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TRANSMEMBRANE PROTEIN 79; TMEM79

TRANSMEMBRANE PROTEIN 79; TMEM79

Alternative titles; symbolsMATTRIN, MOUSE, HOMOLOG OF; MATTHGNC Approved Gene Symbol: TMEM79Cytogenetic location: 1q22 Genomic coordinates (GRCh38): 1:156,28...

Alternative titles; symbols

  • MATTRIN, MOUSE, HOMOLOG OF; MATT

HGNC Approved Gene Symbol: TMEM79

Cytogenetic location: 1q22 Genomic coordinates (GRCh38): 1:156,282,931-156,292,442 (from NCBI)

▼ Description
TMEM79 is a skin barrier-related protein (Sasaki et al., 2013).

▼ Cloning and Expression
Sasaki et al. (2013) cloned mouse Tmem79. The deduced 391-amino acid protein has a calculated molecular mass of 43.4 kD. It has a cytoplasmic N-terminal domain followed by 5 C-terminal transmembrane domains. Sasaki et al. (2013) also identified a mouse Tmem79 variant with an alternative first exon. Northern blot analysis detected highest expression of an approximately 2-kb transcript in skin, followed by testis, kidney, thymus, and lung. No expression was detected in heart, brain, spleen, or liver. Quantitative RT-PCR confirmed that Tmem79 expression was highest in skin, predominantly in epidermis. Immunohistochemical analysis revealed highest TMEM79 expression in the cytoplasm of human and mouse stratum granulosum cells, where it colocalized with a marker for the trans-Golgi network.

Independently, Saunders et al. (2013) cloned mouse Tmem79, which they called mattrin, and by database analysis, they identified human mattrin. RT-PCR of 48 human tissues detected widespread mattrin mRNA expression, with high expression in skin. Immunohistochemical analysis detected mattrin in epidermal granular layer cells and hair follicles in mouse and human.

▼ Gene Structure
Saunders et al. (2013) stated that the TMEM79 gene contains 5 exons.

▼ Mapping
Saunders et al. (2013) reported that the TMEM79 gene maps to chromosome 1q23.1. The mouse Tmem79 gene maps to a region of chromosome 3F1 that shares homology of synteny with human chromosome 1q23.1.

▼ Gene Function
Kannan et al. (2011) identified a chimeric transcript in several prostate cancers and prostate cancer cell lines that resulted from splicing between the upstream SMG5 gene (610962) and the downstream TMEM79 gene on the opposite strand. RT-PCR also detected expression of the individual SMG5 and TMEM79 genes in prostate cancers, prostate cancer cell lines, and normal prostate epithelium. However, the SMG5-TMEM79 chimeric transcript was not detected in normal prostate epithelium or in a normal prostate epithelial cell line.

▼ Molecular Genetics
By metaanalysis using a fixed-effect model of 4,245 patients with atopic dermatitis (AD; see 603165) from the U.K. and Germany and 10,558 controls, Saunders et al. (2013) found that the minor allele (A) of the SNP rs6684514 within TMEM79 showed a small but significant protective effect against atopic dermatitis (odds ratio (OR) = 0.91; 95% CI = 0.86-0.96; p = 0.001). A random-effects metaanalysis produced similar results (OR = 0.90; 95% CI = 0.82-0.98; p = 0.015).

▼ Animal Model
Mice homozygous for the matted (ma) mutation develop matted hair and eczema that resembles human atopic dermatitis, and they exhibit scratching behavior. Sasaki et al. (2013) found that ma/ma mice showed higher transepithelial water loss and lower stratum corneum hydration than wildtype, with histologic changes, such as acanthosis with leukocyte infiltration. Skin defects in ma/ma mice were observed as early as 1 week. Sasaki et al. (2013) identified a tyr280-to-ter (Y280X) mutation in the Tmem79 gene in ma/ma mice. The mutation deleted the last 3 transmembrane domains of the Tmem79 protein. Skin of ma/ma mice showed reduced secretion of proteins into the stratum granulosum layer for formation of the stratum corneum. Mutant skin also showed reduced resistance to physical stress. The ma/ma phenotype was reversed by transgenic expression of wildtype Tmem79. Sasaki et al. (2013) concluded that TMEM79 is a skin barrier-related protein involved in secretion via the lamellar granule secretory system.

Independently, Saunders et al. (2013) identified the Y280X mutation in Tmem79 as the ma mutation. Compared with wildtype skin, ma/ma skin showed disorganized cornified cell envelopes with a defect in keratinization, fragile and clumping hairs with distorted follicles, marked skin inflammation with a broad spectrum of pathology, and elevated IgE levels. Ma/ma mice were also highly sensitive to challenge with house dust mite allergen.

Tags: 1q22