Juan Ramón González García

Transient myeloproliferative disorder progression and acquired chromosomal abnormalities in children with Down syndrome.

To the Editor: Transient myeloproliferative disorder (TMD) is frequent in children with Down syndrome (DS). Most cases undergo a clinical and biological regression; however, 13–33% will progress to acute myeloid leukemia (ML-DS) by the age 4 years [1–4]. Whether acquired chromosomal abnormalities (ACAs) play a pivotal role in this progression is debatable. Massey et al. [1] found a significant association between ACAs and the progression of TMD to ML-DS, but this association was not observed in three later publications [2–4]. We evaluated this question by analyzing the reported karyotypes obtained from non-stimulated cell cultures of 47 children with DS, non-mosaic, who were serially studied during both the TMD and ML-DS phases (Supplemental Table I). These data were organized into three categories according to the number of ACAs (Table I), which showed different distributions (Wilcoxon signed-rank test, P < 0.001). Fourteen patients (30%) at TMD phase showed ACAs in contrast with 39 (83%) at ML-DS phase (McNemar’s test, P < 0.001; 177% increase). Of these 14 cases, 8 showed related clones in both phases: 5 showed clonal evolution during the ML-DS phase (Supplemental Table I; cases 9, 10, 15, 22, and 45), and 3 displayed the same abnormal clone (cases 1, 26, and 42). The remaining six had cytogenetic unrelated clones (cases 13, 25, 27, 34, 36, and 39). Similarly, unrelated GATA1 gene mutations during both the TMD and the ML-DS phases have been described [4–6]. Complex karyotypes increased from 2 cases (4%) at TMD phase to 15 cases (32%) at ML-DS phase (McNemar’s test, P < 0.001; 700% increase). Complex karyotypes have been reported to be associated with an unfavorable therapy outcome in malignant myeloid disorders [7–9]. Patients’ ages at the diagnosis of both TMD and ML-DS were compiled in 31 of the 47 children (Supplemental Table I). The time to develop ML-DS was shorter in children with ACAs (n 1⁄4 8; mean 1⁄4 14.13 months; SD 1⁄4 7.6) than in those without ACAs (n 1⁄4 23; mean 1⁄4 20.57 months; SD 1⁄4 7.58; Student’s t test, P < 0.047; 95% CI, 0.76–12.8). Karyotypes of 230 children with DS, non-mosaic, and with spontaneous TMD regression were recorded (Supplemental Table II), categorized (Table I), and compared with those of the 47 children with TMD and progression. Thirty percent (14/47) of children whose disease progressed showed ACAs whereas 16% (36/230) of children with regression had ACAs (Fisher exact test, P < 0.026; relative risk 1⁄4 1.93 (1.12 < RR < 3.32)). The frequency of complex karyotypes in children with progression was not different from that observed in children with regression. We note the possibility of some bias in this analysis due to an unreported later progression of TMD. ACAs appear to be a risk factor for the development of MLDS in children with TMD who should be routinely karyotyped. The presence of ACAs could be an important variable to test whether chemotherapy works or does not work in children with TMD.

Secondary chromosomal changes in 34 Philadelphia-chromosome–positive chronic myelocytic leukemia patients from the Mexican West

The clonal evolution in t(9;22)-positive chronic myelocytic leukemia (CML) is well established. Four major changes occur in more than 70% of patients: +8, i(17q), +19, and an extra Philadelphia chromosome. The frequencies of secondary chromosomal changes in 34 patients from the states of Jalisco, Nayarit, Michoacán, and Colima (the Mexican West) with Philadelphia-chromosome-positive CML were assessed. The most frequent abnormalities were tetraploidy (12 cases); +8, inv(3)(q21q26), and octoploidy (3 cases each); and +der(22)(2 cases). Some translocations not previously associated with CML were observed, such as t(2;7)(p12;q36), t(3;6)(q26;p25), t(3;17)(q26;p13), and t(6;17)(q21;q23 approximately q25). Significant differences were found for +8 with respect to population results from Japan and from southern, eastern, and western Europe; for i(17)(q10) from eastern Europe; for +19 from Japan and western Europe; and for +der(22) from Japan, southern Europe, and western Europe. Although polyploidy could result from endomitosis, there is no direct evidence that the BCR/ABL protein influences such a process; however, protein kinases such as MAPK, which are involved in endomitosis, are activated by the BCR/ABL protein, and so the BCR/ABL protein could promote endomitosis through the MAPK pathway.

