13)(q14.3)[25]/47,XX,+13[7].ish del(13)(RB1+)[17]/13q14(RB1x3)[2].arr[GRCh37] 13q11q14.3(19436286_51726415)x3,13q11q34(19436286_115107733)x2-3 dn. CONCLUSIONS: The wide spectrum of clinical manifestations observed in our patient mainly results from the proximal trisomy 13q, and her phenotype is modified by the presence of a free trisomy 13 cell line. We propose that her mosaicism probably derived from a trisomic zygote that underwent a failed trisomic rescue associated with chromothripsis, originating the cell line with partial 13q proximal trisomy, whose selective advantage could explain the long survival of our patient.

Displasia ectodérmica hipohidrótica ligada al cromosoma X de novo por variante recurrente en un paciente mexicano / X-linked hypohidrotic ectodermal dysplasia by a de novo recurrent variant in a Mexican patient

Resumen Introducción: Las displasias ectodérmicas son un grupo de genodermatosis que se caracterizan por distrofia de las estructuras derivadas del ectodermo. De ellas, la variedad más común es la hipohidrótica, con una incidencia de 7/100,000 nacidos vivos observada en todos los grupos étnicos. La displasia ectodérmica hipohidrótica tiene distintas etiologías. La presentación más frecuente es la asociada a un patrón de herencia ligado al cromosoma X, causada por variantes patogénicas del gen EDA en Xq13.1. EDA codifica a la ectodisplasina A, una molécula de señalización que participa en la comunicación epitelio-mesénquima durante el desarrollo de la piel y los anexos. Caso clínico: Varón de 6 años con las características clínicas cardinales de la displasia ectodérmica hipohidrótica ligada al cromosoma X (DEHLX), que incluyen hipotricosis, oligodoncia e hipohidrosis. El análisis del gen EDA por secuenciación directa mostró la presencia de la variante patogénica c.466C>T, p.Arg156Cys, rs132630313 con presentación de novo en el paciente. Esta variante ya ha sido reportada en diferentes poblaciones, incluyendo familias mexicanas, y constituye un punto caliente para mutación en EDA. Se analizaron los hallazgos clínicos, la etiología y el manejo de la DEHLX, en la que de manera reciente se ha planteado la posibilidad de otorgar tratamiento prenatal para prevenir sus manifestaciones clínicas. Conclusiones: Se pone de relevancia que el análisis molecular en pacientes con DEHLX corrobora el diagnóstico clínico y permite brindar asesoramiento genético con bases moleculares.

Abstract Background: Ectodermal dysplasias are a group of genodermatoses characterized by dystrophy of ectodermal derived structures. The most frequent presentation of the ectodermal dysplasias is the hypohidrotic type, which has an incidence of 7/100,000 newborns and has been described in all ethnic groups. The hypohidrotic ectodermal dysplasia (HED) has different etiologies, and it is more frequently associated with an X-linked pattern of inheritance caused by pathogenic variants of the EDA gene in Xq13.1. EDA encodes the protein ectodisplasin A, a signal molecule which participates in epithelium and mesenchymal development of the skin. Case report: A 6 year-old male patient with the main clinical characteristics of the X-linked HED including hypotrichosis, hypodontia and hypohidrosis. The direct sequencing analysis of EDA in our patient detected a de novo pathogenic variant, c.466C>T, p.Arg156Cys, rs132630313. This variant has been previously described in different ethnic groups, including Mexican families, and is considered a mutational hotspot. The clinical characteristics, etiology and management of the X-linked HED, including the possibility of prenatal therapy in order to avoid the clinical manifestations are discussed. Conclusions: The molecular analysis in patients with X-linked HED is of relevance, as it enables to confirm the clinical diagnosis and also, it allows a genetic assessment with molecular bases.

X-linked hypohidrotic ectodermal dysplasia by a de novo recurrent variant in a Mexican patient.

