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Zheng X, Xu C, Ganesan K, Chen H, Cheung YS, Chen J. Does Laterality in Breast Cancer still have the Importance to be Studied? A Meta-analysis of Patients with Breast Cancer. Curr Med Chem 2024; 31:3360-3379. [PMID: 37933213 DOI: 10.2174/0109298673241301231023060322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 07/28/2023] [Accepted: 09/15/2023] [Indexed: 11/08/2023]
Abstract
BACKGROUND Breast cancer (BC) is one of the most common cancers in the world. Studies show that left-sided BC in pre and post-menopausal women leads to double the risk of worse morbidity and mortality and the reasons are uncertain. Finding the relationship between BC laterality and other possible risk factors can be advantageous for the prognosis of BC. OBJECTIVE This present study aimed to analyze the relationship between BC laterality and possible risk factors. METHODS A total of 6089 studies were screened. 23 studies from 1971 to 2021 met the inclusion criteria and were included in the meta-analysis. A pooled relative risk was generated via meta-analysis with a 95% confidence interval. RESULTS Left-side BC laterality was significant (p < 0.00001) in the women populations compared to the right side based on the pooled size with possible high-risk factors, including handedness, older women, body mass index, people with black skin, invasive type carcinoma, and estrogen receptor-negative BC. These findings suggest that there may be a complex interplay of genetic, environmental, and lifestyle factors that contribute to left-side BC laterality. CONCLUSION Results suggest an increased rate of BC on the left side, with high-risk factors contributing to BC laterality, which may be useful in predicting prognosis. This study provides significant insights into the relationship between high-risk factors and BC laterality. By identifying potential risk factors associated with left-side BC, it may be possible to improve the ability to predict prognosis and develop more targeted treatment strategies. This information could be particularly useful for healthcare providers and patients, as it may guide decisions regarding screening, prevention, and treatment, ultimately improving patient outcomes and reducing the overall burden of BC.
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Affiliation(s)
- Xiao Zheng
- School of Chinese Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Cong Xu
- School of Chinese Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Kumar Ganesan
- School of Chinese Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Haiyong Chen
- School of Chinese Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Yuen Shan Cheung
- School of Chinese Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Jianping Chen
- School of Chinese Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Shenzhen Institute of Research and Innovation, The University of Hong Kong, Shenzhen, China
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Yao X, Wang X, Ding J. Exploration of possible cell chirality using material techniques of surface patterning. Acta Biomater 2021; 126:92-108. [PMID: 33684535 DOI: 10.1016/j.actbio.2021.02.032] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 02/10/2021] [Accepted: 02/19/2021] [Indexed: 02/07/2023]
Abstract
Consistent left-right (LR) asymmetry or chirality is critical for embryonic development and function maintenance. While chirality on either molecular or organism level has been well established, that on the cellular level has remained an open question for a long time. Although it remains unclear whether chirality exists universally on the cellular level, valuable efforts have recently been made to explore this fundamental topic pertinent to both cell biology and biomaterial science. The development of material fabrication techniques, surface patterning, in particular, has afforded a unique platform to study cell-material interactions. By using patterning techniques, chirality on the cellular level has been examined for cell clusters and single cells in vitro in well-designed experiments. In this review, we first introduce typical fabrication techniques of surface patterning suitable for cell studies and then summarize the main aspects of preliminary evidence of cell chirality on patterned surfaces to date. We finally indicate the limitations of the studies conducted thus far and describe the perspectives of future research in this challenging field. STATEMENT OF SIGNIFICANCE: While both biomacromolecules and organisms can exhibit chirality, it is not yet conclusive whether a cell has left-right (LR) asymmetry. It is important yet challenging to study and reveal the possible existence of cell chirality. By using the technique of surface patterning, the recent decade has witnessed progress in the exploration of possible cell chirality within cell clusters and single cells. Herein, some important preliminary evidence of cell chirality is collected and analyzed. The open questions and perspectives are also described to promote further investigations of cell chirality in biomaterials.
