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The trophectoderm acts as a niche for the inner cell mass through IL-6 signaling [reprogramming_embryo]

ABSTRACT: IL-6 has been shown to be required for somatic cell reprogramming into induced pluripotent stem cells (iPSCs). However, how the cytokine is regulated and if it plays a role during embryo development remains unknown. Here we describe that IL-6 is strictly necessary for C/EBPa-enhanced reprogramming of B cells into iPSCs but not for B cell to macrophage transdifferentiation. C/EBPa induces the expression of both Il6 and Il6ra genes in B cells and in PSCs. During preimplantation embryo development C/EBPa is expressed in blastocysts where it is required for the maintenance of Il6. The expression of Cebpa is enriched in trophectoderm together with Il6 whereas the receptor gene Il6ra is predominantly expressed in the inner cell mass (ICM), in both mouse and humans. Blastocysts secrete IL-6 and neutralization of the cytokine delays the morula to blastocyst transition. Our study indicates that the trophectoderm acts as a niche for the ICM through the secretion of C/EBPa-regulated IL-6, facilitating efficient blastocyst development.

ORGANISM(S): Mus musculus

PROVIDER: GSE202613 | GEO | 2022/08/11

REPOSITORIES: GEO

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Project description:Preimplantation genetic diagnosis (PGD) of aneuploidy by fluorescence in situ hybridisation (FISH) has not delivered the expected clinical benefit. Many previous re-analysis studies of embryos deemed aneuploid by FISH on day 3 have found a high degree of chromosomal normalcy at the blastocyst stage. While most have interpreted this as âself correction,â there remains a lack of evidence for such a phenomenon. A more comprehensive technique for 24 chromosome aneuploidy screening was utilised here to re-evaluate blastocysts previously diagnosed as abnormal by FISH and investigate possible self correction mechanisms, including extrusion or duplication of aneuploid chromosomes resulting in uniparental isodisomy (UPID), and preferential segregation of aneuploidy to the trophectoderm (TE). Embryos that developed to a morphologically normal blastocyst after an aneuploidy diagnosis by cleavage stage FISH were biopsed into 4 sections, 3 TE and 1 inner cell mass (ICM), and randomised for evaluation by single nucleotide polymorphism (SNP) microarray based 24 chromosome aneuploidy screening (MA-PGD). Fifty-eight percent of blastocysts were euploid for all 24 chromosomes despite an aneuploid FISH result on day 3. Only 18% were consistent with the original FISH diagnosis, while the remaining 24% identified abnormalities that were different from the original FISH diagnosis. Abnormalities did not preferentially segregate to the TE and aneuploid chromosome extrusion or duplication resulting in UPID did not occur. Cleavage stage FISH is poorly predictive of aneuploidy in an embryo that develops into a morphologically normal blastocyst. Clinicians should consider re-evaluating embryos diagnosed as aneuploid by FISH that form morphologically normal blastocysts using a validated comprehensive 24 chromosome aneuploidy screening method. Affymetrix SNP arrays were processed according to the manufacturer's directions on DNA extracted from 50 cryopreserved blastocysts that were biopsied into 3 sections of trophectoderm and 1 inner cell mass section. Affymetrix SNP array analysis was successfully completed on 145 trophectoderm samples and 47 ICM samples from embryos, 8 lymphocyte samples from cell lines and 6 mixed male and female samples.

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The trophectoderm acts as a niche for the inner cell mass through IL-6 signaling [reprogramming_embryo]

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