Epigenetic control of the imprinted growth regulator Cdkn1c in cadmium-induced placental dysfunction

Cadmium (Cd) is a toxic metal ubiquitous in the environment. In utero, Cd is inefficiently transported to the foetus but causes foetal growth restriction (FGR), likely through impairment of the placenta where Cd accumulates. However, the underlying molecular mechanisms are poorly understood. Cd can modulate the expression of imprinted genes, defined by their transcription from one parental allele, which play critical roles in placental and foetal growth. The expression of imprinted genes is governed by DNA methylation at Imprinting Control Regions (ICRs), which are susceptible to environmental perturbation. The imprinted gene Cdkn1c/CDKN1C is a major regulator of placental development, is implicated in FGR, and shows increased expression in response to Cd exposure in mice. Here, we use a hybrid mouse model of in utero Cd exposure to determine if the increase in placental Cdkn1c expression is caused by changes to ICR DNA methylation and loss of imprinting (LOI). Consistent with prior studies, Cd causes FGR and impacts placental structure and Cdkn1c expression at late gestation. Using polymorphisms to distinguish parental alleles, we demonstrate that increased Cdkn1c expression is not driven by changes to DNA methylation or LOI. We show that Cdkn1c is expressed primarily in the placental labyrinth which is proportionally increased in size in response to Cd. We conclude that the Cd-associated increase in Cdkn1c expression can be fully explained by alterations to placental structure. These results have implications for understanding mechanisms of Cd-induced placental dysfunction and, more broadly, for the study of FGR associated with increased Cdkn1c/CDKN1C expression.

Changes on chromosome 11p15.5 as specific marker for embryonal rhabdomyosarcoma?

Rhabdomyosarcomas (RMS) constitute a heterogeneous spectrum of tumors with respect to clinical behavior and tumor morphology. The paternal uniparental disomy (pUPD) of 11p15.5 is a molecular change described mainly in embryonal RMS. In addition to LOH, UPD, the MLPA technique (ME030kit) also determines copy number variants and methylation of H19 and KCNQ1OT1 genes, which have not been systematically investigated in RMS. All 127 RMS tumors were divided by histology and PAX status into four groups, pleomorphic histology (n = 2); alveolar RMS PAX fusion-positive (PAX+; n = 39); embryonal RMS (n = 70) and fusion-negative RMS with alveolar pattern (PAX-RMS-AP; n = 16). The following changes were detected; negative (n = 21), pUPD (n = 75), gain of paternal allele (n = 9), loss of maternal allele (n = 9), hypermethylation of H19 (n = 6), hypomethylation of KCNQ1OT1 (n = 6), and deletion of CDKN1C (n = 1). We have shown no difference in the frequency of pUPD 11p15.5 in all groups. Thus, we have proven that changes in the 11p15.5 are not only specific to the embryonal RMS (ERMS), but are often also present in alveolar RMS (ARMS). We have found changes that have not yet been described in RMS. We also demonstrated new potential diagnostic markers for ERMS (paternal duplication and UPD of whole chromosome 11) and for ARMS PAX+ (hypomethylation KCNQ1OT1).

Identification and validation of core genes for type 2 diabetes mellitus by integrated analysis of single-cell and bulk RNA-sequencing

BACKGROUND

The exact mechanisms of type 2 diabetes mellitus (T2DM) remain largely unknown. We intended to authenticate critical genes linked to T2DM progression by tandem single-cell sequencing and general transcriptome sequencing data.

METHODS

T2DM single-cell RNA-sequencing data were submitted by the Gene Expression Omnibus (GEO) database and ArrayExpress (EBI), from which gene expression matrices were retrieved. The common cell clusters and representative marker genes were ascertained by principal component analysis (PCA), t-distributed stochastic neighbor embedding (t-SNE), CellMarker, and FindMarkers in two datasets (GSE86469 and GSE81608). T2DM-related differentially expressed marker genes were defined by intersection analysis of marker genes and GSE86468-differentially expressed genes. Receiver operating characteristic (ROC) curves were utilized to assign representative marker genes with diagnostic values by GSE86468, GSE29226 and external validation GSE29221, and their prospective target compounds were forecasted by PubChem. Besides, the R package clusterProfiler-based functional annotation was designed to unveil the intrinsic mechanisms of the target genes. At last, western blot was used to validate the alternation of CDKN1C and DLK1 expression in primary pancreatic islet cells cultured with or without 30mM glucose.

RESULTS

Three common cell clusters were authenticated in two independent T2DM single-cell sequencing data, covering neurons, epithelial cells, and smooth muscle cells. Functional ensemble analysis disclosed an intimate association of these cell clusters with peptide/insulin secretion and pancreatic development. Pseudo-temporal trajectory analysis indicated that almost all epithelial and smooth muscle cells were of neuron origin. We characterized CDKN1C and DLK1, which were notably upregulated in T2DM samples, with satisfactory availability in recognizing three representative marker genes in non-diabetic and T2DM samples, and they were also robustly interlinked with the clinical characteristics of patients. Western blot also demonstrated that, compared with control group, the expression of CDKN1C and DLK1 were increased in primary pancreatic islet cells cultured with 30 mM glucose for 48 h. Additionally, PubChem projected 11 and 21 potential compounds for CDKN1C and DLK1, respectively.

CONCLUSION

It is desirable that the emergence of the 2 critical genes indicated (CDKN1C and DLK1) could be catalysts for the investigation of the mechanisms of T2DM progression and the exploitation of innovative therapies.

Promoter methylation and enhanced SKP2 are associated with the downregulation of CDKN1C in cervical squamous cell carcinoma

PURPOSE

Cervical Squamous Cell Carcinoma (CSCC) is one of the significant causes of cancer deaths among women. Distinct genetic and epigenetic-altered loci, including chromosomal 11p15.5-15.4, have been identified. CDKN1C (Cyclin-Dependent Kinase Inhibitor 1C, p57KIP2), a member of the CIP/KIP family of cyclin-dependent kinase inhibitors (CDKIs), located at 11p15.4, is a putative tumor suppressor. Apart from transcriptional control, S-Phase Kinase Associated Protein 2 (SKP2), an oncogenic E3 ubiquitin ligase, regulates the protein turnover of CDKN1C. But the molecular status of CDKN1C in CSCC and the underlying mechanistic underpinnings have yet to be explored.

METHODS

TCGA and other publicly available datasets were analyzed to evaluate the expression of CDKN1C and SKP2. The expression (transcript/protein) was validated in independent CSCC tumors (n = 155). Copy number alteration and promoter methylation were correlated with the expression. Finally, in vitro functional validation was performed.

RESULTS

CDKN1C was down-regulated, and SKP2 was up-regulated at the transcript and protein levels in CSCC tumors and the SiHa cell line. Notably, promoter methylation (50%) was associated with the downregulation of the CDKN1C transcript. However, high expression of SKP2 was found to be associated with the decreased expression of CDKN1C protein. Independent treatments with 5-aza-dC, MG132, and SKP2i (SKPin C1) in SiHa cells led to an enhanced expression of CDKN1C protein, validating the mechanism of down-regulation in CSCC.

CONCLUSION

Collectively, CDKN1C was down-regulated due to the synergistic effect of promoter hyper-methylation and SKP2 over-expression in CSCC tumors, paving the way for further studies of its role in the pathogenesis of the disease.

Beckwith-Wiedemann Syndrome in Newborn of Mother with HELLP Syndrome/Preeclampsia: An Analysis of Literature and Case Report with Fetal Growth Restriction and Absence of CDKN1C Typical Pathogenic Genetic Variation

Beckwith-Wiedemann Syndrome (BWS) is an imprinting disorder, which manifests by overgrowth and predisposition to embryonal tumors. The evidence on the relationship between maternal complications such as HELLP (hemolysis, elevated liver enzymes, and low platelet count) and preeclampsia and the development of BWS in offspring is scarce. A comprehensive clinical evaluation, with genetic testing focused on screening for mutations in the CDKN1C gene, which is commonly associated with BWS, was conducted in a newborn diagnosed with BWS born to a mother with a history of preeclampsia and HELLP syndrome. The case study revealed typical clinical manifestations of BWS in the newborn, including hemihyperplasia, macroglossia, midfacial hypoplasia, omphalocele, and hypoglycemia. Surprisingly, the infant also exhibited fetal growth restriction, a finding less commonly observed in BWS cases. Genetic analysis, however, showed no mutations in the CDKN1C gene, which contrasts with the majority of BWS cases. This case report highlights the complex nature of BWS and its potential association with maternal complications such as preeclampsia and HELLP syndrome. The atypical presence of fetal growth restriction in the newborn and the absence of CDKN1C gene mutations have not been reported to date in BWS.

CDKN1C gene mutation causing familial Silver–Russell syndrome: A case report and review of literature

BACKGROUND

Cyclin-dependent kinase inhibitor 1C (CDKN1C) is a cell proliferation inhibitor that regulates the cell cycle and cell growth through G1 cell cycle arrest. CDKN1C mutations can lead to IMAGe syndrome (CDKN1C allele gain-of-function mutations lead to intrauterine growth restriction, metaphyseal dysplasia, adrenal hypoplasia congenital, and genitourinary malformations). We present a Silver-Russell syndrome (SRS) pedigree that was due to a missense mutation affecting the same amino acid position, 279, in the CDKN1C gene, resulting in the amino acid substitution p.Arg279His (c.836G>A). The affected family members had an SRS phenotype but did not have limb asymmetry or adrenal insufficiency. The amino acid changes in this specific region were located in a narrow functional region that contained mutations previously associated with IMAGe syndrome. In familial SRS patients, the PCNA region of CDKN1C should be analysed. Adrenal insufficiency should be excluded in all patients with functional CDKN1C variants.

