Delineating the phenotype and genetic basis of AMPD2-related pontocerebellar hypoplasia

Pontocerebellar hypoplasia is a group of disorders with a wide range of presentations. We describe here the genetic and phenotypic features of PCH type 9 due to mutations in AMPD2. All patients have severe intellectual disability, and the vast majority manifest abnormal tone, cortical blindness, and microcephaly. Almost all have agenesis of the corpus callosum and severe cerebellar hypoplasia. The course is not progressive, however, few die in the first decade of life. Mutations are spread throughout the gene, and no hot spot can be identified. One of the mutations we report here is the most distal truncating variant known in this gene and is predicted to result in a truncated protein. The phenotype is severe in all cases; thus, no clear genotype-phenotype correlation can be established.

Overexpression of AMPD2 indicates poor prognosis in colorectal cancer patients via the Notch3 signaling pathway

BACKGROUND

AMPD2 is a critical enzyme catalyzing smooth muscle energy supply and metabolism; however, its cellular biological function and clinical implication in colorectal cancer (CRC) are largely unknown.

AIM

To clarify the role of AMPD2 in CRC and study the pathway and prognostic value of its role.

METHODS

AMPD2 expression was analyzed by integrated bioinformatics analysis based on TCGA data sets and immunohistochemistry in tissue microarrays, and the correlation between AMPD2 expression and clinicopathological parameters, Notch3 expression, and prognostic features was assessed. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis were then performed to investigate the regulatory pathway involved. The effects of AMPD2 expression on CRC cells and Notch3 protein expression were investigated by downregulation and overexpression of AMPD2.

RESULTS

AMPD2 mRNA was significantly overexpressed in tumor tissue when compared with normal tissue in a cohort of the TCGA-COAD data set. Biological function enrichment analysis indicated that the Notch pathway strongly correlated with AMPD2 expression, and that the expression of Notch3 and JAG2 mRNA was positively associated with AMPD2 in CRC tissues. In vitro, AMPD2 overexpression markedly reduced Notch3 protein expression in CRC cells, while knockdown of AMPD2 showed the opposite findings. In addition, protein expression was significantly up-regulated in our CRC cohort as indicated by tissue microarray analysis. High expression of AMPD2 protein correlated with advanced depth of tumor and poor differentiation. Furthermore, high AMPD2 expression in CRC tissues was an indicator of poor outcome for CRC patients.

CONCLUSION

AMPD2 is commonly overexpressed in CRC, and acts as a metabolism oncogene to induce CRC progression through the Notch signaling pathway. Thus, AMPD2 may be a novel prognostic biomarker for CRC.

Homozygous variants in AMPD2 and COL11A1 lead to a complex phenotype of pontocerebellar hypoplasia type 9 and Stickler syndrome type 2

Pontocerebellar hypoplasia type 9 (PCH9) is an autosomal recessive neurodevelopmental disorder caused by pathogenic variants in the AMPD2 gene. We evaluated the son of a consanguineous couple who presented with profound hypotonia and global developmental delay. Other features included sensorineural hearing loss, asymmetric astigmatism, and high myopia. Clinical whole-exome sequence analysis identified a homozygous missense variant in AMPD2 (NM_001257360.1:c.2201C > T, p.[Pro734Leu]) that has not been previously reported. Given the strong phenotypic overlap with PCH9, including the identification of the typical "Figure 8" appearance of the brainstem on neuroimaging, we suspect this variant was causative of the neurodevelopmental disability in this individual. An additional homozygous nonsense variant in COL11A1 (NM_001854.4:c.1168G > T, p.[Glu390Ter]) was identified. Variants in this alternatively spliced region of COL11A1 have been identified to cause an autosomal recessive form of Stickler syndrome type 2 characterized by sensorineural hearing loss and eye abnormalities, but without musculoskeletal abnormalities. The COL11A1 variant likely also contributed to the individual's phenotype, suggesting two potentially relevant genetic findings. This challenging case highlights the importance of detailed phenotypic characterization when interpreting whole exome data.

NovelmiRNA-25 inhibits AMPD2 in peripheral blood mononuclear cells of patients with systemic lupus erythematosus and represents a promising novel biomarker

Background

Systemic lupus erythematosus (SLE) is a multisystemic autoimmune disease with various clinical manifestations. MicroRNAs (miRNAs) and immunometabolism are recognized as key elements in SLE pathogenesis; however, the relationship between miRNAs in peripheral blood mononuclear cells (PBMCs) and metabolism in SLE remains unclear.

