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Turner syndrome (TS), also known as 45,X, or 45,X0, is a genetic disorder in which cells have only one X chromosome or are partially missing an X chromosome leading to the complete or partial deletion of the pseudoautosomal regions in the affected X chromosome. Most people have two sex chromosomes. The chromosomal abnormality is often present in just some cells, in which case it is known as Turner syndrome with mosaicism. 45,X0 with mosaicism can occur in males or females, but Turner syndrome without mosaicism only occurs in females. Signs and symptoms vary among those affected. Often, a short and webbed neck, low-set ears, low hairline at the back of the neck, short stature, and swollen hands and feet are seen at birth. Typically, those affected do not develop menstrual periods or breasts without hormone treatment and are unable to have children without reproductive technology. Heart defects, diabetes, and hypothyroidism occur in the disorder more frequently than average. Most people with Turner syndrome have normal intelligence; however, many have problems with spatial visualization that may be needed in order to learn mathematics. Vision and hearing problems also occur more often than average.
Haploinsufficiency in genetics describes a model of dominant gene action in diploid organisms, in which a single copy of the wild-type allele at a locus in heterozygous combination with a variant allele is insufficient to produce the wild-type phenotype. Haploinsufficiency may arise from a de novo or inherited loss-of-function mutation in the variant allele, such that it yields little or no gene product. Although the other, standard allele still produces the standard amount of product, the total product is insufficient to produce the standard phenotype. This heterozygous genotype may result in a non- or sub-standard, deleterious, and (or) disease phenotype. Haploinsufficiency is the standard explanation for dominant deleterious alleles.
Madelung's deformity is usually characterized by malformed wrists and wrist bones and is often associated with Léri-Weill dyschondrosteosis. It can be bilateral or just in the one wrist. It has only been recognized within the past hundred years. Named after Otto Wilhelm Madelung (1846–1926), a German surgeon, who described it in detail, it was noted by others. Guillaume Dupuytren mentioned it in 1834, Auguste Nélaton in 1847, and Joseph-François Malgaigne in 1855.
The pseudoautosomal regions or PARs are homologous sequences of nucleotides found within the sex chromosomes of species with an XY or ZW mechanism of sex determination.
Léri–Weill dyschondrosteosis or LWD is a rare pseudoautosomal dominant genetic disorder which results in dwarfism with short forearms and legs and a bayonet-like deformity of the forearms.
22q13 deletion syndrome, known as Phelan–McDermid syndrome (PMS), is a genetic disorder caused by deletions or rearrangements on the q terminal end of chromosome 22. Any abnormal genetic variation in the q13 region that presents with significant manifestations (phenotype) typical of a terminal deletion may be diagnosed as 22q13 deletion syndrome. There is disagreement among researchers as to the exact definition of 22q13 deletion syndrome. The Developmental Synaptopathies Consortium defines PMS as being caused by SHANK3 mutations, a definition that appears to exclude terminal deletions. The requirement to include SHANK3 in the definition is supported by many but not by those who first described 22q13 deletion syndrome.
LIM homeobox transcription factor 1-beta, also known as LMX1B, is a protein which in humans is encoded by the LMX1B gene.
Homeobox protein Hox-D13 is a protein that in humans is encoded by the HOXD13 gene. This gene belongs to the homeobox family of genes. The homeobox genes encode a highly conserved family of transcription factors that play an important role in morphogenesis in all multicellular organisms.
Homeobox protein Hox-A13 is a protein that in humans is encoded by the HOXA13 gene.
Paired-like homeodomain 1 is a protein that in humans is encoded by the PITX1 gene.
Homeobox protein aristaless-like 4 is a protein that in humans is encoded by the ALX4 gene. Alx4 belongs to the group-1 aristaless-related genes, a majority of which are linked to the development of the craniofacial and/or appendicular skeleton, along with PRRX1, SHOX, ALX3, and CART1. The Alx4 protein acts as a transcriptional activator and is predominantly expressed in the mesenchyme of the developing embryonic limb buds. Transcripts of this gene are detectable in the lateral plate mesoderm just prior to limb induction. Alx4 expression plays a major role in the determination of spatial orientation of the growing limb bud by aiding in the establishment of anteroposterior polarity of the limb. It does this by working in conjunction with Gli3 and dHand to restrict the expression of Sonic Hedgehog (SHh) to the posterior mesenchyme, which will eventually give rise to the Zone of Polarizing Activity (ZPA). This gene has been proven to be allelic with mutations and deletions giving rise to a host of craniofacial dismorphologies and several forms of polydactyly in mammalian development. A mouse-model knockout of this gene, dubbed Strong's luxoid, was originally created by Forstheofel in the 1960s and has been extensively studied to understand the partial and complete loss-of-function properties of this gene.