CASE SUMMARY

We describe the case of an 8-year-old girl who initially presented with short stature. Her height was 91.6 cm, and her weight was 10.2 kg. Physical examination revealed that she had a relatively large head, an inverted triangular face, a protruding forehead, a low ear position, sunken eye sockets, and irregular cracked teeth but no limb asymmetry. Family history: The girl’s mother, great-grandmother, and grandmother’s brother also had a prominent forehead, triangular face, and severely proportional dwarfism but no limb asymmetry or adrenal insufficiency. Exome sequencing of the girl revealed a new heterozygous CDKN1C (NM_000076. 2) c.836G>A mutation, resulting in a variant with a predicted evolutionarily highly conserved arginine substituted by histidine (p.Arg279His). The same causative mutation was found in both the proband’s mother, great-grandmother, and grandmother’s brother, who had similar phenotypes. Thus far, we found an SRS pedigree, which was due to a missense mutation affecting the same amino acid position, 279, in the CDKN1C gene, resulting in the amino acid substitution p.Arg279His (c.836G>A). Although the SRS-related CDKN1C mutation is in the IMAGe-related mutation hotspot region [the proliferating cell nuclear antigen (PCNA) domain], no adrenal insufficiency was reported in this SRS pedigree. The reason may be that the location of the genomic mutation and the type of missense mutation determines the phenotype. The proband was treated with recombinant human growth hormone (rhGH). After 1 year of rhGH treatment, the height standard deviation score of the proband increased by 0.93 standard deviation score, and her growth rate was 8.1 cm/year. No adverse reactions, such as abnormal blood glucose, were found.

CONCLUSION

Functional mutations in CDKN1C can lead to familial SRS without limb asymmetry, and some patients may have glucose abnormalities. In familial SRS patients, the PCNA region of CDKN1C should be analysed. Adrenal insufficiency should be excluded in all patients with functional CDKN1C variants.

p57Kip2 acts as a transcriptional corepressor to regulate intestinal stem cell fate and proliferation

p57Kip2 is a cyclin/CDK inhibitor and a negative regulator of cell proliferation. Here, we report that p57 regulates intestinal stem cell (ISC) fate and proliferation in a CDK-independent manner during intestinal development. In the absence of p57, intestinal crypts exhibit an increased proliferation and an amplification of transit-amplifying cells and of Hopx+ ISCs, which are no longer quiescent, while Lgr5+ ISCs are unaffected. RNA sequencing (RNA-seq) analyses of Hopx+ ISCs show major gene expression changes in the absence of p57. We found that p57 binds to and inhibits the activity of Ascl2, a transcription factor critical for ISC specification and maintenance, by participating in the recruitment of a corepressor complex to Ascl2 target gene promoters. Thus, our data suggest that, during intestinal development, p57 plays a key role in maintaining Hopx+ ISC quiescence and repressing the ISC phenotype outside of the crypt bottom by inhibiting the transcription factor Ascl2 in a CDK-independent manner.

PIK3R3 is upregulated in liver cancer and activates Akt signaling to control cancer growth by regulation of CDKN1C and SMC1A

BACKGROUND

Liver cancer is a highly malignant disease and the third leading cause of cancer death worldwide. Abnormal activation of PI3K/Akt signaling is common in cancer, but whether phosphoinositide-3-kinase regulatory subunit 3 (PIK3R3) plays a role in liver cancer is largely unexplored.

METHODS

We determined the expression of PIK3R3 in liver cancer by using TCGA data and our clinical samples and knocked it down by siRNA or overexpressing it by the lentivirus vector system. We also investigated the function of PIK3R3 by colony formation, 5-Ethynyl-2-Deoxyuridine, flow cytometry assay, and subcutaneous xenograft model. The downstream of PIK3R3 was explored by RNA sequence and rescue assays.

RESULTS

We found that PIK3R3 was significantly upregulated in liver cancer and correlated with prognosis. PIK3R3 promoted liver cancer growth in vitro and in vivo by controlling cell proliferation and cell cycle. RNA sequence revealed that hundreds of genes were dysregulated upon PIK3R3 knockdown in liver cancer cells. CDKN1C, a cyclin-dependent kinase inhibitor, was significantly upregulated by PIK3R3 knockdown, and CDKN1C siRNA rescued the impaired tumor cell growth. SMC1A was partially responsible for PIK3R3 regulated function, and SMC1A overexpression rescued the impaired tumor cell growth in liver cancer cells. Immunoprecipitation demonstrated there is indirect interaction between PIK3R3 and CNKN1C or SMC1A. Importantly, we verified that PIK3R3-activated Akt signaling determined the expression of CDKN1C and SMC1A, two downstream of PIK3R3 in liver cancer cells.

CONCLUSION

PIK3R3 is upregulated in liver cancer and activates Akt signaling to control cancer growth by regulation of CDNK1C and SMC1A. Targeting PIK3R3 could be a promising treatment strategy for liver cancer that deserves further investigation.

Familial Beckwith-Wiedemann syndrome in a multigenerational family: Forty years of careful phenotyping

Beckwith-Wiedemann Spectrum (BWSp) is an overgrowth and cancer predisposition disorder characterized by a wide spectrum of phenotypic manifestations including macroglossia, abdominal wall defects, neonatal hypoglycemia, and predisposition to embryonal tumors. In 1981, Best and Hoekstra reported four patients with BWSp in a single family which suggested autosomal dominant inheritance, but standard clinical testing for BWSp was not available during this time. Meticulous phenotyping of this family has occurred over the past 40 years of follow-up with additional family members being identified and samples collected for genetic testing. Genetic testing revealed a pathogenic mutation in CDKN1C, consistent with the most common cause of familial BWSp. CDKN1C mutations account for just 5% of sporadic cases of BWSp. Here, we report the variable presentation of BWSp across the individuals affected by the CDKN1C mutation and other extended family members spanning multiple generations, all examined by the same physician. Additional phenotypes thought to be atypical in patients with BWSp were reported which included cardiac abnormalities. The incidence of tumors was documented in extended family members and included rhabdomyosarcoma, astrocytoma, and thyroid carcinoma, which have previously been reported in patients with BWSp. These observations suggest that in addition to the inheritance of the CDKN1C variant, there are modifying factors in this family driving the phenotypic spectrum observed. Alternative theories are suggested to explain the etiology of clinical variability including diffused mosaicism, anticipation, and the presence of additional variants tracking in the family. This study highlights the necessity of long-term follow-up in patients with BWSp and consideration of individual familial characteristics in the context of phenotype and/or (epi)genotype associations.

Dual inhibition of EZH1/2 induces cell cycle arrest of B cell acute lymphoblastic leukemia cells through upregulation of CDKN1C and TP53INP1

Disease-risk stratification and development of intensified chemotherapy protocols have substantially improved the outcome of acute lymphoblastic leukemia (ALL). However, outcomes of relapsed or refractory cases remain poor. Previous studies have discussed the oncogenic role of enhancer of zeste homolog 1 and 2 (EZH1/2), and the efficacy of dual inhibition of EZH1/2 as a treatment for hematological malignancy. Here, we investigated whether an EZH1/2 dual inhibitor, DS-3201 (valemetostat), has antitumor effects on B cell ALL (B-ALL). DS-3201 inhibited growth of B-ALL cell lines more significantly and strongly than the EZH2-specific inhibitor EPZ-6438, and induced cell cycle arrest and apoptosis in vitro. RNA-seq analysis to determine the effect of DS-3201 on cell cycle arrest-related genes expressed by B-ALL cell lines showed that DS-3201 upregulated CDKN1C and TP53INP1. CRIPSR/Cas9 knockout confirmed that CDKN1C and TP53INP1 are direct targets of EZH1/2 and are responsible for the antitumor effects of DS-3201 against B-ALL. Furthermore, a patient-derived xenograft (PDX) mouse model showed that DS-3201 inhibited the growth of B-ALL harboring MLL-AF4 significantly. Thus, DS-3201 provides another option for treatment of B-ALL.

Clinical Spectrum and Tumour Risk Analysis in Patients with Beckwith-Wiedemann Syndrome Due to CDKN1C Pathogenic Variants

Beckwith-Wiedemann syndrome spectrum (BWSp) is an overgrowth disorder caused by imprinting or genetic alterations at the 11p15.5 locus. Clinical features include overgrowth, macroglossia, neonatal hypoglycaemia, omphalocele, hemihyperplasia, cleft palate, and increased neoplasm incidence. The most common molecular defect observed is hypomethylation at the imprinting centre 2 (KCNQ1OT1:TSS DMR) in the maternal allele, which accounts for approximately 60% of cases, although CDKN1C pathogenic variants have been reported in 5-10% of patients, with a higher incidence in familial cases. In this study, we examined the clinical and molecular features of all cases of BWSp identified by the Spanish Overgrowth Registry Initiative with pathogenic or likely pathogenic CDKN1C variants, ascertained by Sanger sequencing or next-generation sequencing, with special focus on the neoplasm incidence, given that there is scarce knowledge of this feature in CDKN1C-associated BWSp. In total, we evaluated 21 cases of BWSp with CDKN1C variants; 19 were classified as classical BWS according to the BWSp scoring classification by Brioude et al. One of our patients developed a mediastinal ganglioneuroma. Our study adds evidence that tumour development in patients with BWSp and CDKN1C variants is infrequent, but it is extremely relevant to the patient's follow-up and supports the high heterogeneity of BWSp clinical features associated with CDKN1C variants.