Background: Ectodermal dysplasias are a group of genodermatoses characterized by dystrophy of ectodermal derived structures. The most frequent presentation of the ectodermal dysplasias is the hypohidrotic type, which has an incidence of 7/100,000 newborns and has been described in all ethnic groups. The hypohidrotic ectodermal dysplasia (HED) has different etiologies, and it is more frequently associated with an X-linked pattern of inheritance caused by pathogenic variants of the EDA gene in Xq13.1. EDA encodes the protein ectodisplasin A, a signal molecule which participates in epithelium and mesenchymal development of the skin. Case report: A 6 year-old male patient with the main clinical characteristics of the X-linked HED including hypotrichosis, hypodontia and hypohidrosis. The direct sequencing analysis of EDA in our patient detected a de novo pathogenic variant, c.466C>T, p.Arg156Cys, rs132630313. This variant has been previously described in different ethnic groups, including Mexican families, and is considered a mutational hotspot. The clinical characteristics, etiology and management of the X-linked HED, including the possibility of prenatal therapy in order to avoid the clinical manifestations are discussed. Conclusions: The molecular analysis in patients with X-linked HED is of relevance, as it enables to confirm the clinical diagnosis and also, it allows a genetic assessment with molecular bases.

Introducción: Las displasias ectodérmicas son un grupo de genodermatosis que se caracterizan por distrofia de las estructuras derivadas del ectodermo. De ellas, la variedad más común es la hipohidrótica, con una incidencia de 7/100,000 nacidos vivos observada en todos los grupos étnicos. La displasia ectodérmica hipohidrótica tiene distintas etiologías. La presentación más frecuente es la asociada a un patrón de herencia ligado al cromosoma X, causada por variantes patogénicas del gen EDA en Xq13.1. EDA codifica a la ectodisplasina A, una molécula de señalización que participa en la comunicación epitelio-mesénquima durante el desarrollo de la piel y los anexos. Caso clínico: Varón de 6 años con las características clínicas cardinales de la displasia ectodérmica hipohidrótica ligada al cromosoma X (DEHLX), que incluyen hipotricosis, oligodoncia e hipohidrosis. El análisis del gen EDA por secuenciación directa mostró la presencia de la variante patogénica c.466C>T, p.Arg156Cys, rs132630313 con presentación de novo en el paciente. Esta variante ya ha sido reportada en diferentes poblaciones, incluyendo familias mexicanas, y constituye un punto caliente para mutación en EDA. Se analizaron los hallazgos clínicos, la etiología y el manejo de la DEHLX, en la que de manera reciente se ha planteado la posibilidad de otorgar tratamiento prenatal para prevenir sus manifestaciones clínicas. Conclusiones: Se pone de relevancia que el análisis molecular en pacientes con DEHLX corrobora el diagnóstico clínico y permite brindar asesoramiento genético con bases moleculares.

Liver disease in pregnancy: Medical aspects and their implications for mother and child.

Liver disease during pregnancy is more common than expected and may require specialized intervention. It is important to determine if changes in liver physiology may develop into liver disease, to assure early diagnosis. For adequate surveillance of mother-fetus health outcome, liver disease during pregnancy might require intervention from a hepatologist. Liver diseases have a prevalence of at least 3% of all pregnancies in developed countries, and they are classified into two main categories: related to pregnancy; and those non- related that are present de novo or are preexisting chronic liver diseases. In this review we describe and discuss the main characteristics of those liver diseases associated with pregnancy and only some frequent pre-existing and co-incidental in pregnancy are considered. In addition to the literature review, we compiled the data of liver disease occurring during pregnancies attended at the National Institute of Perinatology in Mexico City in a three-year period. In our tertiary referral women hospital, liver disease was present in 11.24 % of all pregnancies. Associated liver disease was found in 10.8% of all pregnancies, mainly those related to pre-eclampsia (9.9% of pregnancies). Only 0.56% was due to liver disease that was co-incidental or preexisting; the acute or chronic hepatitis C virus was the most frequent in this group (0.12%). When managing pregnancy in referral hospitals in Latin America, it is important to discard liver alterations early for adequate follow up of the disease and to prevent adverse consequences for the mother and child.

Niemann-Pick disease A or B in four pediatric patients and SMPD1 mutation carrier frequency in the Mexican population.

