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Newly identified ZNHIT3 variants, which cause intrauterine fetal loss, disrupt snoRNP assembly

ABSTRACT: Newly identified ZNHIT3 variants, which cause intrauterine fetal loss, disrupt snoRNP assembly

PROVIDER: PRJNA1140199 | ENA |

REPOSITORIES: ENA

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Project description:ZNHIT3 (zinc finger HIT type containing protein 3) is an evolutionarily conserved protein required for ribosome biogenesis by mediating the assembly of small nucleolar RNAs (snoRNAs) of class C/D into ribonucleoprotein complexes (snoRNPs). Missense mutations in the gene encoding ZNHIT3 protein have been previously reported to cause PEHO syndrome, a severe neurodevelopmental disorder typically presenting after birth. We present here the case of two fetuses from a single family who presented with isolated hydrops during the early second trimester of pregnancy, resulting in intrauterine demise. Autopsy revealed no associated malformation. Through whole-genome quartet analysis, we identified two novel variants within the ZNHIT3 gene, both inherited from healthy parents and occurring as compound heterozygotes in both fetuses. The c.40T>C p.Cys14Arg variant originated from the father, while the c.251_254delAAGA r.? p.? variant was of maternal origin. Western capillary analysis of ZNHIT3 protein in lymphoblastoid cell lines of the parents shows that the parental c.40T>C p.Cys14Arg variant causes a significant drop in steady-state ZNHIT3 protein level. Analysis of the variants in human cell culture models reveals that both variants reduce cell growth, albeit to different extents, and impact the protein's stability and function in distinct ways. The c.251_254delAAGA results in production of a stable form of ZNHIT3 that lacks a domain required for mediating snoRNP biogenesis, whereas the c.40T>C p.Cys14Arg variation behaves similarly to the previously described PEHO-associated ZNHIT3 variants that destabilize the protein. Interestingly, both variations lead to a marked decrease in specific box C/D snoRNA levels, reduced rRNA levels and cellular translation. Analysis of rRNA methylation pattern in fetus samples reveals distinct sites of hypo 2’-O-methylation. RNA-seq analysis of undifferentiated and differentiated SHSY5Y cells transfected with the ZNHIT3 variants reveals differential expression of a set of genes, many of which are associated with developmental processes and RNA binding compared to cells expressing wild-type ZNHIT3. In summary, this work adds two novel ZNHIT3 variants to the other human disease-linked variants of this protein and describes the molecular defects caused by these pathogenic variants.

Project description:The contraceptive effectiveness of intrauterine devices has been attributed in part to effects of a foreign body reaction on the endometrium. We performed this study to identify compare the effects on the endometrial transcriptome of intrauterine devices and combined oral contraceptives, to better understand their mechanisms of action. We collected endometrial and cervical biopsies from women using the levonorgestrel-intrauterine device, copper intrauterine device or levonorgestrel-containing combined oral contraceptives, and from women not using contraceptives (control group). Transcriptional profiling was performed with Affymetrix arrays, Principal Component Analysis and the bioconductor package limma. Pathway analysis was performed using EnrichR and Reactome 2016. In endometrial samples from copper intrauterine device users (n=13), there were no genes with statistically significant differential expression compared to controls (n=11), whereas in levonorgestrel-intrauterine device users (n=11), 2509 genes were significantly dysregulated and mapped onto several immune and inflammatory pathways. In combined oral contraceptive users (n=12), 133 genes were significantly dysregulated and mapped predominantly onto pathways involving regulation of metal ions. Both levonorgestrel-intrauterine device and combined oral contraceptive use were associated with significant downregulation of members of the metallothionein gene family. In cervical samples, none of the groups showed statistically significant differential gene expression compared to controls. In conclusion, hormonal and copper intrauterine devices differ significantly in their effects on the endometrial transcriptome, with endometrium from copper intrauterine device users being indistinguishable from luteal phase endometrium. These results suggest that the contraceptive mechanisms of intrauterine devices are unlikely to rely on a common pathway involving a foreign body reaction in the endometrium.

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Newly identified ZNHIT3 variants, which cause intrauterine fetal loss, disrupt snoRNP assembly

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