Generation of Isogenic hiPSCs with Targeted Edits at Multiple Intronic SNPs to Study the Effects of the Type 2 Diabetes Associated KCNQ1 Locus in American Indians

The top genetic association signal for type 2 diabetes (T2D) in Southwestern American Indians maps to intron 15 of KCNQ1, an imprinted gene. We aim to understand the biology whereby variation at this locus affects T2D specifically in this genomic background. To do so, we obtained human induced pluripotent stem cells (hiPSC) derived from American Indians. Using these iPSCs, we show that imprinting of KCNQ1 and CDKN1C during pancreatic islet-like cell generation from iPSCs is consistent with known imprinting patterns in fetal pancreas and adult islets and therefore is an ideal model system to study this locus. In this report, we detail the use of allele-specific guide RNAs and CRISPR to generate isogenic hiPSCs that differ only at multiple T2D associated intronic SNPs at this locus which can be used to elucidate their functional effects. Characterization of these isogenic hiPSCs identified a few aberrant cell lines; namely cell lines with large hemizygous deletions in the putative functional region of KCNQ1 and cell lines hypomethylated at the KCNQ1OT1 promoter. Comparison of an isogenic cell line with a hemizygous deletion to the parental cell line identified CDKN1C and H19 as differentially expressed during the endocrine progenitor stage of pancreatic-islet development.

High Maternal Serum Estradiol in First Trimester of Multiple Pregnancy Contributes to Small for Gestational Age via DNMT1-Mediated CDKN1C Upregulation

High maternal serum estradiol (E₂) levels in the first trimester of pregnancy are associated with a high incidence of low birth weight (LBW) and small for gestational age (SGA). This study aimed to investigate the effect of first-trimester high maternal serum E₂ levels on fetal growth and the underlying mechanisms in multiple pregnancies. Maternal serum E₂ levels of women at 8 weeks of gestation were measured. The expression levels of imprinted genes and DNMT1 were determined by RT-qPCR, and KvDMR1 methylation in embryo tissue, placenta, and newborn cord blood samples was examined by bisulfite sequencing PCR. The effect of E₂ on CDKN1C expression was investigated in HTR8 cells. The incidence of SGA was significantly higher in multiple pregnancies reduced to singleton than that in primary singleton pregnancies (11.4% vs. 2.9%) (P < 0.01) and multiple pregnancies reduced to twins than primary twins (38.5% vs. 27.3%) (P < 0.01). The maternal serum E₂ level at 8 weeks of gestation increased with the number of fetuses and was negatively correlated with offspring birth weight. CDKN1C and DNMT1 expression was significantly upregulated in embryo tissue, placenta, and cord blood from multiple pregnancies. Furthermore, there was a positive correlation between CDKN1C mRNA expression and KvDMR1 methylation levels. In HTR8 cells, DNMT1 mediated the estrogen-induced upregulation of CDKN1C, which might contribute to SGA. To minimize the risks of LBW and SGA, our findings suggest that abnormally high maternal serum E₂ levels should be avoided during the first trimester of multiple pregnancies from assisted reproductive technology (ART).

CDKN1C as a prognostic biomarker correlated with immune infiltrates and therapeutic responses in breast cancer patients

Breast cancer (BC) prognosis and therapeutic sensitivity could not be predicted efficiently. Previous evidence have shown the vital roles of CDKN1C in BC. Therefore, we aimed to construct a CDKN1C‐based model to accurately predicting overall survival (OS) and treatment responses in BC patients. In this study, 995 BC patients from The Cancer Genome Atlas database were selected. Kaplan‐Meier curve, Gene set enrichment and immune infiltrates analyses were executed. We developed a novel CDKN1C‐based nomogram to predict the OS, verified by the time‐dependent receiver operating characteristic curve, calibration curve and decision curve. Therapeutic response prediction was followed based on the low‐ and high‐nomogram score groups. Our results indicated that low‐CDKN1C expression was associated with shorter OS and lower proportion of naïve B cells, CD8 T cells, activated NK cells. The predictive accuracy of the nomogram for 5‐year OS was superior to the tumour‐node‐metastasis stage (area under the curve: 0.746 vs. 0.634, p < 0.001). The nomogram exhibited excellent predictive performance, calibration ability and clinical utility. Moreover, low‐risk patients were identified with stronger sensitivity to therapeutic agents. This tool can improve BC prognosis and therapeutic responses prediction, thus guiding individualized treatment decisions.

miR-92b-3p Regulates Cell Cycle and Apoptosis by Targeting CDKN1C, Thereby Affecting the Sensitivity of Colorectal Cancer Cells to Chemotherapeutic Drugs

Simple Summary

Multidrug resistance (MDR) limits the effectiveness of colorectal cancer (CRC) treatment and miRNAs play an important role in drug resistance. To search for miRNA targets that may be involved in the CRC MDR phenotype, this study used small RNAomic screens to analyze the expression profiles of miRNAs in CRC HCT8 cell line and its chemoresistant counterpart HCT8/T cell line. It was found that miR-92b-3p was highly expressed in HCT8/T cells and chemotherapeutic drugs could stimulate CRC cells to up-regulate miR-92b-3p expression and conferred cellular resistance to chemotherapeutic drugs. This study revealed a new mechanism of MDR in CRC, elucidating for the first time the direct link between miR-92b-3p/CDKN1C and chemoresistance. In summary, this study suggested that miR-92b-3p could be used as a potential therapeutic target for reversing MDR in chemotherapy and as a candidate biomarker for predicting the efficacy of chemotherapy.

Abstract

Colorectal cancer (CRC) is the third most common malignant tumor in the world and the second leading cause of cancer death. Multidrug resistance (MDR) has become a major obstacle in the clinical treatment of CRC. The clear molecular mechanism of MDR is complex, and miRNAs play an important role in drug resistance. This study used small RNAomic screens to analyze the expression profiles of miRNAs in CRC HCT8 cell line and its chemoresistant counterpart HCT8/T cell line. It was found that miR-92b-3p was highly expressed in HCT8/T cells. Knockdown of miR-92b-3p reversed the resistance of MDR HCT8/T cells to chemotherapeutic drugs in vitro and in vivo. Paclitaxel (PTX, a chemotherapy medication) could stimulate CRC cells to up-regulate miR-92b-3p expression and conferred cellular resistance to chemotherapeutic drugs. In studies on downstream molecules, results suggested that miR-92b-3p directly targeted Cyclin Dependent Kinase Inhibitor 1C (CDKN1C, which encodes a cell cycle inhibitor p57Kip2) to inhibit its expression and regulate the sensitivity of CRC cells to chemotherapeutic drugs. Mechanism study revealed that the miR-92b-3p/CDKN1C axis exerted a regulatory effect on the sensitivity of CRC cells via the regulation of cell cycle and apoptosis. In conclusion, these findings showed that miR-92b-3p/CDKN1C was an important regulator in the development of drug resistance in CRC cells, suggesting its potential application in drug resistance prediction and treatment.

A Case report: Co-occurrence of IMAGe syndrome and Rhabdomyosarcoma

IMAGe syndrome is a rare congenital disorder, presenting with intrauterine growth restriction, metaphyseal dysplasia, adrenal hypoplasia congenita and genital anomalies (in males). So far only 17 individuals have been diagnosed molecularly with IMAGe syndrome, this patient is the first case of an individual diagnosed with IMAGe and concurrent rhabdomyosarcoma. The patient was born at 30 weeks' gestation and received treatment for hyponatremia and hyperkalemia. At 4 9/12 years of age the patient showed a painless, non-mobile mass on the left thigh. In the biopsy performed a sarcoma weave with solid, nest-like growth, with characteristics of rhabdomyosarcoma was identified. The family history and physical examination indicated IMAGe syndrome so genetic testing was requested. A whole exome sequencing procedure with use of SureSelectXT Human ALL Exon V7, confirmed a single nucleotide variant NM_000076.2(CDKN1C):c.820G>A (p.Asp274Asn); identifying a missense mutation in the imprinted gene CDKN1C associated with IMAGe syndrome. Although tumours associated with CDKN1C are rare, deregulation of imprinted genes is increasingly being recognised as a mechanism of tumorigenesis in cancer; chromosomal region 11p15.5 contains a cluster of imprinted genes. This same region is the most consistent site of allele loss in rhabdomyosarcoma and is the same region altered in both IMAGe and Beckwith-Wiedemann syndrome. Molecular studies have found genetic changes in the 11p15 region in a variety of embryonal tumours like Wilms tumours which are commonly developed in Beckwith-Wiedemann syndrome and embryonal rhabdomyosarcoma. Through this case we aim to present the possibility of oncogenesis in patients with IMAGe syndrome, specifically rhabdomyosarcoma.

Variable Expressivity of the Beckwith-Wiedemann Syndrome in Four Pedigrees Segregating Loss-of-Function Variants of CDKN1C

Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder characterized by prenatal and/or postnatal overgrowth, organomegaly, abdominal wall defects and tumor predisposition. CDKN1C is a maternally expressed gene of the 11p15.5 chromosomal region and is regulated by the imprinting control region IC2. It negatively controls cellular proliferation, and its expression or activity are frequently reduced in BWS. In particular, loss of IC2 methylation is associated with CDKN1C silencing in the majority of sporadic BWS cases, and maternally inherited loss-of-function variants of CDKN1C are the most frequent molecular defects of familial BWS. We have identified, using Sanger sequencing, novel CDKN1C variants in three families with recurrent cases of BWS, and a previously reported variant in a woman with recurrent miscarriages with exomphalos. Clinical evaluation of the patients showed variable manifestation of the disease. The frameshift and nonsense variants were consistently associated with exomphalos, while the missense variant caused a less severe phenotype. Pregnancy loss and perinatal lethality were found in the families segregating nonsense mutations. Intrafamilial variability of the clinical BWS features was observed, even between siblings. Our data are indicative of severe BWS phenotypes that, with variable expressivity, may be associated with both frameshift and nonsense variants of CDKN1C.