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Miletto Petrazzini ME, Sovrano VA, Vallortigara G, Messina A. Brain and Behavioral Asymmetry: A Lesson From Fish. Front Neuroanat 2020; 14:11. [PMID: 32273841 PMCID: PMC7113390 DOI: 10.3389/fnana.2020.00011] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 03/05/2020] [Indexed: 11/27/2022] Open
Abstract
It is widely acknowledged that the left and right hemispheres of human brains display both anatomical and functional asymmetries. For more than a century, brain and behavioral lateralization have been considered a uniquely human feature linked to language and handedness. However, over the past decades this idea has been challenged by an increasing number of studies describing structural asymmetries and lateralized behaviors in non-human species extending from primates to fish. Evidence suggesting that a similar pattern of brain lateralization occurs in all vertebrates, humans included, has allowed the emergence of different model systems to investigate the development of brain asymmetries and their impact on behavior. Among animal models, fish have contributed much to the research on lateralization as several fish species exhibit lateralized behaviors. For instance, behavioral studies have shown that the advantages of having an asymmetric brain, such as the ability of simultaneously processing different information and perform parallel tasks compensate the potential costs associated with poor integration of information between the two hemispheres thus helping to better understand the possible evolutionary significance of lateralization. However, these studies inferred how the two sides of the brains are differentially specialized by measuring the differences in the behavioral responses but did not allow to directly investigate the relation between anatomical and functional asymmetries. With respect to this issue, in recent years zebrafish has become a powerful model to address lateralization at different level of complexity, from genes to neural circuitry and behavior. The possibility of combining genetic manipulation of brain asymmetries with cutting-edge in vivo imaging technique and behavioral tests makes the zebrafish a valuable model to investigate the phylogeny and ontogeny of brain lateralization and its relevance for normal brain function and behavior.
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Affiliation(s)
| | - Valeria Anna Sovrano
- Center for Mind/Brain Sciences, University of Trento, Rovereto, Italy.,Department of Psychology and Cognitive Science, University of Trento, Rovereto, Italy
| | | | - Andrea Messina
- Center for Mind/Brain Sciences, University of Trento, Rovereto, Italy
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4
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Cheng SA, Liang LZ, Liang QL, Huang ZY, Peng XX, Hong XC, Luo XB, Yuan GL, Zhang HJ, Jiang L. Breast cancer laterality and molecular subtype likely share a common risk factor. Cancer Manag Res 2018; 10:6549-6554. [PMID: 30568509 PMCID: PMC6278699 DOI: 10.2147/cmar.s182254] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Background To investigate the epidemiological features of breast cancer laterality and molecular subtypes in southern China. Materials and methods A total of 2,049 cases who were diagnosed with unilateral breast cancer in the past 5 years were classified based on laterality and molecular subtypes. Molecular subtypes were defined in accordance with the 2013 St. Gallen recommendations. Results Breast cancer was more likely to be diagnosed in the left breast than in the right at a rate of around 5%. In the case of invasive carcinomas, the right breast was more commonly affected than the left in young (<40 years old) patients (left-to-right [L:R] ratio 0.80, 95% CI 0.65, 0.98), whereas the opposite trend was found in old (≥40 years old) patients (L:R ratio 1.06, 95% CI 1.02, 1.73). Except for invasive mucinous and invasive medullary breast cancers, the other histological types occurred more frequently on the left side than on the right. In situ cancer with a defined subtype was likely to be diagnosed as luminal B(HER-2+). Except for invasive medullary and invasive nonspecific cancers, other invasive carcinomas with a defined subtype were most likely to be diagnosed as luminal B(HER-2−). The age of ≥40 years was a risk factor for luminal B(HER-2+), and a significant correlation was present between the right breast and luminal B(HER-2+). Conclusion We explored the risk factors of breast cancer laterality and various molecular subtypes and found that age may be a predictor of breast cancer laterality. We found that age and laterality are the probable risk factors of the luminal B(HER-2+) type of breast cancer. These results provide a basis for the epidemiological characterization of breast cancer.
