Supernumerary Chromosomes Research Articles

Dysfunctional sodium channel kinetics as a novel epilepsy mechanism in chromosome 15q11-q13 duplication syndrome.

Duplication of the maternal chromosome 15q11.2-q13.1 region causes Dup15q syndrome, a highly penetrant neurodevelopmental disorder characterized by severe autism and refractory seizures. Although UBE3A, the gene encoding the ubiquitin ligase E3A, is thought to be the main driver of disease phenotypes, the cellular and molecular mechanisms that contribute to the development of the syndrome are yet to be determined. We previously established the necessity of UBE3A overexpression for the development of cellular phenotypes in human Dup15q neurons, including increased action potential firing and increased inward current density, which prompted us to further investigate sodium channel kinetics. We used a Dup15q patient-derived induced pluripotent stem cell line that was CRISPR-edited to remove the supernumerary chromosome and create an isogenic control line. We performed whole cell patch clamp electrophysiology on Dup15q and corrected control neurons at two time points of in vitro development. Compared to corrected neurons, Dup15q neurons showed increased sodium current density and a depolarizing shift in steady-state inactivation. Moreover, onset of slow inactivation was delayed, and a faster recovery from both fast and slow inactivation processes was observed in Dup15q neurons. A fraction of sodium current in Dup15q neurons (~15%) appeared to be resistant to slow inactivation. Not unexpectedly, a higher fraction of persistent sodium current was also observed in Dup15q neurons. These phenotypes were modulated by the anticonvulsant drug rufinamide. Sodium channels play a crucial role in the generation of action potentials, and sodium channelopathies have been uncovered in multiple forms of epilepsy. For the first time, our work identifies in Dup15q neurons dysfunctional inactivation kinetics, which have been previously linked to multiple forms of epilepsy. Our work can also guide therapeutic approaches to epileptic seizures in Dup15q patients and emphasize the role of drugs that modulate inactivation kinetics, such as rufinamide.

Impact of supraphysiologic MDM2 expression on chromatin networks and therapeutic responses in sarcoma

Amplification of MDM2 on supernumerary chromosomes is a common mechanism of P53 inactivation across tumors. Here, we investigated the impact of MDM2 overexpression on chromatin, gene expression, and cellular phenotypes in liposarcoma. Three independent regulatory circuits predominate in aggressive, dedifferentiated tumors. RUNX and AP-1 family transcription factors bind mesenchymal gene enhancers. P53 and MDM2 co-occupy enhancers and promoters associated with P53 signaling. When highly expressed, MDM2 also binds thousands of P53-independent growth and stress response genes, whose promoters engage in multi-way topological interactions. Overexpressed MDM2 concentrates within nuclear foci that co-localize with PML and YY1 and could also contribute to P53-independent phenotypes associated with supraphysiologic MDM2. Importantly, we observe striking cell-to-cell variability in MDM2 copy number and expression in tumors and models. Whereas liposarcoma cells are generally sensitive to MDM2 inhibitors and their combination with pro-apoptotic drugs, MDM2-high cells tolerate them and may underlie the poor clinical efficacy of these agents.

Trisomy 21: Experience at the Children's Hospital of Rabat

Introduction: Trisomy 21 is a congenital chromosomal abnormality caused by the presence of a supernumerary chromosome for the 21st pair. It is characterized by cognitive retardation associated with particular morphological changes. This is one of the most common genetic diseases, with an incidence about 1/770 births. We report a case series observed at the delivery room of Souissi Maternity Center in Rabat (Morocco) during one-year period. Material and methods: This is a prospective study of the neonatal registry during maternity consultations. All cases of trisomy 21 were recorded during the year 2015. Results: There were a total of 17257 births, with 44 cases of Trisomy 21; Resulting in an incidence of 0.25% (1 for 392 births). These were 25 males (56.81%) and 19 females (43.19%). The average age of women at the time of delivery was 34,4 ± 7 years . The most affected age group was those with an age greater than or equal to 35-year-old (23 cases) with also a significant number of cases in women under 35-year-old of age (21 cases). Consanguinity was found in only one case. There was no history of trisomy 21 in previous pregnancies. Conclusion: Trisomy 21 is quite common in our maternity. Patients' advanced age seems to be the main risk factor. However, patients under the age of 35-year-old deserve more surveillance in our context.