CDKN1C-mediated growth inhibition by an EZH1/2 dual inhibitor overcomes resistance of mantle cell lymphoma to ibrutinib

Mantle cell lymphoma (MCL) is a rare subtype of non‐Hodgkin's lymphoma, which is characterized by overexpression of cyclin D1. Although novel drugs, such as ibrutinib, show promising clinical outcomes, relapsed MCL often acquires drug resistance. Therefore, alternative approaches for refractory and relapsed MCL are needed. Here, we examined whether a novel inhibitor of enhancer of zeste homologs 1 and 2 (EZH1/2), OR‐S1 (a close analog of the clinical‐stage compound valemetostat), had an antitumor effect on MCL cells. In an ibrutinib‐resistant MCL patient–derived xenograft (PDX) mouse model, OR‐S1 treatment by oral administration significantly inhibited MCL tumor growth, whereas ibrutinib did not. In vitro growth assays showed that compared with an established EZH2‐specific inhibitor GSK126, OR‐S1 had a marked antitumor effect on MCL cell lines. Furthermore, comprehensive gene expression analysis was performed using OR‐S1–sensitive or insensitive MCL cell lines and showed that OR‐S1 treatment modulated B‐cell activation, differentiation, and cell cycle. In addition, we identified Cyclin Dependent Kinase Inhibitor 1C (CDKN1C, also known as p57, KIP2), which contributes to cell cycle arrest, as a direct target of EZH1/2 and showed that its expression influenced MCL cell proliferation. These results suggest that EZH1/2 may be a potential novel target for the treatment of aggressive ibrutinib‐resistant MCL via CDKN1C‐mediated cell cycle arrest.

Stimulation of c-Jun/AP-1-Activity by the Cell Cycle Inhibitor p57Kip2

p57 is a member of the Cip/Kip family of cell cycle inhibitors which restrict the eukaryotic cell cycle by binding to and inhibiting cyclin/CDK complexes. They are considered as tumor suppressors and inactivating genomic mutations of p57 are associated with human overgrowth disorders. Increasing evidence suggests that p57 controls additional cellular processes beyond cell cycle control such as apoptosis, cell migration or transcription. Here we report that p57 can stimulate AP-1 promotor activity. While transactivation by c-Jun is strongly activated by p57, it did not enhance c-Fos induced transcription. This indicates that c-Jun is the target of p57 in the canonical AP-1 heterodimeric transcription factor. We could detect endogenous p57/c-Jun containing complexes in cells by co-immunoprecipitation. The strong stimulation of c-Jun activity is not the consequence of activating phosphorylation in the transactivation domain (TAD) of c-Jun, but rather due to negative interference with c-Jun repressors and positive interference with c-Jun activators. In contrast to full-length p57, the amino- and carboxy-terminal domains of p57 are insufficient for a significant activation of c-Jun induced transcription. When expressed in presence of full length p57, the p57 C-terminus abrogated and the N-terminus enhanced c-Jun activation. This indicates that the C-terminus may bind and sequester a putative activator of c-Jun, whereas the N-terminus may sequester a c-Jun repressor. Interestingly, the p57 aminoterminus is sufficient for binding to the two c-Jun repressors HDAC1 and HDAC3. These data are consistent with a model of c-Jun activation where p57 is a part of large nuclear remodeling/transcription complexes. p57 might stimulate transcription by inhibiting transcription repressor proteins like HDACs via its N-terminus and/or attracting transcription activators through its C-terminus. These data suggest that in addition to its role as a CDK inhibitor and tumor suppressor, p57 may also exert tumor promoting functions by activation of the proto-oncoprotein c-Jun.

Identification of novel myelin repair drugs by modulation of oligodendroglial differentiation competence

BACKGROUND

In multiple sclerosis loss of myelin and oligodendrocytes impairs saltatory signal transduction and leads to neuronal loss and functional deficits. Limited capacity of oligodendroglial precursor cells to differentiate into mature cells is the main reason for inefficient myelin repair in the central nervous system. Drug repurposing constitutes a powerful approach for identification of pharmacological compounds promoting this process.

METHODS

A phenotypic compound screening using the subcellular distribution of a potent inhibitor of oligodendroglial cell differentiation, namely p57kip2, as differentiation competence marker was conducted. Hit compounds were validated in terms of their impact on developmental cell differentiation and myelination using both rat and human primary cell cultures and organotypic cerebellar slice cultures, respectively. Their effect on spontaneous remyelination was then investigated following cuprizone-mediated demyelination of the corpus callosum.

FINDINGS

A number of novel small molecules able to promote oligodendroglial cell differentiation were identified and a subset was found to foster human oligodendrogenesis as well as myelination ex vivo. Among them the steroid danazol and the anthelminthic parbendazole were found to increase myelin repair.

INTERPRETATION

We provide evidence that early cellular processes involved in differentiation decisions are applicable for the identification of regeneration promoting drugs and we suggest danazol and parbendazole as potent therapeutic candidates for demyelinating diseases.

FUNDING

This work was supported by the Jürgen Manchot Foundation, Düsseldorf; Research Commission of the Medical Faculty of Heinrich-Heine-University Düsseldorf; Christiane and Claudia Hempel Foundation; Stifterverband/Novartisstiftung; James and Elisabeth Cloppenburg, Peek and Cloppenburg Düsseldorf Stiftung and International Progressive MS Alliance (BRAVEinMS).

Long non-coding RNA linc00665 inhibits CDKN1C expression by binding to EZH2 and affects cisplatin sensitivity of NSCLC cells

Long non-coding RNAs (lncRNAs) can play significant regulatory roles in cells that affect the development and acquired drug resistance of lung cancer. Herein, we report that lncRNA linc00665 is significantly upregulated in non-small cell lung cancer (NSCLC) tissues compared with adjacent normal tissues. linc00665 affects the sensitivity of NSCLC cells to the chemotherapy drug cisplatin (DDP), making it a potential target for the treatment of NSCLC. Functional experiments showed that linc00665 enhanced the proliferation and migration of NSCLC cells in vivo and in vitro, and knocking down linc00665 could enhance the drug sensitivity of NSCLC cells to DDP. Further work revealed that linc00665 could recruit enhancer of zeste homolog 2 (EZH2) to the promoter region of cyclin-dependent kinase inhibitor 1C (CDKN1C) to inhibit its transcription and thus carry out its tumorigenic role. In conclusion, our study elucidated the carcinogenic role of the linc00665-EZH2-CDKN1C axis in NSCLC tumors and its ability to influence the sensitivity of these tumors to DDP. These results suggest that linc00665 may be a potential diagnostic marker and therapeutic target in NSCLC, and they also provide a new direction for the development of clinical reversal methods for acquired drug resistance in patients with NSCLC.

Familial Beckwith-Wiedemann syndrome: Prenatal manifestation and a possible expansion of the phenotype

We describe a case of Beckwith-Wiedemann syndrome (BWS) demonstrating pre- and post-natal intra-familial variability. Our first encounter with the family occurred in the 1990s following the birth of 3 affected offspring. The first two pregnancies presented with exomphalos and elevated second trimester maternal serum alpha-fetoprotein (msAFP, 3.43 and 4.01 MOM, respectively) as well as elevated maternal human chorionic gonadotrophin (mhCG, 4.33 and 8.8 MOM, respectively). The diagnosis of BWS was confirmed postnatally in both cases. The third ongoing pregnancy presented only with elevated mhCG (7.09 MOM) and no malformation. Nonetheless BWS was suspected. The diagnosis was confirmed postnatally with clinical manifestations including macroglossia and cleft palate. Two affected female siblings were also diagnosed with Mullerian agenesis in adulthood. Suspecting a common genetic etiology, sequencing of the CDKN1C gene revealed a maternally inherited, likely pathogenic variant (NM_000076.2: c.367_385del; p.(Ala123Serfs*143)) causative of BWS. Chromosomal microarray and whole exome sequencing did not reveal any other pathogenic variant that would explain the Mullerian agenesis. One of the affected females underwent successful preimplantation genetic testing (PGT) with a surrogate and gave birth to a healthy female. To the best of our knowledge, this is the first report of Mullerian agenesis as a possible rare expansion of the BWS phenotype. In addition, this case highlights the potential role of abnormal second trimester biochemical markers (msAFP, mHCG) as possible indicators of BWS, especially in familial cases.

Novel mutation points to a hot spot in CDKN1C causing Silver-Russell syndrome

BACKGROUND

Pathogenic CDKN1C gain-of-function variants on the maternal allele were initially reported as a cause of IMAGe syndrome characterized by intrauterine growth retardation, metaphyseal dysplasia, primary adrenal insufficiency and genital anomalies. Recently, a maternally inherited CDKN1C missense mutation (p.Arg279Leu) was identified in several members of a single family clinically diagnosed with Silver-Russell syndrome (SRS) but without adrenal insufficiency. Thereafter, two half siblings from UK with familial SRS were described who carried the same mutation. This specific amino acid change is located within a narrow functional region containing the mutations previously associated with IMAGe syndrome.

RESULTS

Here, we describe a third familial case with maternally inherited SRS due to a missense variant affecting the same amino acid position 279 but leading to a different amino acid substitution (p. (Arg279Ser)). The two affected family members (mother and son) presented with the complete SRS phenotype (both Netchine-Harbison CSS score 5 of 6) but without body asymmetry or adrenal insufficiency.

CONCLUSIONS

In comparison with loss-of-function genomic IGF2 mutations, CDKN1C gain-of-function mutations are a less frequent cause of SRS and seem to affect a cluster of few amino acids.

