Maria Isabel Melaragno

Cytogenetic aspects of Werner's syndrome lymphocyte cultures

Lymphocyte cultures from five patients with Werners syndrome (WS) and five healthy controls revealed significantly slower proliferation kinetics in four out of five patients. Higher frequencies of chromosome aberration and aneuploidy were also present with evidence of variegated translocation mosaicism in one of the patients. The study revealed no differences in sister chromatid exchange frequencies.

Sister chromatid exchange and proliferation pattern in lymphocytes from newborns, elderly subjects and in premature aging syndromes

Sister chromatid exchange (SCE) frequency and cell proliferation were examined in lymphocyte cultures from a group of newborns, a group of elderly subjects and from patients with syndromes who exhibit progeriform characteristics (progeria, Cockayne syndrome, Rothmund-Thomson syndrome and Christ-Siemens-Touraine syndrome) by using the bromodeoxyuridine incorporation differential staining technique. We observed a significantly increase in basal SCE frequency and a less intensive cell proliferation in cultures from elderly subjects than from newborns, as shown by the significant increase in percentage of cells in first generation simultaneous with a reduction of cells in more advanced generations. Lymphocyte cultures from each one of the patients studied also showed a decreased cell proliferation in relation to their respective control and to newborn cultures. Each of these syndromes showed higher baseline SCE levels than the control and than the newborn and elderly groups. Only the patient with progeria showed values similar to those for the elderly group. Thus, in addition to showing clinical characteristics similar to those observed during the normal aging process, these progeriform syndromes also show cytogenetic characteristics similar to those of older individuals.

INVESTIGATION OF THE EFFECT OF HYDROGEN PEROXIDE ON THE CHROMOSOMES OF YOUNG AND ELDERLY INDIVIDUALS

Active oxygen species have been considered to be responsible for the aging process and for the induction and initiation of neoplastic processes. The effect of hydrogen peroxide, an active oxygen species, was investigated in the chromosomes of three young women (20-21 years of age) and of three elderly women (73-79 years of age) in a culture medium favorable to the appearance of folate-sensitive fragile sites. Hydrogen peroxide at a final concentration of 5 X 10(-6) during the final hours of culture caused a significant increase in hypodiploidy and structural aberrations, chromatid gaps in particular, only in the cultures from the three elderly women, suggesting that the chromosomes of older women are more sensitive to this agent than those of younger women. The preferential chromosome loss in both treated and untreated cultures from the elderly women involved chromosome X. The preferential sites for structural aberrations were 9p12, a constitutive heterochromatin site and 6q21, where the gene of mitochondrial superoxide dismutase, an enzyme involved in antioxidant processes in the cell, is located. Hydrogen peroxide significantly intensified the effect naturally occurring in the cells of elderly persons, such as hypodiploidy and increased structural aberrations, thus acting at the chromosome level in a manner similar to that of the natural aging process of the organism.

Lymphocyte Proliferation and Sister Chromatid Exchange in Alzheimer's Disease

Sister chromatid exchange (SCE) and lymphocyte proliferation were studied in peripheral lymphocyte cultures derived from 5 patients with Alzheimer disease (AD), 5 control elderly subjects and 5 young donors. These parameters did not differ significantly between the AD group and the elderly control group, but higher SCE frequency and less intensive proliferation were observed in the AD group and in the elderly control group when compared to the young donors.

A novel de novo mutation in MYT1 , the unique OAVS gene identified so far

Oculo-auriculo-vertebral spectrum (OAVS) is a developmental disorder characterized by hemifacial microsomia associated with ear, eyes and vertebrae malformations showing highly variable expressivity. Recently, MYT1, encoding the myelin transcription factor 1, was reported as the first gene involved in OAVS, within the retinoic acid (RA) pathway. Fifty-seven OAVS patients originating from Brazil were screened for MYT1 variants. A novel de novo missense variant affecting function, c.323C>T (p.(Ser108Leu)), was identified in MYT1, in a patient presenting with a severe form of OAVS. Functional studies showed that MYT1 overexpression downregulated all RA receptors genes (RARA, RARB, RARG), involved in RA-mediated transcription, whereas no effect was observed on CYP26A1 expression, the major enzyme involved in RA degradation, Moreover, MYT1 variants impacted significantly the expression of these genes, further supporting their pathogenicity. In conclusion, a third variant affecting function in MYT1 was identified as a cause of OAVS. Furthermore, we confirmed MYT1 connection to RA signaling pathway.

Atypical 581-kb 22q11.21 Deletion in a Patient with Oculo-Auriculo-Vertebral Spectrum Phenotype.

The oculo-auriculo-vertebral spectrum (OAVS) is defined as a group of malformations involving the ears, mouth, mandible, eyes, and cervical spine. Establishing an accurate clinical diagnosis of OAVS is a challenge for clinical geneticists, not only because these patients display heterogeneous phenotypes, but also because its etiology encompasses environmental factors, unknown genetic factors and different chromosome aberrations. To date, several chromosomal abnormalities have been associated with the syndrome, most frequently involving chromosome 22. In the literature, six 22q11.2 microdeletions have been described within the same region, suggesting possible OAVS candidate genes in this segment. Here, we report on a patient with an ∼581-kb 22q11.21 deletion, detected by genomic array and MLPA. This is the 7th case described with OAVS and 22q deletion, suggesting that the 22q11.2 region may be related to the regulation of body symmetry and facial development.