Biochemical Screening for Fetal Trisomy 21: Pathophysiology of Maternal Serum Markers and Involvement of the Placenta.

It is now well established that maternal serum markers are often abnormal in fetal trisomy 21. Their determination is recommended for prenatal screening and pregnancy follow-up. However, mechanisms leading to abnormal maternal serum levels of such markers are still debated. Our objective was to help clinicians and scientists unravel the pathophysiology of these markers via a review of the main studies published in this field, both in vivo and in vitro, focusing on the six most widely used markers (hCG, its free subunit hCGβ, PAPP-A, AFP, uE3, and inhibin A) as well as cell-free feto-placental DNA. Analysis of the literature shows that mechanisms underlying each marker's regulation are multiple and not necessarily directly linked with the supernumerary chromosome 21. The crucial involvement of the placenta is also highlighted, which could be defective in one or several of its functions (turnover and apoptosis, endocrine production, and feto-maternal exchanges and transfer). These defects were neither constant nor specific for trisomy 21, and might be more or less pronounced, reflecting a high variability in placental immaturity and alteration. This explains why maternal serum markers can lack both specificity and sensitivity, and are thus restricted to screening.

Morbidity, mortality, and socioeconomics in Klinefelter syndrome and 47,XYY syndrome: a comparative review.

Klinefelter syndrome (KS, 47,XXY) and 47,XYY syndrome are genetic conditions characterized by a supernumerary sex chromosome. The conditions share many traits, but considerable phenotypic differences are seen between the two. Focusing on morbidity, mortality, and socioeconomics, this review highlights similarities and differences. Relevant literature was identified through PubMed with the following search terms; 'Klinefelter', '47,XXY', '47,XYY', and 'Jacobs syndrome'. Included journal articles were chosen at the authors' discretion. KS and 47,XYY are the most common sex chromosome disorders in males, with an expected prevalence of 152 and 98 per 100,000 newborn males, respectively. Non-diagnosis is extensive, as only about 38% of KS and 18% of 47,XYY are diagnosed. Both conditions are associated with an increased mortality risk and increased risk of a variety of diseases and other health-related problems affecting virtually every organ system. Early diagnosis seems to predict a lesser comorbidity burden. Neurocognitive deficits as well as social and behavioral problems are commonly described. Both syndromes are associated with poor socioeconomicfor example, lower income and educational level and higher rates of crime. Infertility is a hallmark of KS, but fertility seems also reduced in 47,XYY. Being born as a boy with an extra X or Y chromosome is associated with increased mortality and excess morbidity, partially expressed in a sex chromosome-specific pattern.Both syndromes continue to be greatly underdiagnosed, even thoughearly intervention may improve the overall outcome. Earlier diagnosis to initiate timely counseling and treatment should be emphasized.

Genomic analysis of Leishmania turanica strains from different regions of Central Asia.

The evolution in Leishmania is governed by the opposite forces of clonality and sexual reproduction, with vicariance being an important factor. As such, Leishmania spp. populations may be monospecific or mixed. Leishmania turanica in Central Asia is a good model to compare these two types. In most areas, populations of L. turanica are mixed with L. gerbilli and L. major. Notably, co-infection with L. turanica in great gerbils helps L. major to withstand a break in the transmission cycle. Conversely, the populations of L. turanica in Mongolia are monospecific and geographically isolated. In this work, we compare genomes of several well-characterized strains of L. turanica originated from monospecific and mixed populations in Central Asia in order to shed light on genetic factors, which may drive evolution of these parasites in different settings. Our results illustrate that evolutionary differences between mixed and monospecific populations of L. turanica are not dramatic. On the level of large-scale genomic rearrangements, we confirmed that different genomic loci and different types of rearrangements may differentiate strains originated from mixed and monospecific populations, with genome translocations being the most prominent example. Our data suggests that L. turanica has a significantly higher level of chromosomal copy number variation between the strains compared to its sister species L. major with only one supernumerary chromosome. This suggests that L. turanica (in contrast to L. major) is in the active phase of evolutionary adaptation.

