Talk:Genetics - Chromosome 7
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Cite this page: Hill, M.A. (2021, June 20) Embryology Genetics - Chromosome 7. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Talk:Genetics_-_Chromosome_7
Wlodarski MW, Sahoo SS & Niemeyer CM. (2018). Monosomy 7 in Pediatric Myelodysplastic Syndromes. Hematol. Oncol. Clin. North Am. , 32, 729-743. PMID: 30047423 DOI. Monosomy 7 in Pediatric Myelodysplastic Syndromes
Myelodysplastic syndromes (MDS) in children and adolescents are a rare heterogeneous group of clonal stem cell disorders. Complete or partial loss of chromosome 7 constitutes the most common cytogenetic abnormality encountered in any type of childhood MDS, is associated with more advanced disease, and usually requires a timely allogeneic stem cell transplantation. This article provides insights into the current understanding of the genotype, phenotype, and clonal evolution patterns in pediatric MDS associated with loss of chromosome 7. Copyright © 2018 Elsevier Inc. All rights reserved. KEYWORDS: GATA2; Monosomy 7; Pediatric MDS; SAMD9; SAMD9L DOI: 10.1016/j.hoc.2018.04.007
The enigma of monosomy 7
Since a report of some 50 years ago describing refractory anemia associated with group C monosomy, monosomy 7 (-7) and interstitial deletions of chromosome 7 (del(7q)) have been established as one of the most frequent chromosomal aberrations found in essentially all types of myeloid tumors regardless of patient age and disease etiology. In the last century, researchers sought recessive myeloid tumor-suppressor genes by attempting to determine commonly deleted regions (CDRs) in del(7q) patients. However, these efforts were not successful. Today, tumor suppressors located in 7q are believed to act in a haploinsufficient fashion, and powerful new technologies such as microarray comparative genomic hybridization and high-throughput sequencing allow comprehensive searches throughout the genes encoded on 7q. Among those proposed as promising candidates, 4 have been validated by gene targeting in mouse models. SAMD9 (sterile α motif domain 9) and SAMD9L (SAMD9-like) encode related endosomal proteins, mutations of which cause hereditary diseases with strong propensity to infantile myelodysplastic syndrome (MDS) harboring monosomy 7. Because MDS develops in SAMD9L-deficient mice over their lifetime, SAMD9/SAMD9L are likely responsible for sporadic MDS with -7/del(7q) as the sole anomaly. EZH2 (enhancer of zeste homolog 2) and MLL3 (mixed lineage leukemia 3) encode histone-modifying enzymes; loss-of-function mutations of these are detected in some myeloid tumors at high frequencies. In contrast to SAMD9/SAMD9L, loss of EZH2 or MLL3 likely contributes to myeloid tumorigenesis in cooperation with additional specific gene alterations such as of TET2 or genes involved in the p53/Ras pathway, respectively. Distinctive roles with different significance of the loss of multiple responsible genes render the complex nature of myeloid tumors carrying -7/del(7q). © 2018 by The American Society of Hematology. Comment in Puzzling pieces of chromosome 7 loss or deletion. [Blood. 2018] DOI: 10.1182/blood-2017-12-822262
Maintenance of Mest imprinted methylation in blastocyst-stage mouse embryos is less stable than other imprinted loci following superovulation or embryo culture
Environ Epigenet. 2017 Aug 29;3(3):dvx015. doi: 10.1093/eep/dvx015. eCollection 2017 Jul.
Velker BAM1,2,3, Denomme MM1,2,3,4, Krafty RT5, Mann MRW6,7.
Assisted reproductive technologies are fertility treatments used by subfertile couples to conceive their biological child. Although generally considered safe, these pregnancies have been linked to genomic imprinting disorders, including Beckwith-Wiedemann and Silver-Russell Syndromes. Silver-Russell Syndrome is a growth disorder characterized by pre- and post-natal growth retardation. The Mest imprinted domain is one candidate region on chromosome 7 implicated in Silver-Russell Syndrome. We have previously shown that maintenance of imprinted methylation was disrupted by superovulation or embryo culture during pre-implantation mouse development. For superovulation, this disruption did not originate in oogenesis as a methylation acquisition defect. However, in comparison to other genes, Mest exhibits late methylation acquisition kinetics, possibly making Mest more vulnerable to perturbation by environmental insult. In this study, we present a comprehensive evaluation of the effects of superovulation and in vitro culture on genomic imprinting at the Mest gene. Superovulation resulted in disruption of imprinted methylation at the maternal Mest allele in blastocysts with an equal frequency of embryos having methylation errors following low or high hormone treatment. This disruption was not due to a failure of imprinted methylation acquisition at Mest in oocytes. For cultured embryos, both the Fast and Slow culture groups experienced a significant loss of maternal Mest methylation compared to in vivo-derived controls. This loss of methylation was independent of development rates in culture. These results indicate that Mest is more susceptible to imprinted methylation maintenance errors compared to other imprinted genes. KEYWORDS: DNA methylation; Mest; assisted reproduction; genomic imprinting; mouse PMID: 29492315 PMCID: PMC5804554 DOI: 10.1093/eep/dvx015