Factors affecting clinical manifestation of chromosomal imbalance in carriers of segmental autosomal mosaicism: differential impact of gender

Mosaicism for unbalanced chromosomal rearrangements segmental mosaicism (SM) is rare, both in patients referred for cytogenetic testing and in prenatal diagnoses. In contrast, in preimplantation embryos SM is a frequent finding and, therefore, is even more challenging. However, there is no consistency among results of published studies on the clinical outcomes of embryos with SM, primarily due to the small number of reported cases. Moreover, there is the problem of predicting the potential for the optimal development of a mosaic embryo to a healthy individual. Therefore, we suggested comparing factors predisposing to favorable and poor prognoses, identified in postnatal and prenatal cohorts of SM carriers, with those obtained from studies on preimplantation embryos. We analyzed 580 published cases of SM including (i) postnatally diagnosed affected carriers, (ii) clinically asymptomatic carriers, (iii) prenatally diagnosed carriers, and (iv) miscarriages. We observed a concordance with preimplantation diagnoses regarding the clinical significance of the extent of mosaicism as well as a predominance of deletions over other types of rearrangements. However, there is no concordance regarding excessive involvement of chromosomes 1, 5, and 9 in unbalanced rearrangements and a preferential involvement of larger chromosomes compared to short ones. Paternal age was not found to be associated with SM in postnatally disease-defined individuals. We have identified maternal age and preferential involvement of chromosome 18 in rearrangements associated with clinical manifestations. Male predominance was found among normal pregnancy outcomes and among disease-defined carriers of rearrangements resulting in a gain of genomic material. Female predominance was found among abnormal pregnancy outcomes, among disease-defined carriers of loss and gain/loss rearrangements, and among transmitting carriers of gonadal SM, both affected and asymptomatic. According to data obtained from “post-embryo” studies, clinical manifestations of chromosomal imbalance are associated with a high proportion of abnormal cells, female gender, the type of rearrangement and involved chromosome(s), and maternal age. We believe these data are instructive in the challenging medical genetic counseling of parents faced with no option other than transfer of an embryo with segmental mosaicism.

Complex approach to the study of the Derivative Chromosome 8

Введение. Дериватная хромосома (der) - структурно аномальная хромосома, формирование которой может происходить как в результате перестроек с участием двух и более негомологичных хромосом, так и вследствие аберраций внутри одной хромосомы. Дифференциальная диагностика дериватных хромосом очень важна для выяснения происхождения хромосомной аномалии и для определения тактики медико-генетического консультирования с целью оценки повторного риска рождения ребенка с хромосомным дисбалансом. В данной работе представлены семь случаев дериватной хромосомы 8, имеющих различное происхождение и механизмы формирования, а также протокол обследования пациентов с дериватной хромосомой 8 в кариотипе. Цель: изучить структуру и механизмы формирования дериватных хромосом 8. Методы: стандартное цитогенетическое исследование, M-FISH, MCB8, FISH с локус-специфичными субтеломерными ДНК-зондами, FISH с несерийными ДНК-зондами на район р23.1 хромосомы 8. Результаты. В результате проведенного стандартного цитогенетического исследования в кариотипе семи неродственных пробандов была обнаружена дериватная хромосома 8. При использовании цитогенетического и молекулярно-цитогенетического подходов было установлено, что у четырех пациентов дериватная хромосома 8 возникла в результате инвертированной дупликации/делеции 8р, а у трех - несбалансированной транслокации с участием хромосомы 8: der(8)t(8;17), der(8)t(8;12) и der(8)t(7;8). Во всех случаях был определен механизм формирования хромосомных перестроек. Дериватные хромосомы транслокационного происхождения в двух случаях были сформированы de novo, а в одном случае - как результат патологической мейотической сегрегации отцовской реципрокной транслокации. Все дериватные хромосомы с инвертированной дупликацией/делецией 8р были следствием эктопической рекомбинации. Заключение. Представленные результаты демонстрируют целесообразность комплексного лабораторного подхода в изучении структуры и происхождения дериватной хромосомы 8. Характеристика происхождения хромосомного дисбаланса является неотъемлемой частью обследования пациентов со структурно аномальной хромосомой 8 в кариотипе. Background. Derivative chromosome (der) is a structurally abnormal chromosome, the formation of which can occur as a result of rearrangements with the participation of two or more non-homologous chromosomes, or be the result of aberrations within one chromosome. Differential diagnosis of derivative chromosomes is very important for clarifying the origin of the chromosomal abnormality and for determining the tactics of medical genetic counseling in order to assess the repeated risk of chromosomal imbalance. This work presents seven cases of a derivative chromosome with different origins and mechanisms of formation, as well as a protocol for examining patients with derivative chromosome 8 in the karyotype. Aim: to study the structure and mechanisms of formation of the derivative chromosome 8. Methods. GTG-banded chromosomal analysis, M-FISH, MCB8, FISH with subtelomeric DNA probes, FISH with home-made DNA probes for 8p23.1. Results. As a result of a conventional cytogenetic study of seven unrelated probands a derivative chromosome 8 was found. In all cases, the mechanism of the formation of chromosomal rearrangements was determined. Derivative chromosomes of translocation origin were formed de novo in two cases- der(8)t(8;12) and der(8)t(7;8), and in one case -der(8)t(8;17) - as a result of malsegregation of the paternal reciprocal translocation. In the remaining four cases, the derivative chromosomes were identified as an inverted duplication/deletion 8p due to ectopic recombination. Conclusion. The presented results demonstrate the feasibility of an integrated laboratory approach in the diagnosis of derivative chromosome 8. Characterization of the origin of chromosomal imbalance is an integral part of the examination of patients with structurally abnormal chromosome 8 in the karyotype.

