1 ǀ INTRODUCTION
Orientation and connection of trophectoderm of the migrated blastocyst
to the luminal epithelial surface of the uterus is the critical period
to harmonize the implantation cascade1. In this
period, embryo mortality is most prevalent in all domestic
ruminants2,3 and may be due to deficiencies attributed
to immune functions, uterine functions, inappropriate conceptus
development, and implantation4,5. Mononuclear cells of
trophoectoderm of a preimplant embryo produces and release interferon
tau (IFNT) between 11 to 24 day of pregnancy in
ruminants5,6. This IFNT binds to the Type-1 IFN
receptor (IFNR) located on luminal epithelial cells of
endometrium7 and exerts its anti-luteolytic activity
by different mechanisms8. Interferon tau induces and
up-regulates the expression of several genes in the endometrium during
pregnancy including 2’-5’-oligoadenylate synthetase-1
(OAS1)9,10,11.
The mammalian 2’-5’ oligoadenylate synthetases (2’-5’OASs) are enzymes
that play a crucial role in mediating resistance to virus infection,
control of cell growth, differentiation, and
apoptosis12,13,14. It binds to double-stranded RNA and
catalyzes the polymerization of ATP into 2’-5’-linked oligoadenylates
which activate a constitutively expressed latent endonuclease, RNase L,
to block viral replication and initiate apoptosis in some cell types.
The mammalian OAS genes have undergone multiple gene duplication events
resulting in three size classes of enzymes: small (40/46-kDa isoforms),
intermediate (69/71-kDa isoforms), and large
(100-kDa)15,16,17,18,19. The biological significance
of these multiple OAS forms is unknown, but each has distinct
subcellular locations and functional differences in activation
requirements and catalytic parameters17,20,21,22. This
protein is associated with different subcellular fractions such as
mitochondrial, nuclear, and rough/smooth microsomal fractions.
OAS1 is the novel and most abundant gene expressed in cyclic and
increased the level during early pregnancy in the endometrium of bovine
and ovine, and is regulated by IFNT and
progesterone9,11,23. Its level increases in the
endometrium during early pregnancy and plays an important role in
antiviral responses, control of cellular growth and differentiation for
successful implantation, and pregnancy establishment in bovine and
ovine9,10,11. In addition, intrauterine administration
of IFNT along with progesterone stimulates OAS expression in the cyclic
endometrium of the animals and/or in-vitro culture endometrial
cells10,11. Even though the OAS1 is involved in
uterine receptivity, implantation, and survivability of the embryo, it
has not yet been studied in goats (Capra hircus) except one
predicted sequence is available in NCBI (GenBank Acc. No.
XM_005691488).
Goat (Capra hircus ) being a multi-functional animal and commonly
known as the poor man’s cow, acts as a source of crop insurance and
supplementary income along with nutritional security for lower, poor and
marginal farmers in South Asian countries, especially in
India24. The goat sector contributes 8.4 % to India’s
livestock gross domestic product (GDP) through meat, milk, skin and
manure25. Considering the important role of OAS1 in
uterine receptivity and embryonic survival, in addition to its antiviral
function, the present work was undertaken to amplify, sequence,
characterize, analyze the integrative bioinformatics and elucidate
expression patterns in goat endometrium.