Juan J. Yunis

Bio: Juan J. Yunis is an academic researcher from Harvard University. The author has contributed to research in topics: Medicine & Population. The author has an hindex of 22, co-authored 36 publications receiving 1541 citations. Previous affiliations of Juan J. Yunis include Boston University & National University of Colombia.

HLA-B38, DR4, DQw3 and clozapine-induced agranulocytosis in Jewish patients with schizophrenia.

Abstract: • Agranulocytosis develops in approximately 1% of patients with chronic schizophrenia treated with the atypical neuroleptic drug clozapine. Previous studies have not identified the mechanism or risk factors for this adverse reaction. Because of an observed association between Jewish ethnic background and the development of agranulocytosis in our patient sample treated with clozapine for refractory symptoms, HLA typing was performed in 31 patients (19.4% of whom had developed agranulocytosis). The HLA-B38 phenotype was found in 83% of patients who developed agranulocytosis and in 20% of clozapine-treated patients who did not develop agranulocytosis. Because B38 is part of a haplotype known to occur frequently in the Ashkenazi Jewish population, the frequencies of the combined alleles HLA-B38, DR4 and DQw3 were examined. The incidence of HLA-B38, DR4, DQw3 was significantly increased in patients with agranulocytosis (five of five patients) compared with control patients of Ashkenazi Jewish ancestry (two of 17 patients). These findings indicate that genetic factors marked by major histocompatibility complex haplotypes may be associated with the susceptibility of Jewish schizophrenic patients treated with clozapine to develop agranulocytosis. We postulate that gene products contained in the haplotype may be involved in mediating drug toxicity.

A Common Major Histocompatibility Complex Class II Allele HLA-DQB1 * 0301 is Present in Clinical Variants of Pemphigoid

Abstract: Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease seen primarily in elderly persons. It is characterized clinically by the development of tense bullae and by the presence of an antibasement membrane antibody. In BP, the antigens involved in the autoimmunity are epidermal basement membrane peptides BPAg1 and BPAg2. We have compared high resolution typing of major histocompatibility complex class II loci (HLA-DRB1, DQB1) in 21 patients with BP, 17 with ocular cicatricial pemphigoid (OCP), and 22 with oral pemphigoid (OP) to a panel of 218 haplotypes of normal individuals. We found that the three diseases (BP, OCP, and OP) have significant association with DQB1*0301 (P = 0.005, P < 0.0001, and P = 0.001, respectively). The frequencies of alleles DQB1*0302, 0303, and 06, which share a specific amino acid sequence from position 71 to 77 (Thr-Arg-Ala-Glu-Leu-Val-Thr) were also increased (P = 0.01). We suggest that an identical major histocompatibility complex class II allele (DQB1*0301) is a common marker for enhanced susceptibility and that the same amino acid residues in positions 71-77 (DQB1*0301, -0302, -0305, -0602, -0603 alleles) are found in patients with BP, OCP and OP. Our findings propose that the autoimmune response in the three different clinical variants of pemphigoid, involves the recognition by T cells of a class II region of DQB1, bound to a peptide from the basement membrane of conjunctiva, oral mucosa, and skin.

Polymorphic Alu insertions and the Asian origin of native American populations

Abstract: A rapid PCR-based assay was used to study the distribution of 5 polymorphic Alu insertions in 895 unrelated individuals from 30 populations, 24 from North, Central, and South America Although a significant level of interpopulation variability was detected, the variability was less than that observed in a worldwide population survey This is consistent with the bottleneck effect and genetic drift forces that may have acted on the migrating founder groups The results corroborate the Asian origin of native American populations but do not support the multiple-wave migration hypothesis supposedly responsible for the tri-partite Eskaleut, Nadene, and Amerind linguistic groups Instead, these populations exhibit three major identifiable clusters reflecting geographic distribution Close similarity between the Chinese and native Americans suggests recent gene flow from Asia

Disputed Maternity Leading to Identification of Tetragametic Chimerism

Abstract: Chimerism is the presence of two genetically distinct cell lines in an organism. This report describes a phenotypically normal woman who was found to have tetragametic chimerism after histocompatibility testing of family members suggested that she was not the biologic mother of two of her three children. She had only one cell line in peripheral blood but had more than one in other tissues. Her T lymphocytes showed full tolerance of cells from family members with any combination of four familial HLA haplotypes.