Methods

We detected PBMC miRNA and mRNA profiles from 3 pooled SLE patients and 3 healthy controls (HCs) using next-generation sequencing, predicted miRNA targets in dysregulated mRNAs, predicted functions and interactions of differentially expressed genes using bioinformatics analysis, validated candidate miRNAs using qRT-PCR, and investigated the association between the expression of candidate miRNAs and SLE clinical characteristics. Moreover, we validated the direct and transcriptional regulatory effect of NovelmiRNA-25 on adenosine monophosphate deaminase 2 (AMPD2) using a dual-luciferase reporter assay and western blot and confirmed AMPD2 mRNA and protein expression in PBMCs using qRT-PCR and western blot, respectively.

Results

Multilayer integrative analysis of microRNA and mRNA regulation showed that 10 miRNAs were down-regulated and 19 miRNAs were up-regulated in SLE patient PBMCs compared with HCs. Bioinformatics analysis of regulatory networks between miRNAs and mRNAs showed that 19 miRNAs were related to metabolic processes. Two candidate miRNAs, NovelmiRNA-25 and miR-1273h-5p, which were significantly increased in the PBMCs of SLE patients (P < 0.05), represented diagnostic biomarkers with sensitivities of 94.74% and 89.47%, respectively (area under the curve = 0.574 and 0.788, respectively). NovelmiRNA-25 expression in PBMCs was associated with disease activity in SLE patients, in both active and stable groups (P < 0.05). NovelmiRNA-25 overexpression downregulated AMPD2 expression in HEK293T cells through direct targeting of the AMPD2 3ʹUTR (P < 0.01), while inhibition of NovelmiRNA-25 activity led to increased AMPD2 expression (P < 0.01). NovelmiRNA-25 overexpression also downregulated AMPD2 protein expression in HEK293T cells; AMPD2 protein expression in SLE patient PBMCs was decreased. Our results show that differentially expressed miRNAs play an important role in SLE.

Conclusions

Our data demonstrate a novel mechanism in SLE development that involves the targeting of AMPD2 expression by NovelmiRNA-25. miRNAs may serve as novel biomarkers for the diagnosis and evaluation of disease activity of SLE and represent potential therapeutic targets for this disease.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1739-5) contains supplementary material, which is available to authorized users.

High expression of AMPD2 and obesity are associated with poor prognosis in colorectal cancer

The protein-coding gene adenosine monophosphate deaminase (AMPD) 2 plays a critical role in energy metabolism by converting adenosine-5-monophosphate (AMP) to iosine inosine-5-monophosphate (IMP). Obesity affects metabolic abnormalities in tumor cells and has been associated with high expression levels of AMPD2 and colorectal cancer (CRC). In this study, we performed immunohistochemical analysis of AMPD2 expression in 158 patients with CRC. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to determine AMPD2 mRNA expression levels, which were validated by The Cancer Genome Atlas (TCGA) datasets. Chi-square test and Fisher's exact test were used to evaluate the correlation between the expression of AMPD2 and clinicopathological parameters of CRC. Overall survival (OS) rates of the CRC patients were calculated using Kaplan-Meier survival analysis and a Cox proportional regression model was performed for univariate and multivariate analysis. A logistic regression model was used to plot the receiver operating characteristic (ROC) curve and to evaluate the predictive effect of multivariate studies on prognosis outcomes of CRC. We found a significant increase in AMPD2 expression in tumor tissue (91.8%, 146/158) compared to adjacent normal tissue (52.5%, 83/158, P < 0.01). The positive rate of AMPD2 expression was 72.7% (39/54) in overweight individuals versus 51.9% (54/104) in individuals with a normal weight (P = 0.014). AMPD2 mRNA levels as determined by qRT-PCR elevated levels of AMPD2 transcripts were higher in CRC samples compared to adjacent normal tissues (P < 0.05). In both the TCGA colon adenocarcinoma and rectal adenocarcinoma dataset, the number of CRC patients with increased levels of AMPD2 in tumor tissues was significantly higher compared to patients with adjacent normal tissue (P < 0.001). High expression of AMPD2 was associated with TNM stage, higher histological grade, obesity, and lower OS rates in patients with CRC. Obesity and high expression of AMPD2 in patients are with poor prognosis. Moreover, multivariate analysis indicated that AMPD2 levels and TNM stage were significant independent prognostic factors in CRC patients. The logistic regression predictive effect of the area under the curve (AUC) was 0.821 (P < 0.001). In conclusion, high levels of AMPD2 and obesity are associated with poor prognosis in patients with CRC.