Sylvia Satomi Takeno

Mechanisms of ring chromosome formation, ring instability and clinical consequences.

BackgroundThe breakpoints and mechanisms of ring chromosome formation were studied and mapped in 14 patients.MethodsSeveral techniques were performed such as genome-wide array, MLPA (Multiplex Ligation-Dependent Probe Amplification) and FISH (Fluorescent in situ Hybridization).ResultsThe ring chromosomes of patients I to XIV were determined to be, respectively: r(3)(p26.1q29), r(4)(p16.3q35.2), r(10)(p15.3q26.2), r(10)(p15.3q26.13), r(13)(p13q31.1), r(13)(p13q34), r(14)(p13q32.33), r(15)(p13q26.2), r(18)(p11.32q22.2), r(18)(p11.32q21.33), r(18)(p11.21q23), r(22)(p13q13.33), r(22)(p13q13.2), and r(22)(p13q13.2). These rings were found to have been formed by different mechanisms, such as: breaks in both chromosome arms followed by end-to-end reunion (patients IV, VIII, IX, XI, XIII and XIV); a break in one chromosome arm followed by fusion with the subtelomeric region of the other (patients I and II); a break in one chromosome arm followed by fusion with the opposite telomeric region (patients III and X); fusion of two subtelomeric regions (patient VII); and telomere-telomere fusion (patient XII). Thus, the r(14) and one r(22) can be considered complete rings, since there was no loss of relevant genetic material. Two patients (V and VI) with r(13) showed duplication along with terminal deletion of 13q, one of them proved to be inverted, a mechanism known as inv-dup-del. Ring instability was detected by ring loss and secondary aberrations in all but three patients, who presented stable ring chromosomes (II, XIII and XIV).ConclusionsWe concluded that the clinical phenotype of patients with ring chromosomes may be related with different factors, including gene haploinsufficiency, gene duplications and ring instability. Epigenetic factors due to the circular architecture of ring chromosomes must also be considered, since even complete ring chromosomes can result in phenotypic alterations, as observed in our patients with complete r(14) and r(22).

Genomic alterations in diffuse-type gastric cancer as shown by high-resolution comparative genomic hybridization

Gastric adenocarcinoma is a serious public health concern, especially in northern Brazil. Gastric cancer can be subdivided into diffuse and intestinal types. Genetic imbalances in diffuse-type gastric cancer remain largely unknown. In the present study, we analyzed 24 advanced diffuse-type gastric cancer samples from northern Brazil subjects using high-resolution comparative genomic hybridization. We found chromosomal alterations in 75% of samples. In cancers with aneusomies, the mean genomic copy number alteration was 6.4. Losses of chromosome regions exceeded gains. The most frequent losses were located at chromosome regions 11q and 18q (five samples for each region), 1pq, 3q, 4q, 5q, 13q, and 14q (four samples), followed by 2pq, 7p, 9pq, 11p, and 16p (three samples). Our results confirm that gastric cancer has a complex pattern of chromosomal alterations that can be due to general chromosomal instability related to the advanced stage of gastric carcinogenesis. Loss of 11q and 18q were the most frequent chromosomal changes in diffuse-type gastric adenocarcinoma in individuals from northern Brazil. Frequent loss of 11q chromosome region in this gastric cancer may be peculiar among this population.

Marfan syndrome with a complex chromosomal rearrangement including deletion of the FBN1 gene

BackgroundThe majority of Marfan syndrome (MFS) cases is caused by mutations in the fibrillin-1 gene (FBN1), mapped to chromosome 15q21.1. Only few reports on deletions including the whole FBN1 gene, detected by molecular cytogenetic techniques, were found in literature.ResultsWe report here on a female patient with clinical symptoms of the MFS spectrum plus craniostenosis, hypothyroidism and intellectual deficiency who presents a 1.9 Mb deletion, including the FBN1 gene and a complex rearrangement with eight breakpoints involving chromosomes 6, 12 and 15.DiscussionThis is the first report of MFS with a complex chromosome rearrangement involving a deletion of FBN1 and contiguous genes. In addition to the typical clinical findings of the Marfan syndrome due to FBN1 gene haploinsufficiency, the patient presents features which may be due to the other gene deletions and possibly to the complex chromosome rearrangement.

19q13.33→qter trisomy in a girl with intellectual impairment and seizures

Rearrangements in chromosome 19 are rare. Among the 35 patients with partial 19q trisomy described, only six have a breakpoint defined by array. The 19q duplication results in a variable phenotype, including dysmorphisms, intellectual disability and seizure. In a female patient, although G-banding at 550 band-resolution was normal, multiplex ligation-dependent probe amplification (MLPA) technique and genomic array showed a 10.6 Mb terminal duplication of chromosome 19q13. Fluorescent in situ hybridization (FISH) revealed that the duplicated region was attached to the short arm of chromosome 21 and silver staining showed four small acrocentrics with nucleolar organization region (NOR) activity, suggesting that the breakpoint in chromosome 21 was at p13. This is the first de novo translocation between 19q13.33 and 21p13 described in liveborn. The chromosome 19 is known to be rich in coding and non-coding regions, and chromosomal rearrangements involving this chromosome are very harmful. Furthermore, the 19q13.33→qter region is dense in pseudogenes and microRNAs, which are potent regulators of gene expression. The trisomic level of this region may contribute to deregulation of global gene expression, and consequently, may lead to abnormal development on the carriers of these rearrangements.

