Breast-cancer anti-estrogen resistance 4 (BCAR4) encodes a novel maternal-effect protein in bovine and is expressed in the oocyte of humans and other non-rodent mammals. Angulo L et al. STUDY QUESTION: Does BCAR4 have a role in mammalian embryo development? SUMMARY ANSWER: Expression, localization and functional data support that BCAR4 is a maternal-effect protein in non-rodent mammals. WHAT IS KNOWN ALREADY: BCAR4 was previously identified as an oocyte-specific gene in cattle, and as a marker of certain breast tumors in humans. STUDY DESIGN, SIZE, DURATION: Human oocytes were obtained from patients undergoing IVF, but had failed to mature after ovarian stimulation. Dog oocytes were obtained from ovariectomized bitches. Pig, horse and bovine ovaries were obtained from commercial slaughterhouses for extraction of immature oocyte-cumulus complexes. In vivo matured bovine matured oocytes were obtained after ovulation induction and ovulation inducing treatment of Montbeliard heifers. MATERIALS, SETTING AND METHODS: Expression at the RNA level was analyzed by reverse transcription coupled to polymerase chain reaction. Western blot and immunolabeling coupled to confocal or electronic microscopy were used to analyze bovine protein expression and intracellular localization. For the functional approach, short-interfering RNA were microinjected into mature bovine oocytes, followed by IVF; cleavage and embryo development were recorded. MAIN RESULTS AND THE ROLE OF CHANCE: The BCAR4 gene is conserved in mammalian species from various orders and has been lost in rodents after divergence with lagomorphs. The transcript is expressed in the oocytes of humans and domestic species. We bring the first experimental evidence of the BCAR4 protein in mammals. In cattle, the protein is not detected in immature oocytes but starts to be synthesized during maturation, increases in the zygote and persists until the morula stage. The protein is detected throughout the cytoplasm in mature oocytes, concentrates in and around the pronuclei in the zygote, and appears to shuttle in and out of the nuclei starting in the 2-cell embryo; BCAR4 is also present at the junctions between blastomeres from 2-cell to morula. In our functional approach, targeting the BCAR4 transcript by small-interfering RNA significantly compromised development to the morula or/and blastocyst stages (P < 0.05, logistic regression). LIMITATIONS, REASONS FOR CAUTION: As indicated above, protein expression and function were investigated in cattle and mostly in vitro matured oocytes were used. WIDER IMPLICATIONS OF THE FINDINGS: This study provides a novel candidate gene whose mutation or deregulation may underlie certain cases of unexplained female infertility. STUDY FUNDING/COMPETING INTEREST(S): This work was sponsored by grants from the French Ministry of Research (#03P409), Agence Nationale de la Recherche (#ANR-07-GANI-004-01) and Apisgene. No competing interests declared.
NCBI Summary:
This gene produces a spliced long non-coding RNA (lncRNA) that has been implicated in breast cancer metastasis. It was originally identified in a screen for genes responsible for the development of resistance to anti-estrogens in breast cancer cells. It is thought that release of CCL21 enables this lncRNA to bind to the SNIP1 and PNUTS transcription factors, thereby activating a non-canonical GLI-dependent hedgehog signaling pathway that promotes cancer cell migration and invasion. A similar gene in cow expresses a protein in mature oocytes and preimplantation embryos. Alternatively spliced transcript variants have been identified. [provided by RefSeq, Apr 2015]
General function
Cell proliferation
Comment
Cellular localization
Comment
Ovarian function
Early embryo development
Comment
Expression regulated by
Comment
Ovarian localization
Oocyte
Comment
Differential regulation of abundance and deadenylation of maternal transcripts during bovine oocyte maturation in vitro and in vivo. Th?e A et al. BACKGROUND: In bovine maturing oocytes and cleavage stage embryos, gene expression is mostly controlled at the post-transcriptional level, through degradation and deadenylation/polyadenylation. We have investigated how post transcriptional control of maternal transcripts was affected during in vitro and in vivo maturation, as a model of differential developmental competence. RESULTS: Using real time PCR, we have analyzed variation of maternal transcripts, in terms of abundance and polyadenylation, during in vitro or in vivo oocyte maturation and in vitro embryo development. Four genes are characterized here for the first time in bovine: ring finger protein 18 (RNF18) and breast cancer anti-estrogen resistance 4 (BCAR4), whose oocyte preferential expression was not previously reported in any species, as well as Maternal embryonic leucine zipper kinase (MELK) and STELLA. We included three known oocyte marker genes (Maternal antigen that embryos require (MATER), Zygote arrest 1 (ZAR1), NACHT, leucine rich repeat and PYD containing 9 (NALP9)). In addition, we selected transcripts previously identified as differentially regulated during maturation, peroxiredoxin 1 and 2 (PRDX1, PRDX2), inhibitor of DNA binding 2 and 3 (ID2, ID3), cyclin B1 (CCNB1), cell division cycle 2 (CDC2), as well as Aurora A (AURKA). Most transcripts underwent a moderate degradation during maturation. But they displayed sharply contrasted deadenylation patterns that account for variations observed previously by DNA array and correlated with the presence of a putative cytoplasmic polyadenylation element in their 3' untranslated region. Similar variations in abundance and polyadenylation status were observed during in vitro maturation or in vivo maturation, except for PRDX1, that appears as a marker of in vivo maturation. Throughout in vitro development, oocyte restricted transcripts were progressively degraded until the morula stage, except for MELK ; and the corresponding genes remained silent after major embryonic genome activation. CONCLUSION: Altogether, our data emphasize the extent of post-transcriptional regulation during oocyte maturation. They do not evidence a general alteration of this phenomenon after in vitro maturation as compared to in vivo maturation, but indicate that some individual messenger RNA can be affected.
Follicle stages
Comment
Phenotypes
Mutations
1 mutations
Species: None
Mutation name: type: null mutation fertility: subfertile Comment: Investigating the role of BCAR4 in ovarian physiology and female fertility by genome editing in rabbit. Peyny M et al. (2020) Breast Cancer Anti-estrogen Resistance 4 (BCAR4) was previously characterised in bovine species as a gene preferentially expressed in oocytes, whose inhibition is detrimental to in vitro embryo development. But its role in oogenesis, folliculogenesis and globally fertility in vivo remains unknown. Because the gene is not conserved in mice, rabbits were chosen for investigation of BCAR4 expression and function in vivo. BCAR4 displayed preferential expression in the ovary compared to somatic organs, and within the ovarian follicle in the oocyte compared to somatic cells. The transcript was detected in follicles as early as the preantral stage. Abundance decreased throughout embryo development until the blastocyst stage. A lineage of genome-edited rabbits was produced; BCAR4 expression was abolished in follicles from homozygous animals. Females of wild-type, heterozygous and homozygous genotypes were examined for ovarian physiology and reproductive parameters. Follicle growth and the number of ovulations in response to hormonal stimulation were not significantly different between genotypes. Following insemination, homozygous females displayed a significantly lower delivery rate than their heterozygous counterparts (22 ± 7% vs 71 ± 11% (mean ± SEM)), while prolificacy was 1.8 ± 0.7 vs 6.0 ± 1.4 kittens per insemination. In conclusion, BCAR4 is not essential for follicular growth and ovulation but it contributes to optimal fertility in rabbits.//////////////////