User:Nataliegallant/sandbox

Elongation
Elongation of the sheep conceptus is an essential process for survival and growth. Conceptus elongation results in production of IFNT which is a pregnancy recognition signal. This stimulates both the corpus luteum to continue to secrete progesterone and the onset of implantation.

Presence of enJSRV
In sheep, enJSRVs are highly expressed in the epithelia lining different reproductive tissues, including the vagina, uterus and oviduct. The RNA of enJSRVs is first detected in the conceptus on day 12.

enJSRV mechanism in sheep reproduction
Experiments have found that the enJSRV envelope regulates trophoblast growth and differentiation within the peri-implantation conceptus. It was discovered that enJSRVs are expressed in the trophectoderm cells of the placenta. Their expression coincides with the key events of conceptus elongation and onset of trophoblast giant binucleate cells (BNC) differentiation. Furthermore, it was observed that an injection of morpholinos (an enJSRV envelope production inhibitor) into the uteri of pregnant sheep on day 8 of pregnancy resulted in reduced conceptus elongation and inhibition of trophoblast giant BNC differentiation. Elongation is an essential process as it results in the production of IFNT which is a pregnancy recognition signal required for conceptus survival. Following the injection of morpholinas, it was observed that pregnancy loss occurred 12 days later. This work supports the hypothesis that enJSRVs are crucial in sheep reproduction and placental morphogenesis.

Viral protection
In vitro assays found that enJSRVs can block JSRV replication at various stages in the replication cycle. Thus the endogenous JSRV can protect the host against pathogenic retrovirus infections.

HYAL2
Hyaluronidase 2 (HYAL2) serves as a cell-surface receptor for both the exogenous and endogenous JSRV envelopes. HYAL2 mRNA can be detected in the BNCs and multinucleated syncytia of sheep placentomes during pregnancy, but not in the trophectoderm cells or any cells of the endometrium. It is hypothesised that enJSRV interactions with HYAL2 are vital for placental growth and differentiation. Whilst the cellular and molecular mechanism are still unclear, it is apparent it has a role in protecting the uterus against viral infection and placental morphogenesis.