Sexually dimorphic roles for the type 2 diabetes-associated C2cd4b gene in murine glucose homeostasis

Abstract

Aims/hypothesis Variants close to the VPS13C/C2CD4A/C2CD4B locus are associated with altered risk of type 2 diabetes in genome-wide association studies. While previous functional work has suggested roles for VPS13C and C2CD4A in disease development, none has explored the role of C2CD4B. Methods CRISPR/Cas9-induced global C2cd4b-knockout mice and zebrafish larvae with c2cd4a deletion were used to study the role of this gene in glucose homeostasis. C2 calcium dependent domain containing protein (C2CD)4A and C2CD4B constructs tagged with FLAG or green fluorescent protein were generated to investigate subcellular dynamics using confocal or near-field microscopy and to identify interacting partners by mass spectrometry. Results Systemic inactivation of C2cd4b in mice led to marked, but highly sexually dimorphic changes in body weight and glucose homeostasis. Female C2cd4b mice displayed unchanged body weight compared with control littermates, but abnormal glucose tolerance (AUC, p = 0.01) and defective in vivo, but not in vitro, insulin secretion (p = 0.02). This was associated with a marked decrease in follicle-stimulating hormone levels as compared with wild-type (WT) littermates (p = 0.003). In sharp contrast, male C2cd4b null mice displayed essentially normal glucose tolerance but an increase in body weight (p < 0.001) and fasting blood glucose (p = 0.003) after maintenance on a high-fat and -sucrose diet vs WT littermates. No metabolic disturbances were observed after global inactivation of C2cd4a in mice, or in pancreatic beta cell function at larval stages in C2cd4a null zebrafish. Fasting blood glucose levels were also unaltered in adult C2cd4a-null fish. C2CD4B and C2CD4A were partially localised to the plasma membrane, with the latter under the control of intracellular Ca2+. Binding partners for both included secretory-granule-localised PTPRN2/phogrin. Conclusions/interpretation Our studies suggest that C2cd4b may act centrally in the pituitary to influence sex-dependent circuits that control pancreatic beta cell function and glucose tolerance in rodents. However, the absence of sexual dimorphism in the impact of diabetes risk variants argues for additional roles for C2CD4A or VPS13C in the control of glucose homeostasis in humans. Data availability The datasets generated and/or analysed during the current study are available in the Biorxiv repository (www.biorxiv.org/content/10.1101/2020.05.18.099200v1). RNA-Seq (GSE152576) and proteomics (PXD021597) data have been deposited to GEO (www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE152576) and ProteomeXchange (www.ebi.ac.uk/pride/archive/projects/PXD021597) repositories, respectively. Graphical abstract

Reflections on the state of diabetes research and prospects for treatment

“…An impairment of this process can result in metabolic inflexibility via increased lipid utilization [39]. The Rutter group independently identified the neighboring C2CD4B gene as the potential diabetessusceptibility locus [40]. Given that the genes are physically close and structurally related, it's possible that they both contribute and that functional studies that involve both will be required to fully assess their contribution to diabetes pathogenesis and β-cell function.…”

Transcriptomic analysis of the submandibular gland under psychological stress condition

“…Interestingly, among the top 10 DEGs, genes such as Cngb1, Gosr1, Slc45a4, Trpc1, and Ttc13 were involved in the salivary gland's ion and protein transport system (Table 1). [20][21][22][23][24][25][26][27][28] This system includes a cation channel, an H +/ sugar cotransporter, and a calcium entry channel. These transport systems are vital in regulating salivary gland secretion and normal function.…”

Selective Transcription Factor Blockade Reduces Human Retinal Endothelial Cell Expression of Intercellular Adhesion Molecule-1 and Leukocyte Binding

“…Originally described in 2004 and named nuclear localized factor (NFL)2, C2CD4B was measured at relatively high levels in human endothelial cells in comparison to epithelial cells, smooth muscle cells, fibroblasts, and monocytes, and was found to be induced by IL-1β and TNF-α [ 19 ]. Subsequent genetics-focused research has linked C2CD4B to glucose homeostasis, with increased activity promoting the development of type 2 diabetes mellitus by mechanisms that may be sexually dimorphic [ 29 , 30 , 31 ], and to regulation of coagulation factor VII and von Willebrand factor, with a potential causal role in vascular occlusive disease [ 32 ]. Interestingly, although most studied in relation to non-infectious uveitis, interactions between leukocytes and the retinal endothelium also occur in diabetic retinopathy and retinal vein occlusion [ 33 , 34 ], suggesting a role for C2CD4B beyond immune-mediated eye disease.…”