New developments and future trajectories in supernumerary sex chromosome abnormalities: a summary of the 2022 3rd International Workshop on Klinefelter Syndrome, Trisomy X, and XYY.

The 3rd International Workshop on Klinefelter Syndrome, Trisomy X, and 47,XYY syndrome was held in Leiden, the Netherlands, on September 12-14, 2022. Here, we review new data presented at the workshop and discuss scientific and clinical trajectories. We focus on shortcomings in knowledge and therefore point out future areas for research. We focus on the genetics and genomics of supernumerary sex chromosome syndromes with new data being presented. Most knowledge centre specifically on Klinefelter syndrome, where aspects on testosterone deficiency and the relation to bone, muscle and fat were discussed, as was infertility and the treatment thereof. Both trisomy X and 47,XYY syndrome are frequently affected by infertility. Transitioning of males with Klinefelter syndrome was addressed, as this seemingly simple process in practise is often difficult. It is now realized that neurocognitive changes are pervasive in all supernumerary sex chromosome syndromes, which were extensively discussed. New intervention projects were also described, and exciting new data concerning these were presented. Advocacy organizations were present, describing the enormous burden carried by parents when having to explain their child's specific syndrome to most professionals whenever in contact with health care and education systems. It was also pointed out that most countries do not have health care systems that diagnose patients with supernumerary sex chromosome syndromes, thus pinpointing a clear deficiency in the current genetic testing and care models. At the end of the workshop, a roadmap towards the development of new international clinical care guidelines for Klinefelter syndrome was decided.

Supernumerary Marker Chromosome Identified in Asian Elephant (Elephas maximus).

We identified a small, supernumerary marker chromosome (sSMC) in two phenotypically normal Asian elephants (Elephas maximus): a female (2n = 57,XX,+mar) and her male offspring (2n = 57,XY,+mar). sSMCs are defined as structurally abnormal chromosomes that cannot be identified by conventional banding analysis since they are usually small and often lack distinct banding patterns. Although current molecular techniques can reveal their origin, the mechanism of their formation is not yet fully understood. We determined the origin of the marker using a suite of conventional and molecular cytogenetic approaches that included (a) G- and C-banding, (b) AgNOR staining, (c) preparation of a DNA clone using laser microdissection of the marker chromosome, (d) FISH with commercially available human painting and telomeric probes, and (e) FISH with centromeric DNA derived from the centromeric regions of a marker-free Asian elephant. Moreover, we present new information on the location and number of NORs in Asian and savanna elephants. We show that the metacentric marker was composed of heterochromatin with NORs at the terminal ends, originating most likely from the heterochromatic region of chromosome 27. In this context, we discuss the possible mechanism of marker formation. We also discuss the similarities between sSMCs and B chromosomes and whether the marker chromosome presented here could evolve into a B chromosome in the future.

Profiling Blautia at high taxonomic resolution reveals correlations with cognitive dysfunction in Chinese children with Down syndrome.

