China
Africa
Explore chapters and articles related to this topic
Basic genetics and patterns of inheritance
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Online, 2021
There are an increasing number of recognizable microdeletion syndromes (Table 2). For example, Prader–Willi and Angelman syndromes are microdeletion syndromes, both involving a deletion at 15q11q13. Prader–Willi syndrome is a complex disorder associated with hypotonia and failure to thrive in early infancy, followed by rapid weight gain after about 2 years of age and severe obesity, mental retardation, hypogonadism, and craniofacial dysmorphic features. By contrast, the Angelman syndrome phenotype is very different, even though both syndromes are associated with the same microdeletion. Angelman syndrome, also called the “happy puppet” syndrome, presents with severe mental retardation, seizures, ataxia, and inappropriate laughter. It is now known that genomic imprinting is responsible for the phenotypic differences between these two syndromes. Genomic imprinting implies that maternally and paternally derived genetic information at the same locus is not identical and interchangeable, at least for some portions of the genome. In Prader–Willi, the deletion always occurs on the paternally derived number 15 chromosome, resulting in lack of genetic influence from the father in this region. About 70% to 75% of Prader–Willi patients have such a deletion, while the remainder have no visible abnormalities; virtually all of these remaining patients have maternal disomy, meaning that they have two copies of the mother’s chromosome 15 and neither of the father’s, again resulting in lack of paternal genetic influence in this region (1). The disomy can be either isodisomy, in which there are two identical copies of one of the maternal 15 chromosomes, or heterodisomy in which the two copies represent one of each of the maternal number 15 chromosomes. The mirror image situation exists in Angelman syndrome; if a deletion is found, it is always on the maternally derived number 15, and if there is no deletion, there is paternal disomy for 15, both cases resulting in loss of maternal genetic influence in this region of 15 (1). Thus, genomic imprinting of the genes in this area at 15q11q13 is taking place, since lack of influence from either parent can result in two very different syndromes.
UPD16 itself is not a cause of intrauterine growth restriction
Published in Fetal and Pediatric Pathology, 2018
Hui Wang, Caiqun Luo, Yang Liu, Shengli Li, Niping Jiang, Guanglin Zhang, Jiansheng Xie, Mei Zhong
That is in the fetus, the paternal chromosome 16 bearing the heterozygous –SEA deletion was duplicated resulting in complete paternal isodisomy. Homozygous variants leading to recessive genetic disease as uniparental isodisomy is not a novel mechanism [14–18]. Fetal Hb Bart’s disease due to paternal uniparental isodisomy 16 and maternal uniparental isodisomy 16 have both been reported previously [18, 19]. This fetus with Hb Bart’s disease was due to paternal UPD for chromosome 16.