China
Africa
Explore chapters and articles related to this topic
The Nude (nu) and Streaker (nustr) Mutations, Chromosome 11
Published in John P. Sundberg, Handbook of Mouse Mutations with Skin and Hair Abnormalities, 2020
The thymic agenesis found in nu/nu and nustf/nustf mice, but not the alopecia, resembles thymic agenesis of human newborns which has been called DiGeorge syndrome. Humans have hypoplasia or aplasia of the thymus with marked depletion of paracortical areas of lymph nodes. Differences in humans are that patients develop neonatal tetany and major anomalies of the great vessels. These are due to embryologic defects in the third and fourth pharyngeal pouches which cause malformation of the parathyroid and heart. Although DiGeorge syndrome does not appear to have a familial tendency,2 some familial cases have been reported to be associated with deletions in Chromosome 22.32
Immunoglobulins
Published in Constantin A. Bona, Francisco A. Bonilla, Textbook of Immunology, 2019
Constantin A. Bona, Francisco A. Bonilla
The overall organization of heavy and light chain genes is very similar. The ϰ locus on chromosome 2 consists of from 100–200 Vϰ genes, followed by five Jϰ genes, and one Cϰgene (Figure 4–2). Similarly, the heavy chain locus on chromosome 14 contains about 100–200 VH genes, between 20 and 30 D genes, six JH genes (along with three nonfunctional JH pseudogenes) and 11 CH region genes (Figure 4–3 and 5–5). Each of these CH genes corresponds to a particular immunoglobulin class or subclass (see below). The human λ locus on chromosome 22 is somewhat different, being composed of several (an unknown number) Vλ seven Jλ and seven Cλ genes (Figure 4–4). Immunoglobulin V genes may be found in other chromosomal locations where they cannot be expressed. These loci are called “orphons” and are believed to have arisen via gene inversions and conversions and have been maintained during evolution. A VH orphon can be found on chromosome 16. A Vϰ orphon is found near the centromere of chromosome 2. Most genes in orphon loci are pseudogenes since there is no selection pressure to limit accumulation of deleterious mutations.
Practical Approach to Molecular Biology in Hematopathology
Published in Harold R. Schumacher, William A. Rock, Sanford A. Stass, Handbook of Hematologic Pathology, 2019
Anwar Mikhael, Harold R. Schumacher
As a consequence of the translocation, sequences of the ABL proto-oncogene are moved from chromosome 9 to chromosome 22, where they are located in the 3’ region of the BCR gene. The breakpoints on chromosome 9 are widely distributed and range from about 15 to over 40 kb upstream of the most proximal region (first exon) of the ABL gene. However, the breakpoint on chromosome 22 occurs over a much shorter region of approximately 5–10 kb. This region is referred as the major breakpoint cluster region (M-bcr) (11).
The successful strategy of comprehensive pre-implantation genetic testing for beta-thalassaemia–haemoglobin E disease and chromosome balance using karyomapping
Published in Journal of Obstetrics and Gynaecology, 2022
Sirivipa Piyamongkol, Suchada Mongkolchaipak, Pimlak Charoenkwan, Rungthiwa Sirapat, Wanwisa Suriya, Tawiwan Pantasri, Theera Tongsong, Wirawit Piyamongkol
Nine embryos from family B were subjected to PGT. Karyomapping results of family B (beta-thalassaemia (c.17A>T)-Hb E disease) revealed six Hb E trait embryos (B1, B3, B4, B5, B6 and B9) and three affected with beta-thalassaemia–Hb E disease (B2, B7 and B8) (Figure 3). Standard mutation analysis using multiplex F-PCR and mini-sequencing confirmed haplotyping results in all embryos (Tables 2 and 3). Polymorphic marker analysis revealed the absence of extraneous DNA contamination in all samples. Additionally, karyomapping demonstrated three embryos with chromosome imbalance, 45, XY,-21 (embryo B2, affected), 45, XY,-22 (embryo B5, Hb E trait) and 47, XX,+16 (embryo B6, Hb E trait) (Figure 3). The absence of chromosome 21 in embryo B2 and chromosome 22 in embryo B5 was maternal. The gain of chromosome 16 of embryo B6 was maternal. Therefore, four Hb E trait embryos (B1, B3, B4 and B9) were identified for potential transfer. One Hb E trait embryo (B4) was chosen for transfer and patient B gave birth to a normal baby boy. Prenatal testing confirmed PGT results (Table 3).
Blood brain barrier permeability increases with age in individuals with 22q11.2 deletion syndrome
Published in The World Journal of Biological Psychiatry, 2022
Michal Taler, Ehud Mekori–Domachevsky, Elfi Vergaelen, Stephan Claes, Yaffa Serur, Shira Dar, Yael Levy-Shraga, Abraham Weizman, Ann Swillen, Doron Gothelf
The 22q11.2 deletion syndrome (22q11.2DS), also known as velocardiofacial syndrome or DiGeorge syndrome, is caused by a microdeletion in the long arm of chromosome 22, with an estimated prevalence varying between 1 per 3000 and 1 per 6000 live births (McDonald-Mcginn and Sullivan 2011). The phenotype of 22q11.2DS involves multiple organs, including typical facial features, cleft palate and congenital cardiovascular anomalies, as well as hypocalcaemia and immunological abnormalities. Most individuals with 22q11.2DS sustain at least one psychiatric disorder, including schizophrenia, attention deficit/hyperactivity disorder (ADHD) and anxiety disorders (Schneider et al. 2014). About one-third of individuals with 22q11.2DS develop schizophrenia-like psychotic disorders, making it the most common genetic syndrome currently associated with schizophrenia (Schneider et al. 2014). And yet, the processes that lead to the evolution of psychosis are largely unknown in both 22q11.2DS and non-syndromic schizophrenia. One of the suggested pathways is anomalies of the microvasculature of the brain and specifically the blood-brain barrier (BBB) (Najjar et al. 2017).
Mosaic cat eye syndrome in a child with unilateral iris coloboma
Published in Ophthalmic Genetics, 2021
Cristina Hernández-Medrano, Alberto Hidalgo-Bravo, Cristina Villanueva-Mendoza, Teresa Bautista-Tirado, David Apam-Garduño
Cat eye syndrome (CES) is a chromosomal disorder with an incidence of 1 per 50,000–150,000 live newborns (1). The classic triad of iris coloboma, anorectal malformations, and auricular abnormalities is present in 40% of patients (2). CES has a variable clinical spectrum, from patients with minor dysmorphias to patients with severe malformations. Among the minor dysmorphias, a high forehead, downslanting palpebral fissures, epicanthus, and preauricular pits or tags have been documented (3). Other ocular malformations described are microphthalmia, cataract, strabismus, and Duane anomaly (2,4,5). In addition, congenital heart defects and renal and gastrointestinal malformations have been reported in severe cases. Although cognition is usually normal, 30% of patients have an intellectual deficit (6). The genetic basis of CES was described in 1965 by Schachenmann, who noted the presence of a supernumerary bi-satellited marker chromosome derived from chromosome 22 (7). The ultimate result is a trisomy or partial tetrasomy of chromosome 22, specifically of the region 22pter to 22q11.1. Despite an analysis of several patients, the establishment of a genotype-phenotype correlation has not been possible (2,3,8).