INTRODUCTION AND OBJECTIVES: Niemann-Pick disease type A (NPD-A) and B (NPD-B) are lysosomal storage diseases with a birth prevalence of 0.4-0.6/100,000. They are caused by a deficiency in acid sphingomyelinase, an enzyme encoded by SMPD1. We analyzed the phenotype and genotype of four unrelated Mexican patients, one with NPD-A and three with NPD-B. PATIENTS AND METHODS: Four female patients between 1 and 7 years of age were diagnosed with NPD-A or NPD-B by hepatosplenomegaly, among other clinical characteristics, and by determining the level of acid sphingomyelinase enzymatic activity and sequencing of the SMPD1 gene. Additionally, a 775bp amplicon of SMPD1 (from 11:6393835_6394609, including exons 5 and 6) was analyzed by capillary sequencing in a control group of 50 unrelated healthy Mexican Mestizos. RESULTS: An infrequent variant (c.1343A>G p.Tyr448Cys) was observed in two patients. One is the first NPD-A homozygous patient reported with this variant and the other a compound heterozygous NPD-B patient with the c.1829_1831delGCC p.Arg610del variant. Another compound heterozygous patient had the c.1547A>G p.His516Arg variant (not previously described in affected individuals) along with the c.1805G>A p.Arg602His variant. A new c.1263+8C>T pathogenic variant was encountered in a homozygous state in a NPD-B patient. Among the healthy control individuals there was a heterozygous carrier for the c.1550A>T (rs142787001) pathogenic variant, but none with the known pathogenic variants in the 11:6393835_6394609 region of SMPD1. CONCLUSIONS: The present study provides further NPD-A or B phenotype-genotype correlations. We detected a heterozygous carrier with a pathogenic variant in 1/50 healthy Mexican mestizos.

Monosomía 9p24 secundaria a translocación (2; 9) en dos pacientes no relacionadas / Monosomy 9p24 in two non-related patients as result of a translocation (2; 9)

En pacientes con malformaciones congénitas y retraso del desarrollo psicomotor, deben descartarse cromosomopatías. Las más frecuentes son las translocaciones recíprocas balanceadas, presentes en 1:500 recién nacidos vivos. Por lo general, los portadores tienen fenotipo normal, aunque, ocasionalmente, presentan infertilidad, abortos o hijos con malformaciones. La translocación balanceada entre los cromosomas 2 y 9 puede originar descendencia con monosomías y trisomías de estos cromosomas. La monosomía del brazo corto del cromosoma 9 puede presentarse con trigonocefalia, dismorfias faciales, anomalías genitales y retraso del desarrollo psicomotor. En este trabajo, se revisaron las alteraciones de los cromosomas 2 y/o 9 en los cariotipos realizados en nuestra Institución en 2005-2014. Se presentan dos pacientes con monosomía 9p asociada a translocación (2;9). Las pacientes comparten datos de monosomía 9p24-pter; la correlación genotipo-fenotipo es compleja por el tamaño de los segmentos involucrados. Se resalta la importancia del diagnóstico cromosómico para el asesoramiento genético.

In patients with malformations and delayed psychomotor development it is important to discard chromosomopathies. Balanced reciprocal translocations are the most frequent chromosomopathies present in 1:500 live newborns. In general, carriers have normal phenotype, but they may have infertility, abortions or children with congenital malformations. The reciprocal translocation between chromosomes 2 and 9 can lead to offspring with monosomies and trisomies of these chromosomes. Short arm monosomy of chromosome 9 may present delayed psychomotor development, trigonocephaly, facial dysmorphia and genital abnormalities. We reviewed GTG karyotype records from our Institution to identify cases with chromosomes 2 and/or 9 alterations from 2005 to 2014. We describe two cases with monosomy 9p secondary to a translocation between chromosomes 2 and 9. The patients share features of monosomy 9p24-pter, however the genotype-phenotype correlation is complex due to the extension of the involved segments. We emphasize the importance of chromosomal diagnosis to offer genetic assessment.

Monosomy 9p24 in two non-related patients as result of a translocation (2;9). / Monosomía 9p24 secundaria a translocación (2;9) en dos pacientes no relacionadas.