Stereocilin is a protein that in humans is encoded by the STRC gene.
Klinefelter syndrome (KS), also known as 47,XXY, is a chromosome anomaly where a male has an extra X chromosome. These complications commonly include infertility and small, poorly functioning testicles. These symptoms are often noticed only at puberty, although this is one of the most common chromosomal disorders, occurring in one to two per 1,000 live births. It is named after American endocrinologist Harry Klinefelter, who identified the condition in the 1940s, along with his colleagues at Massachusetts General Hospital.
X-linked intellectual disability refers to medical disorders associated with X-linked recessive inheritance that result in intellectual disability.
Pitt–Hopkins syndrome (PTHS) is a rare genetic disorder characterized by developmental delay, moderate to severe intellectual disability, distinctive facial features, and possible intermittent hyperventilation followed by apnea. Epilepsy often occurs in Pitt-Hopkins. It is part of the clinical spectrum of Rett-like syndromes. Pitt-Hopkins syndrome is clinically similar to Angelman syndrome, Rett-syndrome, Mowat Wilson syndrome, and ATR-X syndrome.
Special AT-rich sequence-binding protein 2 (SATB2) also known as DNA-binding protein SATB2 is a protein that in humans is encoded by the SATB2 gene. SATB2 is a DNA-binding protein that specifically binds nuclear matrix attachment regions and is involved in transcriptional regulation and chromatin remodeling. SATB2 shows a restricted mode of expression and is expressed in certain cell nuclei. The SATB2 protein is mainly expressed in the epithelial cells of the colon and rectum, followed by the nuclei of neurons in the brain.
Short-stature homeobox 2, also known as homeobox protein Og12X or paired-related homeobox protein SHOT, is a protein that in humans is encoded by the SHOX2 gene.
Liebenberg syndrome is a rare autosomal genetic disease that involves a deletion mutation upstream of the PITX1 gene, which is one that's responsible for the body's organization, specifically in forming lower limbs. In animal studies, when this deletion was introduced to developing birds, their wing buds were noted to take on limb-like structures.
45,X/46,XY mosaicism, also known as X0/XY mosaicism and mixed gonadal dysgenesis, is a mutation of sex development in humans associated with sex chromosome aneuploidy and mosaicism of the Y chromosome. It is a fairly rare chromosomal disorder at birth, with an estimated incidence rate of about 1 in 15,000 live births. Mosaic loss of the Y chromosome in previously non-mosaic men grows increasingly common with age.
Langer Mesomelic Dysplasia (LMD) is a rare congenital disorder characterised by altered bone formation, which typically causes affected individuals to experience shortening of the bones of the extremities as well as an abnormally short stature.
References
- ↑ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
- 1 2 "SHOX - short stature homeobox - Genetics Home Reference". U.S. National Library of Medicine. 2005-09-01. Archived from the original on 2007-10-12. Retrieved 2008-02-18.
- ↑ Kanaka-Gantenbein C, Kitsiou S, Mavrou A, Stamoyannou L, Kolialexi A, Kekou K, et al. (2004). "Tall stature, insulin resistance, and disturbed behavior in a girl with the triple X syndrome harboring three SHOX genes: offspring of a father with mosaic Klinefelter syndrome but with two maternal X chromosomes". Hormone Research. 61 (5): 205–10. doi:10.1159/000076532. PMID 14752208. S2CID 41958098.
- ↑ Raudsepp T, Chowdhary BP (2015). "The Eutherian Pseudoautosomal Region". Cytogenetic and Genome Research. 147 (2–3): 81–94. doi: 10.1159/000443157 . hdl: 10576/22940 . PMID 26730606.