Two novel mutations in the ABCG5 gene, c.144 -1G>A and c.1523 delC, in a Mexican family with sitosterolemia

Sitosterolemia is a disease characterized by an intestinal hyperabsorption of plant sterols and cholesterol. Affected individuals have mutations in both alleles of either ABCG5 or ABCG8 genes, leading to a total loss of one of the proteins and subsequent functional deficiency. We here report a Mexican family with clinical and biochemical features of sitosterolemia carrying 2 new mutations of the ABCG5 gene. Concentrations of sitosterol, campesterol, and cholesterol were found to be higher for the index case (a 10-year-old girl) than for her also affected sibling (64.1 vs 19 mg/dL, 32 vs 12.1 mg/dL, and cholesterol 295 vs 235 mg/dL, respectively). Both individuals showed 2 new ABCG5 gene mutations identified by sequencing, which is concordant with their biochemical diagnosis of sitosterolemia. The first mutation was a c.144 -1G>A transition that disrupts the intron 1 splicing acceptor site. The second mutation is the deletion c.1523 delC, which occurred in exon 11, causing an amino acid change at codon 510 (p.His510Thr) and a stop codon at codon 511 (p.Leu511X). The father is heterozygote for the mutation c.144 -1G>A, whereas the mother is heterozygote for the mutation c.1523 delC. In conclusion, we here report the first case of a Mexican family with sitosterolemia carrying two new ABCG5 gene mutations.

1,2:3,4-Diepoxybutane Induces Multipolar Mitosis in Cultured Human Lymphocytes.

1,3-Butadiene, a colorless gas regularly used in the production of plastics, thermoplastic resins, and styrene-butadiene rubber, poses an increased leukemia mortality risk to workers in this field. 1,3-Butadiene is also produced by incomplete combustion of motor fuels or by tobacco smoking. It is absorbed principally through the respiratory system and metabolized by several enzymes rendering 1,2:3,4-diepoxybutane (DEB), which has the highest genotoxic potency of all metabolites of 1,3-butadiene. DEB is considered a carcinogen mainly due to its high potential as clastogen, which induces structural chromosome aberrations such as sister chromatid exchanges, chromosomal breaks, and micronuclei. Due to its clastogenic effect, DEB is one of the most used agents for diagnostic studies of Fanconi anemia, a recessively inherited disease related to mutations affecting several genes involved in a common DNA repair pathway. When performing Fanconi anemia diagnostic tests in our laboratory, we have observed occasional multipolar mitosis (MM) in lymphocyte cultures exposed to 0.1 μg/ml of DEB and harvested in the absence of any mitotic spindle inhibitor. Although previous studies reported an aneugenic effect (i.e. it induces aneuploidy) of DEB, no mechanism was suggested to explain such observations. Therefore, the aim of this study was to investigate whether exposure to 0.1 μg/ml of DEB is significantly associated with the occurrence of MM. We blindly assessed the frequency of MM in lymphocyte cultures from 10 nonsmoking healthy individuals. Two series of 3 cultures were performed from each sample under different conditions: A, without DEB; B, with 0.1 μg/ml of DEB, and C, with 25 μM of mitomycin C as positive control. Cultures exposed to DEB showed higher frequencies of MM (23 of 2,000 cells) than did the unexposed ones (3 of 2,000 cells).1,3-Butadiene, a colorless gas regularly used in the production of plastics, thermoplastic resins, and styrene-butadiene rubber, poses an increased leukemia mortality risk to workers in this field. 1,3-Butadiene is also produced by incomplete combustion of motor fuels or by tobacco smoking. It is absorbed principally through the respiratory system and metabolized by several enzymes rendering 1,2:3,4-diepoxybutane (DEB), which has the highest genotoxic potency of all metabolites of 1,3-butadiene. DEB is considered a carcinogen mainly due to its high potential as clastogen, which induces structural chromosome aberrations such as sister chromatid exchanges, chromosomal breaks, and micronuclei. Due to its clastogenic effect, DEB is one of the most used agents for diagnostic studies of Fanconi anemia, a recessively inherited disease related to mutations affecting several genes involved in a common DNA repair pathway. When performing Fanconi anemia diagnostic tests in our laboratory, we have observed occasional multipolar mitosis (MM) in lymphocyte cultures exposed to 0.1 μg/ml of DEB and harvested in the absence of any mitotic spindle inhibitor. Although previous studies reported an aneugenic effect (i.e. it induces aneuploidy) of DEB, no mechanism was suggested to explain such observations. Therefore, the aim of this study was to investigate whether exposure to 0.1 μg/ml of DEB is significantly associated with the occurrence of MM. We blindly assessed the frequency of MM in lymphocyte cultures from 10 nonsmoking healthy individuals. Two series of 3 cultures were performed from each sample under different conditions: A, without DEB; B, with 0.1 μg/ml of DEB, and C, with 25 μM of mitomycin C as positive control. Cultures exposed to DEB showed higher frequencies of MM (23 of 2,000 cells) than did the unexposed ones (3 of 2,000 cells).