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Affiliation(s)
- Shao-Ang Cheng
- Oncology Center, Affiliated Hospital of Guangdong Medical University, Zhanjiang 524001, China
| | - Li-Zhong Liang
- Medical Insurance Office, Affiliated Hospital of Guangdong Medical University, Zhanjiang 524001, China,
| | - Qi-Lian Liang
- Oncology Center, Affiliated Hospital of Guangdong Medical University, Zhanjiang 524001, China
| | - Zhen-Yi Huang
- Department of Finance, Central Hospital of Guangdong Agriculture Reclamation, Zhanjiang 524002, China,
| | - Xiao-Xia Peng
- Oncology Center, Affiliated Hospital of Guangdong Medical University, Zhanjiang 524001, China
| | - Xiao-Cui Hong
- Oncology Center, Affiliated Hospital of Guangdong Medical University, Zhanjiang 524001, China
| | - Xing-Bo Luo
- Oncology Center, Affiliated Hospital of Guangdong Medical University, Zhanjiang 524001, China
| | - Gao-Le Yuan
- Oncology Center, Affiliated Hospital of Guangdong Medical University, Zhanjiang 524001, China
| | - Hui-Jie Zhang
- Oncology Center, Affiliated Hospital of Guangdong Medical University, Zhanjiang 524001, China
| | - Liang Jiang
- Interventional Ward, Affiliated Hospital of Guangdong Medical University, Zhanjiang 524001, China
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McDowell G, Rajadurai S, Levin M. From cytoskeletal dynamics to organ asymmetry: a nonlinear, regulative pathway underlies left-right patterning. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0409. [PMID: 27821521 DOI: 10.1098/rstb.2015.0409] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/15/2016] [Indexed: 12/25/2022] Open
Abstract
Consistent left-right (LR) asymmetry is a fundamental aspect of the bodyplan across phyla, and errors of laterality form an important class of human birth defects. Its molecular underpinning was first discovered as a sequential pathway of left- and right-sided gene expression that controlled positioning of the heart and visceral organs. Recent data have revised this picture in two important ways. First, the physical origin of chirality has been identified; cytoskeletal dynamics underlie the asymmetry of single-cell behaviour and patterning of the LR axis. Second, the pathway is not linear: early disruptions that alter the normal sidedness of upstream asymmetric genes do not necessarily induce defects in the laterality of the downstream genes or in organ situs Thus, the LR pathway is a unique example of two fascinating aspects of biology: the interplay of physics and genetics in establishing large-scale anatomy, and regulative (shape-homeostatic) pathways that correct molecular and anatomical errors over time. Here, we review aspects of asymmetry from its intracellular, cytoplasmic origins to the recently uncovered ability of the LR control circuitry to achieve correct gene expression and morphology despite reversals of key 'determinant' genes. We provide novel functional data, in Xenopus laevis, on conserved elements of the cytoskeleton that drive asymmetry, and comparatively analyse it together with previously published results in the field. Our new observations and meta-analysis demonstrate that despite aberrant expression of upstream regulatory genes, embryos can progressively normalize transcriptional cascades and anatomical outcomes. LR patterning can thus serve as a paradigm of how subcellular physics and gene expression cooperate to achieve developmental robustness of a body axis.This article is part of the themed issue 'Provocative questions in left-right asymmetry'.
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Affiliation(s)
- Gary McDowell
- Biology Department, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155-4243, USA.,Allen Discovery Center, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155-4243, USA
| | - Suvithan Rajadurai
- Biology Department, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155-4243, USA.,Allen Discovery Center, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155-4243, USA
| | - Michael Levin
- Biology Department, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155-4243, USA .,Allen Discovery Center, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155-4243, USA
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Robichaux JP, Fuseler JW, Patel SS, Kubalak SW, Hartstone-Rose A, Ramsdell AF. Left-right analysis of mammary gland development in retinoid X receptor-α+/- mice. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0416. [PMID: 27821527 DOI: 10.1098/rstb.2015.0416] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/01/2016] [Indexed: 12/31/2022] Open
Abstract
Left-right (L-R) differences in mammographic parenchymal patterns are an early predictor of breast cancer risk; however, the basis for this asymmetry is unknown. Here, we use retinoid X receptor alpha heterozygous null (RXRα+/-) mice to propose a developmental origin: perturbation of coordinated anterior-posterior (A-P) and L-R axial body patterning. We hypothesized that by analogy to somitogenesis-in which retinoic acid (RA) attenuation causes anterior somite pairs to develop L-R asynchronously-that RA pathway perturbation would likewise result in asymmetric mammary development. To test this, mammary glands of RXRα+/- mice were quantitatively assessed to compare left- versus right-side ductal epithelial networks. Unlike wild-type controls, half of the RXRα+/- thoracic mammary gland (TMG) pairs exhibited significant L-R asymmetry, with left-side reduction in network size. In RXRα+/- TMGs in which symmetry was maintained, networks had bilaterally increased size, with left networks showing greater variability in area and pattern. Reminiscent of posterior somites, whose bilateral symmetry is refractory to RA attenuation, inguinal mammary glands (IMGs) also had bilaterally increased network size, but no loss of symmetry. Together, these results demonstrate that mammary glands exhibit differential A-P sensitivity to RXRα heterozygosity, with ductal network symmetry markedly compromised in anterior but not posterior glands. As TMGs more closely model human breast development than IMGs, these findings raise the possibility that for some women, breast cancer risk may initiate with subtle axial patterning defects that result in L-R asymmetric growth and pattern of the mammary ductal epithelium.This article is part of the themed issue 'Provocative questions in left-right asymmetry'.