Identification of IL11RA and MELK amplification in gastric cancer by comprehensive genomic profiling of gastric cancer cell lines

AIM To identify common copy number alterations on gastric cancer cell lines. METHODS Four gastric cancer cell lines (ACP02, ACP03, AGP01 and PG100) underwent chromosomal comparative genome hybridization and array comparative genome hybridization. We also confirmed the results by fluorescence in situ hybridization analysis using the bacterial artificial chromosome clone and quantitative real time PCR analysis. RESULTS The amplification of 9p13.3 was detected in all cell lines by both methodologies. An increase in the copy number of 9p13.3 was also confirmed by fluorescence in situ hybridization analysis. Moreover, the interleukin 11 receptor alpha (IL11RA) and maternal embryonic leucine zipper kinase (MELK) genes, which are present in the 9p13.3 amplicon, revealed gains of the MELK gene in all the cell lines studied. Additionally, a gain in the copy number of IL11RA and MELK was observed in 19.1% (13/68) and 55.9% (38/68) of primary gastric adenocarcinoma samples, respectively. CONCLUSION The characterization of a small gain region at 9p13.3 in gastric cancer cell lines and primary gastric adenocarcinoma samples has revealed MELK as a candidate target gene that is possibly related to the development of gastric cancer.

Wolf-Hirschhorn Syndrome with Epibulbar Dermoid: An Unusual Association in a Patient with 4p Deletion and Functional Xp Disomy

Wolf-Hirschhorn syndrome (WHS) is a contiguous gene and multiple malformation syndrome that results from a deletion in the 4p16.3 region. We describe here a 6-month-old girl that presented with WHS features but also displayed unusual findings, such as epibulbar dermoid in the left eye, ear tags, and left microtia. Although on G-banding her karyotype appeared to be normal, chromosomal microarray analysis revealed an ∼13-Mb 4p16.3p15.33 deletion and an ∼9-Mb Xp22.33p22.31 duplication, resulting from a balanced maternal t(X;4)(p22.31;p15.33) translocation. The patient presented with functional Xp disomy due to an unbalanced X-autosome translocation, a rare cytogenetic finding in females with unbalanced rearrangements. Sequencing of both chromosome breakpoints detected no gene disruption. To the best of our knowledge, this is the first patient described in the literature with WHS and epibulbar dermoid, a typical characteristic of the oculoauriculovertebral spectrum (OAVS). Our data suggest that possible candidate genes for OAVS may have been deleted along with the WHS critical region.

Call for Nomination of Members of the International Standing Committee of Human Cytogenomic Nomenclature

The present Committee (Jaclyn Biegel, Myriam Chaabouni, Johan T. den Dunnen, Jin-Yeong Han, Nils Mandahl, Jean McGowan-Jordan, Kathleen W. Rao, Annet Simons) was elected in the fall of 2011, with Lisa Shaffer as Chair. The Committee elected a new Chair, Jean McGowan-Jordan, during their meeting in Seattle in 2012. Several new members of the Committee now need to be elected. To facilitate continuity and maintain geographic distribution, the Chair of the new Committee will remain, along with Nils Mandahl, Johan T. den Dunnen, and Jin-Yeong Han. New members from the Americas (2), Europe (1), Africa and Australia/New Zealand/Oceania (1) are therefore required. The nominations of potential new Committee members shall be by e-mail. Nominations for candidates including their name, affiliation, postal address and e-mail address should be e-mailed to the Chair at jordan@cheo.on.ca before February 15, 2018, after which the list of nominated candidates will be published with the call for voting. Ballots for voting can be requested from the Chair at jordan@cheo.on.ca after February 15, 2018, by including your name, affiliation, postal address, and e-mail. The election ballots with voting procedures will then be distributed after March 15, 2018, to the requested address. Instructions for returning the ballots will accompany the ballot requests. Published online: January 23, 2018

Deletion 21pterq22.11: Report of a Patient with Dysmorphic Features, Hypertonia, and Café-au-Lait Macules and Review of the Literature

Partial monosomy 21 results in a great variability of clinical features that may be associated with the size and location of the deletion. In this study, we report a 22-month-old girl who showed a 45,XX,add(12)(p13)dn,-21 karyotype. The final cytogenomic result was 45,XX,der(12)t(12;21)(p13;q22.11) dn,-21.arr[hg19] 21q11.2q22.11(14824453_33868129)×1 revealing a deletion from 21pter to 21q22.11. Clinical manifestation of the patient included hypertonia, a long philtrum, epicanthic folds, low-set ears, and café-au-lait macules - a phenotype considered as mild despite the relatively large size of the deletion compared to patients from the literature.