Non-alcoholic fatty liver disease in mice with heterozygous mutation in TMED2

Abstract

The transmembrane emp24 domain/p24 (TMED) family are essential components of the vesicular transport machinery. Members of the TMED family serve as cargo receptors implicated in selection and packaging of endoplasmic reticulum (ER) luminal proteins into coatomer (COP) II coated vesicles for anterograde transport to the Golgi. Deletion or mutations of Tmed genes in yeast and Drosophila results in ER-stress and activation of the unfolded protein response (UPR). The UPR leads to expression of genes and proteins important for expanding the folding capacity of the ER, degrading misfolded proteins, and reducing the load of new proteins entering the ER. The UPR is activated in non-alcoholic fatty liver disease (NAFLD) in human and mouse and may contribute to the development and the progression of NAFLD. Tmed2, the sole member of the vertebrate Tmed β subfamily, exhibits tissue and temporal specific patterns of expression in embryos and developing placenta but is ubiquitously expressed in all adult organs. We previously identified a single point mutation, the 99J mutation, in the signal sequence of Tmed2 in an N-ethyl-N-nitrosourea (ENU) mutagenesis screen. Histological and molecular analysis of livers from heterozygous mice carrying the 99J mutation, Tmed299J/+, revealed a requirement for TMED2 in liver health. We show that Tmed299J/+ mice had decreased levels of TMED2 and TMED10, dilated endoplasmic reticulum membrane, and increased phosphorylation of eIF2α, indicating ER-stress and activation of the UPR. Increased expression of Srebp1a and 2 at the newborn stage and increased incidence of NAFLD were also found in Tmed299J/+ mice. Our data establishes Tmed299J/+ mice as a novel mouse model for NAFLD and supports a role for TMED2 in liver health.

Control of anterior GR adient 2 ( AGR 2) dimerization links endoplasmic reticulum proteostasis to inflammation

“…TMED2 mutant mice —For TMED2 mutant mice, all procedures and experiments were performed according to the guidelines of the Canadian Council on Animal Care and approved by the Animal Care Committee of the Montreal Children's Hospital. The 99J (TMED2 mutant) mouse line was generated on a C57/BL6J genetic background and maintained on a mixed C3H genetic background (C3HeB/FeJ and C3HeB/FeV) as previously described (Hou et al , ). Six‐month‐old male TMED2 mutants ( n = 6) and their wild‐type littermate ( n = 6) were analyzed.…”

Transmembrane emp24 domain proteins in development and disease.

“…Overall, TMED proteins are expressed in a tissue-dependent, developmental age-dependent and even sex-specific pattern, suggesting non-redundant functions across various species (Rotter et al, 2002;Carney & Taylor, 2003;Boltz et al, 2007;Jerome-Majewska et al, 2010;Hou et al, 2017). The TMED family is implicated in developmental processes such as wing morphogenesis in Drosophila, reproductive system development in C. elegans, embryonic development in rats and mice and placental development in mice and humans (Jerome-Majewska et al, 2010;Buechling et al, 2011;Hou & Jerome-Majewska, 2018).…”

“…The aforementioned homozygous null mouse embryos, with no functional TMED2, were smaller than their littermates prior to death at mid-gestation, suggesting a requirement for TMED2 in normal cell proliferation (Table 4) (Jerome-Majewska et al, 2010). Moreover, heterozygotes were more susceptible to liver cancer compared to their wild-type littermates (Hou et al, 2017). Therefore, in liver cells, a reduction in TMED2 results in increased liver tumorigenesis and demonstrates a possible tumour suppressor-like property for TMED2.…”

“…The transmembrane emp24 domain (TMED) family consists of type I single-pass transmembrane proteins that are found in all eukaryotes. Members of the TMED family have emerged as important regulators of protein transport (Carney & Bowen, 2004;Dancourt & Barlowe, 2010;Jerome-Majewska et al, 2010;Zakariyah et al, 2012;Viotti, 2016;Wada et al, 2016;Hou et al, 2017;Hou & Jerome-Majewska, 2018), and although they are found in the early and late secretory pathways (Figure 2), most studies focus on the function of TMED proteins in the early secretory pathway (Figure 2a): the endoplasmic reticulum (ER), the ER-Golgi intermediate compartment (ERGIC) and the Golgi (Shevchenko et al, 1997;Dominguez et al, 1998;Fullekrug et al, 1999;Jenne et al, 2002;Chen et al, 2006;Hosaka et al, 2007;Blum & Lepier, 2008;Montesinos et al, 2012Montesinos et al, , 2013.…”

Mis-splicing ofMdm2leads to Increased P53-Activity and Craniofacial Defects in a MFDMEftud2Mutant Mouse Model

“…Genomic DNA was extracted from mouse tails or yolk sacs as previously described (Hou et al, 2017). For Eftud2, genotyping was performed using 3-primers targeting exon 2 of Eftud2 using the following program: 30 sec 95 o C, 30 sec 55 o C, 30 sec 72 o C for 35 cycles followed by an elongation step of 10 minutes at 72 o C. As depicted in Fig.…”