In patients with malformations and delayed psychomotor development it is important to discard chromosomopathies. Balanced reciprocal translocations are the most frequent chromosomopathies present in 1:500 live newborns. In general, carriers have normal phenotype, but they may have infertility, abortions or children with congenital malformations. The reciprocal translocation between chromosomes 2 and 9 can lead to offspring with monosomies and trisomies of these chromosomes. Short arm monosomy of chromosome 9 may present delayed psychomotor development, trigonocephaly, facial dysmorphia and genital abnormalities. We reviewed GTG karyotype records from our Institution to identify cases with chromosomes 2 and/or 9 alterations from 2005 to 2014. We describe two cases with monosomy 9p secondary to a translocation between chromosomes 2 and 9. The patients share features of monosomy 9p24-pter, however the genotypephenotype correlation is complex due to the extension of the involved segments. We emphasize the importance of chromosomal diagnosis to offer genetic assessment.

En pacientes con malformaciones congénitas y retraso del desarrollo psicomotor, deben descartarse cromosomopatías. Las más frecuentes son las translocaciones recíprocas balanceadas, presentes en 1:500 recién nacidos vivos. Por lo general, los portadores tienen fenotipo normal, aunque, ocasionalmente, presentan infertilidad, abortos o hijos con malformaciones. La translocación balanceada entre los cromosomas 2 y 9 puede originar descendencia con monosomías y trisomías de estos cromosomas. La monosomía del brazo corto del cromosoma 9 puede presentarse con trigonocefalia, dismorfias faciales, anomalías genitales y retraso del desarrollo psicomotor. En este trabajo, se revisaron las alteraciones de los cromosomas 2 y/o 9 en los cariotipos realizados en nuestra Institución en 2005-2014. Se presentan dos pacientes con monosomía 9p asociada a translocación (2;9). Las pacientes comparten datos de monosomía 9p24-pter; la correlación genotipo-fenotipo es compleja por el tamaño de los segmentos involucrados. Se resalta la importancia del diagnóstico cromosómico para el asesoramiento genético.

Nance-Horan syndrome in females due to a balanced X;1 translocation that disrupts the NHS gene: Familial case report and review of the literature.

The Nance-Horan syndrome is an X-linked disorder characterized by congenital cataract, facial features, microcornea, microphthalmia, and dental anomalies; most of the cases are due to NHS gene mutations on Xp22.13. Heterozygous carrier females generally present less severe features, and up to 30% of the affected males have intellectual disability. We describe two patients, mother and daughter, manifesting Nance-Horan syndrome. The cytogenetic and molecular analyses demonstrated a 46,X,t(X;1)(p22.13;q22) karyotype in each of them. No copy-number genomic imbalances were detected by high-density microarray analysis. The mother had a preferential inactivation of the normal X chromosome; expression analysis did not detect any mRNA isoform of NHS. This is the first report of Nance-Horan syndrome due to a skewed X chromosome inactivation resulting from a balanced translocation t(X;1) that disrupts the NHS gene expression, with important implications for clinical presentation and genetic counseling.

Cytogenetic profile in 1,921 cases of trisomy 21 syndrome.

BACKGROUND AND AIMS: Trisomy 21 is the most frequent genetic cause of intellectual disability. It is caused by different cytogenetic aberrations: free trisomy, Robertsonian translocations, mosaicism, duplication of the critical region and other structural rearrangements of chromosome 21. The aim of the study was to identify in Mexican trisomy 21 patients who attended Hospital Infantil de México Federico Gómez from 1992-2011 the type and frequency of the cytogenetic aberration and to evaluate the effect of maternal age. METHODS: A retrospective analysis of epidemiological data and karyotype reports were carried out; type and frequency of the cytogenetic variants were determined. RESULTS: We identified 2,018 cases referred with a clinical diagnosis of trisomy 21. In 1,921 analyses (95.2%) a cytogenetic variant of trisomy 21 was identified: free trisomy 21 in 1,787 cases (93.02%), four cases (0.21%) had an additional non-contributory aberration; Robertsonian translocations in 92 cases (4.79%); mosaicism in 31 cases (1.61%) and seven cases (0.36%) had other chromosomal abnormalities, five (0.26%) had other contributory structural rearrangements and two corresponded to double aneuploidies (0.10%). Gender distribution was 1,048 (54.56%) males and 873 (45.44%) females. A maternal age effect was observed in patients with free trisomy 21 with mothers >36 years of age. CONCLUSION: The present work reports the experience of a Mexican referral center regarding the karyotype diagnosis of patients with trisomy 21 and is one of the most extensive studies published so far. Percentages of the cytogenetic abnormalities present in our population reflect the ones previously reported for these cytogenetic alterations worldwide.