Partial Trisomy 13q/Monosomy 3p Resulting from a Paternal Reciprocal 3p;13q Translocation in a Boy with Facial Dysmorphism and Hypertrophic Cardiomyopathy

Individuals with 3p deletion show a great clinical variability. Apparently, a 1.5-Mb terminal deletion, including the <i>CRBN</i> and <i>CNTN4</i> genes, is sufficient to cause this syndrome. Partial trisomy 13q is a rare chromosomal abnormality with a variable phenotypic expression, but in most cases, patients have a phenotype resembling complete trisomy 13. The aim of the present study is to describe a 9-month-old Mexican male patient with 3p deletion/13q duplication and a novel clinical finding. He presented with facial dysmorphism and multiple congenital alterations. Echocardiogram revealed cardiac insufficiency with hypertrophic cardiomyopathy and pulmonary hypertension, not previously reported. Karyotype from the patient and his father were 46,XY,add(3)(p26) and 46,XY,t(3;13), respectively. Microarray assay of the proband exhibited an approximately 2.6-Mb loss at terminal 3p26.3 and a 27.7-Mb gain of the long arm in terminal chromosome 13 at q31.1q34. A chromosomal imbalance with a partial trisomy 13q31.1q34 and monosomy 3p26.3 of paternal origin were detected. Microarray assay of both parents were normal. The proband has a cardiomyopathy not previously reported. These data enrich the spectrum of clinical manifestations in 3p deletion/3q duplication chromosomopathy.

Clinical and genetic findings in patients with congenital cataract and heart diseases

