Mice Deficient in Oocyte-Specific Oligoadenylate Synthetase-Like Protein OAS1D Display Reduced Fertility

Abstract

The double-stranded RNA (dsRNA)-induced interferon response is a defense mechanism against viral infection. Upon interferon activation by dsRNA, 2,5-oligoadenylate synthetase 1 (OAS1A) is induced; it binds dsRNA and converts ATP into 2,5-linked oligomers of adenosine (called 2-5A), which activate RNase L that in turn degrades viral and cellular RNAs. In a screen to identify oocyte-specific genes, we identified a novel murine cDNA encoding an ovary-specific 2,5-oligoadenylate synthetase-like protein, OAS1D, which displays 59% identity with OAS1A. OAS1D is predominantly cytoplasmic and is exclusively expressed in growing oocytes and early embryos. Like OAS1A, OAS1D binds the dsRNA mimetic poly(I-C), but unlike OAS1A, it lacks 2-5 adenosine linking activity. OAS1D interacts with OAS1A and inhibits the enzymatic activity of OAS1A. Mutant mice lacking OAS1D (Oas1d ؊/؊ ) display reduced fertility due to defects in ovarian follicle development, decreased efficiency of ovulation, and eggs that are fertilized arrest at the one-cell stage. These effects are exacerbated after activation of the interferon/OAS1A/RNase L pathway by poly(I-C). We propose that OAS1D suppresses the interferon/OAS/RNase L-mediated cellular destruction by interacting with OAS1A during oogenesis and early embryonic development.Interferons (IFN) play an important role in the host defense mechanism against viral infection (38). The 2Ј-5Ј-oligoadenylate synthetases (OASs) belong to a family of IFN-induced antiviral proteins that are highly induced by alpha/beta IFN and to a lesser extent by gamma IFN (57). OAS proteins are produced as latent enzymes, which must bind double-stranded RNA (dsRNA) to form an enzymatically active complex that catalyzes the synthesis of 2Ј-5Ј-oligoadenylates (2-5A) from ATP. The 2-5A products bind to latent endoribonuclease RNase L, leading to its dimerization, activation, and degradation of cellular and viral RNA (16,27,69). dsRNA produced in virus-infected cells by either viral replication or symmetric transcription of the viral genome allows OAS enzymes to sense and react to viral infection (10, 28, 44), the outcome being a global inhibition of protein synthesis that blocks viral proliferation (38).OAS family genes have been characterized extensively in humans, and orthologous genes are also reported in mouse, rat, pig, chicken, and marine sponges (38). In humans, the OAS family consists of four classes of genes: OAS1 (p40/p46, short form), OAS2 (p69/p71, middle form), OAS3 (p100, long form), and OASL (p59, or OAS-related protein). The three human OAS genes (OAS1 to -3) are located on chromosome segment 12q24.1 where they form a cluster within a 130-kb genomic region, representing the OAS locus (24). The gene encoding OASL has been mapped to 12q24.2 (23). The two isoforms of OAS1 (p40/p46) are identical in their first 346 amino acids but have different carboxy termini generated by alternative splicing (1). Similarly, differential splicing of the transcripts from the OAS2 gene generates the p69/p71 isoforms (33). The shor...

Cracking the egg: molecular dynamics and evolutionary aspects of the transition from the fully grown oocyte to embryo

“…In mice, the Mater (Nalp5) gene, a member of the Nalp family, was one of the first identified mammalian maternal effect genes; i.e., it encodes mRNA required for successful development of a fertilized oocyte (Tong et al 2000a). Targeted deletion of one of the Oasl genes, Oasl1d, causes reduced fertility in females but does not affect males (Yan et al 2005), demonstrating that members of this family are maternal effect genes. Tcl1, a gene whose duplication gave rise to TCL1B/Tcl1b loci in H. sapiens and M. musculus, is essential for female fertility and viability of cleavage stage embryos as well (Narducci et al 2002).…”

Cloning and expression profiling of small RNAs expressed in the mouse ovary

“…To collect oocytes (metaphase II), CD-1 female mice (Charles River Laboratories) were treated with 5 IU of PMSG (Sigma), followed by 5 IU of hCG (Sigma) to induce superovulation as described previously (Yan et al 2005). Oocytes were recovered from oviducts 18-24 h after hCG treatment in M2 medium (Sigma) containing 1 mg/mL hyaluronidase (Sigma).…”

Identification of Novel Host Cell Binding Partners of Oas1b, the Protein Conferring Resistance to Flavivirus-Induced Disease in Mice

“…Expression of a dominant negative RNase L did not overcome the less efficient virus replication phenotype of resistant MEFs (36). Also, two of the six inactive Oas1 proteins, Oas1b and Oas1d, were reported to act as dominant negative inhibitors of Oas1a synthetase activity (7,48). The Oas/RNase L pathway is involved in mRNA regulation during cell differentiation and apoptosis as well as during the innate immune response (8,33), and it was postulated that the inactive mouse Oas1 proteins function to tightly regulate Oas1 production of 2-5A to prevent deleterious effects on the cell (7,48).…”

“…Also, two of the six inactive Oas1 proteins, Oas1b and Oas1d, were reported to act as dominant negative inhibitors of Oas1a synthetase activity (7,48). The Oas/RNase L pathway is involved in mRNA regulation during cell differentiation and apoptosis as well as during the innate immune response (8,33), and it was postulated that the inactive mouse Oas1 proteins function to tightly regulate Oas1 production of 2-5A to prevent deleterious effects on the cell (7,48). The data obtained to date indicate that Oas1b does not exert its flavivirus-specific antiviral activity through the Oas/RNase L pathway (36).…”