19q13.11 microdeletion concomitant with ins(2;19)(p25.3;q13.1q13.4)dn in a boy: potential role of UBA2 in the associated phenotype.

The 19q13.11 microdeletion syndrome (MIM613026) is a clinically recognisable condition in which a 324-kb minimal overlapping critical region has been recently described. However, genes not included within this region, such as WTIP and UBA2, have been proposed to contribute to the clinical characteristics observed in patients. Using cytogenetic techniques, single nucleotide polymorphism arrays, and the quantitative polymerase chain reaction, we identified a novel case with a 2.49-Mb deletion derived from a de novo chromosomal rearrangement. Based on a review of the literature, we support the notion that UBA2 haploinsufficiency could contribute to the phenotype of this rare genomic disorder. UBA2 belongs to a protein complex with sumoylation activity, and several transcription factors, hormone receptors, and signalling proteins related to brain and sexual development are regulated by this post-translational modification. Additional clinical reports and further research on UBA2 molecular function are warranted.

Trisomy 1q41-qter and monosomy 3p26.3-pter in a family with a translocation (1;3): further delineation of the syndromes.

BACKGROUND: Trisomy 1q and monosomy 3p deriving from a t(1;3) is an infrequent event. The clinical characteristics of trisomy 1q41-qter have been described but there is not a delineation of the syndrome. The 3p25.3-pter monosomy syndrome (MIM 613792) characteristics include low birth weight, microcephaly, psychomotor and growth retardation and abnormal facies. CASE PRESENTATION: A 2 years 8 months Mexican mestizo male patient was evaluated due to a trisomy 1q and monosomy 3p derived from a familial t(1;3)(q41;q26.3). Four female carriers of the balanced translocation and one relative that may have been similarly affected as the proband were identified. The implicated chromosomal regions were defined by microarray analysis, the patient had a trisomy 1q41-qter of 30.3 Mb in extension comprising about 240 protein coding genes and a monosomy 3p26.3-pter of 1.7 Mb including only the genes CNTN6 (MIM 607220) and CHL1 (MIM 607416), which have been implicated in dendrite development. Their contribution to the phenotype, regarding the definition of trisomy 1q41-qter and monosomy 3p26.3-pter syndromes are discussed. CONCLUSION: We propose that a trisomy 1q41-qter syndrome should be considered in particular when the following characteristics are present: postnatal growth delay, macrocephaly, wide fontanelle, triangular facies, frontal bossing, thick eye brows, down slanting palpebral fissures, hypertelorism, flat nasal bridge, hypoplasic nostrils, long filtrum, high palate, microretrognathia, ear abnormalities, neural abnormalities (in particular ventricular dilatation), psychomotor developmental delay and mental retardation. Our patient showed most of these clinical characteristics with exception of macrocephaly, possibly due to a compensatory effect by haploinsufficiency of the two genes lost from 3p. The identification of carriers has important implications for genetic counseling as the risk of a new born with either a der(3) or der(1) resulting from an adjacent-1 segregation is of 25% for each of them, as the products of adjacent-2 or 3:1 segregations are not expected to be viable.

In vitro drug metabolism testing using blood-monocyte derivatives.

INTRODUCTION: Monocytes and their cell derivatives can participate in drug metabolism. These cells express different Phase-I or -II drug metabolizing enzymes and can be differentiated into neo-hepatocytes (NeoHep) and represent a promising alternative strategy to test drug metabolism. This is particularly useful as primary human hepatocytes (PHH), are difficult to obtain and maintain in culture. AREAS COVERED: The authors analyze the use of blood monocytes and their derivatives for the study of drug metabolism. They also compare them to the in vitro ability of cells from different sources including: PHH, immortalized hepatocytes, tumor cell lines and NeoHep. EXPERT OPINION: The use of monocytes, macrophages, dendritic or Kupffer cells, to test drug metabolism, has serious limitations because these cells express lower levels of cytochrome P450 enzymes than PHH. The best available option, to replace PHH, have been tumor cell lines such as HepaRG, as well as immortalized hepatocytes from adult or fetal sources. Monocyte-derived NeoHep cells are novel and easily accessible cells, which express many drug metabolizing enzymes at levels comparable to PHH. These cells allow drug evaluation under a diverse genetic background. While these cells are in the early stages of evaluation and do need to be examined more thoroughly, they constitute a promising new tool for in vitro drug testing.