Background Congenital cataract (CC) and congenital heart disease (CHD) are significant birth defects. In clinical practice, the concurrence of CC and CHD is frequently observed in patients. Additionally, some monogenic diseases, copy number variation (CNV) syndromes, and diseases associated with intrauterine infection involve both cataract and heart defects. However, little is known about the association between CC and CHD. Here, we characterised the demographic, clinical, and genetic features of patients with CC and heart defects. Methods Medical records for 334 hospitalised patients diagnosed with CC were reviewed. Demographic and clinical features of patients with CC with and without CHD were compared. Clinical and genomic information for patients with ‘cataract’ and ‘cardiac defects’ were reviewed from Database of Chromosomal Imbalance and Phenotype in Humans using Ensembl Resources (DECIPHER). Microarray-based comparative genomic hybridisation and whole-exome sequencing were performed in 10 trio families with CC and CHD to detect de novo genomic alterations, including copy number variants and single nucleotide changes. Results In a retrospective analysis of 334 patients with CC over the past 10 years at our hospital, we observed a high proportion of patients (41.13%) with CHD (including innocent CHD, which reported as left-to-right shunt in echocardiography test). The CC with CHD group had higher incidences of preterm birth and Down’s syndrome than the CC without CHD group. Atrial septal defect was the most frequent heart defect. A total of 44 cases with cataracts and heart diseases were retrieved from Database of Chromosomal Imbalance and Phenotype in Humans using Ensembl Resources (DECIPHER). In total, 52 genomic alterations were reported, 44% of which were de novo germline variants. In the 10 trio families with CC and CHD, we found de novo CNVs responsible for two well-known chromosomal disorders and identified a novel pathogenic mutation in GJA8 responsible for CC. Conclusions We observed significant associations between CHD and CC in our 10-year patient cohort. Based on the cohort and data from DECIPHER, developmental syndromes in some patients were due to genetic defects, thus explaining the concurrence of CC and CHD. Additionally, we detected de novo mutations as an independent cause of cataracts. Our findings suggest that developmental syndromes in patients with CC deserve more attention in clinical practice by ophthalmologists.

Interchromosomal insertion (11;2): analysis of segregation in 4 generation of the family and characterization of segmental monoand trisomy phenotype in offspring

Межхромосомная инсерция - редкий вариант сбалансированной перестройки, когда интерстициальный фрагмент одной хромосомы встраивается в другую негомологичную хромосому. Носители инсерций имеют нормальный фенотип и фертильность, но повышенный риск как спонтанных абортов (СА), так и рождения детей с хромосомным дисбалансом. Цель исследования: оценить сегрегацию хромосом у носителей межхромосомной инсерции ins(11;2)(q21;q31.1q32.3) для уточнения риска наследования потомством несбалансированного набора хромосом, провести анализ фенотипических проявлений при сегментных моно- и трисомии 2q31.1q32.3. Представлены клинико-цитогенетические данные носителей межхромосомной ins(11;2)(q21;q31.1q32.1) с длиной инсертированного фрагмента 0,8-0,9% гаплоидной длины аутосом. У 6 носителей зарегистрировано 15 беременностей, из которых 47% завершилось неблагополучным исходом: удельный вес СА составил 20%, в 1 случае диагностирована неразвивающаяся беременность (кариотип плода 46,XY), унаследованный