Down syndrome (DS), the presence of a supernumerary chromosome 21, is associated with cognitive dysfunction caused by early neurodegenerative processes. Alterations in the gut microbiota were observed in Chinese children with DS, and the genus Blautia was associated with cognitive function in these children. Therefore, it is crucial to understand the detailed composition of this group at the species level and to explore the effect of specific species on cognitive function. In this study, Blautia-specific amplicon sequencing was conducted to identify the specific Blautia species in 15 children with DS and 15 matched healthy children. The taxonomic analyses suggested that the Blautia taxa were clustered by disease status. The diversity of Blautia at the species level differed between DS patients and healthy controls, with the abundances of Blautia massiliensis and Blautia argi decreasing in DS children, while Blautia faecis was increased. Acetic acid, one of the metabolites of Blautia, was significantly reduced in the DS group. Of particular interest, Kyoto Encyclopaedia of Genes and Genomes analysis revealed decreased modules related to starch and sucrose metabolism and glycolysis. In addition, B. argi was positively related to DS cognitive scores, and B. faecis was negatively related to cognitive function, implying its role on the DS cognitive impairments. Our study has important implications for understanding the important effects of specific species of Blautia on cognitive function and thus possibly provides a new strategy for future studies of cognitive improvement in individuals with DS.

Association of Supernumerary Sex Chromosome Aneuploidies With Venous Thromboembolism

An increased risk of venous thromboembolism (VTE) has been reported in men with an additional sex chromosome. The association between other sex chromosome aneuploidies and VTE is not well characterized. To determine if sex chromosome aneuploidy is associated with VTE. Retrospective cohort study of sex chromosome aneuploidy and VTE, performed by analyzing X- and Y-chromosome dosage and VTE incidence in 642 544 individuals from 2 population-scale biobanks: the US Geisinger MyCode Community Health Initiative (N = 154 519) and the UK Biobank (N = 488 025); analysis was limited to participants self-identified as White because of inadequate sample sizes for other race and ethnicity groups. A total of 108 461 unrelated MyCode participants with electronic health record follow-up ranging from September 1996 to December 2020 and 418 725 unrelated British and Irish UK Biobank participants who attended the baseline assessment between March 2006 and October 2010, with follow-up extending to November 2020, were included in analyses of VTE. Sex chromosome aneuploidies. Individuals with 1 primary inpatient VTE diagnosis, 2 primary outpatient VTE diagnoses, or a self-reported VTE diagnosis were defined as VTE cases. P values were adjusted for multiple comparisons. Identification of sex chromosome aneuploidy was undertaken among 642 544 individuals aged 18 to 90 years. Identification of a diagnosis of VTE was undertaken among 108 461 unrelated MyCode participants (65 565 [60.5%] female; mean age at last visit, 58.0 [SD, 17.6] years; median follow-up, 15.3 [IQR, 9.7] years) and among 418 725 unrelated UK Biobank participants (224 695 [53.7%] female; mean age at baseline interview, 56.9 [SD, 8.0] years; median follow-up, 12.0 [IQR, 1.6] years). Among MyCode participants, during 10 years of follow-up, 17 incident VTE events per 1353 person-years were detected among those with supernumerary sex chromosome aneuploidy (1.3% per person-year) compared with 2060 per 816 682 person-years among those with 46,XX or 46,XY (0.25% per person-year) (hazard ratio, 5.4 [95% CI, 3.4-8.7]; 10-year risk difference, 8.8% [95% CI, 4.2%-14.0%]; P < .001). Among UK Biobank participants, during 10 years of follow-up, 16 incident VTE events per 3803 person-years were detected among those with supernumerary sex chromosome aneuploidy (0.42% per person-year) compared with 4491 per 3 970 467 person-years among those with 46,XX or 46,XY (0.11% per person-year) (hazard ratio, 4.1 [95% CI, 2.5-6.7]; 10-year risk difference, 3.7% [95% CI, 1.4%-5.9%]; P < .001). Adults with supernumerary sex chromosome aneuploidies compared with 2 sex chromosomes had a small but statistically significant increased risk of VTE. Further research is needed to understand the clinical implications of this association.

