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Genetics
Published in Rachel U Sidwell, Mike A Thomson, Concise Paediatrics, 2020
Rachel U Sidwell, Mike A Thomson
Genomic imprinting is the differential activation of genes depending on which parent they were inherited from. Examples are Prader–Willi, Angelman syndrome and Beckwith–Wiedemann syndromes.
Methylome and epigenetic markers
Published in Moshe Hod, Vincenzo Berghella, Mary E. D'Alton, Gian Carlo Di Renzo, Eduard Gratacós, Vassilios Fanos, New Technologies and Perinatal Medicine, 2019
Skevi Kyriakou, Marios Ioannides, George Koumbaris, Philippos Patsalis
Genomic imprinting is an epigenetic phenomenon that controls gene expression in a parent-of-origin–specific manner. Genomic imprinting is inherited independent of Mendelian inheritance and takes place during embryonic development. Thus, loss of imprinting as a result of deletions, mutations, or uniparental disomy (UPD) can lead to a number of disorders such as Prader–Willi syndrome, Angelman syndrome, and Beckwith-Wiedemann syndrome (18).
Animal Models of Down Syndrome and Other Genetic Diseases Associated with Mental Retardation
Published in Merlin G. Butler, F. John Meaney, Genetics of Developmental Disabilities, 2019
Angela J. Villar, Charles J. Epstein
Genomic imprinting is the epigenetic process that causes a reversible gamete-of-origin specific marking or an “imprinting” of the genome that is replicated faithfully in somatic cells and ultimately results in mono-allelic gene expression or the inactivation of either the maternal or paternal allele of a particular locus. Although the mechanism of imprinting not fully understood, one modification that is believed to play a role is the reversible addition of methyl groups to specific cytosine residues within the DNA sequence, a process that occurs differently in the production of the egg and the sperm (145). Within the past decade, mutations of imprinted genes on several different chromosomes have been found to cause a wide range of phenotypic effects. This genetic mechanism underlies two well-known genetic disorders, namely, Prader–Willi and Angelman syndromes, the first disorders recognized as occurring because of genomic imprinting(146).
Impact of waterpipe and tobacco cigarette smoking on global DNA methylation and nuclear proteins genes transcription in spermatozoa: a comparative investigation
Published in Inhalation Toxicology, 2023
Mohammed M. Laqqan, Said S. Al-Ghora, Maged M. Yassin
In general, smoking has been shown to be associated with epigenetic alterations that might predispose smokers to infertility (Xia et al. 2015; Olszewska et al. 2017; Kahl et al. 2018). This includes the silencing or overexpression of genes via changing the level of DNA methylation (Gao et al. 2015). DNA methylation is a major epigenetic modification involving the addition of the CH3 group to the 5th position of the cytosine nucleotide by DNA methyltransferase (DNMTs) to form 5-methylcytosine (Rang and Boonstra 2014; Jenkins et al. 2017). DNA methylation plays a vital role in different cellular processes such as genomic imprinting, silencing of transposons, X-chromosome inactivation, and regulation of gene expression (Hackett and Surani 2013). Previous studies showed an association between the alteration in the methylation level and the gene transcription level in males suffering from infertility problems (Xia et al. 2015; Nasri et al. 2017; Laqqan and Yassin 2022). This may be explained on the basis that prolonged smoking leads to an increase in the leukocyte concentration in human semen fluid, which can potentially increase reactive oxygen species (ROS) (Agarwal et al. 2015), which has harmful effects on human spermatozoa in terms of affecting the semen parameters and altering sperm DNA methylation (Wu and Ni 2015; Aitken 2018; Parameswari and Sridharan 2021).
Establishing perinatal and neonatal features of Prader-Willi syndrome for efficient diagnosis and outcomes
Published in Expert Opinion on Orphan Drugs, 2020
Lili Yang, Bo Ma, Shujiong Mao, Qiong Zhou, Chaochun Zou
Prader-Willi syndrome (PWS, OMIM 176270) is a rare multisystem genetic disorder caused by genomic imprinting errors and firstly reported in 1956 [1]. PWS is characterized by severe hypotonia, poor sucking, and feeding difficulties in early infancy, followed by excessive eating and gradual development of morbid obesity in early childhood, short stature, typical facial dysmorphism, psychomotor delay, behavioral abnormalities, and cognitive disability [2,3]. The prevalence of PWS is about 1 in 10,000–30,000 independent of gender and ethnicity [2,4,5]. PWS has several genetic subtypes: 1) deletion of the paternal copy of 15q11–13 (in 65%-70% of the cases), which including type I (BPI-BPIII), type II (BPII-BPIII), type III (BPI-BPIV), and type IV (BPI-BPV) at least according to the breakpoints. Type III and IV deletions are very rare and not typical; 2) maternal uniparental disomy (UPD) for chromosome 15 (in 20–30%), 3) imprinting center defect or epimutation in less than 5%, and 4) very rare cases of translocation in the region of chromosome 15q11-q13 [2,3] or small deletions in the key gene of PWS (e.g. Snord116 gene cluster) [6–11].
Prader-Willi syndrome and Angelman syndrome: Visualisation of the molecular pathways for two chromosomal disorders
Published in The World Journal of Biological Psychiatry, 2019
Friederike Ehrhart, Kelly J. M. Janssen, Susan L. Coort, Chris T. Evelo, Leopold M. G. Curfs
Over 6,000 diseases that are caused by mutations in one or more genes are currently known and reported in the Online Mendelian Inheritance in Man (OMIM) database (OMIM 2017). Many of them are rare diseases, meaning that they occur in less than 1,500 (USA), 2,000 (EU) or 2,500 (Japan) individuals. However, there are also disorders that are caused by incorrect genomic imprinting, the epigenetic pattern of the DNA which is inherited by the parents (Cassidy and Schwartz 1998). A wide variety of health conditions are suspected to be regulated by such imprinting, including cancers, cognitive dysfunction, and respiratory, cardiovascular, reproductive, autoimmune, and neurobehavioral disorders (Weinhold 2006). Two interesting rare disorders that are subject to both (genetic variation and epigenetics) are Prader-Willi syndrome (PWS) and Angelman syndrome (AS). Both occur in approximately one in 10,000–15,000 individuals (Cassidy and Schwartz 1998). Both disorders are caused by a deletion in the range of 15q11.2-q13 (Driscoll et al. 1993; Duker et al. 2010) (or another defect which leads to the loss or defective change of imprinting) but due to epigenetic imprinting several genes in the region of the ‘healthy’ chromosome are silenced so the deletion on one chromosome leads to the total loss of the gene product. Due to difference in parental specific methylation patterns there is a different set of genes lost and PWS occurs if the deletion is on chromosome 15 from paternal origin, while AS occurs if it is on chromosome 15 of maternal origin.