There are no official guidelines to assist in answering this question. I will search for relevant research papers instead.
From the Research
Role of Transcobalamin II (TCII) in the Body
- Transcobalamin II (TCII) is a plasma protein that binds vitamin B12 (cobalamin) and facilitates its cellular uptake by receptor-mediated endocytosis 1, 2, 3, 4, 5
- TCII is essential for the transport of cobalamin to all cells, and its deficiency can lead to intracellular cobalamin deficiency, megaloblastic anemia, and neurological disorders 1, 2, 3, 4, 5
- The TCII-cobalamin complex binds to receptors on the plasma membrane of tissue cells, which is then internalized by receptor-mediated endocytosis 2
- TCII is expressed in multiple tissues, including the kidney and liver, and its level of expression varies within the same and across species 4
- The TCII gene has been cloned and characterized, and its expression is regulated by various transcription factors, including the epidermal growth factor receptor gene (EGFR) and the c-myc ligand 3
Function of TCII in Cobalamin Transport
- TCII plays a crucial role in the transport of cobalamin from the intestine to the tissues, where it is needed for various cellular processes, including DNA synthesis and fatty acid metabolism 1, 2, 3, 4, 5
- The binding of TCII to cobalamin is specific and high-affinity, allowing for efficient transport of the vitamin to the tissues 2, 3
- The TCII-cobalamin complex is recognized by a specific receptor on the surface of tissue cells, which triggers receptor-mediated endocytosis and internalization of the complex 2
Clinical Significance of TCII Deficiency
- TCII deficiency is a rare autosomal recessive disorder that can cause severe clinical symptoms, including megaloblastic anemia, failure to thrive, and neurological complications 5
- Early detection and aggressive treatment of TCII deficiency are essential to prevent long-term complications and improve patient outcomes 5
- Mutation analysis and in silico structural analysis can help identify the underlying genetic defects and predict the severity of the disease 5