Molecular delineation of de novo small supernumerary marker chromosomes in prenatal diagnosis, a retrospective study

ObjectivesTo define the genotype-phenotype correlation of small supernumerary marker chromosomes (sSMCs) and conduct precise genetic counseling, we retrospectively searched and reviewed de novo sSMCs cases detected during prenatal diagnosis at The First Affiliated Hospital of Zhengzhou University. Materials and methodsChromosome karyotypes of 20,314 cases of amniotic fluid from pregnant women were performed. For 16 samples with de novo sSMCs, 10 were subjected to single-nucleotide polymorphism (SNP) array or low-coverage massively parallel copy number variation sequencing (CNV-seq) analysis. ResultsAmong the 10 sSMCs cases, two sSMCs derived from chromosome 9, and three sSMCs derived from chromosomes 12, 18 and 22. The remaining 5 cases were not identified by SNP array or CNV-seq because they lacked euchromatin or had a low proportion of mosaicism. Four of them with a karyotype of 47,XN,+mar presented normal molecular cytogenetic results (seq[hg19] 46,XN), and the remaining patient with a karyotype of 46,XN,+mar presented with Turner syndrome (seq[hg19] 45,X). Five sSMCs samples were mosaics of all 16 cases. ConclusionConsidering the variable origins of sSMCs, further genetic testing of sSMCs should be performed by SNP array or CNV-seq. Detailed molecular characterization would allow precise genetic counseling for prenatal diagnosis.

P329: Mosaic Potocki-Lupski syndrome due to a supernumerary ring chromosome containing RAI1

P329: Mosaic Potocki-Lupski syndrome due to a supernumerary ring chromosome containing RAI1

P457: A case of hexasomy 15q due to a tricentric supernumerary chromosome 15

P457: A case of hexasomy 15q due to a tricentric supernumerary chromosome 15

Мейотическая сегрегация и межхромосомный эффект гетерохроматиновых малых сверхчисленных маркерных хромосом

Введение. Малые сверхчисленные маркерные хромосомы (мСМХ), состоящие из гетерохроматиновых районов, могут быть обнаружены у индивидуумов без видимых аномалий фенотипа. Их наличие в кариотипе иногда приводит к репродуктивным проблемам, связанным с риском возникновения ошибок мейоза вследствие нарушения межхромосомного синапсиса и процесса расхождения гомологичных хромосом. Цель: изучение мейотической сегрегации и оценка частоты формирования гамет с анеуплоидией у мужчин с кариотипом 47,XY,+mar без клинически значимых аномалий фенотипа. Материалы и методы: флуоресцентная in situ гибридизация (FISH) на препаратах из эякулята семи мужчин, асимптоматических носителей мСМХ. Результаты: у всех носителей мСМХ частота сперматозоидов, содержащих маркерную хромосому, не превышала 28% и в среднем составляла 15,04±9,4 (±SD). Доля анеуплоидных сперматозоидов не превышала 3,1% и в среднем составляла 1,9±1,1 что сопоставимо с частотой анеуплоидии в гаметах индивидуумов с различными показателями спермы и нормальным кариотипом, которая не превышает 5,9% и в среднем составляет 2,2±1,8. Выводы: в мейозе носителей гетерохроматиновых мСМХ гаметы преимущественно формируются без маркерной хромосомы. Показано, что присутствие мСМХ в клетках эякулята не оказывает существенного влияния на мейотическую сегрегацию других хромосом, т.е. межхромосомный эффект отсутствует. Introduction. Small supernumerary marker chromosomes (sSMCs) consisting of heterochromatin regions can be found in individuals without visible phenotypic abnormalities. Their presence in the karyotype sometimes leads to reproductive problems associated with the risk of meiosis errors due to interchromosomal synapses and the process of non-disjunction of homologous chromosomes. Aim: to investigate meiotic segregation and evaluate the frequency of gamete formation with aneuploidy in males with karyotype 47,XY,+mar without clinically significant phenotypic abnormalities. Materials and Methods: fluorescence in situ hybridization (FISH) on fixed sperm preparations in 7 male patients-asymptomatic carriers of sSMC. Results. In all sSMC carriers, the frequency of spermatozoa containing the marker chromosome did not exceed 30% and averaged 15.04±9.4 (±SD). The proportion of aneuploid spermatozoa did not exceed 3.1% and, on average, was 1.9%±1.1, which does not differ from the frequency of aneuploidy in gametes in individuals with normal karyotype (does not exceed 5.9% and, on average, is 2.2±1.8). Conclusions. In carriers of heterochromatinous sSMC gametes in meiosis are predominantly formed without a marker chromosome. It has been shown that the presence of a high proportion of sSMC in the ejaculate cells does not significantly affect the meiotic segregation of other chromosomes, i.e., there is no interchromosomal effect.