Clinical, Cytogenetic and Molecular Study in a Case of r(3) with 3p Deletion and Review of the Literature

Ring chromosome 3 is a rare abnormality with only 10 patients described in the literature. We report a patient with r(3) and ∼6-Mb distal 3p deletion. Single nucleotide polymorphism array, multiplex ligation-dependent probe amplification and fluorescence in situ hybridization techniques revealed that the ring was formed by a break in 3p26.1 and fusion with the subtelomeric region of 3q. The patient presents delayed psychomotor development, growth failure, minor anomalies and other features similar to patients with 3p monosomy. The analysis of 300 metaphase cells using G-banding and fluorescence in situ hybridization with centromeric probe revealed ring instability resulting in cells with secondary aberrations and with ring loss that could also be related to some phenotypic characteristics such as growth delay. This is the first patient with r(3) studied using molecular techniques that determined the exact breakpoints in order to establish a better karyotype-phenotype correlation.

Duplication 4p and deletion 4p (Wolf-Hirschhorn syndrome) due to complementary gametes from a 3:1 segregation of a maternal balanced t(4;13)(p16;q11) translocation.

We present clinical and cytogenetic data on a family with a t(4;13)(p16;q11) translocation present in four generations. The balanced translocation resulted in one individual with monosomy 4p and one individual with trisomy 4p, due to 3:1 segregation. The male patient with trisomy 4p was fertile and transmitted the extra chromosome to his daughter.

Twenty-year cytogenetic and molecular follow-up of a patient with ring chromosome 15: a case report.

IntroductionRing chromosome 15 is a rare disorder, with only a few over 40 cases reported in the literature. There are only two previous reports of cases where patients with ring chromosome 15 have been followed-up.Case presentationWe report here on the 20-year clinical and cytogenetic follow-up of a patient with a ring chromosome 15. Our patient, a Caucasoid Asian woman, presented with short stature, microcephaly, minor dysmorphic features, hyperextensible knees, generalized hirsutism, café-au-lait and small hypochromic spots spread over her face and the front of her chest and abdomen, dorsolumbar scoliosis and mild intellectual disability. She was followed-up from the age of eight to 28 years. When she was 27 years old, she was reported by her mother to present with compulsive overeating and an aggressive mood when challenged. Karyotyping revealed that the majority of her cells harbored one normal chromosome and one ring chromosome. Silver staining revealed the presence of the nucleolar organizer region in the ring chromosome. Ring loss and/or secondary aberrations exhibited a slight increase over time, from 4.67% in 1989 to 7.67% in 2009, with the presence of two monocentric rings, cells with interlocked rings, a dicentric ring, and broken or open rings. A genome-wide array technique detected a 5.5Mb deletion in 15q26.2.ConclusionsWe observed that some phenotypic alterations in our patient can be associated with gene loss and haploinsufficiency. Other features may be related to different factors, including ring instability and epigenetic factors.

Interstitial 4q Deletion and Isodicentric Y-Chromosome in a Patient with Dysmorphic Features.

We present a 2-year-old boy with a de novo 46,XY,idic(Y)(q11.221),del(4)(q26q31.1) karyotype. G-banding, FISH, MLPA, and SNP-array techniques were used to characterize the 24-Mb deletion in 4q and the breakpoint in the isodicentric Y-chromosome region between 15,982,252 and 15,989,842 bp. The patient presented with mild facial dysmorphism, hemangioma, mild frontal cerebral atrophy, and Dandy-Walker variant. Essentially, this case reveals that patients can present more complex genomic imbalances than initially suspected.

Cytogenomic delineation and clinical follow‐up of two siblings with an 8.5 Mb 6q24.2‐q25.2 deletion inherited from a paternal insertion

The chromosomal segment 6q24‐q25 comprises a contiguous gene microdeletion syndrome characterized by intrauterine growth retardation, growth delay, intellectual disability, cardiac anomalies, and a dysmorphic facial phenotype. We describe here a 10‐year follow‐up with detailed clinical, neuropsychological, and cytomolecular data of two siblings, male and female, who presented with developmental delay, microcephaly, short stature, characteristic facial dysmorphisms, multiple organ anomalies, and intellectual disability. Microarray analysis showed an 8.5 Mb 6q24.2‐q25.2 interstitial deletion. Fluorescence in situ hybridization analyses confirmed the deletions and identified an insertion of 6q into 8q13 in their father, resulting in a high recurrence risk. This is the first report in sibs with distinct neuropsychological involvement, one of them with stenosis of the descending branch of the aorta.

Clinical Phenotypes and ABCC6 Gene Mutations in Brazilian Families with Pseudoxanthoma Elasticum

Pseudoxanthoma elasticum (PXE; OMIM 264800) manifests with characteristic skin lesions of yellowish papules which coalesce into plaques of inelastic and leathery skin on the predilection sites (1). The ocular findings consist of angioid streaks, choroidal neovascularization and subretinal hemorrhages resulting in loss of visual acuity and occasional blindness. Cardiovascular problems include hypertension, intermittent claudication, and occasional myocardial infarcts and stroke. The prevalence of PXE is estimated to be in the range of 1:50,000–70,000 and to be more frequent in females than in males. The diagnosis can be challenging to clinicians due to late-onset of clinical manifestations and considerable heterogeneity. PXE is associated with mutations in the ABCC6 gene which encodes a transmembrane efflux transporter expressed primarily in the liver and the kidneys (2). Consequently, PXE has been suggested to be a metabolic disorder with ectopic mineralization of the peripheral connective tissues. Recent studies have also suggested that cutaneous features of PXE can be found in patients with generalized arterial calcification of infancy due to mutations in the ENPP1 gene (3, 4). Previous studies, which have documented close to 600 distinct mutations in the ABCC6 gene, have suggested the presence of unique mutations affecting certain ethnic groups with different ancestral backgrounds (5, 6). In this study, we asked the specific question whether Brazilian patients of mixed European, Native Indian and African ancestry with PXE harbor unique ABCC6 mutations, and whether such mutations might be correlated with the clinical phenotypes in this population with particular reference to heterozygous carriers.