Alu repeats and human genomic diversity

Abstract: During the past 65 million years, Alu elements have propagated to more than one million copies in primate genomes, which has resulted in the generation of a series of Alu subfamilies of different ages. Alu elements affect the genome in several ways, causing insertion mutations, recombination between elements, gene conversion and alterations in gene expression. Alu-insertion polymorphisms are a boon for the study of human population genetics and primate comparative genomics because they are neutral genetic markers of identical descent with known ancestral states.

Clozapine-induced agranulocytosis. Incidence and risk factors in the United States

Abstract: Background Clozapine is an atypical antipsychotic agent that is more effective than standard neuroleptic drugs in the treatment of patients with refractory schizophrenia. Unlike classic neuroleptic agents, clozapine is not associated with the development of acute extrapyramidal symptoms or tardive dyskinesia. The main factor limiting its use is the risk of potentially fatal agranulocytosis, estimated to occur in 1 to 2 percent of treated patients. After clozapine was approved by the Food and Drug Administration, it became available for marketing in the United States in February 1990 only as part of a special surveillance system (the Clozaril Patient Management System, or CPMS), in which a weekly white-cell count was required for the patient to receive a supply of the drug. Methods We evaluated the CPMS data for February 1990 through April 1991 by survival analysis to determine the incidence of agranulocytosis and the effects of potential risk factors such as age and sex. Data were available for 11,555 pat...

Donor-Derived Brain Tumor Following Neural Stem Cell Transplantation in an Ataxia Telangiectasia Patient

Abstract: Background Neural stem cells are currently being investigated as potential therapies for neurodegenerative diseases, stroke, and trauma. However, concerns have been raised over the safety of this experimental therapeutic approach, including, for example, whether there is the potential for tumors to develop from transplanted stem cells. Methods and Findings A boy with ataxia telangiectasia (AT) was treated with intracerebellar and intrathecal injection of human fetal neural stem cells. Four years after the first treatment he was diagnosed with a multifocal brain tumor. The biopsied tumor was diagnosed as a glioneuronal neoplasm. We compared the tumor cells and the patient's peripheral blood cells by fluorescent in situ hybridization using X and Y chromosome probes, by PCR for the amelogenin gene X- and Y-specific alleles, by MassArray for the ATM patient specific mutation and for several SNPs, by PCR for polymorphic microsatellites, and by human leukocyte antigen (HLA) typing. Molecular and cytogenetic studies showed that the tumor was of nonhost origin suggesting it was derived from the transplanted neural stem cells. Microsatellite and HLA analysis demonstrated that the tumor is derived from at least two donors. Conclusions This is the first report of a human brain tumor complicating neural stem cell therapy. The findings here suggest that neuronal stem/progenitor cells may be involved in gliomagenesis and provide the first example of a donor-derived brain tumor. Further work is urgently needed to assess the safety of these therapies.

Cytokine gene polymorphism in human disease: on-line databases.

Abstract: The pathologies of many infectious, autoimmune and malignant diseases are influenced by the profiles of cytokine production in pro-inflammatory (TH1) and anti-inflammatory (TH2) T cells. Interindividual differences in cytokine profiles appear to be due, at least in part, to allelic polymorphism within regulatory regions of cytokine gene. Many studies have examined the relationship between cytokine gene polymorphism, cytokine gene expression in vitro, and the susceptibility to and clinical severity of diseases. A review of the findings of these studies is presented. An on-line version featuring appropriate updates is accessible from the World Wide Web site, http://www.pam.bris.ac.uk/services/GAI/cytokine4.htm.

A module map showing conditional activity of expression modules in cancer.

Abstract: DNA microarrays are widely used to study changes in gene expression in tumors, but such studies are typically system-specific and do not address the commonalities and variations between different types of tumor. Here we present an integrated analysis of 1,975 published microarrays spanning 22 tumor types. We describe expression profiles in different tumors in terms of the behavior of modules, sets of genes that act in concert to carry out a specific function. Using a simple unified analysis, we extract modules and characterize gene-expression profiles in tumors as a combination of activated and deactivated modules. Activation of some modules is specific to particular types of tumor; for example, a growth-inhibitory module is specifically repressed in acute lymphoblastic leukemias and may underlie the deregulated proliferation in these cancers. Other modules are shared across a diverse set of clinical conditions, suggestive of common tumor progression mechanisms. For example, the bone osteoblastic module spans a variety of tumor types and includes both secreted growth factors and their receptors. Our findings suggest that there is a single mechanism for both primary tumor proliferation and metastasis to bone. Our analysis presents multiple research directions for diagnostic, prognostic and therapeutic studies.