endoplasmic reticulum membrane,
endoplasmic reticulum lumen
Thromboxane-A synthase (TBXAS1), an enzyme of the arachidonic acid cascade, produces thromboxane A2 (TXA2) from prostaglandin H2 (PGH2). Together with prostacyclin (PGI2), TXA2 plays a key role in the maintenance of haemostasis. It is also a constrictor of vascular and respiratory smooth muscle and implicated in the induction of osteoclast differentiation and activation. Defects in TBXAS1 can cause Ghosal hematodiaphyseal dysplasia (GHDD; MIM:231095), a rare autosomal recessive disorder characterised by increased bone density with predominant diaphyseal involvement and aregenerative anemia, a bone marrow failure where functional marrow cells are regenerated slowly or not at all. Mutations that can cause GHDD are L488P, L83P, G482W and R413E (Genevieve et al. 2008).