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.
Rodney recovered but suffered neurological damage; because his skull was never closed, he wore a helmet until his death at age 11. This was the first case where craniopagual twins were separated and one survived. Lotti and Rosemarie Knaack, who were born in Germany in 1951, were separated at age 6, with Lotti dying in surgery. Rosemarie survived until 2008. Lori and George Schappell, born in 1961, are believed to be the longest-surviving craniopagus twins still living. Ladan and Laleh Bijani, who were born in Iran,  were separated in 2003 at age 29, only to die 90 minutes apart after surgery. Ahmed and Mohamed Ibrahim, who were born in Egypt, were successfully separated in Dallas, Texas, in October 2001, when they were 28 months old. Lea and Tabea Block, who were born in Germany in 2003, were separated in September 2004 at Johns Hopkins Hospital in Baltimore, Maryland. Tabea died of cardiac arrest an hour after separation. Anastasia and Tatiana Dogaru were born in 2004 with the crown of Tatianas head joined to the back of Anastasias. Doctors determined in 2007 that they could not be separated. Krista and Tatiana Hogan, born on October 25, 2006. After a series of tests doctors also determined these twins could also not be separated. Joseph and Luka Banda from Zambia, born in 1997, were separated successfully the same year in South Africa by a team of surgeons led by Ben Carson.