LEFT A, LEFT B

Role in the organism:

Although the human body on the outside looks bilaterally symmetrical, many of our internal organs are lateralized (either on the left or on the right). For example, the heart, liver, digestive organs and spleen are all on one side, and the lungs have different numbers of lobes on each side of the body (the lungs do not have the same number of lobes). Since we all originate from a single cell, then there must be a point in embryonic development when the human embryo first shows signs of left to right asymmetry. The first physical sign is the asymmetrical position of the heart. Prior to this, however, several genes are expressed either on the left or right side of the embryo, including the LEFT A and LEFT B genes, which can only be expressed on the left side. The function of the LEFT A gene is to suppress LEFT B and another gene called NODAL (on chromosome number 10), whereas later these genes determine the characteristics of the left side of the embryo. (see DNAH-5 gene on chromosome 5). LEFT A is also known as factor associated with endometrial hemorrhage.

Role in the disorder (state):

Mutations in the LEFTA and LEFTB genes are associated with a range of malformations of human body axes, including left-to-right axis reversal (situs inversus), mirror symmetry (isomerism). These malformations can affect the entire body and sometimes some of the internal organs. The LEFTA gene is also associated with abnormal uterine bleeding, so the product of this gene is also called endometrial bleeding factor (EBAF).