Functional Versatility of the CDK Inhibitor p57Kip2

The cyclin/CDK inhibitor p57^Kip2 belongs to the Cip/Kip family, with p21^Cip1 and p27^Kip1, and is the least studied member of the family. Unlike the other family members, p57^Kip2 has a unique role during embryogenesis and is the only CDK inhibitor required for embryonic development. p57^Kip2 is encoded by the imprinted gene CDKN1C, which is the gene most frequently silenced or mutated in the genetic disorder Beckwith-Wiedemann syndrome (BWS), characterized by multiple developmental anomalies. Although initially identified as a cell cycle inhibitor based on its homology to other Cip/Kip family proteins, multiple novel functions have been ascribed to p57^Kip2 in recent years that participate in the control of various cellular processes, including apoptosis, migration and transcription. Here, we will review our current knowledge on p57^Kip2 structure, regulation, and its diverse functions during development and homeostasis, as well as its potential implication in the development of various pathologies, including cancer.

lncRNA STEAP3-AS1 Modulates Cell Cycle Progression via Affecting CDKN1C Expression through STEAP3 in Colon Cancer

Previous studies have reported that long noncoding RNAs (lncRNAs) have acted as new players during tumorigenesis. Metallothionein also plays an important role in tumor progression. It is mainly considered to be involved in the process of cell proliferation, oxidative stress, and multidrug resistance. However, the potential involvement of metallothionein-related lncRNAs in colon cancer remains poorly understood. In our study, we found that MT1M affected the expression of lncRNA STEAP3-AS1. STEAP3-AS1 is located in physical contiguity with STEAP3 and notably increased in colon cancer tissues and cell lines. STEAP3-AS1 expression was negatively associated with the expression of STEAP3. High levels of STEPA3-AS1 were associated with poor overall survival in colon cancer patients. In in vitro assays, STEAP3-AS1 knockdown could inhibit colon cancer cell proliferation and migration and arrest colon cancer cells at the G₀-G₁ phase. In tumorigenicity assays, STEAP3-AS1 knockdown could strongly inhibit tumor growth. Mechanistic investigations demonstrated that STEAP3-AS1 downregulation could increase the expression of cyclin-dependent kinase inhibitor 1C (CDKN1C) by STEAP3 upregulation. Overall, we identify the underlying role of MT1M-related lncRNA STEAP3-AS1 in colon cancer progression, which provides a novel strategy for colon cancer therapy.

Contribution of gene mutations to Silver-Russell syndrome phenotype: multigene sequencing analysis in 92 etiology-unknown patients

BACKGROUND

Silver-Russell syndrome (SRS) is characterized by growth failure and dysmorphic features. Major (epi)genetic causes of SRS are loss of methylation on chromosome 11p15 (11p15 LOM) and maternal uniparental disomy of chromosome 7 (upd(7)mat). However, IGF2, CDKN1C, HMGA2, and PLAG1 mutations infrequently cause SRS. In addition, other imprinting disturbances, pathogenic copy number variations (PCNVs), and monogenic disorders sometimes lead to SRS phenotype. This study aimed to clarify the frequency and clinical features of the patients with gene mutations among etiology-unknown patients with SRS phenotype.

RESULTS

Multigene sequencing was performed in 92 out of 336 patients referred to us for genetic testing for SRS. The clinical features of the patients were evaluated based on the Netchine-Harbison clinical scoring system. None of the patients showed 11p15 LOM, upd(7)mat, abnormal methylation levels for six differentially methylated regions (DMRs), namely, PLAGL1:alt-TSS-DMR on chromosome 6, KCNQ1OT1:TSS-DMR on chromosome 11, MEG3/DLK1:IG-DMR on chromosome 14, MEG3:TSS-DMR on chromosome 14, SNURF:TSS-DMR on chromosome 15, and GNAS A/B:TSS-DMR on chromosome 20, PCNVs, or maternal uniparental disomy of chromosome 16. Using next-generation sequencing and Sanger sequencing, we screened four SRS-causative genes and 406 genes related to growth failure and/or skeletal dysplasia. We identified four pathogenic or likely pathogenic variants in responsible genes for SRS (4.3%: IGF2 in two patients, CDKN1C, and PLAG1), and five pathogenic variants in causative genes for known genetic syndromes presenting with growth failure (5.4%: IGF1R abnormality (IGF1R), SHORT syndrome (PIK3R1), Floating-Harbor syndrome (SRCAP), Pitt-Hopkins syndrome (TCF4), and Noonan syndrome (PTPN11)). Functional analysis indicated the pathogenicity of the CDKN1C variant. The variants we detected in CDKN1C and PLAG1 were the second and third variants leading to SRS, respectively. Our patients with CDKN1C and PLAG1 variants showed similar phenotypes to previously reported patients. Furthermore, our data confirmed IGF1R abnormality, SHORT syndrome, and Floating-Harbor syndrome are differential diagnoses of SRS because of the shared phenotypes among these syndromes and SRS. On the other hand, the patients with pathogenic variants in causative genes for Pitt-Hopkins syndrome and Noonan syndrome were atypical of these syndromes and showed partial clinical features of SRS.

CONCLUSIONS

We identified nine patients (9.8%) with pathogenic or likely pathogenic variants out of 92 etiology-unknown patients with SRS phenotype. This study expands the molecular spectrum of SRS phenotype.

Long non-coding RNA GAS5 accelerates oxidative stress in melanoma cells by rescuing EZH2-mediated CDKN1C downregulation

Background

The significance of long non-coding RNAs (lncRNAs) in mediating oxidative stress of cancers has been implicated recently. This study proposed a potential therapeutic target lncRNA growth arrest-specific transcript 5 (GAS5) for melanoma, due to its crucial role in oxidative stress and apoptosis of melanoma cells by regulating the enhancer of zeste homolog 2 (EZH2)-mediated CDKN1C expression.

Methods

The lncRNA GAS5 expression pattern was examined in melanoma tissues and cells. The correlation of lncRNA GAS5, EZH2, and CDKN1C with survival rate of melanoma patients was analyzed. In melanoma cell lines, lncRNA GAS5 expression was overexpressed or knocked down to clarify its effects on cell viability, apoptosis, and oxidative stress. The interaction between lncRNA GAS5 and EZH2 was examined by RIP and RNA pull-down assays followed by verification of the target relationship between EZH2 and CDKN1C.

Results

High expression of EZH2 and poor expression of lncRNA GAS5 and CDKN1C was observed in melanoma tissues and found to be correlated with the reduction in survival expectancy of melanoma patients. Overexpression of lncRNA GAS5 or CDKN1C or EZH2 knockdown could inhibit cell viability but enhance melanoma cell apoptosis and oxidative stress. Importantly, lncRNA GAS5 attenuated EZH2 expression by recruiting E2F4 to the EZH2 promoter region and knockdown of EZH2 upregulated CDKN1C expression by inhibiting the H3K27me3.

Conclusion

The evidence provided by our study highlighted the involvement of lncRNA GAS5 in the translational suppression of EZH2 as well as the upregulation of CDKN1C, resulting in the promotion of melanoma cell apoptosis and oxidative stress.

Silencing of microRNA-517a induces oxidative stress injury in melanoma cells via inactivation of the JNK signaling pathway by upregulating CDKN1C

Background

Melanoma is notoriously resistant to current treatments, and less than 25% of metastatic melanoma cases respond to existing therapies. Growing evidence has shown that microRNAs (miRNAs) play a vital role in the prognosis of melanoma. MiR-517a has been implicated in many types of cancer; however, its expressional features and potential biological functions in melanoma remain unclear. The present study aimed to investigate the possible effects of miR-517a on oxidative stress (OS) in melanoma cells.

Methods

miR-517a expression in melanoma was determined using RT-qPCR. After treatment with different concentrations of H₂O₂, cell viability was determined in order to identify the most appropriate H₂O₂ concentration. Through loss and gain of function experiments, the interactions between miR-517a, the cyclin dependent kinase inhibitor 1C (CDKN1C) and the c-Jun NH2-terminal kinase (JNK) signaling pathway, as well as their roles in OS of melanoma cells were identified. Moreover, the expression of Cleaved Caspase-3, extent of ERK1/2 phosphorylation, Bax/Bcl-2 ratio, levels of T-AOC, ROS and MDA, and SOD activity were also tested. Finally, melanoma cell viability and apoptosis were detected.

Results

MiR-517a was upregulated, while CDKN1C was downregulated in melanoma tissues and cells. MiR-517a targets CDKN1C and consequently reduced its expression. Inhibition of miR-517a was shown to increase Cleaved Caspase-3 expression, Bax/Bcl-2 ratio, levels of ROS and MDA, as well as cell apoptosis but decrease extent of ERK1/2 phosphorylation, T-AOC levels, SOD activity, along with cell proliferation and mitochondrial membrane potential.

Conclusions

Overall, silencing miR-517a results in upregulated CDKN1C expression, and inhibited JNK signaling pathway activation, consequently promoting OS in melanoma cells.

LncRNA-BLACAT1 Facilitates Proliferation, Migration and Aerobic Glycolysis of Pancreatic Cancer Cells by Repressing CDKN1C via EZH2-Induced H3K27me3

OBJECTIVE

To investigate the role of lncRNA-BLACAT1 in promoting H3K27 trimethylation of CDKN1C gene by recruiting EZH2 to regulate CCNE on glycolysis and mitochondrial oxidative phosphorylation of pancreatic cancer (PC) cells.

METHODS

Following bioinformatic prediction, EZH2 and BLACAT1 in PC cells were interfered, and cells proliferation, migration and invasion in each group were detected. Western blotting detected the expression of key proteins of mitochondrial complex. The sub-cellular localization of BLACAT1 was tested, followed by testing the binding of CDKN1C and BLACAT1 with EZH2, followed by in vivo verification.

RESULTS

Based on bioinformatic prediction, EZH2 and BLACAT1 were highly expressed in PC, while CDKN1C was lowly expressed (all P < 0.05). Interference with EZH2 and BLACAT1 inhibited cell proliferation, migration and aerobic glycolysis, and promoted mitochondrial oxidative phosphorylation (all P < 0.05). BLACAT1 promoted H3K27 trimethylation of CDKN1C through recruiting EZH2 (all P < 0.05). In vivo results showed that BLACAT1 interference inhibited tumor formation (all P < 0.05).