дисбаланс установлен у 3 потомков. Распределение вариантов с кариотипами нормальный : сбалансированная инсерция : der(2) : der(11) составило 3:6:1:1, эмпирический риск образования зигот с хромосомным дисбалансом - 18% (2/11). Данные сравнительного анализа проявлений моносомии 2q31.1q32.1 (2 представленных родственника) и моносомии 2q31q33 (18 ранее описанных живорожденных пациентов) демонстрируют высокую степень фенотипического сходства. Фенотипические признаки у двух пациентов с der(2)ins(11;2) соответствуют симптомокомплексу, который рассматривается клинически очерченным синдромом моносомии 2q31q32. Наличие эктродактилии у 2 детей подтверждает связь порока с утратой генов, локализованных в сегменте 2q31.1. Результаты анализа репродуктивных исходов в представленной семье и описанных в литературе случаев демонстрируют возможность рождения потомства как с моно-, так и с трисомией 2q31q32, и позволяют оценивать риски повторного рождения детей с данными сегментными анеусомиями на уровне 30-40%, а вероятность СА - в 20-33%. У плода с трисомией 2q31.1q32.3 отмечены неспецифические признаки аутосомного дисбаланса. Микроцефалия, расщелина неба/губы и неба, эктродактилия являются основными диагностическими маркерами патологии плода, значимыми для пренатальной УЗ диагностики. Interchromosomal insertion is a rare balanced chromosomal rearrangement that occur when an interstitial segment of one chromosome is translocated into another non-homologous chromosome. Carriers of insertions display normal phenotype and fertility, but have an increased risks of spontaneous abortions (SA) and viable offspring with inherited chromosomal imbalance. The aim of study: to assess the interchromosomal ins(11;2)(q21;q31.1q32.3) segregation to determine the genetic risk of inheriting an unbalanced karyotype by the outcome; to analyze segmental mono- and trisomy 2q31.1q32.3 phenotypic manifestations.Family with reproductive failure history was investigated using a clinical, genealogical, ultrasound, cytogenetical (GTG-banding) and morphological methods. Risks of reproductive loss and aneusomic offspring birth were calculated. The outcome prognosis and prenatal diagnostics results were discussed. Clinical, cytogenetical and reproductive history data of carriers ins(11;2) (q21;q31.1q32.3) were presented. The size of insertional segment is about 0,8-0,9% haploid autosomal length (HAL). Outcomes of 15 pregnancies of 6 carriers were as follows: rate of miscarries - 20%, one miscarriage - fetus with karyotype 46,XY, 3 cases - chromosomal imbalance. The segregation ratio for normal:balanced:der(2):der(11) is 3:6:1:1; the empirical risk for forming aneuploid zygotes is 18% (2/11). Segmental monosomy 2q31.1q32.1 phenotypic features in 2 presented patients are similar with clinical signs of 18 previously reported live-born children with monosomy 2q31q33. Ectrodactyly in 2 our patients confirms association of malformation with 2q31.1 region loss. The presented and reported cases data illustrate a possibility of giving birth of offspring with segmental monosomy as well as trisomy 2q31q32, risk of viable offspring with inherited imbalance may be estimated as 30-40%, spontaneous abortions rate - 20-33%. Fetus with trisomy 2q31.1q32.3 showed unspecific signs of autosomal imbalance. Pattern of phenotypical features reported in 2 relatives with der(2)ins(11;2) correlates with clinically recognizable monosomy 2q31q32 syndrome. Microcephaly, cleft palate/cleft lip and palate, ectrodactyly are the main diagnostic markers of fetal pathology which can be identified using prenatal ultrasound investigation.

