Identification of the MYST3-CREBBP fusion gene in infants with acute myeloid leukemia and hemophagocytosis

ABSTRACT Background: Acute myeloid leukemia presenting the MYST3-CREBBP fusion gene is a rare subgroup associated with hemophagocytosis in early infancy and monocytic differentiation. The aim of this study was to define the relevant molecular cytogenetic characteristics of a unique series of early infancy acute myeloid leukemia cases (≤24 months old), based on the presence of hemophagocytosis by blast cells at diagnosis. Methods: A series of 266 infant cases of acute myeloid leukemia was the reference cohort for the present analysis. Acute myeloid leukemia cases with hemophagocytosis by blast cells were reviewed to investigate the presence of the MYST3-CREBBP fusion gene by fluorescence in situ hybridization (FISH) and reverse transcription polymerase chain reaction. Results: Eleven cases with hemophagocytosis were identified with hemophagocytic lymphohistiocytosis being ruled out. Six cases were classified as myelomonocytic leukemia, three as AML-M7 and two as AML-M2. In five cases, the presence of the MYST3-CREBBP fusion gene identified by molecular cytogenetics was confirmed by fluorescence in situ hybridization. All patients received treatment according to the Berlin-Frankfürt-Münster acute myeloid leukemia protocols and only one out of the five patients with the MYST3-CREBBP fusion gene is still alive. Conclusions: Our findings demonstrate that the presence of hemophagocytosis in acute myeloid leukemia was not exclusively associated to the MYST3-CREBBP fusion gene. Improvements in molecular cytogenetics may help to elucidate more complex chromosomal rearrangements in infants with acute myeloid leukemia and hemophagocytosis.

Auditory Neuropathy/Dyssynchrony: A Retrospective Analysis of 15 Cases

Introduction Auditory neuropathy/dyssynchrony (AN/AD) comprises a spectrum of pathology affecting the auditory pathways anywhere from the inner hair cells to the brainstem. It is characterized by an absent or atypical auditory brainstem response (ABR) with preservation of the cochlear microphonics and/or otoacoustic emissions (OAEs). Objective Retrospective analysis of patients with AN/AD. Methods Fifteen patients with AN/AD were included in this study and their records were retrospectively investigated. Results Possible etiology of AN/AD was neonatal hyperbilirubinemia in three patients, family history of hearing loss in three patients, consanguineous marriage in two patients, head trauma in two patients, mental motor retardation in one patient, cerebrovascular disease in one patient, and there was no apparent cause in three patients. Conclusion Otolaryngologists should keep in mind the diagnosis of AN/AD especially in patients complaining of difficulty in hearing and speech and audiological evidence of disassociation between pure tone and speech audiometry. ABR and OAE testing is recommended in these patients for AN/AD diagnosis. .

Research of the origin of a particular Tunisian group using a physical marker and Alu insertion polymorphisms

The aim of this study was to show how, in some particular circumstances, a physical marker can be used along with molecular markers in the research of an ancient people movement. A set of five Alu insertions was analysed in 42 subjects from a particular Tunisian group (El Hamma) that has, unlike most of the Tunisian population, a very dark skin, similar to that of sub-Saharans, and in 114 Tunisian subjects (Gabes sample) from the same governorate, but outside the group. Our results showed that the El Hamma group is genetically midway between sub-Saharan populations and North Africans, whereas the Gabes sample is clustered among North Africans. In addition, The A25 Alu insertion, considered characteristic to sub-Saharan Africans, was present in the El Hamma group at a relatively high frequency. This frequency was similar to that found in sub-Saharans from Nigeria, but significantly different from those found in the Gabes sample and in other North African populations. Our molecular results, consistent with the skin color status, suggest a sub-Saharan origin of this particular Tunisian group.

Identification and characterization of two critical sequences in SV40PolyA that activate the green fluorescent protein reporter gene

Alu repeats or Line-1-ORF2 (ORF2) inhibit expression of the green fluorescent protein (GFP) gene when inserted downstream of this gene in the vector pEGFP-C1. In this work, we studied cis-acting elements that eliminated the repression of GFP gene expression induced by Alu and ORF2 and sequence characteristics of these elements. We found that sense and antisense PolyA of simian virus 40 (SV40PolyA, 240 bp) eliminated the repression of GFP gene expression when inserted between the GFP gene and the Alu (283 bp) repeats or ORF2 (3825 bp) in pAlu14 (14 tandem Alu repeats were inserted downstream of the GFP gene in the vector pEGFP-C1) or pORF2. Antisense SV40PolyA (PolyAas) induced stronger gene expression than its sense orientation (PolyA). Of four 60-bp segments of PolyAas (1F1R, 2F2R, 3F3R and 4F4R) inserted independently into pAlu14, only two (2F2R and 3F3R) eliminated the inhibition of GFP gene expression induced by Alu repeats. Deletion analysis revealed that a 17 nucleotide AT repeat (17ntAT; 5'-AAAAAAATGCTTTATTT-3') in 2F2R and the fragment 3F38d9 (5'-ATAAACAAGTTAACAACA ACAATTGCATT-3') in 3F3R were critical sequences for activating the GFP gene. Sequence and structural analyses showed that 17ntAT and 3F38d9 included imperfect palindromes and may form a variety of unstable stem-loops. We suggest that the presence of imperfect palindromes and unstable stem-loops in DNA enhancer elements plays an important role in GFP gene activation.