CONCLUSION

Interference with BLACAT1 inhibits H3K27 trimethylation of CDKN1C gene by blocking EZH2 recruitment to promote CDKN1C expression and inhibit CCNE expression, thus suppressing PC cell proliferation, migration and aerobic glycolysis, and promoting mitochondrial oxidative phosphorylation.

CDYL promotes the chemoresistance of small cell lung cancer by regulating H3K27 trimethylation at the CDKN1C promoter

Rationale: Chemoresistance frequently occurs in patients with small cell lung cancer (SCLC) and leads to a dismal prognosis. However, the mechanisms underlying this process remain largely unclear.

Methods: The effects of chromodomain Y-like (CDYL) on chemoresistance in SCLC were determined using Western blotting, immunohistochemistry, cell counting kit-8 assays, flow cytometry, and tumorigenicity experiments, and the underlying mechanisms were investigated using mRNA sequencing, chromatin immunoprecipitation-qPCR, electrophoretic mobility shift assays, co-immunoprecipitation, GST pull down assays, bisulfite sequencing PCR, ELISA, and bioinformatics analyses.

Results: CDYL is expressed at high levels in chemoresistant SCLC tissues from patients, and elevated CDYL levels correlate with an advanced clinical stage and a poor prognosis. Furthermore, CDYL expression is significantly upregulated in chemoresistant SCLC cells. Using gain- and loss-of-function methods, we show that CDYL promotes chemoresistance in SCLC in vitro and in vivo. Mechanistically, CDYL promotes SCLC chemoresistance by silencing its downstream mediator cyclin-dependent kinase inhibitor 1C (CDKN1C). Further mechanistic investigations showed that CDYL recruits the enhancer of zeste homolog 2 (EZH2) to regulate trimethylation of lysine 27 in histone 3 (H3K27me3) at the CDKN1C promoter region and promotes transcriptional silencing. Accordingly, the EZH2 inhibitor GSK126 de-represses CDKN1C and decreases CDYL-induced chemoresistance in SCLC.

Principal conclusions: Based on these results, the CDYL/EZH2/CDKN1C axis promotes chemoresistance in SCLC, and these markers represent promising therapeutic targets for overcoming chemoresistance in patients with SCLC.

Analysis of CDKN1C in fetal growth restriction and pregnancy loss

Background: Cyclin-dependent kinase inhibitor 1C (CDKN1C) is a key negative regulator of cell growth encoded by a paternally imprinted/maternally expressed gene in humans. Loss-of-function variants in CDKN1C are associated with an overgrowth condition (Beckwith-Wiedemann Syndrome) whereas "gain-of-function" variants in CDKN1C that increase protein stability cause growth restriction as part of IMAGe syndrome ( Intrauterine growth restriction, Metaphyseal dysplasia, Adrenal hypoplasia and Genital anomalies). As three families have been reported with CDKN1C mutations who have fetal growth restriction (FGR)/Silver-Russell syndrome (SRS) without adrenal insufficiency, we investigated whether pathogenic variants in CDKN1C could be associated with isolated growth restriction or recurrent loss of pregnancy. Methods: Analysis of published literature was undertaken to review the localisation of variants in CDKN1C associated with IMAGe syndrome or fetal growth restriction. CDKN1C expression in different tissues was analysed in available RNA-Seq data (Human Protein Atlas). Targeted sequencing was used to investigate the critical region of CDKN1C for potential pathogenic variants in SRS (n=66), FGR (n=37), DNA from spontaneous loss of pregnancy (n= 22) and women with recurrent miscarriages (n=78) (total n=203). Results: All published single nucleotide variants associated with IMAGe syndrome are located in a highly-conserved "hot-spot" within the PCNA-binding domain of CDKN1C between codons 272-279. Variants associated with familial growth restriction but normal adrenal function currently affect codons 279 and 281. CDKN1C is highly expressed in the placenta compared to adult tissues, which may contribute to the FGR phenotype and supports a role in pregnancy maintenance. In the patient cohorts studied no pathogenic variants were identified in the PCNA-binding domain of CDKN1C. Conclusion: CDKN1C is a key negative regulator of growth. Variants in a very localised "hot-spot" cause growth restriction, with or without adrenal insufficiency. However, pathogenic variants in this region are not a common cause of isolated fetal growth restriction phenotypes or loss-of-pregnancy/recurrent miscarriages.

Analysis of CDKN1C in fetal growth restriction and pregnancy loss

Background: Cyclin-dependent kinase inhibitor 1C (CDKN1C) is a key negative regulator of cell growth encoded by a paternally imprinted/maternally expressed gene in humans. Loss-of-function variants in CDKN1C are associated with an overgrowth condition (Beckwith-Wiedemann Syndrome) whereas "gain-of-function" variants in CDKN1C that increase protein stability cause growth restriction as part of IMAGe syndrome ( Intrauterine growth restriction, Metaphyseal dysplasia, Adrenal hypoplasia and Genital anomalies). As two families have been reported with CDKN1C mutations who have fetal growth restriction (FGR)/Silver-Russell syndrome (SRS) without adrenal insufficiency, we investigated whether pathogenic variants in CDKN1C could be associated with isolated growth restriction or recurrent loss of pregnancy. Methods: Analysis of published literature was undertaken to review the localisation of variants in CDKN1C associated with IMAGe syndrome or fetal growth restriction. CDKN1C expression in different tissues was analysed in available RNA-Seq data (Human Protein Atlas). Targeted sequencing was used to investigate the critical region of CDKN1C for potential pathogenic variants in SRS (n=58), FGR (n=26), DNA from spontaneous loss of pregnancy (n= 21) and women with recurrent miscarriages (n=71) (total n=176). Results: All published single nucleotide variants associated with IMAGe syndrome are located in a highly-conserved "hot-spot" within the PCNA-binding domain of CDKN1C between codons 272-279. Variants associated with familial growth restriction but normal adrenal function currently affect codons 279 and 281. CDKN1C is highly expressed in the placenta compared to adult tissues, which may contribute to the FGR phenotype and supports a role in pregnancy maintenance. In the patient cohorts studied no pathogenic variants were identified in the PCNA-binding domain of CDKN1C. Conclusion: CDKN1C is a key negative regulator of growth. Variants in a very localised "hot-spot" cause growth restriction, with or without adrenal insufficiency. However, pathogenic variants in this region are not a common cause of isolated fetal growth restriction phenotypes or loss-of-pregnancy/recurrent miscarriages.

Expression analysis of miR-221-3p and its target genes in horses

BACKGROUND

A microRNA (miRNA) is a small non-coding RNA (ncRNA) approximately 20 nucleotides long and it affects gene expression through mRNA cleavage or translational repression. Horses (Equus caballus) have been domesticated and bred to enhance their speed for racing. It has been studied extensively with genetic diversity, origins and evolution.

OBJECTIVES

We examined expression patterns of miR-221-3p and its target gene CDKN1C in various horse tissues.

METHODS

We used bioinformatic tools to examine target gene, seed region and evolutionary conservation of miR-221-3p. The expression patterns of miR-221-3p and its target gene CDKN1C were analyzed by quantitative polymerase chain reaction (qPCR).

RESULTS

Among eight tissues of horse, miR-221-3p was highly expressed in cerebellum and spleen. On the other hand, only medulla was highly expressed in CDKN1C gene.

CONCLUSION

Our study provides expression data of miR-221-3p and CDKN1C gene in horse and suggests the fundamental information for future studies in relation to functional importance.

Genetic and Epigenetic Control of CDKN1C Expression: Importance in Cell Commitment and Differentiation, Tissue Homeostasis and Human Diseases

The CDKN1C gene encodes the p57^Kip2 protein which has been identified as the third member of the CIP/Kip family, also including p27^Kip1 and p21^Cip1. In analogy with these proteins, p57^Kip2 is able to bind tightly and inhibit cyclin/cyclin-dependent kinase complexes and, in turn, modulate cell division cycle progression. For a long time, the main function of p57^Kip2 has been associated only to correct embryogenesis, since CDKN1C-ablated mice are not vital. Accordingly, it has been demonstrated that CDKN1C alterations cause three human hereditary syndromes, characterized by altered growth rate. Subsequently, the p57^Kip2 role in several cell phenotypes has been clearly assessed as well as its down-regulation in human cancers. CDKN1C lies in a genetic locus, 11p15.5, characterized by a remarkable regional imprinting that results in the transcription of only the maternal allele. The control of CDKN1C transcription is also linked to additional mechanisms, including DNA methylation and specific histone methylation/acetylation. Finally, long non-coding RNAs and miRNAs appear to play important roles in controlling p57^Kip2 levels. This review mostly represents an appraisal of the available data regarding the control of CDKN1C gene expression. In addition, the structure and function of p57^Kip2 protein are briefly described and correlated to human physiology and diseases.

Ezh2 Regulates Activation-Induced CD8+ T Cell Cycle Progression via Repressing Cdkn2a and Cdkn1c Expression

Transition from resting to cell cycle in response to antigenic stimulation is an essential step for naïve CD8⁺ T cells to differentiate to effector and memory cells. Leaving the resting state requires dramatic changes of chromatin status in the key cell cycle inhibitors but the details of these concerted events are not fully elucidated. Here, we showed that Ezh2, an enzymatic component of polycomb repressive complex 2 (PRC2) catalyzing the trimethylation of lysine 27 on histone 3 (H3K27me3), regulates activation induced naïve CD8⁺ T cells proliferation and apoptosis. Upon deletion of Ezh2 during thymocyte development (Ezh2^fl/flCd4Cre⁺ mice), naive CD8⁺ T cells displayed impaired proliferation and increased apoptosis in response to antigen stimulation. However, naive CD8⁺ T cells only had impaired proliferation but no increase in apoptosis when Ezh2 was deleted after activation (Ezh2^fl/flGzmBCre⁺ mice), suggesting cell cycle and apoptosis are temporally separable events controlled by Ezh2. We then showed that deletion of Ezh2 resulted in the increase in expression of cyclin-dependent kinase inhibitors Cdkn2a (p16 and Arf) and Cdkn1c (p57) in activated naïve CD8⁺ T cells as the consequence of reduced levels of H3K27me3 at these two gene loci. Finally, with real time imaging, we observed prolonged cell division times of naïve CD8⁺ T cells in the absence of Ezh2 post in vitro stimulation. Together, these findings reveal that repression of Cdkn1c and Cdkn2a by Ezh2 plays a critical role in execution of activation-induced CD8⁺ T cell proliferation.

