Skewed secondary sex ratio in the offspring of carriers of the 214G > A mutation of the RS1 gene

Carriers of X-linked juvenile retinoschisis (RS) were previously suggested to give birth to an excess of boys We determined the carrier stat us for th e 214G > A mutation of the RSI gene in 202 females belonging to a large RS founder pedigree. The secondary sex ratio (SSR) in the offspring of 149 car riers was 129.8 (z = 2.25), which differed significantly from that of the F innish population (SSR 106) but not from that of 53 non-carrier females bel onging to the same pedigree (SSR 116.7; z = 0.51). Since possible causes fo r the skewed SSR include factors affecting fertilisation, implantation and embryonic death, we searched for expression of RSI in various placental and uterine cells and found that, in addition to the retina, RS1 is expressed in the uterus. We hypothesize that the RS1 protein has a role in implantati on or embryonic survival.