Diagnosis of familial Wolf-Hirschhorn syndrome due to a paternal cryptic chromosomal rearrangement by conventional and molecular cytogenetic techniques.

The use of conventional cytogenetic techniques in combination with fluorescent in situ hybridization (FISH) and single-nucleotide polymorphism (SNP) microarrays is necessary for the identification of cryptic rearrangements in the diagnosis of chromosomal syndromes. We report two siblings, a boy of 9 years and 9 months of age and his 7-years- and 5-month-old sister, with the classic Wolf-Hirschhorn syndrome (WHS) phenotype. Using high-resolution GTG- and NOR-banding karyotypes, as well as FISH analysis, we characterized a pure 4p deletion in both sibs and a balanced rearrangement in their father, consisting in an insertion of 4p material within a nucleolar organizing region of chromosome 15. Copy number variant (CNV) analysis using SNP arrays showed that both siblings have a similar size of 4p deletion (~6.5 Mb). Our results strongly support the need for conventional cytogenetic and FISH analysis, as well as high-density microarray mapping for the optimal characterization of the genetic imbalance in patients with WHS; parents must always be studied for recognizing cryptic balanced chromosomal rearrangements for an adequate genetic counseling.

[Sensitivity and specificity of endoscopy for the detection of velocardiofacial syndrome]. / Sensibilidad y especificidad de la endoscopia para la detección del síndrome velocardiofacial.

INTRODUCTION: Velo-cardio-facial syndrome (VCFS) (also known as DiGeorge sequence, and 22q11.2 deletion syndrome among other labels) is now recognized as the most common syndrome associated with cleft palate and velopharyngeal insufficiency. 22q11.2 deletion syndrome has been associated with medially positioned internal carotid arteries. This anomaly may be associated with posterior pharyngeal pulsations seen on endoscopy. The purpose of this paper is to study the diagnostic efficacy of the endoscopy for the detection of patients with 22q11.2 deletion syndrome, using as gold standard test the fluorescence in situ hybridization (FISH) test. MATERIAL AND METHODS: Twenty nine patients with submucous cleft palate, velopharyngeal insufficiency, and 22q11.2 deletion as demonstrated by FISH were studied. Also, 29 patients with submucous cleft palate, and without abnormalities in the FISH procedure, were studied as controls. All patients from both groups underwent endoscopy. A double-blind procedure was utilized whereby all videonasopharyngoscopies were independently revised by the two examiners. RESULTS: Twenty five patients with VCFS demonstrated posterior pharyngeal pulsations seen on endoscopy (sensitivity of 86%). In contrast, none of the patients from the control group showed posterior pulsations (specificity of 100%). Positive predictive value was 100%, and negative predictive value was 87%. CONCLUSIONS: Endoscopy seems to be a safe and reliable procedure for evaluating patients with 22q11.2 deletion syndrome. The observations of posterior pharyngeal wall pulsations on endoscopy should alert clinicians to the diagnosis of 22q11.2 deletion, and also, can be useful for preventing the risk of damage to the carotid arteries during velopharyngeal surgery. This indicates another important role of endoscopy in the preoperative assessment of children for palatopharyngoplasty.

[DNA methylation: an epigenetic process of medical importance]. / Metilación del ADN: un fenómeno epigenético de importancia médica.

