Geneticists at the University of Tartu have identified a previously unknown link: a rare variant of the MGRN1 gene may cause severe congenital heart defects in a fetus. Prior to this discovery, this gene had not been associated with any human disease. The findings were published in the Journal of Medical Genetics.

The study was prompted by a clinical case in an Estonian family: two consecutive pregnancies were terminated due to serious developmental abnormalities detected by ultrasound. Autopsies confirmed congenital heart defects, and in one case, abnormal positioning of internal organs. Notably, the same parents already had two healthy children, and standard genetic tests did not reveal any known mutations.

Extended DNA analysis of the entire family showed that both parents were carriers of a recessive variant of the MGRN1 gene. This pattern of inheritance means that the condition develops only when a child inherits a defective copy from both parents. The healthy children did not carry two defective copies.

The findings were supported by animal models: mice with suppressed MGRN1 function exhibited similar developmental abnormalities and a higher rate of prenatal death.

The authors emphasize the practical importance of the discovery: it may expand the possibilities of genetic diagnostics and help families facing unexplained fetal developmental defects obtain clear answers about their causes.