Upregulation of INS-IGF2 read-through expression and identification of a novel INS-IGF2 splice variant in insulinomas

Recurrent Hypoglycemia Secondary to Insulinoma in an Adult With Beckwith-Wiedemann Syndrome

Beckwith-Wiedemann syndrome (BWS) is a rare genetic disorder characterized by genetic and epigenetic changes on the chromosome 11p15.5 region, which includes genes that are important for fetal and postnatal growth. Children with BWS have a higher chance of having hypoglycemia, hyperinsulinemia, and malignancies early in life, although hypoglycemia caused by an insulinoma that develops later in life has not been reported. We describe the diagnosis of insulinoma in a 53-year-old man with BWS in this case report. This is the first case report of insulinoma in an adult with this syndrome.

The uprise of RNA biology in neuroendocrine neoplasms: altered splicing and RNA species unveil translational opportunities

Neuroendocrine neoplasms (NENs) comprise a highly heterogeneous group of tumors arising from the diffuse neuroendocrine system. NENs mainly originate in gastrointestinal, pancreatic, and pulmonary tissues, and despite being rare, show rising incidence. The molecular mechanisms underlying NEN development are still poorly understood, although recent studies are unveiling their genomic, epigenomic and transcriptomic landscapes. RNA was originally considered as an intermediary between DNA and protein. Today, compelling evidence underscores the regulatory relevance of RNA processing, while new RNA molecules emerge with key functional roles in core cell processes. Indeed, correct functioning of the interrelated complementary processes comprising RNA biology, its processing, transport, and surveillance, is essential to ensure adequate cell homeostasis, and its misfunction is related to cancer at multiple levels. This review is focused on the dysregulation of RNA biology in NENs. In particular, we survey alterations in the splicing process and available information implicating the main RNA species and processes in NENs pathology, including their role as biomarkers, and their functionality and targetability. Understanding how NENs precisely (mis)behave requires a profound knowledge at every layer of their heterogeneity, to help improve NEN management. RNA biology provides a wide spectrum of previously unexplored processes and molecules that open new avenues for NEN detection, classification and treatment. The current molecular biology era is rapidly evolving to facilitate a detailed comprehension of cancer biology and is enabling the arrival of personalized, predictive and precision medicine to rare tumors like NENs.

Understanding Insulin in the Age of Precision Medicine and Big Data: Under-Explored Nature of Genomics

Insulin is amongst the human genome's most well-studied genes/proteins due to its connection to metabolic health. Within this article, we review literature and data to build a knowledge base of Insulin (INS) genetics that influence transcription, transcript processing, translation, hormone maturation, secretion, receptor binding, and metabolism while highlighting the future needs of insulin research. The INS gene region has 2076 unique variants from population genetics. Several variants are found near the transcriptional start site, enhancers, and following the INS transcripts that might influence the readthrough fusion transcript INS-IGF2. This INS-IGF2 transcript splice site was confirmed within hundreds of pancreatic RNAseq samples, lacks drift based on human genome sequencing, and has possible elevated expression due to viral regulation within the liver. Moreover, a rare, poorly characterized African population-enriched variant of INS-IGF2 results in a loss of the stop codon. INS transcript UTR variants rs689 and rs3842753, associated with type 1 diabetes, are found in many pancreatic RNAseq datasets with an elevation of the 3'UTR alternatively spliced INS transcript. Finally, by combining literature, evolutionary profiling, and structural biology, we map rare missense variants that influence preproinsulin translation, proinsulin processing, dimer/hexamer secretory storage, receptor activation, and C-peptide detection for quasi-insulin blood measurements.

Phaeochromocytomas overexpress insulin transcript and produce insulin

INTRODUCTION

Phaeochromocytomas are tumours originating in the medulla of the adrenal gland. They produce catecholamines, and some tumours also produce ectopic hormones. Two types of glucose imbalances occur in phaeochromocytoma patients, hyperglycaemia and hypoglycaemic attacks. Therefore, we tested whether insulin transcript (INS), insulin, and a hybrid read-through transcript between exons from insulin and insulin-like growth factor 2 (INS-IGF2) were expressed in phaeochromocytomas.

METHODS

We measured the expression of insulin using immunohistochemistry. The expression of INS-IGF2 was determined by qRT-PCR in formalin-fixed and paraffin-embedded tissue from 20 phaeochromocytomas. The expression of INS and INS-IGF2 transcriptswas also analysed in 182 phaeochromocytomas and paragangliomas using publicly available datasets in The Cancer Genome Atlas (TCGA) Database.

