Human ring chromosomes and small supernumerary marker chromosomes-do they have telomeres?

Small supernumerary marker chromosomes derived from human chromosome 11

Introduction: With only 39 reported cases in the literature, carriers of a small supernumerary marker chromosome (sSMC) derived from chromosome 11 represent an extremely rare cytogenomic condition. Methods: Herein, we present a review of reported sSMC(11), add 18 previously unpublished cases, and closely review eight cases classified as 'centromere-near partial trisomy 11' and a further four suited cases from DECIPHER. Results and discussion: Based on these data, we deduced the borders of the pericentric regions associated with clinical symptoms into a range of 2.63 and 0.96 Mb for chromosome 11 short (p) and long (q) arms, respectively. In addition, the minimal pericentric region of chromosome 11 without triplo-sensitive genes was narrowed to positions 47.68 and 60.52 Mb (GRCh37). Furthermore, there are apparent differences in the presentation of signs and symptoms in carriers of larger sSMCs derived from chromosome 11 when the partial trisomy is derived from different chromosome arms. However, the number of informative sSMC(11) cases remains low, with overlapping presentation between p- and q-arm-imbalances. In addition, uniparental disomy (UPD) of 'normal' chromosome 11 needs to be considered in the evaluation of sSMC(11) carriers, as imprinting may be an influencing factor, although no such cases have been reported. Comprehensively, prenatal sSMC(11) cases remain a diagnostic and prognostic challenge.

The past, present, and future for constitutional ring chromosomes: A report of the international consortium for human ring chromosomes

Human ring chromosomes (RCs) are rare diseases with an estimated newborn incidence of 1/50,000 and an annual occurrence of 2,800 patients globally. Over the past 60 years, banding cytogenetics, fluorescence in situ hybridization (FISH), chromosome microarray analysis (CMA), and whole-genome sequencing (WGS) has been used to detect an RC and further characterize its genomic alterations. Ring syndrome featuring sever growth retardation and variable intellectual disability has been considered as general clinical presentations for all RCs due to the cellular losses from the dynamic mosaicism of RC instability through mitosis. Cytogenomic heterogeneity ranging from simple complete RCs to complex rearranged RCs and variable RC intolerance with different relative frequencies have been observed. Clinical heterogeneity, including chromosome-specific deletion and duplication syndromes, gene-related organ and tissue defects, cancer predisposition to different types of tumors, and reproductive failure, has been reported in the literature. However, the patients with RCs reported in the literature accounted for less than 1% of its occurrence. Current diagnostic practice lacks laboratory standards for analyzing cellular behavior and genomic imbalances of RCs to evaluate the compound effects on patients. Under-representation of clinical cases and lack of comprehensive diagnostic analysis make it a challenge for evidence-based interpretation of clinico-cytogenomic correlations and recommendation of follow-up clinical management. Given recent advancements in genomic technologies and organized efforts by international collaborations and patient advocacy organizations, the prospective of standardized cytogenomic diagnosis and evidence-based clinical management for all patients with RCs could be achieved at an unprecedented global scale.

X-derived marker chromosome in patient with mosaic Turner syndrome and Dandy-Walker syndrome: a case report

Background

Small supernumerary marker chromosomes can be derived from autosomes and sex chromosomes and can accompany chromosome pathologies, such as Turner syndrome.

Case presentation

Here, we present a case report of a patient with mosaic Turner syndrome and Dandy-Walker syndrome carrying a marker chromosome. We showed the presence of the marker chromosome in 33.8% of blood cells. FISH of the probe derived from the marker chromosome by microdissection revealed that it originated from the centromeric region of chromosome X. Additionally, we showed no telomeric sequences and no XIST sequence in the marker chromosome. This is the first report of these two syndromes accompanied by the presence of a marker chromosome.

Conclusion

Marker chromosome was X-derived and originated from centromeric region. Patient has mild symptoms but there is no XIST gene in marker chromosome.

Trial registration

CPG137. Registered 03 March 2017.

Disorder of sex development in a cat with chromosome mosaicism 37,X/38,X,r(Y)

An 18-month-old European shorthair cat was subjected to genetic studies due to ambiguous external genitalia (underdeveloped both penis and scrotum). Further anatomic and histopathological studies revealed the presence of abdominal, atrophic testes and uterus. Cytogenetic analysis showed two cell lines, one with X monosomy-37,X [90% of the analysed metaphase spreads], and other line had 38 chromosomes with normal X chromosome and abnormally small Y-derived chromosome-38,X,der(Y) [10%]. Further fluorescence in situ hybridization study with telomeric probe revealed a ring structure of the der(Y). Eight Y chromosome-specific genes, SRY, TETY1, TETY2, CUL4BY, CYORF15, HSFY, FLJ36031Y and ZFY, were detected. We conclude that the described abnormality of the reproductive system, leading to sterility, was caused by a very rare type of chromosomal mosaicism-37,X/38,X,r(Y).