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Affiliation(s)
- Jacqulyne P Robichaux
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - John W Fuseler
- Department of Cell Biology and Anatomy, School of Medicine, University of South Carolina, Columbia, SC 29208, USA
| | - Shrusti S Patel
- Department of Cell Biology and Anatomy, School of Medicine, University of South Carolina, Columbia, SC 29208, USA
| | - Steven W Kubalak
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Adam Hartstone-Rose
- Department of Cell Biology and Anatomy, School of Medicine, University of South Carolina, Columbia, SC 29208, USA
| | - Ann F Ramsdell
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA .,Hollings Cancer Center, Medical University of South Carolina, Charleston, SC 29425, USA.,Department of Cell Biology and Anatomy, School of Medicine, University of South Carolina, Columbia, SC 29208, USA.,Program in Women's and Gender Studies, College of Arts and Sciences, University of South Carolina, Columbia, SC 29208, USA
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7
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Porac C. Disorders, Diseases, and Life on the Left. Laterality 2016. [DOI: 10.1016/b978-0-12-801239-0.00009-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Abstract
BACKGROUND Women are more likely to develop cancer in the left breast than the right. Such laterality may influence subsequent management, especially in elderly patients with heart disease who may require radiation therapy. The purpose of this study was to explore possible factors for such cancer laterality. METHODS In this work, clinical data for consecutive patients with histologically confirmed breast cancer were reviewed, with emphasis on clinical presentation and family history. RESULTS Between 2005 and 2012, 687 patients with breast cancer were seen. Two women with incomplete data and eleven men were excluded. In total, 343 (50.9%) patients presented with left breast cancer, 311 (46.1%) with right breast cancer, and 20 (3.0%) with simultaneous bilateral malignancy. There were no significant differences between the three groups, especially in regards to clinical presentation and tumor characteristics. A total of 622 (92.3%) patients had unilateral primary, 20 (3.0%) had simultaneous bilateral, and 32 (4.7%) had metachronous primary breast cancer with subsequent contralateral breast cancer after 7.5-236 months. The worst 10-year survival was for bilateral simultaneous (18%) compared with unilateral (28%) and metachronous primaries (90%). There were no differences in survival in relation to breast cancer laterality, handedness, and presence or absence of a family history of cancer. There were significant similarities between patients and first-degree relatives in regards to breast cancer laterality, namely same breast (30/66, 45.5%), opposite breast (9/66, 13.6%), and bilateral cancer (27/66, 40.9, P=0.01163). This was more evident among patients and their sisters (17/32, 53.1%) or mothers (11/27, 40.7%, P=0.0689). There were also close similarities in relation to age at initial diagnosis of cancer for patients and their first-degree relatives for age differences of ≤5 years (48/166, 28.9%), 6-10 years (34/166, 20.5%), and >11 years (84/166, 50.6%, P=0.12065). CONCLUSION High similarities between patients and their first-degree relatives in regards to cancer laterality and possibly age at initial diagnosis of cancer may suggest an underlying inherited genetic predisposition.
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Affiliation(s)
- Magid H Amer
- Department of Medicine, St Rita's Medical Center, Lima, OH, USA
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Stewart BA, Klar AJS. Can bronchoscopic airway anatomy be an indicator of autism? J Autism Dev Disord 2013; 43:911-6. [PMID: 22926922 DOI: 10.1007/s10803-012-1635-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Bronchoscopic evaluations revealed that some children have double branching of bronchi (designated "doublets") in the lower lungs airways, rather than normal, single branching. Retrospective analyses revealed only one commonality in them: all subjects with doublets also had autism or autism spectrum disorder (ASD). That is, 49 subjects exhibited the presence of initial normal anatomy in upper airway followed by doublets in the lower airway. In contrast, the normal branching pattern was noted in all the remaining 410 subjects who did not have a diagnosis of autism/ASD. We propose that the presence of doublets might be an objective, reliable, and valid biologic marker of autism/ASD.
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Affiliation(s)
- Barbara A Stewart
- Pediatric Pulmonary Department, Children's Health Center, St. Joseph's Hospital and Medical Center, Phoenix, AZ 85013, USA.
