Williams syndrome (WS) is a genetic disorder that affects many parts of the body. Facial features frequently include a broad forehead, underdeveloped chin, short nose, and full cheeks. Mild to moderate intellectual disability is observed in people with WS, with particular challenges with visual spatial tasks such as drawing. Verbal skills are relatively unaffected. Many people with WS have an outgoing personality, an openness to engaging with other people, and a happy disposition. Medical issues with teeth, heart problems (especially supravalvular aortic stenosis), and periods of high blood calcium are common.Williams syndrome is caused by a genetic abnormality, specifically a deletion of about 27 genes from the long arm of one of the two chromosome 7s. Typically, this occurs as a random event during the formation of the egg or sperm from which a person develops. In a small number of cases, it is inherited from an affected parent in an autosomal dominant manner. The different characteristic features have been linked to the loss of specific genes. The diagnosis is typically suspected based on symptoms and confirmed by genetic testing.Treatment of WS includes special education programs and various types of therapy. Surgery may be done to correct heart problems. Dietary changes or medications may be required for high blood calcium. The syndrome was first described in 1961 by New Zealander John C. P. Williams. Williams syndrome affects between one in 20,000 and one in 7,500 people at birth.
A vast amount of carbohydrate binding molecules (lectins) depend on correct glycosylation for appropriate binding; the selectins, involved in leukocyte extravasation, is a prime example. Their binding depends on a correct fucosylation of cell surface glycoproteins. Lack thereof leads to leukocytosis and increase sensitivity to infections as seen in SLC35C1-CDG(CDG-IIc); caused by a GDP-fucose (Fuc) transporter deficiency.All N-linked oligosaccharides originate from a common lipid-linked oligosaccharide (LLO) precursor, synthesized in the ER on a dolichol-phosphate (Dol-P) anchor. The mature LLO is transferred co-translationally to consensus sequence Asn residues in the nascent protein, and is further modified by trimming and re-building in the Golgi. Deficiencies in the genes involved in N-linked glycosylation constitute the molecular background to most of the CDGs. Type I defects involve the synthesis and transfer of the LLO
Type II defects impair the modification process of protein-bound oligosaccharides. Type I
Type II
The mature LLO chain is next transferred to the growing protein chain, a process catalysed by the oligosaccharyl transferase (OST) complex. Once transferred to the protein chain, the oligosaccharide is trimmed by specific glycosidases. This process is vital since the lectin chaperones calnexin and calreticulin, involved in protein quality, bind to the Glc1Man9GlcNAc-structure and assure proper folding. Lack of the first glycosidase (GCS1) causes CDG-IIb. Removal of the Glc residues and the first Man residue occurs in the ER. The glycoprotein then travels to the Golgi, where a multitude of different structures with different biological activities are formed.