Mitotic stability of small supernumerary marker chromosomes depends on their shape and telomeres - a long term in vitro study

Mosaicism is present in more than 50% of the cases with small supernumerary marker chromosomes (sSMCs) and karyotype 47,XX,+mar/46,XX or 47,XY,+mar/46,XY. Recently we provided first evidence that the mitotic stability of sSMC is dependent on their structure, i.e. their shape. Thus, here we performed a long term in vitro study on 12 selected cell lines from the Else Kröner-Fresenius-sSMC-cellbank (http://ssmc-tl.com/ekf-cellbank.html) to test mitotic sSMC stability systematically. The obtained results showed that inverted duplicated shaped and also the so-called complex sSMCs (group 1) are by far more stable, than centric-minute- or ring-shaped sSMCs (groups 2). Generally speaking, the percentage of cells with group-1-sSMCs remained stable over 90 days of cell culture, while that of group-2-sSMCs in parts dramatically decreased. In one group-2-cell line the sSMC was even lost completely after 30 days of in vitro culture, in others the sSMC was depleted in up to 40% of the cells. Still the highest rate of sSMC loss was recorded during EBV-transformation. Overall, the major difference between groups 1 and 2 was the number of telomeres per sSMC. In group 1 the sSMCs had "original" telomeres at both of their ends; in group 2 the sSMCs had either no, possibly secondary acquired and/or only one original telomere. This absence of protective telomeric sequences in group 2 seems to make sSMC more susceptible for loss during cell division. Still, also a growth advantage of cells without sSMC cannot be neglected entirely.

Clinical and genetic characterization of basal cell carcinoma and breast cancer in a single patient

Introduction

Multiple environmental and genetic factors are involved with the development of basal cell carcinomas (BCC), as well as with breast cancers. Tumor initiation and progression are often associated with genomic instability such as aneuploidies, and gains or losses of large chromosomal segments, known as copy number alterations (CNAs). CNAs have been successfully detected using the microarray comparative genomic hybridization technique (array-CGH) at high resolution. Data thus obtained are useful to identify specific genomic aberrations, to classify tumor stages, and to stratify subgroups of patients with different prognosis and clinical behaviors.

Case description

Clinical study of a 66-year-old white female identified two primary tumors, a ductal invasive grade-II carcinoma of the breast, and one nodular BCC. Germline and tumor genomic survey utilized the 180 K array-CGH analysis to investigate chromosomal alterations.

Discussion and evaluation

Several chromosomal anomalies were detected in the breast tumor genome, including focal ~422 Kb 13q13.3 microdeletion. In the BCC, amplification of a chromosome 6 spanning the centromere region between the cytobands 6p23 and 6q12 was identified. Several 6p amplified genes correspond to families of histone and human leukocyte antigen genes, whereas some of the CNAs found in the breast tumor are uncommon. No germline CNA was detected in the normal skin of the patient at this technical resolution.

Conclusion

CNAs found in the two different tumors of the patient constitute independent events arisen in the somatic lineage. Relevant genes to both carcinogenesis and progression are to be affected by these CNAs.

Electronic supplementary material

The online version of this article (doi:10.1186/2193-1801-3-454) contains supplementary material, which is available to authorized users.

Mitotic stability of small supernumerary marker chromosomes: a study based on 93 immortalized cell lines

Small supernumerary marker chromosomes (sSMC) are known for being present in mosaic form as 47,+mar/46 in >50% of the cases with this kind of extra chromosomes. However, no detailed studies have been done for the mitotic stability of sSMC so far, mainly due to the lack of a corresponding in vitro model system. Recently, we established an sSMC-cell bank (Else Kröner-Fresenius-sSMC-cellbank) with >150 cell lines. Therefore, 93 selected sSMC cases were studied here for the presence of the corresponding marker chromosomes before and after Epstein-Barr virus-induced immortalization. The obtained results showed that dicentric inverted duplicated-shaped sSMC are by far more stable in vitro than monocentric centric minute- or ring-shaped sSMC. Simultaneously, a review of the literature revealed that a comparable shape-dependent mitotic stability can be found in vivo in sSMC carriers. Additionally, a possible impact of the age of the sSMC carrier on mitotic stability was found: sSMC cell lines established from patients between 10-20 years of age were predominantly mitotically unstable. The latter finding was independent of the sSMC shape. The present study shows that in vitro models can lead to new and exciting insights into the biology of this genetically and clinically heterogeneous patient group.