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Wan LQ, Ronaldson K, Guirguis M, Vunjak-Novakovic G. Micropatterning of cells reveals chiral morphogenesis. Stem Cell Res Ther 2013; 4:24. [PMID: 23672821 PMCID: PMC3706915 DOI: 10.1186/scrt172] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Invariant left-right (LR) patterning or chirality is critical for embryonic development. The loss or reversal of LR asymmetry is often associated with malformations and disease. Although several theories have been proposed, the exact mechanism of the initiation of the LR symmetry has not yet been fully elucidated. Recently, chirality has been detected within single cells as well as multicellular structures using several in vitro approaches. These studies demonstrated the universality of cell chirality, its dependence on cell phenotype, and the role of physical boundaries. In this review, we discuss the theories for developmental LR asymmetry, compare various in vitro cell chirality model systems, and highlight possible roles of cell chirality in stem cell differentiation. We emphasize that the in vitro cell chirality systems have great promise for helping unveil the nature of chiral morphogenesis in development.
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Harbinder S, Lazzara CA, Klar AJ. Implication of the Strand-Specific Imprinting and Segregation Model: Integrating in utero Hormone Exposure, Stem Cell and Lateral Asymmetry Hypotheses in Breast Cancer Aetiology. HEREDITARY GENETICS : CURRENT RESEARCH 2013; 2013. [PMID: 34589269 PMCID: PMC8478350 DOI: 10.4172/2161-1041.s2-005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Known genetic mutations and familial hereditary factors account for less than 20–25% of breast cancer cases in women, therefore, most instances have been classified as sporadic cases of unknown aetiologies. Single nucleotide polymorphisms (SNPs) were considered as breast cancer risk factors, but numerous studies have failed to support this assertion. Recent evidence correlates aberrant epigenetic mechanisms in the development and metastatic progression of breast cancer, yet there has been limited progress made to identify the primary aetiology underlying sporadic cases of breast cancer. This has led some researchers to consider alternative hypotheses including in utero exposure to deleterious chemical agents during early development, the immortal strand and the strand-specific imprinting and selective chromatid segregation hypotheses. Here, we integrate prominent alternate models to help guide future research on this very important topic concerning human health.
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Affiliation(s)
- Singh Harbinder
- Department of Biological Sciences, Delaware State University, Dover, USA
| | - Carol A Lazzara
- Department of Biological Sciences, Delaware State University, Dover, USA
| | - Amar Js Klar
- Gene Regulation and Chromosome Biology Laboratory, Frederick National Laboratory for Cancer Research, National Institutes of Health, Frederick, USA
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Sauer S, Klar AJS. Left-right symmetry breaking in mice by left-right dynein may occur via a biased chromatid segregation mechanism, without directly involving the Nodal gene. Front Oncol 2012; 2:166. [PMID: 23316472 PMCID: PMC3540932 DOI: 10.3389/fonc.2012.00166] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Accepted: 10/25/2012] [Indexed: 11/29/2022] Open
Abstract
Ever since cloning the classic iv (inversedviscerum) mutation identified the “left-right dynein” (lrd) gene in mice, most research on body laterality determination has focused on its function in motile cilia at the node embryonic organizer. This model is attractive, as it links chirality of cilia architecture to asymmetry development. However, lrd is also expressed in blastocysts and embryonic stem cells, where it was shown to bias the segregation of recombined sister chromatids away from each other in mitosis. These data suggested that lrd is part of a cellular mechanism that recognizes and selectively segregates sister chromatids based on their replication history: old “Watson” versus old “Crick” strands. We previously proposed that the mouse left-right axis is established via an asymmetric cell division prior to/or during gastrulation. In this model, left-right dynein selectively segregates epigenetically differentiated sister chromatids harboring a hypothetical “left-right axis development 1” (“lra1”) gene during the left-right axis establishing cell division. Here, asymmetry development would be ultimately governed by the chirality of the cytoskeleton and the DNA molecule. Our model predicts that randomization of chromatid segregation in lrd mutants should produce embryos with 25% situs solitus, 25% situs inversus, and 50% embryonic death due to heterotaxia and isomerism. Here we confirmed this prediction by using two distinct lrd mutant alleles. Other than lrd, thus far Nodal gene is the most upstream function implicated in visceral organs laterality determination. We next tested whether the Nodal gene constitutes the lra1 gene hypothesized in the model by testing mutant’s effect on 50% embryonic lethality observed in lrd mutants. Since Nodal mutation did not suppress lethality, we conclude that Nodal is not equivalent to the lra1 gene. In summary, we describe the origin of 50% lethality in lrd mutant mice not yet explained by any other laterality-generating hypothesis.
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Affiliation(s)
- Stephan Sauer
- Gene Regulation and Chromosome Biology Laboratory, Frederick National Laboratory for Cancer Research, Frederick MD, USA
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