Molecular Characterization of the Neuronatin Gene in the Porcine Placenta

Abstract

Imprinted genes play important roles in placental and embryonic development. Neuronatin (NNAT), first identified as an imprinted gene in human and mouse brains, played important roles in neuronal differentiation in the brain and in glucose-mediated insulin secretion in pancreatic β cells. In the pig, NNAT was reported to be imprinted in eleven tissues. Our previous microarray hybridization study showed that NNAT was differentially expressed in Yorkshire and Meishan pig placentas, but the imprinting status and function of NNAT in the placenta have not been investigated. We demonstrated for the first time that NNAT was monoallelically expressed in the placenta. Immunochemistry analysis showed that NNAT was located in the uterine luminal and glandular epithelium in placentas. We also confirmed the differential expression of NNAT in Meishan and Yorkshire pig placentas by qPCR. Using IPA software and the published literature, we created a model network of the possible relationships between NNAT and glucose transporter genes. A dual luciferase reporter assay demonstrated that the crucial promoter region of NNAT contained a CANNTG sequence in the +210 to +215 positions, which corresponded to the E-box. Our findings demonstrated important roles of NNAT in placenta function.

Placental expression profile of imprinted genes impacts birth weight

“…This is in contrast to NNAT, a gene putatively linked with glucose transport in the placenta. 20 In our study, this gene demonstrated a U-shaped relationship to growth, where increased expression indicated risk for both LGA and SGA status, suggesting a more complicated connection to these outcomes, and the potential importance of highly coordinated regulation.…”

Neuronatin Protein in Health and Disease

“…In 2012, the study conducted by Gu et al () also confirmed NNAT as an important protein regulating glucose transportation in the pig placenta through the PI3K‐AKT pathway. While a direct link between NNAT and PI3K‐AKT has not been established in this study, the authors detected co‐expression of NNAT (α and β) and IP3K/AKT on the 75th day of gestation.…”

“…It has been demonstrated that the expression prevalence of each isoform can vary depending on the stage of development, tissue specificity, and cellular homeostatic status. For example, during an early stage of brain development, the α‐isoform is predominantly expressed as compared to β‐isoform (Gu et al, ). In β‐cells of diabetic rodents, NNAT‐α is the isoform preferentially reduced (Chu and Tsai, ).…”

Oocyte aging-induced Neuronatin (NNAT) hypermethylation affects oocyte quality by impairing glucose transport in porcine

“…NNAT took roles in neuronal differentiation in the brain13 and increased insulin secretion by regulating intracellular calcium levels and hyperglycemia-induced apoptosis in pancreatic β-cells14. In porcine placenta, NNAT was monoallelically expressed and regulated glucose transporter genes15.…”