Prenatal genetic diagnosis for fetuses with anomalies revealed by fetal echocardiography

To carry out amniocyte karyotyping analysis and chromosomal microarray analysis (CMA) for women with anomalies revealed by fetal echocardiography. From January 2019 to December 2021, genetic testing was carried out for 205 fetuses including 97 with soft marker anomalies and 108 with structural heart abnormalities. Among these, 138 only had abnormal fetal echocardiography, whilst 38 and 29 were complicated with extracardiac soft marker anomalies and extracardiac structural malformation, respectively. No significant difference was detected in the detection rate of genetic anomalies between fetuses with heart-related soft markers and those with abnormal heart structures (P > 0.05). Compared with those with abnormal fetal echocardiography alone, the detection rates of chromosomal aneuploidies in those with abnormal extracardiac soft markers or abnormal extracardiac structures were significantly higher (P < 0.05). Twenty-eight chromosomal aneuploidies (including a rare mosaicism), 2 balanced translocations and 1 supernumerary marker chromosome were detected by karyotyping analysis. Twenty-seven aneuploidies, 19 copy number variations (CNVs) and 1 uniparental disomy were detected by CMA. Prenatal diagnosis has attached great importance to the suggestive role of fetal heart-related soft markers, and chromosomal aneuploidies are more common among fetuses with abnormal extracardiac soft markers and extracardiac structural abnormalities. Chromosomal Karyotyping is useful for the detection of balanced translocations and mosaicisms. CMA is helpful for the detection of CNVs. Identification of the genetic causes can facilitate genetic counseling for the affected couples.

Meiotic transmission patterns of additional genomic elements in Brachionus asplanchnoidis, a rotifer with intraspecific genome size variation

Intraspecific genome size (GS) variation in Eukaryotes is often mediated by additional, nonessential genomic elements. Physically, such additional elements may be represented by supernumerary (B-)chromosomes or by large heterozygous insertions into the regular chromosome set. Here we analyze meiotic transmission patterns of Megabase-sized, independently segregating genomic elements (ISEs) in Brachionus asplanchnoidis, a planktonic rotifer that displays an up to two-fold intraspecific GS variation due to variation in size and number of these elements. To gain insights into the meiotic transmission patterns of ISEs, we measured GS distributions of haploid males produced by individual mother clones using flow cytometry and compared these distributions to theoretical distributions expected under a range of scenarios. These scenarios considered transmission biases resembling (meiotic) drive, or cosegregation biases, e.g., if pairs of ISEs preferentially migrated towards the same pole during meiosis. We found that the inferred transmission patterns were diverse and ranged from positive biases (suggesting drive) to negative biases (suggesting drag), depending on rotifer clone and its ISE composition. Additionally, we obtained evidence for a negative cosegregation bias in some of the rotifer clones, i.e., pairs of ISEs exhibited an increased probability of migrating towards opposite poles during meiosis. Strikingly, these transmission and segregation patterns were more similar among members of a genetically homogeneous inbred line than among outbred members of the population. Comparisons between early and late stages of haploid male embryonic development (e.g., young synchronized male eggs vs. hatched males) showed very similar GS distributions, suggesting that transmission biases occur very early in male development, or even during meiosis. Very large genome size was associated with reduced male embryonic survival, suggesting that excessive amounts of ISEs might be detrimental to male fitness. Altogether, our results indicate considerable functional diversity of ISEs in B. asplanchnoidis, with consequences on meiotic transmission and embryonic survival.

Directed Evolution Detects Supernumerary Centric Chromosomes Conferring Resistance to Azoles in Candida auris.

