Paternally expressed retrotransposon Gag-like 1 gene, RTL1, is one of the crucial elements for placental angiogenesis in horses†.

The researchers established that the retrotransposon Gag-like 1 (RTL1) gene, primarily expressed paternally, is critical for the development of the horse’s placenta, with its malfunction potentially leading to several abnormalities such as placental insufficiency.

Understanding RTL1

• The gene known as RTL1 (retrotransposon Gag-like 1) plays a crucial role in the formation of the placenta in both humans and mice. Its abnormal expression has been linked to several fetal and placental disorders such as intrauterine growth restriction (IUGR) and hydrops conditions.
• Despite extensive studies, the function of RTL1 has not been clearly defined. Notably, RTL1 can be found in a highly conserved region among eutherian mammals, implying that the gene, its mutations, and its functions could possibly share similarities across species.

The Role of RTL1 in Horses

• The researchers in this study concentrated their efforts on investigating RTL1’s role in horses (Equus caballus). They found that the gene is paternally expressed, and it is localized within the endothelial cells of the equine chorioallantois, a significant part of the placenta in horses.
• With the development of an equine placental microvasculature primary cell culture, the research team demonstrated that knocking down the RTL1 gene resulted in a loss of sprouting abilities in these endothelial cells. This suggests they play a key role in the formation of new blood vessels, a process known as angiogenesis.

Implications of Abnormal RTL1 Expression

• Furthermore, the researchers noticed an association between abnormal RTL1 expression and the development of hydrallantois, an abnormal accumulation of fluid in the allantoic cavity during pregnancy in mares.
• The data collected suggests that RTL1 is vital for placental angiogenesis – the formation of new blood vessels within the placenta. Misexpression of RTL1 can lead to placental insufficiency, a condition where the placenta doesn’t work efficiently, not being able to fully support the fetus.
• This placental insufficiency could be the reason behind cases of intrauterine growth restriction (IUGR) and hydrops conditions reported in other species, including humans. Thus, understanding the role and behavior of RTL1 in horses could provide insights into its function and implications in other species.