Cytogenetic and Genome Research最新文献

Introduction: Testis differentiation is initiated by the SRY gene on the Y chromosome in mammalian species. However, the Amami spiny rat, Tokudaia osimensis, lacks both the Y chromosome and the Sry gene and acquired a unique Sox9 regulatory mechanism via a male-specific duplication upstream of Sox9, without Sry. In general mammalian species, the SRY protein binds to a testis-specific enhancer to promote SOX9 gene expression. Several enhancers located upstream of Sox9/SOX9 have been reported in mice and humans. In particular, the binding of SRY to the highly conserved enhancer Enh13 is thought to be a common mechanism underlying testis differentiation and sex determination in mammals.

Methods: Sequences of T. osimensis homologues of three Sox9 enhancers that were previously reported in mice, Enh8, Enh14, and Enh13, were determined. We performed in vitro assays to confirm enhancer activity involved in Sox9 regulation in T. osimensis.

Results: T. osimensis Enh13 showed enhancer activity when co-transfected with NR5A1 and SOX9. Mouse Enh13 was activated by NR5A1 and SRY; however, T. osimensis Enh13 did not respond to SRY, even though the binding sites of SRY and NR5A1 were conserved. To identify the key sequence that is present in mouse but absent from T. osimensis, we performed reporter gene assays using vectors in which partial sequences of T. osimensis Enh13 were replaced with mouse sequences. For T. osimensis Enh13 in which the second half (approximately 430 bp) was replaced with the corresponding mouse sequence, activity in response to NR5A1 and SRY was recovered. Further, reporter assays revealed that multiple regions in the second half of the mouse Enh13 sequence are required for the response to NR5A1 and SRY. The latter 49 bp was particularly important and contained four binding sites for three transcription factors, POU2F1, HOXA3, and GATA1.

Conclusion: We showed that there are unknown sequences responsible for the interaction between NR5A1 and SRY and mEnh13 based on comparative analyses of Sry-dependent and Sry-independent species. Our comparative analyses revealed new molecular mechanisms underlying mammalian sex determination.

Quantification of gene expression signatures has been substantiated as a potential and rapid marker for radiation triage and biodosimetry during nuclear emergencies. Similar to the established biodosimetry assays, the gene expression assay has drawbacks such as being highly dynamic and transient, not specific to ionizing radiation, and also influenced by confounding factors such as gender, health status, lifestyle, and inflammation. In view of that, prior knowledge of baseline expression of certain candidate genes in a population could complement the discrimination of the unexposed from the exposed individuals without the need for individual pre-exposure controls. We intended to establish a baseline expression of reported radiation-responsive genes such as CDKN1A, DDB2, FDXR, and PCNA in the blood samples of healthy human participants and then compare it with diabetic/hypertension participants (as a chronic inflammatory condition) drawn from south Indian population. Further, we have examined the appropriateness of the assay for radiation triage-like situations; i.e., the expression profiles of those genes were examined in the participants who underwent X-ray-based medical imaging. Acute inflammation induced by lipopolysaccharide exposure in the blood significantly increased the fold expression of those genes (p < 0.0001) compared to the control. Whereas the basal expression level of those genes among the participants with the inflammatory condition is marginally higher than those observed in the healthy participants; despite the excess, the fold increase in those genes between the groups did not differ significantly. Consistent with the inflammatory participants, the basal expression level of those genes in the blood sample of participants who received X-radiation during neuro-interventional and computed tomography imaging is marginally higher than those observed in the pre-exposure of respective groups. Nevertheless, the fold increase in those genes did not differ significantly as the fold change fell within the two folds. Thus, overall results suggest that the utility of CDKN1A, DDB2, FDXR, and PCNA gene expression for radiation triage specific after very low-dose radiation exposure needs to be interpreted with caution for a much more reliable triage.

Background: Genome Mapping Technologies (optical and electronic) use ultra-high molecular weight DNA to detect structural variation and have application in constitutional genetic disorders, hematological neoplasms, and solid tumors. Genome mapping can detect balanced and unbalanced structural variation, copy number changes, and haplotypes. The technique is analogous to chromosomal microarray analysis, although genome mapping has the added benefit of being able to detect and ascertain the nature of more abnormalities in a single assay than array, karyotyping, or FISH alone.

Key messages: This paper describes a specific nomenclature for genome mapping that can be used by diagnostic and research centers to report their findings accurately. An international nomenclature is essential for patient results to be understood by different healthcare providers as well as for clear communication in publications and consistency in databases.