Downregulated CDKN1C/p57kip2 drives tumorigenesis and associates with poor overall survival in breast cancer

CDKN1C, also known as p57^kip2, is considered to be a potential tumor suppressor implicated in several kinds of human cancers. However, the current knowledge of CDKN1C in breast cancer remains obscure. In the present study, we demonstrated that CDKN1C was dramatically downregulated in breast cancer compared with normal tissues by using real-time quantitative polymerase chain reaction, western blot and two public data portals: The Cancer Genome Atlas (TCGA) and Oncomine datasets. Moreover, the expression of CDKN1C was correlated with age and tumor size in the TCGA cohort containing 708 cases of breast cancer. Low expression of CDKN1C was significantly associated with poor overall survival (OS) in the TCGA cohort and validated cohort composed of 1402 patients. Multivariate Cox regression analysis indicated that CDKN1C was an independent prognostic factor for worse OS (HR = 1.78, 95% CI: 1.09-2.89, p = 0.020). Furthermore, gene set enrichment analysis (GSEA) revealed that CDKN1C was significantly correlated with gene signatures involving DNA repair, cell cycle, glycolysis, adipogenesis, and two critical signaling pathways mTORC1 and PI3K/Akt/mTOR. In conclusion, our data suggested an essential role of CDKN1C in the tumorgenesis of breast cancer. Targeting CDKN1C may be a promising strategy for anticancer therapeutics.

IMAGe and Related Undergrowth Syndromes: The Complex Spectrum of Gain-of-Function CDKN1C Mutations

CDKN1C is a cyclin-dependent kinase Inhibitor and negative regulator of cellular proliferation. Recently, gain-of-function mutations in the PCNA domain of CDKN1C have been reported as the genetic basis of various growth-retarded syndromes including IMAGe syndrome, Russell Silver syndrome as well as a novel undergrowth syndrome that additionally exhibited early adulthood onset diabetes. This review summarizes the key clinical features and the molecular advances that have contributed to our understanding of this complex phenotypic spectrum.

Sequence variants identification at the KCNQ1OT1:TSS differentially Methylated region in isolated omphalocele cases

Background

Omphalocele is a congenital midline ventral body wall defect that can exist as isolated malformation or as part of a syndrome. It can be considered one of the major and most frequent clinical manifestation of Beckwith-Wiedemann Syndrome (BWS) in case of loss of methylation at KCNQ1OT1: Transcription Star Site-Differentially Methylated Region (TSS-DMR) or in presence of CDKN1C mutations. The isolated form of the omphalocele accounts approximately for about the 14% of the total cases and its molecular etiology has never been fully elucidated.

Methods

Given the tight relationship with BWS, we hypothesized that the isolated form of the omphalocele could belong to the heterogeneous spectrum of the BWS associated features, representing an endophenotype with a clear genetic connection. We therefore investigated genetic and epigenetic changes affecting BWS imprinted locus at 11p15.5 imprinted region, focusing in particular on the KCNQ1OT1:TSS DMR.

Results

We studied 21 cases of isolated omphalocele detected during pregnancy or at birth and identified the following rare maternally inherited variants: i) the non-coding variant G > A at nucleotide 687 (NR_002728.3) at KCNQ1OT1:TSS-DMR, which alters the methylation pattern of the imprinted allele, in one patient; ii) the deletion c.624-629delGGCCCC at exon 1 of CDKN1C, with unknown clinical significance, in two unrelated cases.

Conclusions

Taken together, these findings suggest that KCNQ1OT1:TSS-DMR could be a susceptibility locus for the isolated omphalocele.

Electronic supplementary material

The online version of this article (10.1186/s12881-017-0470-z) contains supplementary material, which is available to authorized users.

Placental Expressions of CDKN1C and KCNQ1OT1 in Monozygotic Twins with Selective Intrauterine Growth Restriction

CDKN1C and KCNQ1OT1 are imprinted genes that might be potential regulators of placental development. This study investigated placental expressions of CDKN1C and KCNQ1OT1 in monozygotic twins with and without selective intrauterine growth restriction (sIUGR). Seventeen sIUGR and fifteen normal monozygotic(MZ) twin pairs were examined. Placental mRNA expressions of CDKN1C and KCNQ1OT1 were detected by real-time fluorescent quantitative PCR. CDKN1C protein expression was detected by immunohistochemical assay and Western-blotting. In the sIUGR group, smaller fetuses had a smaller share of the placenta, and CDKN1C protein expression was significantly increased while KCNQ1OT1 mRNA expression was significantly decreased. The CDKN1C/KCNQ1OT1 mRNA ratio was lower in the larger fetus than in the smaller fetus (p < .05). In the control group, CDKN1C protein expression showed no difference between larger and smaller fetuses, while KCNQ1OT1 mRNA expression was significantly lower in the larger fetus, and the CDKN1C/KCNQ1OT1 mRNA ratio was higher in the larger fetus than in the smaller fetus (p < .05). Our findings showed that pathogenesis of sIUGR may be related to the co-effect of the up-regulated protein expression of CDKN1C and down-regulated mRNA expression of KCNQ1OT1 in the placenta.

Imprinted disorders and growth

Fetal growth is a complex process. Its restriction is associated with morbidity and long-term metabolic consequences. Imprinted genes have a critical role in mammalian fetal growth. Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS) are two imprinting disorders with opposite fetal growth disturbance. SRS is leading to severe fetal and postnatal growth retardation with severe feeding difficulties during early childhood and long-term metabolic consequences and BWS is an overgrowth syndrome with an enhanced risk of tumors during childhood. Epigenetic (abnormal methylation at the imprinting center regions) or genetic (mutations, duplications, uniparental disomy [UPD]) including defects of imprinted genes on chromosome 11 (BWS and SRS), 7 (SRS) and more recently 14 (SRS) have been identified in these two syndromes. In humans, the 11p15 region contains genes important for the regulation of fetal and postnatal growth. This region includes two imprinted domains: the IGF2/H19 domain regulated by imprinting center region 1 (ICR1 or H19/IGF2:IG-DMR) and the CDKN1C/KCNQ1OT1 domain regulated by ICR2 (or KCNQ1OT1: TSS DMR).

Decreased CDKN1C Expression in Congenital Alveolar Rhabdomyosarcoma Associated with Beckwith-Wiedemann Syndrome

The Beckwith-Wiedemann syndrome (BWS) is a genetic disorder characterized by somatic overgrowth and predisposition to embryonal tumors, such as Wilm's tumor, hepatoblastoma, neuroblastoma and rhabdomyosarcoma (RMS). BWS is associated with various genetic alterations: a variety of molecular lesions are described on the chromosome 11p15, affecting gene expression for IGF2, H19, CDKN1C and KCNQ1OT1. Alveolar RMS also recognises characteristic genetic alterations: two types of translocations, t(2,13) or t(1,13), that generate the PAX3-FKHR or PAX7-FKHR fusion proteins. It has been postulated however, that in BWS this kind of tumor occurs without this characteristic chromosomal rearrangement. The authors describe case of a neonate with BWS that presented at birth with cutaneous metastasis due to alveolar RMS. Genetic analysis showed lack of the two characteristic translocations in the tumor tissue, supporting a different oncogenic pathway of alveolar RMS in children with BWS.

Genomic imbalance in the centromeric 11p15 imprinting center in three families: Further evidence of a role for IC2 as a cause of Russell-Silver syndrome

Russell-Silver syndrome is a heterogeneous disorder characterized by intrauterine growth retardation, postnatal growth deficiency, characteristic facial appearance, and other variable features. Genetic and epigenetic alterations are identified in about 60% of individuals with Russell-Silver syndrome. Most frequently, Russell-Silver syndrome is caused by altered gene expression on chromosome 11p15 due to loss of methylation at the telomeric imprinting center. To date there have been a handful of isolated clinical reports implicating the centromeric imprinting center 2 in the etiology of Russell-Silver syndrome. Here we report three new families with genomic imbalances, involving imprinting center 2 resulting in gain of methylation at this center and a Russell-Silver syndrome phenotype, including two families with a maternally inherited microduplication and the first pediatric patient with a paternally derived microdeletion. The findings in our families provide additional evidence of a role for imprinting center 2 in the etiology of Russell-Silver syndrome and suggest that imprinting center 2 imprinting abnormalities may be a more common cause of Russell-Silver syndrome than previously recognized. Furthermore, our findings together with previous clinical reports of genomic imbalances involving imprinting center 2 serve to underscore the complexity of the epigenetic regulation of the 11p15 region making it challenging to predict phenotype on the basis of genotype alone. © 2016 Wiley Periodicals, Inc.

Two maternal duplications involving the CDKN1C gene are associated with contrasting growth phenotypes

Background

The overgrowth-associated Beckwith-Wiedemann syndrome (BWS) and the undergrowth-associated Silver-Russell syndrome (SRS) are characterized by heterogeneous molecular defects affecting a large imprinted gene cluster at chromosome 11p15.5-p15.4. While maternal and paternal duplications of the entire cluster consistently result in SRS and BWS, respectively, the phenotypes associated with smaller duplications are difficult to predict due to the complexity of imprinting regulation. Here, we describe two cases with novel inherited partial duplications of the centromeric domain on chromosome 11p15 associated with contrasting growth phenotypes.