Are submicroscopic chromosomal inversions predisposing factors for the t(9;22)(q34;q11.2) translocation in chronic myeloid leukemia?

A complex chromosomal rearrangement observed in a patient with chronic myeloid leukemia was explained as the consequence of a multistep process. The explanation involved an initial t(9;22) translocation with breakpoints distant from the BCR and ABL1 genes followed by genomic deletions that produced the BCR-ABL1 hybrid gene. We present an alternative model that fits the origin of the patient’s rearrangement better. The present model links submicroscopic inversions with the occurrence of the t(9;22) translocation and opens a new approach on the research on the disease.

Factors associated with abandonment of therapy by children diagnosed with solid tumors in Peru

Abandonment of treatment is a major cause of treatment failure and poor survival in children with cancer in low‐ and middle‐income countries. The incidence of treatment abandonment in Peru has not been reported. The aim of this study was to examine the prevalence of and factors associated with treatment abandonment by pediatric patients with solid tumors in Peru.

Screening of LDLR and APOB gene mutations in Mexican patients with homozygous familial hypercholesterolemia

BACKGROUND Familial hypercholesterolemia (FH) is an autosomal dominant disorder that causes accumulation of serum low-density lipoprotein cholesterol and premature cardiovascular disease. It is mainly related to mutations in the LDLR gene. Homozygous FH (HoFH) patients have the most severe form of the disease accounting for a worldwide prevalence of 1:1,000,000. In Mexico, at least 5 cases of HoFH have been reported. OBJECTIVE The aim of this study was to describe the clinical, biochemical, and molecular data observed in patients with HoFH phenotype. METHODS We included 13 patients, belonging to 11 families, with clinical and biochemical diagnoses suggestive of HoFH. Molecular analyses of the LDLR and APOB genes were performed by means of polymerase chain reaction followed by Sanger sequencing. RESULTS The causal mutation of HoFH was found in 8 of 11 unrelated patients. Excepting 1, all were true homozygotes. Six different variants in LDLR were identified: c.-139delCTCCCCCTGC, p.Glu140Lys, p.Asp360His, p.Asn405Lys, p.Ala755Glyfs*7, and p.Leu759Serfs*6. Of these, p.Asp360His and p.Asn405Lys were detected for the first time in Mexico; p.Leu759Serfs*6 showed to be the most frequent (43.7% of the alleles 7/16), and c.-139delCTCCCCCTGC is a new variant located in the promoter region. CONCLUSIONS This work increases knowledge of biochemical and genetic features in Mexican patients with HoFH. A novel mutation in the LDLR gene promoter was detected: c.-139delCTCCCCCTGC, which possibly inhibits its expression.

Homozygous LPL p.Gly188Glu Mutation in a Mexican Girl With Lipoprotein Lipase Deficiency

Ana Gabriela Colima Fausto, M.S., Juan Ramón González García, Ph.D., Teresita De Jesús Hernández Flores, B.S., Norma Alejandra Vázquez Cárdenas, Ph.D., Nery Eduardo Solís Perales, M.D., and María Teresa Magaña Torres, Ph.D. Genetic Division, Western Biomedical Research Center, Mexican Institute of Social Security, Guadalajara, Jalisco; Doctorate Program in Human Genetics, Health Sciences University Center, University of Guadalajara, Guadalajara, Jalisco; Autonomous University of Guadalajara, Guadalajara; Pediatric Hospital of the Public Health Institute of the State of Guanajuato, Guanajuato, Mexico

21st International Chromosome Conference (ICC). July 10-13, Foz do Iguaçu, Brazil