Cuantificación de ADN libre en plasma sanguíneo de voluntarios sanos en una población bogotana / Quantification of free DNA in blood plasma of healthy volunteers in Bogotá population

El ADN libre en sangre incrementa con algunas condiciones patológicas y ciertos estados fisiológicos. Varios reportes en la literatura han resaltado que el ADN libre en plasma o suero tiene potencial clínico como una posible herramienta para el pronóstico de cáncer en humanos. Sin embargo, hasta el momento no se tienen valores de referencia de individuos sanos con un tamaño de muestra representativo y tampoco se han descrito valores para poblaciones específicas como la bogotana. Es por ello que en el presente estudio se cuantificó la concentración de ADN libre en personas sanas de la población bogotana y así se estableció un rango normal o valor de referencia, adicionalmente se analizó la relación entre los niveles de ADN libre y las características como edad y género. La concentración de ADN libre en la población bogotana fue de 0,72 ng/μL y no se encontraron diferencias significativas entre las edades y los géneros.

Estimating genomic instability mediated by Alu retroelements in breast cancer

Alu-PCR is a relatively simple technique that can be used to investigate genomic instability in cancer. This technique allows identification of the loss, gain or amplification of gene sequences based on the analysis of segments between two Alu elements coupled with quantitative and qualitative analyses of the profiles obtained from tumor samples, surgical margins and blood. In this work, we used Alu-PCR to identify gene alterations in ten patients with invasive ductal breast cancer. Several deletions and insertions were identified, indicating genomic instability in the tumor and adjacent normal tissue. Although not associated with specific genes, the alterations, which involved chromosomal bands 1p36.23, 1q41, 11q14.3, 13q14.2, occurred in areas of well-known genomic instability in breast and other types of cancer. These results indicate the potential usefulness of Alu-PCR in identifying altered gene sequences in breast cancer. However, caution is required in its application since the Alu primer can produce non-specific amplification.

Increased gene coverage and Alu frequency in large linkage disequilibrium blocks of the human genome

The human genome has linkage disequilibrium (LD) blocks, within which single-nucleotide polymorphisms show strong association with each other. We examined data from the International HapMap Project to define LD blocks and to detect DNA sequence features inside of them. We used permutation tests to determine the empirical significance of the association of LD blocks with genes and Alu repeats. Very large LD blocks (>200 kb) have significantly higher gene coverage and Alu frequency than the outcome obtained from permutation-based simulation, whereas there was no significant positive correlation between gene density and block size. We also observed a reduced frequency of Alu repeats at the gaps between large LD blocks, indicating that their enrichment in large LD blocks does not introduce recombination hotspots that would cause these gaps.

A novel polymorphic Alu insertion embedded in a LINE 1 retrotransposon in the human X chromosome (DXS225): identification and worldwide population study

We describe a novel polymorphic Alu insertion (DXS225) on the human X chromosome (Xq21.3) embedded into an L1 retrotransposon. The DXS225 polymorphism was genotyped in 684 males from the CEPH Human Genome Diversity Panel. This insertion was found in all regions of the globe, suggesting that it took place before modern humans spread from Africa ca. 100,000 years ago. However, only one Amerindian population (Karitiana) showed this insertion allele, which may have been introduced by European admixture. Thus, it appears likely that the Alu insertion was absent from pre-Columbian America. Analysis of molecular variance worldwide demonstrated that 92.2% of the genetic variance was concentrated within populations. DXS225 is flanked by two microsatellites (DXS8114 and DXS1002), which are 86 kb apart and are in very strong linkage disequilibrium. The combination of a unique event polymorphism on the X chromosome in linkage disequilibrium with two rapidly evolving microsatellites should provide a useful tool for studies of human evolution.

Elementos Transponíveis e Doenças Humanas: da Instabilidade Genônica à Carcinogênese / Transposable Elements and Human Diseases: from Genomic Instability to Carcinogenesis

Os elementos transponíveis säo sequências de DNA que podem se mover no genoma e por isso säo a principal fonte de mutações espontâneas. Dez a 15 por cento do DNA humano säo compostos pelos transposons Alu e Line-1. O grande número desses elementos, no genoma, propicia ampla oportunidade para recombinaçäo homóloga desigual, ocasionando deleções ou duplicações gênicas e mesmo alterações mais complexas do material genético. Säo citados na literatura diversos casos de doenças causadas pela inserçäo de Alu e Line-1 em diversos genes, tanto na linhagem germinativa como somática. Também tem sido encontrada uma correlaçäo direta entre a hipometilaçäo de sequências regulatórias de Line-1 e a presença de produtos de transcriçäo, ou de proteína por ele produzida, em teratocarcinomas, tumores da linhagem germinativa e em alguns cânceres de cérebro e mama. Tal correlaçäo sugere que esses elementos estäo ativos e podem estar envolvidos na iniciaçäo e na manutençäo do estado maligno, principalmente porque a desmetilaçäo do DNA genômico parece ser um evento precoce na progressäo tumoral