Candida auris exhibits resistance to multiple antifungal drug classes and sterilization agents, posing threats to the immunocompromised worldwide. Among the four major geographical clades, the East Asian clade 2 isolates of C. auris are mostly drug susceptible. In this study, we experimentally evolved one such drug-susceptible isolate for multiple generations in the presence of the antifungal compound fluconazole and analyzed changes in the karyotype, DNA sequence, and gene expression profiles in three evolved drug-resistant isolates. Next-generation sequencing and electrophoretic karyotyping confirm the presence of segmental aneuploidy as supernumerary chromosomes originating from centromere-inclusive chromosomal duplication events in two such cases. A 638-kb region and a 675-kb region, both of which originated from chromosome 5 and contained its centromere region, are instances of supernumerary chromosome formation identified in two evolved fluconazole-resistant isolates. Loss of the supernumerary chromosomes from the drug-resistant isolates results in a complete reversal of fluconazole susceptibility. Transcriptome analysis of the third isolate identified overexpression of drug efflux pumps as a possible non-aneuploidy-driven mechanism of drug resistance. Together, this study reveals how both aneuploidy-driven and aneuploidy-independent mechanisms may operate in parallel in an evolving population of C. auris in the presence of an antifungal drug, in spite of starting from the same strain grown under similar conditions, to attain various levels of fluconazole resistance. IMPORTANCE Fungal pathogens develop drug resistance through multiple pathways by acquiring gene mutations, increasing the copy number of genes, or altering gene expression. In this study, we attempt to understand the mechanisms of drug resistance in the recently emerged superbug, C. auris. One approach to studying this aspect is identifying various mechanisms operating in drug-resistant clinical isolates. An alternative approach is to evolve a drug-susceptible isolate in the presence of an antifungal compound and trace the changes that result in drug resistance. Here, we evolve a drug-susceptible isolate of C. auris in the laboratory in the presence of a widely used antifungal compound, fluconazole. In addition to the already known changes like overexpression of drug efflux pumps, this study identifies a novel mechanism of azole resistance by the emergence of additional chromosomes through segmental duplication of chromosomal regions, including centromeres. The centric supernumerary chromosome helps stable amplification of a set of genes with an extra copy to confer fluconazole resistance.

Pigmentary mosaicism as a recurrent clinical manifestation in three new patients with mosaic trisomy 12 diagnosed postnatally: cases report and literature review

BackgroundTo date, only twenty-one cases diagnosed postnatally with mosaic trisomy 12 have been reported. The most frequent phenotypic manifestations are developmental delay, dysmorphic facial features, congenital heart defects, digital alterations, and pigmentary disorders. In the present report, detailed clinical and genetic profiles of three unrelated new patients with mosaic trisomy 12 are described and compared with previously reported cases.Case presentationIn the present report, we include the clinical, cytogenetic, and molecular description of three Mexican patients diagnosed postnatally with mosaic trisomy 12. At phenotypic level, the three patients present with developmental delay, dysmorphic facial features, congenital heart defects and skin pigmentary anomalies. Particularly, patient 1 showed unique eye alterations as bilateral distichiasis, triple rows of upper lashes, and digital abnormalities. In patient 2 redundant skin, severe hearing loss, and hypotonia were observed, and patient 3 presented with hypertelorism and telecanthus. Hyperpigmentation with disseminated pigmentary anomalies is a common trait in all of them. The cytogenetic study was carried out under the strict criteria of analysis, screening 50–100 metaphases from three different tissues, showing trisomy 12 mosaicism in at least one of the three different tissues analyzed. With SNParray, the presence of low-level mosaic copy number variants not previously detected by cytogenetics, and uniparental disomy of chromosome 12, was excluded. STR markers allowed to confirm the absence of uniparental disomy as well as to know the parental origin of supernumerary chromosome 12.ConclusionsThe detailed clinical, cytogenetic, and molecular description of these three new patients, contributes with relevant information to delineate more accurately a group of patients that show a heterogeneous phenotype, although sharing the same chromosomal alteration. The possibility of detecting mosaic trisomy 12 is directly associated with the sensitivity of the methodology applied to reveal the low-level chromosomal mosaicism, as well as with the possibility to perform the analysis in a suitable tissue.