Static Leukoencephalopathy Associated with 17p13.3 Microdeletion Syndrome: A Case Report

Background Leukoencephalopathy associated with dysmorphic features may be attributed to chromosomal abnormalities such as 17p13.3 microdeletion syndrome. Case A 19-year-old female patient was referred to our hospital for diagnostic evaluation of her leukoencephalopathy. She demonstrated moderate intellectual disability, minor dysmorphic features, and short stature. Serial brain magnetic resonance images obtained within a 16-year interval revealed prolonged T2 signals in the deep cerebral white matter with enlarged Virchow–Robin spaces. A nonsymptomatic atlas anomaly was also noted. Using microarray-based comparative genomic hybridization, we identified a 2.2-Mb terminal deletion at 17p13.3, encompassing YWHAE, CRK, and RTN4RL1 but not PAFAH1B1. Conclusion Except for atlas anomaly, the patient's clinical and imaging findings were compatible with the diagnosis of 17p13.3 microdeletion syndrome. The white matter abnormality was static and nonprogressive. The association between the atlas abnormality and this deletion remains elusive. We note the importance of exploring submicroscopic chromosomal imbalance when patients show prominent but static white matter abnormalities with discrepantly mild and stable neurological signs.

Structure of chromosomal abnormalities in the cycles of IVF-PGS

Актуальность: Ограниченный репродуктивный потенциал у человека и прогрессирующее ухудшение репродуктивного здоровья населения стали причиной развития вспомогательных репродуктивных технологий в последние десятилетия. С целью повышения вероятности имплантации бластоцисты, снижения частоты спонтанных абортов у семейных пар, которые имеют проблемы репродукции, в клиническую практику был введен преимплантационный генетический скрининг (ПГС). Культивирование эмбрионов человека in vitro в циклах экстракорпорального оплодотворении (ЭКО), а также возможность получения генетического материала при проведении ПГС позволяют оценить частоту и спектр хромосомных нарушений в бластоцистах человека. Цель: Анализ частоты и спектра числовых хромосомных аномалий в бластоцистах, полученных в рамках циклов ЭКО-ПГС. Материалы и методы. Проведен ретроспективный анализ молекулярных кариотипов 113 бластоцист, полученных в рамках циклов ЭКО-ПГС от 47 женщин. Полногеномная амплификация (ПГА) ДНК из клеток трофэктодермы проводилась с использованием набора реактивов PicoPlex (Rubicon Genomics, США). Анализ образцов ДНК, полученных после ПГА, был проведен методом микроматричной сравнительной геномной гибридизации (aCGH) с использованием микрочипа GenetiSure Pre-Screen, 8×60K (Agilent Technologies, США). Результаты: Эффективность ПГА составила 97,3% (110/113). Сбалансированный кариотип был установлен в 31% (34/110) бластоцист. Частота бластоцист с хромосомным дисбалансом в группе женщин моложе 35 лет оказалась значимо ниже (46,9 %) по сравнению с частотой бластоцист с хромосомным дисбалансом в группе женщин старше 35 лет (81,0 %) (р < 0,001). Хромосомные аномалии были представлены анеуплоидиями (74 %), в 26 % - структурными нарушениями хромосом. Распределение анеуплоидий имело следующую структуру: трисомии аутосом составили 41 %, моносомии аутосом - 48 %, анеуплоидии половых хромосом - 7%, тетрасомии аутосом - 3 %, нуллисомии аутосом - 1 %. Наиболее часто отмечались анеуплоидии хромосом 5, 15, 16, 17, 19, 21 и 22. Выводы: Анализ хромосомных аберраций в бластоцистах продемонстрировал высокую частоту хромосомного дисбаланса (69%) и широкий спектр как числовых, так и структурных нарушений хромосом. ПГС методом aCGH позволяет отобрать бластоцисты со сбалансированным набором хромосом. По результатам переносов бластоцист в циклах ЭКО-ПГС клиническая беременность наступила в 32% случаев. Introduction: Limited reproductive potential in humans and the progressive decline of the reproductive health of the population have led to the development of assisted reproductive technologies in recent decades. In order to improve pregnancy rates in couples with reproduction problems, preimplantation genetic screening was introduced into clinical practice. Cultivation of human embryos in vitro in in vitro fertilization cycles (IVF), as well as the possibility of obtaining genetic material during preimplantation genetic screening and diagnosis (PGS / PGD), allow us to estimate the frequency and spectrum of chromosomal abnormalities in human blastocysts. Aim: Analysis of the rate and spectrum of aneuploidies in human blastocysts obtained in the IVF-PGD cycles. Material and methods: A retrospective analysis of the molecular karyotypes of 113 blastocysts obtained in the cycles of assisted reproductive technology IVF-PGD from 47 women was carried out. The whole genomic amplification of DNA from trophectoderm cells was performed using the PicoPlex reagent kit (Rubicon Genomics, USA). Analysis of DNA samples obtained after whole genome amplification was carried out by array comparative genomic hybridization (aCGH) using a GenetiSure Pre-Screen microchip, 8×60K (Agilent Technologies, USA). Results: The efficiency of whole genome amplification was 97.3% (110/113). A balanced karyotype was established in 31% (34/110) blastocysts. The rate of a blastocyst with chromosomal imbalance in the group of women under 35 years old was lower (46.9%) compared to the rate of blastocyst with chromosomal imbalance in the group of women over 35 years old (81.0%) (p < 0.001). 74% of the identified chromosomal abnormalities were aneuploidy, 26% - structural chromosomal abberations. The distribution of aneuploidies had the following structure: autosomal trisomies (41%), autosomal monosomies (48%), aneuploidies of sex chromosomes (7%), autosomal tetrasomies (3%), autosomal nullisomies (1%). Aneuploidies of chromosomes 5, 15, 16, 17, 19, 21 and 22 were noted with the greatest frequency. Conclusions: Analysis of chromosomal aberrations in human embryos at the blastocyst stage showed a high frequency of chromosomal imbalance (69%) and a wide range of both numerical and structural abnormalities of chromosomes. PGS with aCGH allows the selection of blastocysts with a balanced karyotype. According to the results of blastocyst transfers in IVF-PGD cycles, clinical pregnancy occurred in 32 % of cases.