RESULTS

Of 20 phaeochromocytomas, 16 stained positive for insulin. The distribution of positive cells was mostly scattered, with some focal expression indicating clonal expansion. Nineteen tumours expressed high levels of INS and INS-IGF2 transcripts. The expression of the two transcripts corresponded closely. In the TCGA dataset, phaeochromocytoma expresses higher levels of INS and INS-IGF2 transcripts compared to the normal non-tumour adrenal glands. Thus, the expression of INS and INS-IGF2 seems to be a general phenomenon in phaeochromocytoma.

CONCLUSION

Most phaeochromocytomas contain cells that overexpress INS and INS-IGF2 transcripts. Most tumours also display heterogeneous expression of polypeptides immunoreactive to monoclonal anti-insulin antibodies. Clinically this may relate to both hyperglycaemia and hypoglycaemic attacks seen in patients with phaeochromocytoma as well as autocrine tumour growth.

Large parental differences in chromatin organization in pancreatic beta cell line explaining diabetes susceptibility effects

Previous GWAS studies identified non-coding loci with parent-of-origin-specific effects on Type 2 diabetes susceptibility. Here we report the molecular basis for one such locus near the KRTAP5-6 gene on chromosome 11. We determine the pattern of long-range contacts between an enhancer in this locus and the human INS promoter 460 kb away, in the human pancreatic β-cell line, EndoC-βH1. 3C long range contact experiments distinguish contacts on the two sister chromosomes. Coupling with allele-specific SNPs allows construction of maps revealing marked differences in organization of the two sister chromosomes in the entire region between KRTAP5-6 and INS. Further mapping distinguishes maternal and paternal alleles. This reveals a domain of parent-of-origin-specific chromatin structure extending in the telomeric direction from the INS locus. This suggests more generally that imprinted loci may extend their influence over gene expression beyond those loci through long range chromatin structure, resulting in parent-of-origin-biased expression patterns over great distances.

A SNP distant from the human insulin (INS) gene near the KRTAP5-6 gene confers increased susceptibility to type 2 diabetes when present on the paternal allele while decreased susceptibility when on the maternal allele. Here the authors show that long-range contacts between the INS locus and the KRTAP5-6 gene locus distinguish paternal and maternal alleles.

Read-through transcripts in lung: germline genetic regulation and correlation with the expression of other genes

Transcripts originating from the transcriptional read through of two adjacent, similarly oriented genes have been identified in normal and neoplastic tissues, but their functional role and the mechanisms that regulate their expression are mostly unknown. Here, we investigated whether the expression of read-through transcripts previously identified in the non-involved lung tissue of lung adenocarcinoma patients was genetically regulated. Data on genome-wide single nucleotide variant genotypes and expression levels of 10 read-through transcripts in 201 samples of lung tissue were combined to identify expression quantitative trait loci (eQTLs). Then, to identify genes whose expression levels correlated with the 10 read-through transcripts, we used whole transcriptome profiles available for 154 patients. For 8 read-though transcripts, we identified 60 eQTLs (false discovery rate <0.05), including 17 cis-eQTLs and 43 trans-eQTLs. These eQTLs did not maintain their behavior on the 'parental' genes involved in the read-through transcriptional event. The expression levels of 7 read-through transcripts were found to correlate with the expression of other genes: CHIA-PIFO and CTSC-RAB38 correlated with CHIA and RAB38, respectively, while 5 other read-through transcripts correlated with 43 unique non-parental transcripts; thus offering indications about the molecular processes in which these chimeric transcripts may be involved. We confirmed 9 eQTLs (for 4 transcripts) in the non-involved lung tissue from an independent series of 188 lung adenocarcinoma patients. Therefore, this study indicates that the expression of four read-through transcripts in normal lung tissue is under germline genetic regulation, and that this regulation is independent of that of the genes involved in the read-through event.

Associations of IGF2 and DRD2 polymorphisms with laying traits in Muscovy duck

Insulin-like growth factor 2 (IGF2) and dopamine receptor 2 (DRD2) play important roles in ovarian follicular development. In this study, we analyzed tissue-specific expression of the Muscovy duck IGF2 and DRD2 genes and cloned those genes transcripts. Polymorphisms in these genes were tightly linked with egg production traits and both genes were highly expressed in the ovary. Moreover, we identified five single nucleotide polymorphisms (SNPs) for IGF1 and 28 for DRD2. Mutations A-1864G and C-1704G of IGF2 were positively correlated with increased egg laying at 59 weeks (E59W) (P < 0.05). The C+7T and C+364G mutations of DRD2 were highly and significantly associated with first-egg age (FEA) and egg numbers at 300 days (E300D) (P < 0.01). Moreover, C+3301G and C+3545G of DRD2 were highly significantly associated with FEA, E59W and E300D (P < 0.01). Other mutations were positively associated with FEA or E300D or E59W (P < 0.05). These data suggest specific roles for IGF1 and DRD2 polymorphisms in egg production in Muscovy ducks.