In vitro propagation of XXY human Klinefelter spermatogonial stem cells: A step towards new fertility opportunities.

Klinefelter Syndrome (KS) is characterized by a masculine phenotype, supernumerary sex chromosomes (47, XXY), and impaired fertility due to loss of spermatogonial stem cells (SSCs). Early testicular cryopreservation could be an option for future fertility treatments in these patients, including SSCs transplantation or in vitro spermatogenesis. It is critically essential to adapt current in vitro SSCs propagation systems as a fertility option for KS patients. KS human testicular samples (13,15- and 17-year-old non-mosaic KS boys) were donated by patients enrolled in an experimental testicular tissue banking program. Testicular cells were isolated from cryopreserved tissue and propagated in long-term culture for 110 days. Cell-specific gene expression confirmed the presence of all four main cell types found in testes: Spermatogonia, Sertoli, Leydig, and Peritubular cells. A population of ZBTB16+ undifferentiated spermatogonia was identified throughout the culture using digital PCR. Flow cytometric analysis also detected an HLA-/CD9+/CD49f+ population, indicating maintenance of a stem cell subpopulation among the spermatogonial cells. FISH staining for chromosomes X and Y showed most cells containing an XXY karyotype with a smaller number containing either XY or XX. Both XY and XX populations were able to be enriched by magnetic sorting for CD9 as a spermatogonia marker. Molecular karyotyping demonstrated genomic stability of the cultured cells, over time. Finally, single-cell RNAseq analysis confirmed transcription of ID4, TCN2, and NANOS 3 within a population of putative SSCs population. This is the first study showing successful isolation and long-term in vitro propagation of human KS testicular cells. These findings could inform the development of therapeutic fertility options for KS patients, either through in vitro spermatogenesis or transplantation of SSC, in vivo.

First characterization of PIWI-interacting RNA clusters in a cichlid fish with a B chromosome

BackgroundB chromosomes are extra elements found in several eukaryote species. Usually, they do not express a phenotype in the host. However, advances in bioinformatics over the last decades have allowed us to describe several genes and molecular functions related to B chromosomes. These advances enable investigations of the relationship between the B chromosome and the host to understand how this element has been preserved in genomes. However, considering that transposable elements (TEs) are highly abundant in this supernumerary chromosome, there is a lack of knowledge concerning the dynamics of TE control in B-carrying cells. Thus, the present study characterized PIWI-interacting RNA (piRNA) clusters and pathways responsible for silencing the mobilization of TEs in gonads of the cichlid fish Astatotilapia latifasciata carrying the B chromosome.ResultsThrough small RNA-seq and genome assembly, we predicted and annotated piRNA clusters in the A. latifasciata genome for the first time. We observed that these clusters had biased expression related to sex and the presence of the B chromosome. Furthermore, three piRNA clusters, named curupira, were identified in the B chromosome. Two of them were expressed exclusively in gonads of samples with the B chromosome. The composition of these curupira sequences was derived from LTR, LINE, and DNA elements, representing old and recent transposition events in the A. latifasciata genome and the B chromosome. The presence of the B chromosome also affected the expression of piRNA pathway genes. The mitochondrial cardiolipin hydrolase-like (pld6) gene is present in the B chromosome, as previously reported, and an increase in its expression was detected in gonads with the B chromosome.ConclusionsDue to the high abundance of TEs in the B chromosome, it was possible to investigate the origin of piRNA from these jumping genes. We hypothesize that the B chromosome has evolved its own genomic guardians to prevent uncontrolled TE mobilization. Furthermore, we also detected an expression bias in the presence of the B chromosome over A. latifasciata piRNA clusters and pathway genes.