amazing diversity of life, including over 2,000 species of vascular plants, exotic mammals such as tapirs, giant anteaters, howler monkeys, ocelots, and jaguars, in addition to hundreds of different bird species and thousands of different insects, the choice of Foz is an excellent analogy for the diverse approaches and systems chromosome biologists explore, and that will be emphasized throughout this conference. The 2016 ICC program offers seven sessions, beginning with a session on Chromosome Structure and Nuclear Architecture, highlighting the influences and interactions chromosomes have on the three-dimensional space of the nucleus. Session II will focus on Specialized Chromosomes, such as sex chromosomes and B chromosomes, whose structure and behavior are often distinguished from that of autosomal chromosomes. Population and Evolutionary Chromosome Biology, the third session, covers a synthesis of chromosome biology and The International Chromosome Conferences (ICC) originated from the Oxford Chromosome Conferences, inaugurated by C.D. Darlington and K.R. Lewis in 1964 and held subsequently in England in 1967 and 1970. The Chromosome Conference grew to an international event with its fourth meeting, held in Jerusalem, Israel in 1972, heralding the beginning of 40 years of technological advances that have expanded our understanding of chromosome biology in model and non-traditional biological systems. Having been hosted in Europe and the United States 16 times since then, this year the ICC will be held across the equator in Foz do Iguaçu, Brazil, on July 10–13, 2016. The event will bring scientists from across the globe to a biannual meeting focused on modern advances in chromosome biology, technology and theory. The Iguaçu National Park, a UNESCO World Heritage Centre, includes the Iguaçu Falls and has been chosen as one of the ‘New Natural Seven Wonders of the World’. Home to an Published online: June 2, 2016I.O. Furo a , R. Kretschmer b , R.J. Gunski c , A.D.V. Garnero c , M.A. Ferguson-Smith d , P.C.M. O ́Brien d , E.H.C. de Oliveira e, f a Programa de Pós-Graduação em Genética e Biologia Molecular, PPGBM, Universidade Federal do Pará, Belém, b PPGBM, Universidade Federal do Rio Grande do Sul, Porto Alegre, and c Programa de Pós-Graduação em Ciências Biológicas, Universidade Federal do Pampa, São Gabriel, Brazil; d Department of Veterinary Medicine, University of Cambridge, Cambridge, UK; e Instituto de Ciências Exatas e Naturais, Universidade Federal do Pará, Belém, and f Laboratório de Cultura de Tecidos e Citogenética, SAMAM, Instituto Evandro Chagas, Ananindeua, Brazil

der(14)t(6;14)(p21;q32) Detected in a Phytohemagglutinin-Stimulated Culture from an Asymptomatic Woman with CD5– Monoclonal B-Cell Lymphocytosis

ties in 5/6 MBL patients. Moreover, trisomy 12 and deletions of 13q14, 11q, and 17p have been detected by fluorescence in situ hybridization (FISH) in CLL-like MBL patients [2] . We studied an 82-year-old woman with persistent lymphocytosis detected in March 2005 that required no treatment. During this time, her peripheral blood lymphocyte counts oscillated between 3.0 and 4.8 ! 10 9 /l. A bone marrow aspirate was hypocellular, with 28% normoblasts, 20% mature granulocytes, 16% myelocytes and metamyelocytes, 26% mature lymphocytes, 4% plasmatic cells, 2% eosinophils, 2% blast cells, and 2% reticular cells. The patient tested negative for chronic infectious diseases such as hepatitis A, B, and C, cytomegalovirus, Epstein Barr virus, parvovirus, and toxoplasmosis. Neither adenopathy nor hepatosplenomegaly was detected in the course of periodic clinical visits and imaging analyses. Flow cytometric analysis of bone marrow cells was performed with 2 panels of markers. The first panel included markers compatible with T cell phenotype that were consistently negative (CD1a – , CD2 – , CD3 – , CD4 – , CD5 – , CD7 – , CD8 – , CD11c – , CD43 – , CD56 – , and CD57 – ). The second panel designed to identify B cell phenotypes Monoclonal B cell lymphocytosis (MBL) is a condition characterized by the absence of clinical and hematological manifestations except for the presence of a clonal B cell population with a count ! 5.0 ! 10 9 /l [1–3] . Three categories of MBL have been recognized according to the immunophenotype of clonal cells: chronic lymphocytic leukemia (CLL)-like (CD5 + , CD23 + ), atypical CLL (CD5 + , CD23 – ), and non-CLL (CD5 – ) [1–3] . The most frequent form of MBL is CD5 + , with a prevalence of 0.14–12% in the general population [2, 3] , while only 1% of individuals in the general population exhibit MBL with the CD5 – phenotype [2] . MBL is associated with a preclinical phase of lymphoproliferative disorders; Landgren et al. [4] reported its previous existence in 44 of 45 patients diagnosed as having CLL, 6 months to 6 years before the clinical symptoms appeared. The risk of progression for individuals with CD5 – non-CLL MBL is not well determined, but this disorder is associated with non-Hodgkin lymphoma [2, 3] . There are few chromosomal studies of MBL patients. Han et al. [5] reported no chromosome abnormalities in 6 cases without progression, but abnormal karyotypes were observed in 3/9 MBL patients with disease progression. Amato et al. [6] also found cytogenetic abnormaliReceived: March 10, 2010 Accepted after revision: July 31, 2010 Published online: October 21, 2010