Summary: Genome mapping can detect aneuploidy, balanced and unbalanced structural variation, as well as copy number changes. The Standing Committee for the International System for Human Cytogenomic Nomenclature (ISCN) recognised there was a need for a specific nomenclature for genome mapping that encompasses the range of abnormalities detected by this technique. This paper explains the general principles of the nomenclature as well as giving specific ISCN examples for the different types of numerical and structural rearrangements.

Introduction: The zinc finger BTB domain-containing protein ZBTB18 binds to FOXG1 to form a transcriptional repressive complex involved in neuronal differentiation. Disruption of the components of this complex results in chromosome 1q43-q44 deletion syndrome/intellectual developmental disorder 22 or in FOXG1 syndrome.

Case presentation: This study reports on five patients with cognitive and behavioral impairment, seizures, microcephaly, and/or congenital brain abnormalities. Whole-exome sequencing identified deleterious ZBTB18 variants in three patients and deleterious FOXG1 variants in the remaining patients. We have detected a missense variant within the BTB domain of ZBTB18 in two affected monozygotic twins. In addition, we observed agenesis of the septum pellucidum in a missense FOXG1 carrier with a severe FOXG1 syndrome.

Conclusion: Although the ZBTB18 zinc finger domains harbor the majority of known deleterious variants, we report a novel de novo rare missense variant within the BTB domain. The agenesis of the septum pellucidum observed in a missense FOXG1 carrier could be considered as a novel clinical feature associated with FOXG1 syndrome. The severe FOXG1 syndrome in this patient contrasts with the milder phenotype expected for a missense. Genetic or environmental factors may explain this phenotypic variability in FOXG1 syndrome.

Introduction: X chromosome architecture and integrity are essential for normal ovarian function. Both numerical and structural X chromosome abnormalities play an important role in female infertility. This study aimed to determine the types and frequency of X chromosome aberrations detected in women referred for cytogenetic investigation due to reproductive problems.

Methods: 2,936 women (average age: 37.5 years) were enrolled in the present study. Peripheral blood karyotyping was performed by conventional cytogenetic techniques. For each woman, 20 G-banded metaphases were studied and in case of suspected mosaicism, analysis was extended to 100 metaphases.

Results: 2,588/2,936 (88.15%) of women had a normal karyotype (46,XX), while 348/2,936 (11.85%) had an abnormal one. Thirty-two women (1.09%) carried autosomal chromosome abnormalities and 316 (10.76%) had X chromosome rearrangements. In 311/2,936 women (10.59%), X chromosome numerical aberrations were detected (low-level mosaicism), and in 5/2,936 cases (0.17%), X structural abnormalities (two with pericentric inversion, one with Xq deletion and two 45,X mosaics, one with an Xp deletion cell line and the other with isochromosome Xq cell line). Low-level X mosaicism was a common finding in women >35 years as compared to younger ones (92.93% vs. 7.07%), a finding consistent with loss of chromosome X with aging. Other X chromosome abnormalities were detected in younger women (32.3 ± 4.13 vs. 41.04 ± 4.5 years). The mean age of women with Turner-like phenotype was 28.75 ± 6.6 years.

Conclusion: The study confirms that the incidence of X chromosome abnormalities is increased in women with fertility problems and that karyotype is the gold standard for their identification. Genetic counseling is recommended in these cases to provide information concerning available treatment and fertility options.

Following a mass-casualty nuclear/radiological event, there will be an important need for rapid and accurate estimation of absorbed dose for biological triage. The cytokinesis-block micronucleus (CBMN) assay is an established and validated cytogenetic biomarker used to assess DNA damage in irradiated peripheral blood lymphocytes. Here, we describe an intercomparison experiment between two biodosimetry laboratories, located at Columbia University (CU) and Health Canada (HC) that performed different variants of the human blood CBMN assay to reconstruct dose in human blood, with CU performing the assay on isolated lymphocytes and using semi-automated scoring whereas HC used the more conventional whole blood assay. Although the micronucleus yields varied significantly between the two assays, the predicted doses closely matched up to 4 Gy - the range from which the HC calibration curve was previously established. These results highlight the importance of a robust calibration curve(s) across a wide age range of donors that match the exposure scenario as closely as possible and that will account for differences in methodology between laboratories. We have seen that at low doses, variability in the results may be attributed to variation in the processing while at higher doses the variation is dominated by inter-individual variation in cell proliferation. This interlaboratory collaboration further highlights the usefulness of the CBMN endpoint to accurately reconstruct absorbed dose in human blood after ionizing radiation exposure.

