Question

You are monitoring a pregnancy in which the heart and stomach are positioned on the incorrect side of the body, while the rest of the organs are positioned normally.

What would be the name of this type of visceral organ defect?

You are able to perform corrected surgery on the infant soon after birth. You perform a genetic analysis and discover this child had a mutation in a stretch activated calcium channel. What are the normal roles of stretch activated calcium channels? Why might this mutation cause the left-right laterality defects you observed?

Answer 1

1. What would be the name of this type of visceral organ defect? -

Heterotaxy defect in particular the situs ambigus defect, since it involves visceral organ's unusual arrangement in the chest and abdomen.

2. Why might this mutation cause the left-right laterality defects you observed?

TRPP2(transient receptor potential polycystin 2), an ion channel while functioning in response to calcium is also expressed in the motile node cell monocilia which is important in laterality during embryogenesis. Excess of TRPP2 causes inhibition of stretch activated calcium channels, mutations in these channels causes embryos exhibit laterality defects as compared to wild type cells which are mutation free. TRPP1 mutations also leads to laterality defects although limited to IMCD cellls.