Methylation of CpG dinucleotides is an epigenetic mechanism involved in the regulation of gene expression in mammals. The patterns of CpG methylation are specie and tissue specific. The biological machinery of this system comprises a variety of regulatory proteins including DNA methyltransferases, putative demethylases, methyl-CpG binding proteins, histones modifying enzymes and chromatin remodeling complexes. DNA methylation maintains gene silencing and participates in normal development, genomic imprinting and X chromosome inactivation. In contrast, alterations in DNA methylation participate in the induction of some human diseases, especially those involving developmental defects and tumorigenesis. This review summarizes the molecular aspects of DNA methylation and its implications in cancer and other human diseases in which this epigenetic mechanism has been involved. Our understanding of the epigenetic changes that occur in human diseases will be very important for future management. Changes in the patterns of methylation can be used as markers in cancer and their potentially reversible state creates a target for therapeutic strategies involving specific gene re-activation or re-silencing.

Metilación del ADN: un fenómeno epigenético de importancia médica / DNA methylation: an epigenetic process of medical importance

Methylation of CpG dinucleotides is an epigenetic mechanism involved in the regulation of gene expression in mammals. The patterns of CpG methylation are specie and tissue specific. The biological machinery of this system comprises a variety of regulatory proteins including DNA methyltransferases, putative demethylases, methyl-CpG binding proteins, histones modifying enzymes and chromatin remodeling complexes. DNA methylation maintains gene silencing and participates in normal development, genomic imprinting and X chromosome inactivation. In contrast, alterations in DNA methylation participate in the induction of some human diseases, especially those involving developmental defects and tumorigenesis. This review summarizes the molecular aspects of DNA methylation and its implications in cancer and other human diseases in which this epigenetic mechanism has been involved. Our understanding of the epigenetic changes that occur in human diseases will be very important for future management. Changes in the patterns of methylation can be used as markers in cancer and their potentially reversible state creates a target for therapeutic strategies involving specific gene re-activation or re-silencing.

La metilación del ADN en dinucleótidos CpG es uno de los mecanismos epigenéticos implicados en la regulación de la expresión génica en mamíferos. Los patrones de metilación son específicos para cada especie y tipo de tejido. La maquinaria implicada comprende diferentes proteínas reguladoras incluyendo a las ADN metiltransferasas, desmetilasas putativas, proteínas de unión a CpG metilados, enzimas modificadoras de histonas y complejos remodeladores de la cromatina. La metilación del ADN es de vital importancia para mantener el silenciamiento génico en el desarrollo normal, la impronta genómica y la inactivación del cromosoma X. En contraste, alteraciones en ella están implicadas en algunas enfermedades humanas, especialmente aquéllas relacionadas con defectos en el desarrollo y el proceso neoplásico. Esta revisión resume los aspectos moleculares de la metilación del ADN y su participación en el desarrollo normal, el cáncer y en algunas patologías humanas en las que los mecanismos epigenéticos han sido implicados. El conocimiento de las modificaciones epigenéticas que ocurren en las enfermedades humanas será importante para su manejo futuro. Los cambios en los patrones de metilación podrán ser empleados como marcadores en cáncer y el estado potencialmente reversible de este proceso constituye un blanco ideal para crear estrategias terapéuticas que impliquen la reactivación o el re-silenciamiento de genes específicos.

Microsatellite analysis in Turner syndrome: parental origin of X chromosomes and possible mechanism of formation of abnormal chromosomes.

Turner syndrome is a chromosomal disorder in which all or part of one X chromosome is missing. The meiotic or mitotic origin of most cases remains unknown due to the difficulty in detecting hidden mosaicism and to the lack of meiotic segregation studies. We analyzed 15 Turner patients, 10 with a 45,X whereas the rest had a second cell line with abnormal X-chromosomes: a pseudodicentric, an isochromosome, one large and one small ring, and the last with a long arm deletion. Our aims were: to detect X cryptic mosaicism in patients with a 45,X constitution; to determine the parental origin of the abnormality; to infer the zygotic origin of the karyotype and to suggest the timing and mechanism of the error(s) leading to the formation of abnormal X chromosomes from maternal origin. Molecular investigation did not revealed heterozygosity for any microsatellite, excluding X mosaicism in the 45,X cases. Parental origin of the single X chromosome was maternal in 90% of these patients. Three of the structurally abnormal Xs were maternally derived whereas the other two were paternal. These results allowed us to corroborate breakpoints in these abnormal X chromosomes and suggest that the pseudodicentric chromosome originated from post-zygotic sister chromatid exchange, whereas the Xq deleted chromosome probably arose after a recombination event during maternal meiosis.