Findings

In a male patient affected by intrauterine growth restriction and postnatal short stature, we identified an in cis maternally inherited duplication of 0.88 Mb including the CDKN1C gene that was significantly up-regulated. The duplication did not include the long non-coding RNA KCNQ1OT1 nor the imprinting control region of the centromeric domain (KCNQ1OT1:TSS-DMR or ICR2) in which methylation was normal. In the mother, also referring a growth restriction phenotype in her infancy, the duplication was de novo and present on her paternal chromosome. A different in cis maternal duplication, 1.13 Mb long and including the abovementioned duplication, was observed in a child affected by Tetralogy of Fallot but with normal growth. In this case, the rearrangement also included most of the KCNQ1OT1 gene and resulted in ICR2 loss of methylation (LOM). In this second family, the mother carried the duplication on her paternal chromosome and showed a normal growth phenotype as well.

Conclusions

We report two novel in cis microduplications encompassing part of the centromeric domain of the 11p15.5-p15.4 imprinted gene cluster and both including the growth inhibitor CDKN1C gene. Likely, as a consequence of the differential involvement of the regulatory KCNQ1OT1 RNA and ICR2, the smaller duplication is associated with growth restriction on both maternal and paternal transmissions, while the larger duplication, although it includes the smaller one, does not result in any growth anomaly.

Our study provides further insights into the phenotypes associated with imprinted gene alterations and highlights the importance of carefully evaluating the affected genes and regulatory elements for accurate genetic counselling of the 11p15 chromosomal rearrangements.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0236-z) contains supplementary material, which is available to authorized users.

p57(Kip2) knock-in mouse reveals CDK-independent contribution in the development of Beckwith-Wiedemann syndrome

CDKN1C encodes the cyclin-CDK inhibitor p57(Kip2) (p57), a negative regulator of the cell cycle and putative tumour suppressor. Genetic and epigenetic alterations causing loss of p57 function are the most frequent cause of Beckwith-Wiedemann syndrome (BWS), a genetic disorder characterized by multiple developmental anomalies and increased susceptibility to tumour development during childhood. So far, BWS development has been attributed entirely to the deregulation of proliferation caused by loss of p57-mediated CDK inhibition. However, a fraction of BWS patients have point mutations in CDKN1C located outside of the CDK inhibitory region, suggesting the involvement of other parts of the protein in the disease. To test this possibility, we generated knock-in mice deficient for p57-mediated cyclin-CDK inhibition (p57(CK) (-) ), the only clearly defined function of p57. Comparative analysis of p57(CK) (-) and p57(KO) mice provided clear evidence for CDK-independent roles of p57 and revealed that BWS is not caused entirely by CDK deregulation, as several features of BWS are caused by the loss of CDK-independent roles of p57. Thus, while the genetic origin of BWS is well understood, our results underscore that the underlying molecular mechanisms remain largely unclear. To probe these mechanisms further, we determined the p57 interactome. Several partners identified are involved in genetic disorders with features resembling those caused by CDKN1C mutation, suggesting that they could be involved in BWS pathogenesis and revealing a possible connection between seemingly distinct syndromes. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Epigenetic Characterization of CDKN1C in Placenta Samples from Non-syndromic Intrauterine Growth Restriction

The cyclin-dependent kinase (CDK)-inhibitor 1C (CDKN1C) gene is expressed from the maternal allele and is located within the centromeric imprinted domain at chromosome 11p15. It is a negative regulator of proliferation, with loss-of-function mutations associated with the overgrowth disorder Beckwith–Wiedemann syndrome. Recently, gain-of-function mutations within the PCNA domain have been described in two disorders characterized by growth failure, namely IMAGe (intra-uterine growth restriction, metaphyseal dysplasia, adrenal hypoplasia congenita and genital abnormalities) syndrome and Silver–Russell syndrome (SRS). Over-expression of CDKN1C by maternally inherited microduplications also results in SRS, suggesting that in addition to activating mutations this gene may regulate growth by changes in dosage. To determine if CDKN1C is involved in non-syndromic IUGR we compared the expression and DNA methylation levels in a large cohort of placental biopsies from IUGR and uneventful pregnancies. We observe higher levels of expression of CDKN1C in IUGR placentas compared to those of controls. All placenta biopsies heterozygous for the PAPA repeat sequence in exon 2 showed appropriate monoallelic expression and no mutations in the PCNA domain were observed. The expression profile was independent of both genetic or methylation variation in the minimal CDKN1C promoter interval and of methylation of the cis-acting maternally methylated region associated with the neighboring KCNQ1OT1 non-coding RNA. Chromatin immunoprecipitation revealed binding sites for CTCF within the unmethylated CDKN1C gene body CpG island and putative enhancer regions, associated with the canonical enhancer histone signature, H3K4me1 and H3K27ac, located ∼58 and 360 kb away. Using 3C-PCR we identify constitutive higher-order chromatin loops that occur between one of these putative enhancer regions and CDKN1C in human placenta tissues, which we propose facilitates expression.

Mutations of the Imprinted CDKN1C Gene as a Cause of the Overgrowth Beckwith-Wiedemann Syndrome: Clinical Spectrum and Functional Characterization

Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder associating macroglossia, abdominal wall defects, visceromegaly, and a high risk of childhood tumor. Molecular anomalies are mostly epigenetic; however, mutations of CDKN1C are implicated in 8% of cases, including both sporadic and familial forms. We aimed to describe the phenotype of BWS patients with CDKN1C mutations and develop a functional test for CDKN1C mutations. For each propositus, we sequenced the three exons and intron-exon boundaries of CDKN1C in patients presenting a BWS phenotype, including abdominal wall defects, without 11p15 methylation defects. We developed a functional test based on flow cytometry. We identified 37 mutations in 38 pedigrees (50 patients and seven fetuses). Analysis of parental samples when available showed that all mutations tested but one was inherited from the mother. The four missense mutations led to a less severe phenotype (lower frequency of exomphalos) than the other 33 mutations. The following four tumors occurred: one neuroblastoma, one ganglioneuroblastoma, one melanoma, and one acute lymphoid leukemia. Cases of BWS caused by CDKN1C mutations are not rare. CDKN1C sequencing should be performed for BWS patients presenting with abdominal wall defects or cleft palate without 11p15 methylation defects or body asymmetry, or in familial cases of BWS.

miR-25 promotes glioma cell proliferation by targeting CDKN1C

MicroRNAs (miRNA) have oncogenic or tumor-suppressive roles in the development and growth of human glioma. Glioma development is also associated with alteration in the activities and expression of cell cycle regulators, and miRNAs are emerging as important regulators of cell cycle progression. Here, we show that miR-25 is overexpressed in 91% of examined human glioma tissues and 4 out of 6 human glioma cell lines. MiR-25 increases cell proliferation in two independent glioma cell lines. Ectopic expression of miR-25 was found to reduce CDKN1C protein levels by directly targeting its 3'-untranslated region (UTR). Notably, ablation of endogenous miR-25 rescued CDKN1C expression and significantly decreased glioma cell proliferation by facilitating normal cell cycle progression. Our clinical investigation found CDKN1C and miR-25 levels were inversely correlated. Lastly, downregulation of CDKN1 by siRNA blocked the activity of miR-25 on promoting glioma cell proliferation. Overall, our results for the first time show an oncogenic role of miR-25 in human glioma by targeting CDKN1C and that miR-25 could potentially be a therapeutic target for glioma intervention.

CDKN1C mutations: two sides of the same coin

Cyclin-dependent kinase (CDK)-inhibitor 1C (CDKN1C) negatively regulates cellular proliferation and it has been shown that loss-of-function mutations in the imprinted CDKN1C gene (11p15.5) are associated with the overgrowth disorder Beckwith-Wiedemann syndrome (BWS). With recent reports of gain-of-function mutations of the PCNA domain of CDKN1C in growth-retarded patients with IMAGe syndrome or Silver-Russell syndrome (SRS), its key role for growth has been confirmed. Thereby, the last gap in the spectrum of molecular alterations in 11p15.5 in growth-retardation and overgrowth syndromes could be closed. Recent functional studies explain the strict association of CDKN1C mutations with clinically opposite phenotypes and thereby contribute to our understanding of the function and regulation of the gene in particular and epigenetic regulation in general.

Beckwith-Wiedemann and IMAGe syndromes: two very different diseases caused by mutations on the same gene

Genomic imprinting is an epigenetically regulated mechanism leading to parental-origin allele-specific expression. Beckwith-Wiedemann syndrome (BWS) is an imprinting disease related to 11p15.5 genetic and epigenetic alterations, among them loss-of-function CDKN1C mutations. Intriguing is that CDKN1C gain-of-function variations were recently found in patients with IMAGe syndrome (intrauterine growth restriction, metaphyseal dysplasia, congenital adrenal hypoplasia, and genital anomalies). BWS and IMAGe share an imprinted mode of inheritance; familial analysis demonstrated the presence of the phenotype exclusively when the mutant CDKN1C allele is inherited from the mother. Interestingly, both IMAGe and BWS are characterized by growth disturbances, although with opposite clinical phenotypes; IMAGe patients display growth restriction whereas BWS patients display overgrowth. CDKN1C codifies for CDKN1C/KIP2, a nuclear protein and potent tight-binding inhibitor of several cyclin/Cdk complexes, playing a role in maintenance of the nonproliferative state of cells. The mirror phenotype of BWS and IMAGe can be, at least in part, explained by the effect of mutations on protein functions. All the IMAGe-associated mutations are clustered in the proliferating cell nuclear antigen-binding domain of CDKN1C and cause a dramatic increase in the stability of the protein, which probably results in a functional gain of growth inhibition properties. In contrast, BWS mutations are not clustered within a single domain, are loss-of-function, and promote cell proliferation. CDKN1C is an example of allelic heterogeneity associated with opposite syndromes.