Established in 2004, the Radiation and Nuclear Countermeasures Program (RNCP), within the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health has the central mission to advance medical countermeasure mitigators/therapeutics, and biomarkers and technologies to assess, triage, and inform medical management of patients experiencing acute radiation syndrome and/or the delayed effects of acute radiation exposure. The RNCP biodosimetry mission space encompasses: (1) basic research to elucidate novel approaches for rapid and accurate assessment of radiation exposure, (2) studies to support advanced development for US Food and Drug Administration (FDA) clearance of promising triage or treatment devices/approaches, (3) characterization of biomarkers and/or assays to determine degree of tissue or organ dose that can predict outcome of radiation injuries (i.e., organ failure, morbidity, and/or mortality), and (4) outreach efforts to facilitate interactions with researchers developing cutting edge biodosimetry approaches. Thus far, no biodosimetry device has been FDA cleared for use during a radiological/nuclear incident. At NIAID, advancement of radiation biomarkers and biodosimetry approaches is facilitated by a variety of funding mechanisms (grants, contracts, cooperative and interagency agreements, and Small Business Innovation Research awards), with the objective of advancing devices and assays toward clearance, as outlined in the FDA's Radiation Biodosimetry Medical Countermeasure Devices Guidance. The ultimate goal of the RNCP biodosimetry program is to develop and establish accurate and reliable biodosimetry tools that will improve radiation preparedness and ultimately save lives during a radiological or nuclear incident.

Radiation-related normal tissue injury sustained during cancer radiotherapy or in a radiological or mass casualty nuclear incident is a major health concern. Reducing the risk and mitigating consequences of radiation injury could have a broad impact on cancer patients and citizens. Efforts to discover biomarkers that can determine radiation dose, predict tissue damage, and aid medical triage are underway. Exposure to ionizing radiation causes changes in gene, protein, and metabolite expression that needs to be understood to provide a holistic picture for treating acute and chronic radiation-induced toxicities. We present evidence that both RNA (mRNA, microRNA, long noncoding RNA) and metabolomic assays may provide useful biomarkers of radiation injury. RNA markers may provide information on early pathway alterations after radiation injury that can predict damage and implicate downstream targets for mitigation. In contrast, metabolomics is impacted by changes in epigenetics, genetics, and proteomics and can be considered a downstream marker that incorporates all these changes to provide an assessment of what is currently happening within an organ. We highlight research from the past 10 years to understand how biomarkers may be used to improve personalized medicine in cancer therapy and medical decision-making in mass casualty scenarios.

Developmental and epileptic encephalopathy (DEE) refers to a group of severe epilepsy encephalopathy and development disorders, and its typical clinical features include seizures, drug resistance, and developmental delay or regression. To date, limited studies have reported DEEs driven by FGF13. Here, we reported a girl with developmental and epileptic encephalopathy 90 caused by variant of FGF13. Her electroencephalogram (EEG) showed discontinuous hypsarrhythmia, and a heterozygous nonsynonymous variant in FGF13 [NM_004114.4: c.5C>G, p.(Ala2Gly)] was identified from the proband. The variant was not reported in public databases such as gnomAD and Exome Aggregation Consortium (ExAC), and was predicted to be damaging to proteins and classified as likely pathogenic according to the ACMG guidelines. The seizure was finally controlled by a combination of ACTH + zonisamide (10 mg/kg.d) + levetiracetam (52 mg/kg.d) + clonazepam (0.7 mg/kg.d).

Fluorescence live-cell microscopy is important in cell biology to perform artifact-free investigations. To analyze the dynamics of chromatin and centromeres at different stages of the cell cycle in nuclei and chromosomes, we performed simultaneous EYFP-CENH3/H2B-DsRed and single H2B-YFP transformations in Arabidopsis wild-type and cohesin T-DNA mutants. All constructs were under the control of the strong CaMV 35S promoter. While a strong silencing of fluorescence expression occurred differently in leaf and root tissues in the double transformants, nearly all single-transformed wild-type and most mutant cells showed H2B-YFP fluorescence. It seems that for an efficient co-expression of two fluorescence proteins, endogenous promoters and terminators should be used.